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Using Aspergillus niger to Bioremediate Soils Contaminated by Heavy Metals
Abstract
A bioremediation process was developed using the fungus AspergiUus niger to produce weak organic acids for the leaching of heavy metals from contaminated soils. The fungus was cultivated on the surface of three contaminated soils (a clay loam, a loam, and a sandy clay loam) for 15 days at 30°C and at a pH <4 to favor the production of citric acid rather than oxalic acid which hinders Pb leaching. For the clay loam, Cr, Mn, Pb, and Hg were leached to levels of 37, 41, 85, and 91%, respectively. For the loam, the leaching of Cd and Pb was found to reach levels of 99.7 and 83%, respectively. For the sandy clay loam, Cd, Cu, Pb, and Zn were leached to levels of 99,94,58, and 99%, respectively. The three contaminated soils could have been remediated to the A category of the Province of Quebec standards for heavy metals after 20 to 25 days of leaching using this technique.
... Very little attention is paid to column bioleaching method by filamentous fungi to remediate metal contaminated sites. Wasay et al. [21] showed that cultivation of A. niger in straws above a soil surface was capable of leaching metals due to production of citric acid by A. niger. It is well known that citric acid production by the fungi is strongly influenced by the presence of metal ions. ...
... In addition, when the pH values are in the range of 2.5-3.5, citric acid production tends to be stimulated. It has been reported that cultivation of fungi on moist solid substrate above contaminated soil surface provided a favorable condition for citric acid production because there is no contact between the soil and the fungi [21]. Ousmanova and Parker [22] used solid-state fermentation (SFF) of low cost substrates by fungal species to generate organic acid solutions for washing of Pb from a contaminated soil in a column study. ...
... The presence of Mn in the tailings strongly inhibits citric acid accumulation by stimulating the enzymes in the TCA cycle [33]. Wasay et al. [21] showed that cultivation of A. niger on the surface of three contaminated soils was capable of producing citric acid. ...
A column bioleaching experiment was carried out to compare the effectiveness of the fungus Aspergillus fumigatus to bioleach arsenic (As) and heavy metals from the tailings using two different methods. In the first method, which is named as distribution method (DM), the fungus was distributed in the column by means of vertical and horizontal layers of coarse sand. In the other method, named as surface applied method (SAM), the fungus was cultivated on the surface of the tailings, which was covered with a few centimeters of coarse sand. Results showed that in the DM, oxalic acid production was stimulated and maximum removal of As, Fe, Mn, and Zn was 53, 51, 81, and 62%, respectively. However, Pb removal was low (8%), which might be due to the precipitation of Pb as its oxalates. On the other hand, the maximum removal of As, Fe, Mn, Pb, and Zn were 22, 28, 37, 64, and 34%, respectively, for the SAM. Results of the sequential extraction study showed that the DM was effective in removing the water soluble, exchangeable, carbonate, and Fe/Mn oxide fractions of As, Fe, Mn, and Zn. Our study suggested that A. fumigatus has a potential to be used in remediation of heavy metal contaminated sites. Distributing the fungus throughout the entire tailings columns improved the bioleaching of heavy metals by the fungus.
... Soil flushing technique using weak organic acids can effectively remediate soils contaminated with heavy metals ( Wasay et al . , 1998 ; Sayer and Gadd , 2001 ) . Organic acids including citric acid , gluconic , oxalic and tartaric acid produced by A . niger have several carboxyl and hydroxyl groups , which compete against soil particles for heavy metal absorption . Among weak organic acids , citric acid produced by A . niger has advantages over chemical chelating agen ...
... lites , it is readily used by fungus . Also , apple peels and pomace , grape pomace , banana extract , sugar cane baggasse and sugar beet molasses have been used to produce citric acid ( Ngadi and Correia , 1992 ; Wang , 1998 ; Gutierrez - Correa et al . , 1999 ) . Some strains of A . niger can convert up to 90% of the glucose into organic acids ( Wasay et al . , 1998a ) . A substrate initiating glycolysis followed by the TCA cycle , glucose is the crucial factor affecting acid production . According to Leangon et al . ( 2000 ) , an increase glucose flux through glycolysis may be the reason for over - production of citric acid in solid substrate fermentation . However , low glucose concentration in t ...
... The number of carboxyl and hydroxyl groups determines the order of effectiveness in chelating heavy metals ( citric acid > tartaric acid > other organic acid anions ) . Metal - citric acid complexes exhibit stronger chelating potential and can form more stable complexes than other acid anions , not surprisingly because citric acid carries three negative charges ( Wasay , 1998 ) The partitioning of heavy metals between their atoms on soil surface groups and the organic acid can be depicted using the following reactions . ...
Among the various fungal strains screened for citric acid production, Aspergillus niger is known to produce considerable amounts of citric acid and other organic acids when cultivated in carbohydrate-rich medium in solid substrate fermentation (SSF). Since A. niger on a solid substrate grows under conditions similar to the natural habitat, SSF is ideal to cultivate A. niger for the purpose of producing citric acid. An initial optimization (study 1) was conducted in batch type fermentation experiments using peat moss supplemented with glucose to simulate an organic waste. The effects of various nutrients (glucose, (NH4)2SO 4, KH2PO4 and NaCl), fermentation parameters (moisture content, temperature, inoculum density, composition of solid substrate and particle size) and of initial level of potential stimulators (ethanol, methanol, phytate and surfactant) were evaluated with respect to citric acid production by A. niger grown on damp peat moss. In these experiments, optimization using a traditional 'one-factor-at-a-time' method was applied to determine key factor ranges for the production of citric acid. When the fermentation was carried out using the final optimal conditions. This allowed for a 50-fold increase in citric acid production compared to the production of citric acid by A. niger grown on peat moss supplemented with 100 g glucose/kg DPM. A second set of experiments (study 2) was conducted to optimize fermentation conditions for citric acid production in a column bioreactor. A. niger NRRL 567 grown on damp peat moss was held within a column bioreactor and periodically irrigated with a glucose-rich solution simulating field conditions. Three variables including aeration, thickness of solid substrate bed and incubation temperature were optimized using a 23 full factorial design (FFD). Under optimum, the total citric acid production and yield were 120.6 g/kg DPM and 18.5% respectively. A third experiment (study 3) compared the production of citric acid by A. niger in submerged fermentation using cheese whey, as opposed to batch and semi-continuous fermentation using peat moss. Various fermentation conditions such as nutrients (glucose, (NH4)2SO 4 and KH2PO4), stimulators (methanol, olive oil and phytate) and fermentation parameters (pH, fermentation time and inoculum density) were optimized using a central composite design (CCD). Citric acid production improved citric acid production by a factor of 13.3 when compared to the production of citric acid by A. niger NRRL 567 using whey-based medium (50 g/l) alone. As compared to submerged and semi-continuous fermentation, Batch type SSF could take higher levels of initial glucose and produce the high concentration of citric acid within a shorter period of time. Thus, SSF may be considered to be better technique than submerged fermentation, if main disadvantage like non-homogeneous fermentation conditions could be overcome.
... Citric acid fermentation broth can be directly used for washing remediation and a complex extraction process can be avoided, which can reduce the cost of production. Furthermore, the citric acid fermentation broth is a kind of environmental friendly material because of its good biological degradation and less secondary pollution (Papagianni 2007;Bosshard et al. 1996;Wasay et al. 1998). ...
... The fermentation medium has only a weak effect on the removal of heavy metals in soil; the removal percentages are that 9.1% for Pb, 3.1% for Cu, 8.6% for Cr, and 7.8% for Cd. However, the citric acid fermentation broth has a strong effect; the removal percentages are that 48.2% for Pb, 30.6% for Cu, 43.7% for Cr, and 58.4% for Cd, indicating that the metabolites produced such as citric acid and a series of by-product acid in the process of microbial fermentation play a role in the removal of heavy metals in soil (Bosshard et al. 1996;Ren et al. 2009;Wasay et al. 1998). The citric acid solution also showed a good removal effect, and the removal percentages are that 44.0% for Pb, 24.4% for Cu, 37.1% for Cr, and 51.6% for Cd, which is a validation that the organic acids can effectively remove heavy metals from soil (Bassi et al. 2000). ...
