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(A) Host cell B. subtilis (B) T- B. subtilis in agar plate containing ampicillin; (C) SDS-PAGE images of protein pro fi les.
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The fundamentals of engineering and structural properties such as mechanical strength, durability, bond strength, and self-healing behaviour of a genetically-enriched microbe-incorporated construction material have been explored in the present study. The alkaliphilic Bacillus subtilis bacterium is able to survive inside the concrete/mortar matrices...
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... constructed from the sequence of carbonic anhydrase II of Bos taurus. 7,12 The DNA fragment was amplied by PCR technique and the product was then transformed into B. subtilis bacterium through a suitable T-vector. The transformation was conrmed by growing the bacterial cells (colonies) in an ampicillin-containing LB-agar plate, as shown in Fig. 1A and B. Fig. 1C shows the whole-cell protein proles of B. subtilis and genetically improved B. subtilis (T-B. subtilis) when analysed by SDS-PAGE. A new protein band appeared in the protein prole of T-B. subtilis bacterium, molecular weight was $28 kDa. This newly expressed protein was puried from the crude mixture of whole cell ...
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... from the sequence of carbonic anhydrase II of Bos taurus. 7,12 The DNA fragment was amplied by PCR technique and the product was then transformed into B. subtilis bacterium through a suitable T-vector. The transformation was conrmed by growing the bacterial cells (colonies) in an ampicillin-containing LB-agar plate, as shown in Fig. 1A and B. Fig. 1C shows the whole-cell protein proles of B. subtilis and genetically improved B. subtilis (T-B. subtilis) when analysed by SDS-PAGE. A new protein band appeared in the protein prole of T-B. subtilis bacterium, molecular weight was $28 kDa. This newly expressed protein was puried from the crude mixture of whole cell protein through the ...
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... Though some anaerobic hot spring bacteria (BKH1 & BKH2) and its secretary protein(s) both are able to increase the compressive strength and durability of the mortar/concrete samples, they fail to survive for a long period in the harsh environment of the concrete. 7,8,12 The biosilicication activity is prolonged inside the concrete through the gene transformation into the spore forming B. subtilis stain for realization of sustainability and true self-healing phenomenon ( Fig. 1 & Table 1). This study demonstrates that the transformed Bacillus sub- tilis bacterial strain possesses better efficacy for the strength and durability of the incorporated mortar specimens ( Fig. 2A and B) due to the formation of gehlenite along with calcite precipitation inside the mortar matrices. ...
Citations
... When compared to controlled concrete, the compressive strength of the structure rises by around 23% when Bacillus subtilis is added during a curing time of 28 days [52]. The optimum strength is also seen for Bacillus subtilis at 10 5 cfu/ml concentration [53]. An alteration in the ongoing process was seen with Bacillus cohnii. ...
Due to its strength and cost-effectiveness, concrete is the preferred construction material globally. Environment substantially affects system behaviour. Changes in temperature, moisture content and drying shrinkage can cause concrete to fracture. This present research work intends to improve concrete strength and durability by adding Bacillus subtilis, Bacillus cereus and Bacillus cohnii creating “Microbial Concrete.” Different tests have been carried out such as compressive strength, water absorption, UPV, RCPT, sorptivity and microstructural analysis on the concrete samples which further have been compared with test results of controlled concrete samples and also compared with each other after the treatment with three different bacterial solutions at 7 days, 14 days and 28 days curing period respectively. The test findings demonstrated that the capability of Bacillus subtilis of precipitating more calcite crystals within the voids of the concrete samples than other bacterial solutions. A minimum concentration of Bacillus subtilis resulted in maximum concrete strength, reduced water absorption rate, reduced permeability, reduced sorptivity and excellent UPV value. Also, the microstructural analysis proved the same about the bacterial solution used as an admixture in the concrete samples.
... Sin embargo, puede ser útil al combinarla con otros materiales como cenizas volantes, humo de sílice, ceniza de cáscara de arroz y metacaolín, o aditivos superplastificantes que mejoran sus propiedades (Ganesh GM et al., 2017;Rais y Khan, 2021;Sarkar et al., 2015). Estos materiales se utilizan como portadores de bacterias con alta actividad ureasa para la autocuración de grietas, llenando espacios porosos y grietas en el concreto. ...
RESUMEN Este estudio de alcance examina los avances en la autocu-ración bacteriana del hormigón. Se revisaron 54 estudios y se observó un aumento en las publicaciones desde 2015, con India liderando la investigación. Se han probado diversos materiales como sustitutos en el hormigón, incluyendo fibras y residuos de construcción reciclados. Las bacterias Baci-llus subtillis y Bacillus sphaericus son las más utilizadas que mejoran la resistencia del hormigón a través de la produc-ción de calcita y la reparación de fisuras. La presencia de fibras, cenizas y residuos de construcción puede ayudar a proteger a las bacterias en un entorno alcalino. Este estudio resalta la importancia de la autocuración bacteriana en el hormigón y ofrece una visión general de los avances en este ámbito de investigación.
... The peak current density of OTC reaches a maximum value of 1.16 mA/cm 2 at pH = 7.2, the optimal pH value for detecting OTC. Its electrochemical behavior is similar to that of Lin et al. (2021), Shetti et al. (2018), and Sarkar et al. (2015). ...
The present study used CeO2-Co3O4 quantum dots@porous carbon/multiwalled carbon nanotube (CeO2-Co3O4 QDs@PC/MWCNT/GE) composites to modify graphite electrodes to fabricate high-sensitivity electrochemical sensors to detect the presence of oxytetracycline (OTC). The quantum dots were made from waste sugarcane bagasse. The electrochemical analysis demonstrated the superior electrochemical performance of CeO2-Co3O4 QDs@PC/MWCNT/GE, with a peak current density of 1.276 mA/cm². Electrochemical impedance spectroscopy (EIS) revealed lower impedance values for CeO2-Co3O4 QDs@PC/MWCNT/GE compared to other electrodes, indicating enhanced conductivity. The modified electrode exhibited an enlarged electrochemically active area, with values of 0.602 cm², almost seven times that of the bare graphite electrode (0.079 cm²). The results showed that the CeO2-Co3O4 QDs@PC/MWCNT/GE had excellent performance for OTC detection, and its linear calibration range was 1.007 × 10⁻⁸ to 2.04 × 10⁻⁷ M (i.e., 0.005–0.1 ppm) and 1.007 × 10⁻⁶ to 1.209 × 10⁻⁴ M (i.e., 0.5–60 ppm). The limit of detection and limit of quantification were 1.23 nM (0.61 ppb) and 4.09 nM (2.03 ppb) (S/N = 3), respectively. The electrode demonstrated long-term stability for up to 7 weeks. This method provides a new way to prepare electrochemical sensors for OTC detection.
Graphical abstract
... Regarding recycled construction waste material, it presents a double configuration in its use; first, it has to be used with care since it can reduce the strength of concrete [26], compared to natural aggregates, and its quality will depend on the original concrete, the loading conditions and exposure of the demolished structure [27,28]. Secondly, it can be useful if combined with other materials such as fly ash, silica fume, rice husk ash and Metakaolin, or superplasticizing admixtures that improve its properties [16,29,30]. Several of these materials are used as carriers for self-healing of cracks in the concrete by bacteria with high urease activity. ...
... I13 (34.6%) [55]; B. megaterium MTCC 1684 (16%), B. megaterium BSKAU (12.12%), B. licheniformis (10.6%) and B. flexus (6.1%) [56] and the genetically improved strain B. subtilis T, which significantly improves compressive strength [30]. ...
... In addition, by using a genetically improved strain (B. subtilis T), a significant increase in resistance was achieved [30]. ...