The citric acid fermentation broth was prepared and it was employed to washing remediation of heavy metal-polluted soil. A well-defined washing effect was obtained, the removal percentages using citric acid fermentation broth are that 48.2% for Pb, 30.6% for Cu, 43.7% for Cr, and 58.4% for Cd and higher than that using citric acid solution. The kinetics of heavy metals desorption can be described by the double constant equation and Elovich equation and is a heterogeneous diffusion process. The speciation analysis shows that the citric acid fermentation broth can effectively reduce bioavailability and environmental risk of heavy metals. Spectroscopy characteristics analysis suggests that the washing method has only a small effect on the mineral composition and does not destroy the framework of soil system. Therefore, the citric acid fermentation broth is a promising washing agent and possesses a potential practical application value in the field of remediation of soils with a good washing performance.
... mg CO2 kg -1 soil), this may be due to the fungal inoculation, the adaptation of these fungi in environmental media contaminated with heavy elements (Kumar et al., 2014). As well as, the A. niger is one of the fungi with a high ability to absorb heavy metal ions in a high pH range (Wasay, 1998). It is clear from figure 2B that the effect of adding humic acid is also important in increasing the bioactivity of soils contaminated with heavy metals. ...
For the purpose of identify the ability of bioremediation or organic treatments of soil to reduce the harmful effect of heavy metals including Zn, pb and cd on the biological activity such as soil respiration, the total number of fungi and the activity of the L-glutaminase enzyme have been studied. A laboratory incubation experiment was applied in the Soil Microbiology Laboratory in the Department of Soil Sciences and Water Resources in the College of Agriculture– Basrah University. The soil of the surface layer (0-30 cm) from Qurna district, north of Basrah province was contaminated with the critical levels of the heavy metals cd, Pb, Zn and were placed in an incubator at 30°C for 14 days. The biological and organic treatments process was applied by inoculating soil contaminated with Aspergillus niger or humic acid (40 L ha-1) or sterilized cow manure (4%), incubated at 25°C for 30 days, then some biological parameters were estimated at the periods of 10, 20 and 30 days. Results have been showed that an inhibitory effect of the studied heavy metals on the biological parameters, and the Cd has been recorded the highest percentage of inhibition of total number of fungi (30.67%), the amount of CO2 released (13.93%) and the activity of the L-glutaminase enzyme (45.33%) compared to the control treatment. The ability of the treatments materials to remove heavy metals were (89.02%) for A. niger compared to humic acid (63.48%) and cow manure (48.71%). It was reflected in an increase in the number of fungi, which recorded 152, 167.75, 174.5 cfu g-1 when treated with A. niger, cow manure and humic acid, respectively compared to the control treatment which was (65.92 cfu g-1). The biological and organic treatments also increased the level of liberated CO2 from the polluted soil to 268.62, 253.86, 303.59 mg CO2 g-1, respectively compared to the control treatment. The activity of the L-glutaminase enzyme has increased due to application of treatments. It was 57.02, 48.97, 70.41 µg NH4+ g-1 2hr.-1 for inoculated with A. niger or treated with cow manure and humic acid, respectively, while the control treatment was 37.19 µg NH4+ g-12hr.-1.
... Arun and Eyini (2011) Schizophyllum commune Matsubara et al. (2006) Stropharia coronilla Steffen (2000) Pentachlorophenol Agrocybe perfecta, T. villosa, T. hirsuta Machado et al. (2005) Ceriporiopsis subvermispora (Lamar and Dietrich, 1990; (Cernansky et al., 2007) copper, lead, arsenic (Clausen, 2004;Mukherjee et al., 2010), chromium (Prasenjit and Sumathi, 2005;Srivastava and Thakur, 2006). A. niger is using to produce a variety of organic acids for the leaching of heavy metals from contaminated soils (Wasay et al., 1998;Ren et al., 2009) and is effective in the bioleaching of nickel laterite ores and Pb (Le et al., 2006;Chakraborty et al., 2014). Dead biomass of Aspergillus can be used as an effective biosorbent of heavy metals (Rostami and Joodaki, 2002). ...
This review presents a comprehensive summary of the latest research in the field of bioremediation with filamentous fungi. The main focus is on the issue of recent progress in remediation of pharmaceutical compounds, heavy metal treatment and oil hydrocarbons mycoremediation that are usually insufficiently represented in other reviews. It encompasses a variety of cellular mechanisms involved in bioremediation used by filamentous fungi, including bio-adsorption, bio-surfactant production, bio-mineralization, bio-precipitation, as well as extracellular and intracellular enzymatic processes. Processes for wastewater treatment accomplished through physical, biological, and chemical processes are briefly described. The species diversity of filamentous fungi used in pollutant removal, including widely studied species of Aspergillus, Penicillium, Fusarium, Verticillium, Phanerochaete and other species of Basidiomycota and Zygomycota are summarized. The removal efficiency of filamentous fungi and time of elimination of a wide variety of pollutant compounds and their easy handling make them excellent tools for the bioremediation of emerging contaminants. Various types of beneficial byproducts made by filamentous fungi, such as raw material for feed and food production, chitosan, ethanol, lignocellulolytic enzymes, organic acids, as well as nanoparticles, are discussed. Finally, challenges faced, future prospects, and how innovative technologies can be used to further exploit and enhance the abilities of fungi in wastewater remediation, are mentioned.
... The predominant fungal isolates identified in the 2018 (Usmani et al., 2006, Syed et al., 1998, Hidayat et al 2012.This is also a silent warning of a changing environment. ...
Onwuachi-Iheagwara, P.N. ; Iheagwara, B.I. ; Oloro, J. ; 3 4 Iheagwara, P. and Ogofure, G.
... • Heavy metal contamination from tanneries by leaching toxifies both soil and ground water. To avoid the entry of heavy metals into the food chain, it is important to remove them from soil and water for which microorganisms such as Pseudomonas aeruginosa and Aspergillus niger are being currently used and could be further engineered to make them more efficient and cost effective in the cleaning process [42][43][44]. • Rubber waste is 12% of total solid waste and can neither be degraded easily nor recycled due to its physical property. ...
... [5] Biological methods solve these drawbacks since they are easy to operate, do not produce (Lloyd, 2002). [7] Sabry et al., 1997, [8] Wasay et al., 1998, [9] Chande et al., ...
Heavy metal pollution is nowadays one of the most important environmental concerns. Anthropogenic activities like metalliferous mining and smelting, agriculture, waste disposal or industry discharge a variety of metals such as Ag, As, Au, Cd, Co, Cr, Cu, Hg, Ni, Pb, Pd, Pt, Rd, Sn, Th, U and Zn, which can produce harmful effects on human health when they are taken up in amounts that cannot be processed by the organism. In this present study, Aspergillus fumigatus were identified and inoculated with chromium to analyse the capability of those microorganism in bioremediation. The results revealed that chromium level decreased in culture media. It was also observed that Aspergillus fumigatus removes the chromium at high rate.
... Akan tetapi produksi mycotoksin harus dikontrol melalui kondisi saat fermentasi. 12) Bahaya terhadap hewan telah dijelaskan karena pengaruh mycotoksin yang dihasilkan oleh Aspergillus niger, seperti kekurangan Kalsium dan sifat fisiologis abnormal lainnya termasuk kematian yang dapat terjadi sehubungan dengan produksi oxalic acid atau malformins dari Aspergillus. 13) Hal ini pun telah dikaji tidak berpengaruh secara signifikan sebagai pathogen bagi ternak jika dikontrol fermentasinya. ...
Indonesia as an agricultural country have many agriculture waste that usefull for feedingredients, contained high energy but low protein. The constraints from the use of thosefeed ingredients are that they have low nutrient content, low economic value as feed,unavailable continously, hard to handle, need certain facility, need high transportationcost, low storage periode and high toxin contamination. Microbiology can handle thoseconstraints by the use of microbes, which recently used in feed industry. This reseachhave goal for improving protein contain of cassava peel, bananas peel and potatos peelwhich fermented by Aspergillus niger. The methodology done by solid fermentation asORTSOM method and IRCHA method.Cassava peel, bananas peel and potatos peelsterilized by boiling and nitrogen analyzed by Kjeldahl method. The result show thatprotein contains of cassava peel, bananas peel and potatos peel increase significantly.(p<0.05.) and they can be as substrat for Aspergillus niger medium for industry
... Bioremediation could be slow and might not be able to completely remove the contaminants from the environment. Living organisms, particularly microorganisms (Bryant, 1987;Avgustin, 1998;Wasay et al., 1998;Pokethiyook et al., 2002;Tsekova and Petrov, 2002) and higher plants (phytoremediation) have been used in cleansing of contaminated sites with impressive results. ...
Bioremediation involves the use of living organisms to breakdown hazardous substances to less or nontoxic substances. The use of plants in bioremediation referred to as phytoremediation is gaining acceptance Some plants are able to bioaccumulate toxins in their parts body parts which are harvested to remove contaminant. The rate of bioaccumulation of most of these plants are slow hence the need for genetically modified plants with more efficient phytoremediation capacity. This paper attempts to elucidate the potentials of genetically modified plants for bioremediation of contaminated soils.
... For direct or indirect toxic effects of heavy metals on life system, the removal of these metals from water and soil are prerequisite but the clean up procedure of heavy metals are expensive, destructive and time consuming [15]. Scientist are engaged themselves to develop some cost effective devices of which exploitation of some specific microorganism are the prime important [27]. Many researchers have noticed that, some plant species are endemic to metalliferous soils and able to withstand in presence of heavy metals in soils [4]. ...
Microbes assisted phyto-remediation technique are widely applied for reducing the risk of heavy metals contamination in the soil. The present study was designed to observe the effect of rhizobacteria on plant growth enhancement under heavy metal stress condition. We examined the growth of rice plant with two isolated PGPR strains under different test concentration (ppm) of Cd and/or Pb (i.e. 20,40and 60ppm). In all studied cases, we observed that different growth parameters in the un inoculated heavy metal treated rice plants (i.e-without PGPR) were reduced as compared with control plants. Cd and Pb toxicity were assessed by observing different growth parameters like stunted growth and poor rooting and low chlorophyll content. Inoculation of PGPR in rice plant reduced the deleterious effects of heavy metals to some extent and enhanced the different growth parameters as compared with un inoculated heavy metal treated plants. Our present study conducted with 2out of 20 different bacterial isolates but observed results indicated that KUBM 20 strain of enhanced more in the growth of rice plant under heavy metal stress condition than KUBM 1.
... Traditional clean up processes of heavy metals pollution are expensive and environmentally destructive (Meagher, 2000). At present, scientists and engineers are emphasizing on generation of cost effective technologies that include the use of micro organisms, biomass and live plants in cleaning process of polluted areas (Boyajian and Carreira, 1997;Wasay et al., 1998), so as to reduce the risk of cadmium being incorporated into food chain. These strategies would help in cleanup of contaminated soils via bioaccumulation and may be of particular interest for agricultural soils as these will help in restoration of soil fertility and the possible re-use of agricultural land (Frey et al., 2000;Perronnet et al., 2000). ...
... Hereupon, soil pollution through the food chain threats health of humankind (McLaughlin et al., 2009). Scientists and engineers have started to generate efficacious technologies that contain the utility of microorganisms, biomass and some plants for the process of removing polluted zones (Ebbs, Kochian, 1997;Wasay et al., 1998). Among heavy metals Cadmium is one of the toxic elements that don't play a vital role for live organs. ...
Cadmium (Cd) is a toxic heavy metal which causes oxidative stress in plants and has a high level of toxicity for
plants, animals and human. Present study carried out in order to evaluate the Cd stress effect on growth parameters in bean
seedlings. This experiment was conducted in the form of factorial in randomized complete block design (RCBD) by three
replications per treatment. In addition, 25 bean seeds genotypes grew in laboratory conditions consist of solution CdCl2
with concentration of 4 mg/lit and distilled water (as a control). The seedlings were harvested after 8 days and the
germination percentage, root and shoot length and its stability, R/S ratio and fresh weight were recorded. The results
revealed that Cd adversely influenced on these traits. As a result, Cd treatment in all genotypes reduced the germination
percentage 9.9%, root and shoots length 83.9% and 66.3%, respectively, R/S ratio 52.2%, and fresh weight 42.3%, in
compared to control. Based on the results we concluded that, these traits of bean plant are seriously affected by Cd
treatment and also these are symptoms of toxicity of Cd element. Therefore less amount of reduction in a special genotype
is referred to the index of tolerance to Cd.
... Metals in the upper soil horizon are mobilized by the stimulation of the soil microflora and transferred to deeper soil layers by drainage where metals are precipitated by the activity of anaerobic sulfate-reducing bacteria forming sulfide. Aspergillus niger was used to remove cadmium, chromium, copper, lead, manganese, mercury, and zinc from metal-polluted soils (WASAY et al., 1998). An effect of the soil type on the leaching efficiency was observed. ...
IntroductionTerminologyHistorical Background
Principles of Microbial Metal LeachingMicrobial Diversity in Bioleaching EnvironmentsCase Studies of Bioleaching ApplicationsEconomics of Metal BioleachingPerspectives of Bioleaching TechnologyConclusion
... At the bench scale, Cr, Hg, and As have shown potential for bioremediation in soils. While the detoxification of Cr has involved aerobic reduction of the Cr VI to Cr III (235,236) in the soils, remediation of Hg (237) and As has involved transformation of the contaminants to volatile phases. Bioremediation of Ascontaminated soils is based on the ability of microbes, mold, or fungi to transform As into either the less toxic forms or a form that allows volatilization of As. ...
... Hereupon, soil pollution through the food chain threats health of humankind (McLaughlin et al., 2009). Scientists and engineers have started to generate efficacious technologies that contain the utility of microorganisms, biomass and some plants for the process of removing polluted zones (Ebbs, Kochian, 1997;Wasay et al., 1998). Among heavy metals Cadmium is one of the toxic elements that don't play a vital role for live organs. ...
growth parameters of bean varieties studied under cadmium stress
... Currently, cleanup processes of heavy metal pollution are expensive and environmentally destructive (Nanda et al., 1995;Moffat, 1995;Meagher, 2000). Recently, scientists and engineers have started to generate costeffective technologies that include the use of microorganisms, biomass, and live plants in the cleaning process of polluted areas (Miller, 1996;Boyajian and Carreira, 1997;Dushenkov et al., 1997;Ebbs and Kochian, 1998;Wasay et al.,1998;Gardea et al., 1996). Some heavy metals at low doses are essential micronutrients for plants, but in higher doses they may cause metabolic disorders and growth inhibition for most of the plants species (Fernandes and Henriques, 1991;Claire et al., 1991). ...
The aim of the present study is to develop phenotypically stable varieties for those soils that are contaminated with mercury or cobalt. This is a novel report about their ability to grow in the contaminated soil. The benefit of this technology is the potential for low cost remediation. Highly significant differences have been observed among the varieties of Linum usitatissimum for all the characters in all the treatment or environment. There has been considerable amount of variability for all the characters in all the treatments. The 10-5 M HgCl2 treatment shows the inhibitory effect in all the varieties and there is no further seedling establishment after seed germination. The highest toxic effect has been observed for the seedling vigour and seed vigour index. The 10-5 M HgCl2 concentration is the last limit of tolerance in plants while 10-4 M CoCl2 could be the last tolerance limit and there may be a specific gene in plants which monitor the toxicity level or tolerance capacity. The maximum magnitude of positive correlation coefficient has been found between seedling fresh and dry weight and negative for 1000 seed weight and germination rate index. The seedling length exerts maximum positive direct effect on seedling vigour followed by absolute seedling water content.