This article is a scoping review analyzing advances in experimental studies on bacterial self-healing of concrete. From Scopus, ScienceDirect, Web of Science and Google Scholar search engine databases, 54 studies were selected for analysis, and an increasing trend of publications since 2015 was found, with India as the country with the largest research presence. Different ma-terials are used as replacement or admixture in concrete, such as fibers, particles and recycled material from construction waste. It was found that the most commonly used bacteria are Bacillus subtilis and Bacillus sphaericus, which can improve the strength of concrete by generating calcite and sealing cracks. In addition, it was found that the presence of materials such as fibers, ashes and construction recyclates can protect bacteria in an alkaline environment. The designs usually in-clude more than two experimental groups and a control. In summary, this study highlights the importance of bacterial self-healing in concrete and provides information on advances in this field of research.
... In particular, the availability of oxygen is vital for bacteria relying on aerobic respiration [24] and urea hydrolysis [25] to perform self-healing. In contrast, oxygen, which diffuses though microcapillaries in concrete, might become a problem for anaerobic bacteria [26]. In addition, some types of bacteria, such as Bacillus pseudofirmus, are reported to negatively affect the compressive and tensile strength of concrete [27]. ...
The transition to sustainable or green(er) cities requires the development and implementation of many innovative technologies. It is vital to ensure that these technologies are themselves as sustainable and green as possible. In this context, smart materials offer excellent prospects for application. They are capable of performing a number of tasks (e.g., repair, opening/closing, temperature measurement, storage and release of thermal energy) without embedded electronics or power supplies. In this short review paper, we present some of the most promising smart material-based technologies for sustainable or green(er) cities. We will briefly present the state-of-the-art in smart concrete for the structural health monitoring and self-healing of civil engineering structures, phase-change materials (PCM) for passive air-conditioning, shape-memory materials (SMA) for various green applications, and meta-surfaces for green acoustics. To better illustrate the potential of some of the solutions discussed in the paper, we present, where appropriate, our most recent experimental results (e.g., embedded SAW sensors for the Structural Health Monitoring of concrete structures). The main aim of this paper is to promote green solutions based on smart materials to engineers and scientists involved in R&D projects for green(er) cities.
... This bacterium has high urease activity that eventually leads to the high production of CaCO 3 precipitation. Pachaivannan et al. 2020;Sarkar et al. 2015;Shahid et al. 2020;Siddique et al. 2016), B. cereus group (Alshalif et al. 2019;Dhami, Reddy & Mukherjee 2013;Shahid et al. 2020), and B. megaterium group (Andalib et al. 2016;Dhami, Reddy & Mukherjee 2014 were found to be able to precipitate CaCO 3 . ...
Microbiologically Induced Calcium Carbonate Precipitation (MICCP) through urea hydrolysis is the most effective way to precipitate a high concentration of calcium carbonate (CaCO3) within a short time. The MICCP process is used to remediate the micro-crack in the concrete. However, limited research has been conducted to determine CaCO3 precipitation by bacteria, especially in Malaysia. Here, Bacillus spp. isolated from the Malaysian stingless bee products were evaluated for CaCO3 precipitation. Bacillus spp. were selected for further study according to their ability to produce urease enzymes. The urease-positive Bacillus spp. were screened for CaCO3 precipitation by culturing on both CaCO3 precipitation agar and broth media. The survivability of the urease-positive Bacillus spp. in various temperatures, pH values, and NaCl concentrations were tested. Seven out of 11 Bacillus spp. were found as ureolytic bacteria. Among the ureolytic bacteria, bacteria belonging to the Bacillus subtilis species complex group showed the highest number of bacteria (36.4%) that are capable of precipitating CaCO3. Bacillus stratosphericus PD6 and B. aryabhattai BD8 exhibited the largest CaCO3 precipitation zones (15 mm). Bacillus stratosphericus PD6 also precipitated the highest amount of CaCO3 (65 mg) and urease activity (0.197 U/mL). All the urease-positive Bacillus spp. were able to grow at 45°C, pH (8 to 12), and 5% NaCl. Only B. subtilis BD3 can withstand high temperatures up to 55°C and 15% NaCl concentration. In conclusion, Bacillus spp. isolated from stingless bee products showed the ability as the CaCO3 precipitating bacteria; suggesting its potential application in self-healing concrete.
... Similarly, some marginal materials have been used as substitutes for natural aggregates in concrete, creating more sustainable building materials. Alternatively, pavement surfaces like roadways and streets make the earth's surface impervious, avoiding rainfall from infiltrating Intergranular micropores [2]. This leads towards "heat islands" in big cities, which release heat into the air during night time. ...
Urban expansion and infrastructure development have
exacerbated environmental issues by creating impermeable
layers on the earth's surface, resulting in flash floods and
reduced groundwater levels. These problems can be alleviated
by using pervious concrete to enhance pavement drainage
capacities. However, pervious concrete has limited applications
due to its lower strength properties, which are attributed to its
mix proportions featuring minimal fine aggregate quantities and
an open-graded mix. This study examines the impact of
incorporating Ground Granulated Blast-furnace Slag (GGBS) as
a supplementary cementitious material in pervious concrete on
its strength, drainage capabilities, and water absorption. Further,
Artificial Neural Networks (ANN) were used to predict the
mechanical and permeability properties of pervious concrete
mixes with varying GGBS proportions. The study's results
indicate that using GGBS as a 35% partial cement replacement
with 10 mm aggregates significantly increases compressive and
flexural strength by 28% and 20%, respectively. While
permeability values were slightly reduced, they remained within
acceptable limits for drainage properties. The developed ANN
models outperformed the traditional MLR model, serving as a
viable substitute logical tool for forecasting strength as well as
permeability. Ultimately, adding GGBS to pervious concrete
not only enhances strength but also contributes to
environmentally friendly construction practices.
... For example, the ability of calcite precipitation of B. pasteurii is maximum at pH 9.5 at 25 • C [107], which indicates that the maximum healing of cracks by B. pasteurii can be achieved at this pH and temperature. Further, Sarkar et al. [108] found that genetically transformed B. subtilis could precipitate gehlenite (calcium aluminium silicate) along with calcite, within the concrete matrix. However, it was reported by Traoré et al. [109] and Ptácek et al. [110] that the presence of metakaolin along with calcite is essential for gehlenite formation. ...
... As per the stipulations of IS 269 [111], metakaolin can be used up to 5% in OPC as a performance improving material. Thus it is possible that the presence of metakaolin in the OPC used by Sarkar et al. [108], mixed with the calcite precipitated by the bacteria, was responsible for the gehlenite formation. ...
... For example, in one case, seven different bacterial concentrations (10 cells/ml to 10 7 cells/ml) of the Shewanella species were investigated and the optimal bacterial concentration was obtained at 10 5 cells/ml, with a corresponding 25% increase in compressive strength at a w/c ratio of 0.40 [86]. Several other studies involving other bacteria, such as Sporoscarcina pasteurii and genetically modified Bacillus subtilis [61,108], have also reported that the maximum increment in compressive strength was achieved at a bacterial cell concentration of 10 5 cells/ml, by 22% and 48% respectively. In a single case, the optimal cell concentration for the maximum enhancement of compressive strength was obtained at 10 7 cells/ml of Bacillus cohnii at a w/c ratio of 0.55 [121]. ...
Effective self-healing and improvement in mechanical properties make microbial concrete a viable alternative for extending the service life of concrete structures. Being a relatively newer technology, there are yet no standards or specific guidelines for the production of microbial concrete. The current paper is a step in this direction, as it presents a consolidated review of the three key steps to be followed by a researcher in the development of bacteria based self-healing concrete. First, the process of biomineralization, through which a bacterium can precipitate calcium carbonate, is discussed, followed by a detailed review on bacterial selection and its application methodology to concrete. The works on surface crack healing and the self-healing of the inner mortar matrix are explained next, with special emphasis on the factors that influence the crack healing ability of microbial concrete, namely, width of cracks, curing conditions, curing temperature, external source of calcium, ageing of concrete and bacterial concentration. Lastly, the existing results on the effect of bacteria, along with the corresponding application methodologies, w/c ratio and bacterial dosing, on concrete properties such as compressive strength, water absorption, water permeability and chloride ion permeability, are presented and summarized.