... Fungal production of low-molecular-weight organic acids (LMWOAs) has been almost exclusively studied in model organisms, such as Aspergillus spp. (2,3,16,27,36,39,56). Despite the fact that it is a process that may contribute significantly to Pb mobilization in soils, no thorough studies of these processes in indigenous soil fungi have been reported. ...
Background/Question/Methods
Lead (Pb) contaminated soils represent severe environmental problems as well as a significant hazard to human health. Prolonged exposure to high levels of toxic metals exerts considerable selective pressure on the soil microbial community and alters soil and ecosystem health. The objective of this study is to understand how the total level of Pb contamination has affected the soil chemistry and fungal community at an abandoned small-arms firing range in east Tennessee. 92 soil samples were collected in a spatially explicit sampling design across two ecosystem types, grassland and forested, surrounding the backstop at the abandoned firing range. Soils were analyzed via qPCR for total fungi and bacteria and fungal:bacterial ratios were calculated. Soil pH, total Pb, extractable Pb, total C and N, nitrate N, organic matter, phosphate, sulfate, and water content were all determined across the site and site maps, or interpolations, were created using ArcGIS 10.1.
Results/Conclusions
Soil Total Pb concentrations values range from below detection to well over 9,000 ppm or mg Pb kg-1 dry soil. Highest values are observed to the northwest of the firing backstop and geographically coincide with an elevated earthen berm behind the backstop. However, high Total and extractable PB was also detected at sampling locations of lower elevation along the first row both to the north and south of the backstop. Fungal:Bacterial ratios ranged from below 1.0 to over 6.3, and displayed a patchy distribution. However several soils with high fungal abundance occur transecting the forested area in a line straight south. Carbon:Nitrogen ratios were roughly 10.0 across most of the site, but ranged up to over 45.0 within the forested area.
Pb appears to be moving from behind the backstop to lower elevations and towards the local water source which could pose a hazard to downstream biota. Based on previous work at this site which revealed fungal species including Phanerochaete flavido-alba present and capable of Pb-mineral dissolution, the transect of high fungal numbers which directly corresponds with the direction of Pb movement, could be a contributing factor to Pb movement across the site. The highest levels of Pb also correspond to areas of carbon accumulation, potentially indicating decreased overall soil microbial activities due to Pb toxicity. Further examination of the soil fungal community for specific genera and functions implicated by previous work in Pb-mineral dissolution and movement is currently being explored.
... As tecnologias de remediação de áreas contaminadas por metais podem ser agrupadas em biológicas, físicoquímicas e térmicas e são aplicáveis na própria área (in situ) ou ex situ, pelo tratamento do solo escavado, sendo estas baseadas na bioacumulação, lixiviação ou dessorção, volatilização, isolamento físico e na imobilização física e química. A remediação dos solos contaminados por metais pesados através das tecnologias ex situ apresenta elevado custo, entre US$ 8 e US$ 12 por habitante nos países industrializados, devido à firme adesão destes elementos às partículas de solo (Wasay, Barrington e Tokunaga, 1998). Geralmente, as tecnologias in situ são mais econômicas e seguras, pois a escavação do solo não é necessária (Di Palma et al, 2003), no entanto, não podem ser aplicadas em solos de baixa permeabilidade (Nyer et al, 1996; Rulkens, Grotenhuis e Tichý, 1995). ...
The aim of this research was to evaluate different leaching processes to the removal of lead (Pb) and zinc (Zn) from tropical soil contaminated by inappropriate past deposition of wastes from ceramic tile industries of Santa Gertrudes (São Paulo, Brazil). Three soil washing processes were investigated: with concentrated sulphuric acid, with a 30% solution of hydrogen peroxide and with 0.1M solution of hydrochloric acid. The results indicated that the treatment with hydrogen peroxide did not remove Pb and Zn significantly; the washing with concentrated sulphuric acid caused a 50% reduction of Zn contents and the 0.1M solution of hydrochloric acid reduced Pb and Zn contents in 15% and 10%, respectively. The Zn content remaining in the soil processed with concentrated sulphuric acid was 117 mg/kg and the Pb and Zn contents remaining in the soil processed with 0.1M solution of hydrochloric acid were 806 mgPb/kg and 213 mgZn/kg, respectively, values which are lower than intervention ones established by São Paulo State environmental protection agency.
... The concentrations may have increased, such as for Ca and Pb, due to higher solubility in combination with low retention capacity of the coarse mine waste (cf. Wasay et al. 1998). Decreased concentrations may be caused by uptake of elements in plants, i.e., increased phytoremediation (cf. ...
Contamination of the environment due to mining and mineral processing is an urgent problem worldwide. It is often desirable to establish a grass cover on old mine waste since it significantly decreases the production of leachates. To obtain sustainable growth, it is often necessary to improve several properties of the waste such as water-holding capacity, nutrient status, and toxicity. This can be done by addition of organic materials such as wood residues, e.g., compost. In this study, we focus on the solution chemistry of the leachates when a substrate containing historic sulfidic mine waste mixed with 30 % (volume) bark compost is overgrown by Agrostis capillaris. The pot experiments also included other growth-promoting additives (alkaline material, mycorrhiza, and metabolizable carbon) to examine whether a more sustainable growth could be obtained. Significant changes in the plant growth and in the leachates composition were observed during 8 weeks of growth. It was concluded that in this time span, the growth of A. capillaris did not affect the composition of the leachates from the pots. Instead, the composition of the leachates was determined by interactions between the bark compost and the mine waste. Best growth of A. capillaris was obtained when alkaline material and mycorrhiza or metabolizable carbon was added to the substrate.
... Chemoorganotrophic microorganisms acidify the local environment by efflux of H+ pumps due to the action of H+-ATPases, or by accumulation of CO 2 due to respiration. Leaching can also be due to the ability of microorganisms to synthesize metabolites (siderophores, biosurfactants, and organic acids) (Braud et al. 2006b; Di Simine et al. 1998; Wasay et al. 1998; Mulligan et al. 1999b). The most efficient acids include citric acid, which is known to solubilize Ni and Zn (Castro et al. 2000; Valix et al. 2001), and oxalic acid for Pb contained in pyromorphite (Sayer et al. 1999). ...
... Currently, cleanup processes of heavy metal pollution are expensive and environmentally destructive (Nanda et al., 1995;Moffat, 1995;Meagher, 2000). Recently, scientists and engineers have started to generate cost-effective technologies that include the use of microorganisms, biomass, and live plants in the cleaning process of polluted areas (Miller, 1996;Boyajian and Carreira, 1997;Dushenkov et al., 1997;Ebbs and Kochian, 1998;Wasay et al., 1998;Gardea-Torresdey et al., 1996). ...
Preliminary studies have shown that alfalfa plants (Medicago sativa) can grow in some heavy metal- contaminated soils. Based on that, we studied the individual effects of several doses of Cd(II), Cr(VI), Cu(II), Ni(II), and Zn(II) on the growth of live alfalfa plants using solid media. The doses used in this study were 0, 5, 10, 20, and 40 ppm. The seed germination and plant growth was significantly affected by Cd(II) and Cr(VI) at 10 ppm, as well as by Cu(II) and Ni(II) at 20 ppm and higher concentrations (P
... 0) reported that this low removal can be attributed to low metal concentrations and ageing. Upon prolonged exposure, cadmium metals in soils establish strong binding. This metal binding can be disrupted with the help of biosurfactant washings; over 1.9% of Cd and 7% of Pb can be removed from the natural soil with the help of biosurfactant washings. Wasay et al. (1998) studied speciation of metals in polluted soils and found that most of the heavy metals were found to be bound to Fe–Mn oxides and the organic fraction (30–40%), except for Cd and Zn, which were mainly present on the exchangeable fraction (63–87%). This was evidenced in the current study from the low release of the organic fractions of c ...