... Schlangen [21] reported resistance of samples containing microorganisms equivalent to that of the reference samples. All other reports found better resistance when applying microorganisms to cementitious materials, in addition to decreased water absorption and calcite crystal formation in microscopic analysis [45,47,32,60,9,16,61,39,54]. Tests carried out under aggressive conditions, simulating harsh and corrosive environments, as previously mentioned [19,57,66], demonstrated that the use of microorganisms in cementitious materials increases structure lifespan, even in aggressive environments. ...
... Although the use of microbial culture directly into the concrete mixture has been shown to be the most common form of application [46,39,54,44,57,1,76,61,16,9,66,19,24,60,32,33,5,4,21,34,35,45,47], literature still hasn't addressed the effect of culture media used for microbial growth in concrete structures. This may be due to the fact that, in these studies, there was no steel frame involved. ...
The use of microorganisms that induce calcium carbonate or calcite precipitation has been proposed as an alternative to solve cracking problems in cement-based materials and to reduce the environmental impact from construction. This review aims to overview the use of microorganisms in concrete or mortar mixtures to enhance the properties of these materials, and was based on published research. Several microorganisms have been applied to concrete or mortar in different ways over the last decades. These experiments tested mechanical strength, porosity, resistance to aggressive environments and crack healing. The application of microbial suspensions directly into concrete or mortar mixtures showed increased compressive and tensile strengths, decreased porosity and lower penetration of aggressive agents when these materials were exposed to sulfates and chlorides. Other studies applied the microbial culture to specific components of the cement mixture, or immobilized the microorganisms in specific materials, and then added it to the concrete or mortar mixture. These studies demonstrated healing of induced cracks in the samples. Altogether, these results suggest that the application of microorganisms that induce calcite precipitation is viable and effective in enhancing the properties of concrete or mortar and repairing cracks in the material.
... Copper slag concrete's compressive strength and workability can be enhanced by a bacterial admixture [27]. Creating bacterial strains and testing their compatibility with green concrete is an intriguing concept that may change the future of construction technology [28]. Based on a survey of copper slag properties, they are in line with those of fine aggregate and their intrusion in concrete proves to be fruitful when substituted for fine aggregate up to 50%. ...
Copper ore processing generates a large amount of copper slag, which has properties that are similar to fine aggregate. Copper slag has a promising future in the construction industry as an alternative to fine aggregate. Up to 50% of fine aggregate substitutions have been successful. The performance of copper slag concrete could be improved by microbiologically induced calcium carbonate precipitation. The impact of micro-organisms on the mechanical properties and flexural behaviour of copper slag concrete was investigated in this study. Five concrete mixtures were created by replacing varying amounts of fine aggregate with copper slag, ranging from 0% to 100%. M30 grade concrete was used, and 1% to 2% of the bacterium Bacillus subtilis by weight of cement was added during the concrete casting procedure. Specimens of different shapes, such as cubes, cylinders, and prisms, were cast and examined at 7, 14, and 28 days. When treated with micro-organisms, the test results revealed that replacing 50% to 75% of the sand with copper slag produced concrete with superior mechanical properties and a greater density. With the optimal ratio of copper slag to micro-organisms, a suitable RCC beam was formed. Load–deflection patterns of bacterial copper slag concrete were used to investigate beam flexural behaviour, and the results were compared using ABAQUS modelling. Microbiologically induced calcium carbonate precipitation can alter regular copper slag concrete, resulting in enhanced concrete performance.