This study investigated the effects of biosurfactant produced by a mangrove isolate
on a heavy metal spiked soil remediation using two different methods of biosurfactant
addition (pretreatment and direct application) at different concentrations (0.5%–5%)
for 10 days employing column and batch method of washings. The FT-IR spectral and
biochemical analysis confirmed the chemical nature of biosurfactant as a glycolipid.
Pre-addition of biosurfactant at 0.5% concentrations and further incubation for amonth
resulted in better chromium removal than the direct biosurfactant washing method. A
maximum recovery of lead (99.77%), nickel (98.23%), copper (99.62%), and cadmium
(99.71%) were achieved with column washing method at 1% biosurfactant concentration.
Release of 26% soluble fractions of nickel (pre-addition with biosurfactant) and
40% copper (direct application) were achieved by column washing method at 1.0%
concentration of biosurfactant. A total of 0.034 mg/10 g of lead, 0.157 mg/10 g of
nickel, 0.022 mg/10 g of copper, 0.025 mg/10 g of cadmium, and 0.538 mg/10 g of
chromium were found to remain in the spiked soil after column washing with 1.0%
biosurfactant solution. However, pre-addition of 0.5% biosurfactant treatment helps in
maximum removal of chromium metal leaving a residual concentration of 0.426 mg/10 g
of soil, suggesting effective removal at very low concentration. The average extraction
concentration of metals in batch washings was between 93–100%, irrespective of the
concentration of biosurfactant studied. In this study, the percentage removal of copper,
cadmium, chromium, nickel, and lead from spiked soils by column washing was
comparatively lower than batch washing.
... It is difficult to compare our results with previous studies since, as mentioned above, very little research has been done on fungal leaching of heavy metals from sediments. In a very recent study, Wasay et al. [33] used Aspergillus niger to bioremediate soils contaminated with heavy metals. The bioleaching yields varied from 37% to 99%. ...
Filamentous fungi were used to leach heavy metals from dredged sediments in semi-pilot scale air-lift bioreactors. Prior to the bioleaching experiments, a physico-chemical characterization of the sediments comprising a sequential extraction study was conducted. The sediments turned out to highly contaminated with heavy metals. Most of the studied metals were found to be strongly linked to the matrix because of their association with the sulphides and with the organic mat-ter. The conditions that favored the solubilization of heavy metals by the filamentous fungi turned out to be favorable for the activity of the sediments organotrophic bacterial microflora as well. The latter played a key role in the biosolubi-lization process by producing organic acids under temporary anoxic conditions. Better solubilization results (Mn: 77%, Zn: 44%, Cu: 12%, Cd and Pb: < 2%) were thus obtained in the uninoculated sugar treatment in comparison to the fun-gal treatment. In general, organotrophic leaching was found to be limited by the poor nature of the organic acids and by their microbial consumption under sugar limited conditions. It was therefore restrained to the relatively mobile metals, namely those linked to the acid-soluble and reducible fractions of the sediments.
... above, very little research has been done on fungal leaching of heavy metals from sediments. Another study [55] used Aspergillus niger to bioremediate soils contaminated with heavy metals. The bioleaching yields varied from 37% to 99%. ...
Filamentous fungi and lithotrophic bacteria were used to leach heavy metals from dredged sediments in semi-pilot scale air-lift bioreactors. A preliminary physico-chemical characterization of the sediments comprising a sequential extraction study revealed their high metallic contamination and a predominant association of the metals with sulphides and organic matter. The mobility of heavy metals from sediments was ranked by decreasing order as follows: Mn > Zn > Cd > Cu > Pb. The conditions that favoured the solubilization of heavy metals by filamentous fungi turned out to be also favourable for the activity of the sediment organotrophic bacteria. The latter produced organic acids under temporary hypoxic conditions and resulted in the solubilization of 77% of manganese, 44% of zinc, 12% of copper, and less than 2% of cadmium or lead. In general, the fungal organotrophic treatments were limited to the relatively mobile metals due to the weak nature of the organic acids produced and to their microbial consumption under limited saccharose conditions. The lithotrophic treatments yielded higher solubilization results than the organotrophic experiments. Sulphur resulted in a faster, and for some metals such as copper and cadmium, in better bioleaching results compared with reduced iron or with a combination of reduced iron and sulphur. The bioleaching percentages varied between 72 and 93% for cadmium, copper, manganese and zinc, except for lead because of the poor solubility of lead sulphate. The sediment's lithotrophic bacteria acidified the matrix through sulphur oxidation, and leached both loosely and tightly bound metals.
... Fungal production of low-molecular-weight organic acids (LMWOAs) has been almost exclusively studied in model organisms , such as Aspergillus spp. (2, 3, 16, 27, 36, 39, 56 ). Despite the fact that it is a process that may contribute significantly to Pb mobilization in soils, no thorough studies of these processes in indigenous soil fungi have been reported. ...
Anthropogenic sources of lead contamination in soils include mining and smelting activities, effluents and wastes, agricultural pesticides, domestic garbage dumps, and shooting ranges. While Pb is typically considered relatively insoluble in the soil environment, some fungi may potentially contribute to mobilization of heavy metal cations by means of secretion of low-molecular-weight organic acids (LMWOAs). We sought to better understand the potential for metal mobilization within an indigenous fungal community at an abandoned shooting range in Oak Ridge, TN, where soil Pb contamination levels ranged from 24 to >2,700 mg Pb kg dry soil(-1). We utilized culture-based assays to determine organic acid secretion and Pb-carbonate dissolution of a diverse collection of soil fungal isolates derived from the site and verified isolate distribution patterns within the community by 28S rRNA gene analysis of whole soils. The fungal isolates examined included both ascomycetes and basidiomycetes that excreted high levels (up to 27 mM) of a mixture of LMWOAs, including oxalic and citric acids, and several isolates demonstrated a marked ability to dissolve Pb-carbonate at high concentrations up to 10.5 g liter(-1) (18.5 mM) in laboratory assays. Fungi within the indigenous community of these highly Pb-contaminated soils are capable of LMWOA secretion at levels greater than those of well-studied model organisms, such as Aspergillus niger. Additionally, these organisms were found in high relative abundance (>1%) in some of the most heavily contaminated soils. Our data highlight the need to understand more about autochthonous fungal communities at Pb-contaminated sites and how they may impact Pb biogeochemistry, solubility, and bioavailability, thus consequently potentially impacting human and ecosystem health.
... New developments utilize metal solubilization by chelates as a process element within phytoremediation (Blaylock et al., 1997;Huang et al., 1997), extraction by surfactants (Nivas et al., 1996;Doong et al., 1998) and electrokinetic remediation (Wong et al., 1997;Yeung et al., 1996). An interesting approach to bioremediate metal polluted soils is to adapt and to manipulate microorganisms so that the qualitative and quantitative exudation of chelating compounds is optimised (Wasay et al., 1998). ...
The -thiol group containing amino acids L-cysteineand L-penicillamine were tested for their ability to releaseheavy metals (Cd, Cr, Cu, Hg, Ni, Pb, Zn) from bondings ontotypical soil components (peat, bentonite, illite) at neutral pHformed by batch adsorption procedure. Following equilibrationthe metal loaded sorbents were extracted by aqueous amino acidsolutions under various physico-chemical conditions.The extractability of metals from peat (metal contents between62.0 and 6170 mg kg-1) increased in thepresence of L-penicillamine following the order Cr < hg="">< pb=""> Zn Cd, ranging from 9% (Cr) to 97% (Cd).The extractability by L-cysteine was slightly lower, followingthe sequence Cr < pb="">< cd="">< ni="">< zn.="" in="" both="" cases="" the="" sequencesdid="" not="" correlate="" with="" the="" order="" of="" the="" stability="" constants="" ofthe="" corresponding="" amino="" acid="" complexes.="" the="" recovery="" of="" metalsfrom="" bentonite="" was="" higher="" generally.="" the="" extent="" of="" removal="" increased="" with="" increasing="" molar="" excess="" of="" the="" amino="" acids="" and,to="" a="" lower="" extent,="" with="" increasing="" extraction="" volume.presumably="" initiated="" by="" oxidation="" of="" amino="" acids="" or="" by="" theformation="" of="" sparingly="" soluble="" polymeric="" metal="" complexes,="" theconcentrations="" of="" dissolved="" metals="" dropped="" after="" an="" agitationperiod="" of="" 2="" to="" 24="" hr="" in="" most="" of="" the="" extracts.="" aspects="" of="" thisprocess="" were="" discussed="" in="">
... Chemoorganotrophic microorganisms acidify the local environment by efflux of H+ pumps due to the action of H+-ATPases, or by accumulation of CO 2 due to respiration. Leaching can also be due to the ability of microorganisms to synthesize metabolites (siderophores, biosurfactants, and organic acids) (Braud et al. 2006b; Di Simine et al. 1998; Wasay et al. 1998; Mulligan et al. 1999b). The most efficient acids include citric acid, which is known to solubilize Ni and Zn (Castro et al. 2000; Valix et al. 2001), and oxalic acid for Pb contained in pyromorphite (Sayer et al. 1999). ...
Bioaugmentation-assisted phytoextraction is a promising method for accelerating the cleanup rate of soils contaminated by
metals. On average, bioaugmentation increases metal accumulated by plant shoots by factors of about two (metal concentration)
and five, as a result of higher bioaccessibility of metals in soils, with few obvious differences between effects by bacteria
or fungi (e.g., plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi). Metal bioaccessibility is always controlled
by microbial siderophores as well as organic acids and surfactants. In cases of excess concentrations, fungi immobilize metals,
in contrast to bacteria. Unfortunately, the typically low inoculant survival rate may impair bioaugmentation efficiency. In
this chapter, microbial inoculant formulations and management are addressed, as well as strategies for selecting the most
relevant plant–microorganism couples for optimum phytoextraction of soil metals. In environments subject to variable conditions,
ecological engineering approaches may help in attaining maximal efficiency. Experiments at field-scale are reported, and environmental
effects of the technique are discussed. Finally, future prospects are addressed with the main question being how maximal concentrations
and amounts of metals in plants can be attained.
... Hereupon, soil pollution through the food chain threats health of humankind (McLaughlin et al., 2009). Scientists and engineers have started to generate efficacious technologies that contain the utility of microorganisms, biomass and some plants for the process of removing polluted zones (Ebbs, Kochian, 1997; Wasay et al., 1998). Among heavy metals Cadmium is one of the toxic elements that don't play a vital role for live organs. ...
Cadmium (Cd) is a toxic heavy metal which causes oxidative stress in plants and has a high level of toxicity for plants, animals and human. Present study carried out in order to evaluation of Cd stress effect on growth parameters in bean seedlings. This experiment was conducted in the form of factorial in randomized complete block design (RCBD) by three replications per treatment. In addition, 25 bean seeds genotypes grew in laboratory conditions consist of solution CdCl2 with concentration of 4mg/lit and distilled water (as a control). The seedlings were harvested after 8days and the germination percentage, root and shoot length and its stability, R/S ratio and fresh weight were recorded. The results revealed that Cd adversely influenced on these traits. As a result Cd treatment in all genotypes reduced the germination percentage 9.9%, root and shoots length 83.9% and 66.3%, respectively, R/S ratio 52.2%, and fresh weight 42.3%, in compared to control. Based on the results we concluded that, these traits of bean plant are seriously affected by Cd treatment and also these are symptoms of toxicity of Cd element. Therefore less amount of reduction in a special genotype is referred to the index of tolerance to Cd.
... A. niger strain, isolated from soil of leather tanning effluent, has been found to remove chromium very effectively from liquid medium as well as from soil microcosm with different concentrations of chromate (Srivastava and Thakur, 2006). Bioremediation process was developed using A. niger to produce a variety of organic acids for the leaching of heavy metals from contaminated soils (Wasay et al., 1998;Ren et al., 2009). Some studies have already been undertaken to understand the mechanism(s) by which arsenate, the main chemical form of arsenic encountered under aerobic conditions can get entry into the cells of the fungus (Rosen, 1999). ...
The arsenate tolerance limit in wild-type Aspergillus niger was determined. Because of its high tolerance, toxic effects of arsenate concentrations ranging from 25 to 100mg/L were investigated in regard to growth, intracellular thiols, proline and malondialdehyde (MDA) contents of wild-type A. niger. Cellular arsenate uptake was analyzed. Activities of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR) and succinate dehydrogenase (SDH) were assayed. Growth of A. niger increased at 25mg/L arsenate, and it survived up to 100mg/L. MDA, intracellular thiol and proline contents increased up to a certain level. Activities of GR, SOD and CAT declined following a rise at low concentration(s); SDH activity decreased gradually with increased arsenate stress. Results indicated that A. niger had high arsenate uptake potential and could tolerate oxidative stress by manipulating its anti-oxidative defense mechanism, a property that may be exploited for removal of arsenate from contaminated aqua-environment.
... Various processes including isoloation, mechanical separation, chemical treatment and soil flushing are effective to clean the heavy metal contaminated soils (Mulligan et al., 2001). Since these processes are costly, labour intensive, time consuming and require special equipment for the purpose, research efforts have been shifted to develop cost effective technology involving microorganisms, biomass and living plants in cleaning polluted sites (Wasay et al., 1998). Phytoextraction, a plant based technology for the removal of contaminants and heavy metals from polluted waters and soils, is evolving rapidly. ...
The present study investigated the effects of Cadmium (Cd) and Chromium (Cr) on the growth of Shisham (Dalbergia sissoo Roxb.) seedlings. Metal elements were applied in the form of Cd(SO4)2 and K2CrO4 at variegated concentrations of 0, 10, 20, 40 and 80 mg L-1 under controlled conditions of light and temperature for four weeks. Response of the seedlings was monitored in terms of number of leaves, shoot and root length, leaves, root and shoot weight (fresh and oven dry) and chlorophyll contents. Decline in growth was recorded after 10 mg L-1 and 40 mg L-1 for Cr and Cd application respectively. Similarly, combined application of Cd and Cr showed growth reduction beyond 20 mg L-1 dose. Chromium appeared to be more toxic to Dalbergia sissoo as compared to Cd at seedling stage.
Cadmium (Cd) pollution in agricultural soils induces oxidative stress in plants that in turn is the foremost limiting factor for agricultural productivity. In past few decades, metal binding ability of microbes is of great interest as an emerging environmentally friendly technology that can be exploited to alleviate metal stress in plants. Considering these, in the present study an endophytic bacterium strain EPS has been isolated from the roots of common bean. The 16S rRNA sequence revealed its identity closely similar to Stenotrophomonas maltophilia . The strain showed tolerance to Cd stress up to 200 mg L − 1 Cd ²⁺ . The inoculation of strain EPS in safflower seeds significantly enhanced the antioxidant defense of plants under Cd-stress conditions throught increasing the levels of antioxidant molecules like phenolics, flavonoids and carotenoids as well as improving the activities of the antioxidative enzymes including guaiacol peroxidase (POX), ascorbate peroxidase (APX) and superoxide dismutase (SOD). The output of this study is that strain EPS inoculation mitigates Cd-induced oxidative damage and consequently strain EPS may be beneficial, especially in Cd-contaminated crop fields.
Heavy metals are systemic toxins with specific neurotoxic, nephrotoxic and phototoxic effects. Heavy metals can directly influence behaviour by impairing mental and neurological function, influencing neurotransmitter production and utilization and altering numerous metabolic processes. In this present study Aspergillus niger and Aspergillus flavus were identified and inoculated with chromium to analyse the capability of those microorganism in bioremediation. The results revealed that chromium level decreased in culture media. It was also observed that Aspergillus niger removes the chromium at higher rate when compared to that of Aspergillus flavus.
Recycled materials replacing part of virgin materials in highway applications has shown great benefits to the society and environment. Beneficial use of recycled materials can save landfill places, sparse natural resources, and energy consumed in milling and hauling virgin materials. Low price of recycled materials is favorable to cost-saving in pavement projects. Considering the availability of recycled materials in the State of Maryland (MD), four abundant recycled materials, recycled concrete aggregate (RCA), recycled asphalt pavement (RAP), foundry sand (FS), and dredged materials (DM), were studied. A survey was conducted to collect the information of current usage of the four recycled materials in States’ Department of Transportation (DOTs). Based on literature review, mechanical and environmental properties, recommendations, and suggested test standards were investigated separately for the four recycled materials in different applications. Constrains in using these materials were further studied in order to provide recommendations for the development of related MD specifications. To measure social and environmental benefits from using recycled materials, life-cycle assessment was carried out with life-cycle analysis (LCA) program, PaLATE, and green highway rating system, BEST-in-Highway. The survey results indicated the wide use of RAP and RCA in hot mix asphalt (HMA) and graded aggregate base (GAB) respectively, while FS and DM are less used in field. Environmental concerns are less, but the possibly low quality and some adverse mechanical characteristics may hinder the widely use of these recycled materials. Technical documents and current specifications provided by State DOTs are good references to the usage of these materials in MD. Literature review showed consistent results with the survey. Studies from experimental research or site tests showed satisfactory performance of these materials in highway applications, when the substitution rate, gradation, temperature, moisture, or usage of additives, etc. meet some requirements. The results from LCA revealed significant cost savings in using recycled materials. Energy and water consumption, gas emission, and hazardous waste generation generally showed reductions to some degree. Use of new recycled technologies will contribute to more sustainable highways.
The effects of Cd+2, Cr+6, Cu+2, Ni +2, and Zn+2 on Alfalfa Plant (Medicago sativa) were studied in this research. The doses of 0, 5, 10, 20, and 40 ppm were used. The seed germination and plant growth were significantly affected by Cd+2 and Cr+6 at 10 ppm, as well as by Cu+2 and Ni +2 at 20 ppm and higher concentrations. Zn+2 did not affect seed germination. The plant roots were exposed to 5 ppm-dose of Cd +2, 5 and 10 ppmdose of Cr+6, Cu+2, Ni +2, and Zn+2. Meanwhile, the dose of 5 ppm of Cr +6, Cu+2, Ni+2, and Zn+2 increased the shoot size by 13.0%, 59.0%, 35.0%, and 6.6%, respectively. Zn+2 were only promoted the shoot growth at the doses of 20 and 40 ppm.
The paper presents an inhibition effect of clay mineral-montmorillonite-on the growth of microscopic filamentous fungus Aspergillus Niger in the aqueous solution. The significant reduction in growth of the final size of spherical fungal pellets as well as total amount of produced microbial biomass was found out. Within the observed range of additions of clay mineral of 1, 5, 10, 15 and 20 g in the total volume of the 80 ml suspension, this size was in indirect relation to the weight of montmorillonite. However, the most significant inhibition effect was observed at the lowest concentration of the sorbent (1 g). Microscopic analysis of pellets referred to the presence of mineral particles in their pore structure and the distribution of particles in the spatial structure of fungal hyphae was variable. The experiment clearly demonstrated an inhibition effect of montmorillonite. This inhibition could be answered by the experiments focused on the detection of the influence of size and shape of inorganic sorption particles together with the influence of the physicochemical properties of its surface. It could be stated that the simultaneous application of the microscopic fungus Aspergillus Niger and the clay mineral montmorillonite for decontamination of waste waters should be disadvantage due to their interaction if compared with the decontamination based on bioaccumulation and sorption separately.
The bioleaching experiment was conducted for the removal of
heavy metals from mine tailings. A fungal strain was isolated from the gold
mine tailings and it has been identified as Aspergillus fumigatus based on its 18S
rDNA analysis. Bioleaching using A. fumigatus was carried out in bioleaching
step processes (one-step and two-step) at various tailings concentrations (1%,
2%, 4%, and 8% [w/v]). In the one-step bioleaching process where fungi were
cultivated in the presence of the tailings, concentration of oxalic acid was the
highest among the organic acids produced. On the other hand, in the two-
step bioleaching process where the metabolic products of fungal growth, which
have been separated from its biomass, were used, citric acid was dominant.
In the one-step process, the highest As (62%), Fe (58%), Mn (100%), and Zn
(54%) removals were observed at the lowest tailings concentration (1%). The
removal of Pb at 1% tailings concentration in the one-step process was 56%,
whereas 88% removal was achieved in the two-step process where citric acid was
dominant. In general, heavy metals removal efficiency decreased with increased
tailings of the concentration in both bioleaching processes. This study shows
the possibility of using A. fumigatus to bioleach hazardous heavy meals from
gold mine tailings.
Waste foundry sand (WFS) is a byproduct of metal casting industry which results from the mold and core making processes. Land filling is not considered to be a good option because it leads to the risks associated with the environment as it generates leachate which may contain heavy metals and organic contaminants. Its beneficial use in construction materials results in reducing the cost of construction materials’ ingredients and also helps in reducing disposal problem. Leaching characteristics are essential in understanding the environmental impact or toxicity, disposal and potential development of beneficial applications of WFS. This study aimed to presents micro-structural and metal analysis of fungal treated leachate obtained from concrete made with various percentages of WFS (0%, 10%, 15% and 20%).Metal concentrations of untreated and fungal treated leachate obtained from concrete made with WFS were analyzed for 15 metals including (Ba, Be, Cd, Cr, Co, Cu, Fe, Hg, Li, Mo, Mg, Mn, Ni and Zn) by using ICP-MS and compared with world Health organization (WHO) standard limits and ground water quality standards (GWQSs). Metal analysis indicates that WFS contribute to the concentration of leachable metals in concrete containing WFS. Results show the reduction in the metal concentration in leachate obtained from fungal treated concrete. In fungus (Aspergillus niger) treated WFS (10%) containing concrete, the metal concentration in Cd, Cr, Fe, Mo, Mn, Ni and Pb were reduced to significant levels. Micro-structural analysis confirms the improvement of concrete by inclusion of fungal treated WFS in concrete due to the formation of calcium rich biomineral in the pores of concrete.
The bioleaching experiment was conducted for the removal of heavy metals from mine tailings. A fungal strain was isolated from the gold mine tailings and it has been identified as Aspergillus fumigatus based on its 18S rDNA analysis. Bioleaching using A. fumigatus was carried out in bioleaching step processes (one-step and two-step) at various tailings concentrations (1%, 2%, 4%, and 8% [w/v]). In the one-step bioleaching process where fungi were cultivated in the presence of the tailings, concentration of oxalic acid was the highest among the organic acids produced. On the other hand, in the two-step bioleaching process where the metabolic products of fungal growth, which have been separated from its biomass, were used, citric acid was dominant. In the one-step process, the highest As (62%), Fe (58%), Mn (100%), and Zn (54%) removals were observed at the lowest tailings concentration (1%). The removal of Pb at 1% tailings concentration in the one-step process was 56%, whereas 88% removal was achieved in the two-step process where citric acid was dominant. In general, heavy metals removal efficiency decreased with increased tailings of the concentration in both bioleaching processes. This study shows the possibility of using A. fumigatus to bioleach hazardous heavy meals from gold mine tailings.
Este trabalho de pesquisa buscou investigar a eficácia da remoção de chumbo (Pb) e zinco (Zn) de uma área contaminada pelo depósito inadequado de resíduos de indústrias de revestimentos cerâmicos do pólo de Santa Gertrudes (São Paulo, Brasil), ocorrido há cerca de trinta anos atrás. Foram avaliados três processos de lixiviação: lavagem com ácido sulfúrico concentrado e por soluções de peróxido de hidrogênio a 30% e de ácido clorídrico 0,1 M. Os resultados obtidos mostraram que o tratamento com peróxido de hidrogênio não removeu Pb e Zn; que a lavagem com ácido sulfúrico concentrado promoveu a redução de 50% dos teores de Zn e a solução de ácido clorídrico 0,1 M reduziu os teores de Pb e Zn em 15% e 10%, respectivamente. O teor remanescente de Zn no solo tratado com ácido sulfúrico concentrado foi de 117 mg/kg e os de Pb e Zn no solo lavado com a solução de ácido clorídrico 0,1 M, de 806 mg/kg e 213 mg/kg, respectivamente, valores estes inferiores aos de intervenção estabelecidos pelo órgão de controle ambiental paulista.
The biodegradable strong transition metal chelant [S,S] stereoisomer of ethylenediamine disuccinate was investigated for its applicability for the washing extraction of heavy metals from soil, sewage sludge, and harbor sediment. Heavy metals Pb, Zn, Cu, and Cd were extracted from authentically polluted samples by means of an ex situ washing procedure at the laboratory scale. The exposure time necessary to achieve maximum metal extraction from the authentically polluted solids used in this study was longer than that reported elsewhere with solids polluted artificially in the laboratory. Required exposure time was I day for the extraction of Pb, 3 days for Zn, and 6 days for Cu, irrespective of solid type. Speed and extent of metal extraction were increased by facilitating mass transfer from the solids to the liquid (e.g., by lowering calcium concentration, increasing temperature, adding fatty acid soap, and most of all, by using intermittent but intense agitation). Slightly alkaline pH was necessary to eliminate the interference by iron. This pH effect as well as observed metal selectivity was explained with a speciation model. It was feasible to achieve 70-90% extraction of Zn, Pb, and Cu from all three solids tested, These extraction efficiencies were equal or superior to those obtained with the benchmark chelants, ethylenediamine tetraacetic acid and nitrilotriacetate, provided extraction time was sufficient.
Extraction of metals (Ni, Co) from chromite overburden of Sukinda mines of Orissa, India, with the culture filtrate of Aspergillus niger was studied. Results showed that the amounts of metals leached varied directly with reaction temperature and period of fermentation. The culture filtrate was analyzed for citric and oxalic acids, and contained only oxalic acid-the concentration of which increased with time. Although this acid played the major role in leaching of metals, other unidentified metabolites present in the culture filtrate influenced the dissolution of the metals significantly. Maximum recovery of metals from raw and roasted ore samples was achieved at 80 °C with the 21-day culture filtrate containing the highest amount of oxalic acid. Under identical experimental conditions, much higher amounts of the metals were leached from roasted ore. Microstructures of the ore particles were studied by scanning electron microscopy and transmission electron microscopy; the bonding behaviors of metal compounds were identified by Fourier transform infrared spectroscopy which showed that the metals were leached after chelation with oxalic acid.
Biological amphiphiles were examined for the removal of Cd2+ or Pb2+ from polluted water within a pH range from 2.5 to 7.5 at a fixed ratio of amphiphilic concentration to heavy metal concentration
(C
A
/C
M
) on a molar basis of approximately 11. Tannic acid, among eight amphiphiles, was selected for Cd2+ or Pb2+ removal because it exerted noticeable improvement within limited pH ranges. In the presence of tannic acid, the removal of
Cd2+ or Pb2+ was investigated as a function of pH ranging from 2.5 to 13 at C
A
/C
M
ratios from 1.2 to 11. The removal capacity (mass of metal/mass of tannic acid) increased with decreasing C
A
/C
M
for both Cd2+ and Pb2+. Removal capacities were 0.084 and 0.154 g/g-tannic acid for Cd2+ and Pb2+ at pH 6.9 and 4.4, respectively. The maximal removals for Cd2+ and Pb2+ were 99 and 96%, respectively.
Citric acid production using Aspergillus niger NRRL 567 grown on peat moss has been optimized in a column bioreactor using a statistically based method. A 23 full factorial
design with eight fermentation conditions was applied to evaluate significance on citric acid production and their interactions
between variables, where the three independent variables evaluated were aeration rate, bed depth and temperature. Aeration
rate and fermentation temperature were identified to be significant variables. Citric acid production markedly increases with
aeration rate and fermentation temperature; however, the bed depth of solid substrate showed an insignificant effect on citric
acid production. The optimum fermentation condition for citric acid production in a column bioreactor consisted of aeration
rate of 0.84 vvm, bed depth of 22 cm and fermentation temperature of 32 °C. Under a given condition, a maximum citric acid
production of 120.6 g/l was predicted and matched well with the experimental value of 123.9 g/kg.
Investigations were made on living strains of fungi in a bioremediation process of three metal (lead) contaminated soils.
Three saprotrophic fungi (Aspergillus niger, Penicillium bilaiae, and a Penicillium sp.) were exposed to poor and rich nutrient conditions (no carbon availability or 0.11M d-glucose, respectively) and metal stress (25µM lead or contaminated soils) for 5days. Exudation of low molecular weight
organic acids was investigated as a response to the metal and nutrient conditions. Main organic acids identified were oxalic
acid (A. niger) and citric acid (P. bilaiae). Exudation rates of oxalate decreased in response to lead exposure, while exudation rates of citrate were less affected.
Total production under poor nutrient conditions was low, except for A. niger, for which no significant difference was found between the poor and rich control. Maximum exudation rates were 20µmol oxalic
acid g−1 biomass h−1 (A. niger) and 20µmol citric acid g−1 biomass h−1 (P. bilaiae), in the presence of the contaminated soil, but only 5µmol organic acids g−1 biomass h−1, in total, for the Penicillium sp. There was a significant mobilization of metals from the soils in the carbon rich treatments and maximum release of Pb
was 12% from the soils after 5days. This was not sufficient to bring down the remaining concentration to the target level
300mg kg−1 from initial levels of 3,800, 1,600, and 370mg kg−1in the three soils. Target levels for Ni, Zn, and Cu, were 120, 500, and 200mg kg−1, respectively, and were prior to the bioremediation already below these concentrations (except for Cu Soil 1). However, maximum
release of Ni, Zn, and Cu was 28%, 35%, and 90%, respectively. The release of metals was related to the production of chelating
acids, but also to the pH-decrease. This illustrates the potential to use fungi exudates in bioremediation of contaminated
soil. Nonetheless, the extent of the generation of organic acids is depending on several processes and mechanisms that need
to be further investigated.
Chromium is one of the toxic and hazardous pollutants in industrial wastewaters leading to soil contamination. In this study, the feasibility of remediating chromium contaminated soil using indigenous microorganisms and Pseudomonas fluorescens was evaluated. The contaminated soil sample was collected from Vellore and the pH, moisture content and chromium content were found to be 8.4, 22.5% and 5.1 mg/kg respectively. The effect of chromium on engineering properties showed decrease in permeability by 45.15%. For Pseudomonas fluorescens, the optimum pH, moisture content, biomass concentration and carbon source were found as 6.5, 20%, 10 mL and 10 mL/100 g respectively and for isolated mixed culture, the optimum parameters were found as 8.4, 25%, 15 mL and 15mL / 100 g respectively. Under optimum conditions, the reactor study showed 71.7% chromium reduction after 20 days. From the study, the bioremediation of chromium-contaminated soil by indigenous microorganisms was found to be a promising solution and after bioremediation, the engineering properties of the soil were found to be improved.
Oligonucleotide primers were designed for the 18S rRNA genes of members of the Neocallimastigales and used in a nested PCR protocol to amplify 787-bp fragments of DNA from landfill site samples. The specificities of the
primers were confirmed by phylogenetic analysis of the environmental clone sequences, and this method can therefore now be
used to investigate the ecology of the obligately anaerobic fungi. To our knowledge, this is the first demonstration of the
occurrence of members of the Neocallimastigales outside the mammalian gut, and their distribution across the landfill samples examined here suggests that they are actively
involved in cellulose degradation.
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