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Harvesting of Euglena gracilis by Pleurotus ostreatus at two fungi to algae ratios, i.e., 1:1 and 1:2. aE. gracilis cell counts in the suspension at both ratios (mean ± SE, n = 4) over time. Cell counts are shown for the following time points: before addition of fungi (T-1), immediately upon addition of fungi (T0) and hourly for up to 6 h. Harvesting efficiency at Tmax is indicated by arrows. b Batch settling curves showing the change in height of the floc/liquid interface over 30 min
Source publication
The high cost and environmental impact of traditional microalgal harvesting methods limit commercialization of microalgal biomass. Fungal bioflocculation of microalgae is a promising low-cost, eco-friendly method but the range of fungal and microalgal species tested to date is narrow. Here, eight non-pathogenic, filamentous fungi were screened for...
Citations
... They also produce many industrially important enzymes and have a balanced amino acid profile making it potentially nutritious [6,18]. Additionally, filamentous fungi can be used for various specific purposes like flocculating microalgae [19], providing a cheap alternative for microalgal harvesting, which is currently an expensive process [20]. Fungal cultivation in FPWS for various applications increases sustainability and develops the circular economy of food processing plants, furthering the EU's SDG 12. ...
... Based on these factors and the fact that some species had similar metabolic rates in CWS and Whey, namely P. ostreatus, L. tigrinus, P. variotii and T. versicolor, CWS's potential as growth media cannot be disregarded. Possible reasons for the lack of growth of L. tigrinus in YMB may be, (1) the formulation of YMB as it grows more slowly than the other species when maintained in YMB, and (2) too high mixing speed as it grew at a lower speed of 90 rpm in our previous study [19]. ...
Food production produces nutrient-rich waste streams which, depending on local legislation, are either sent to wastewater treatment plants or discharged into the environment. In addition to causing environmental harm in the second instance, valuable nutrients are lost. A more circular approach would be to reuse these waste streams. Fungi and yeasts are ideal candidates as they require lots of organic carbon (which is especially high in food production waste streams) for growth, with the potential for producing value-added biomass. Here, we tested the metabolic activity and possible growth of seven fungi and three yeasts in five different food production waste streams. Initial tests were done to find the most promising waste streams for growth and these were chosen for further study. All species were then cultured in these waste streams and oxygen uptake was measured to gauge metabolic activity which we used as a proxy for growth rate. Pelletization’s effect on metabolic rates was tested on the most pellet-forming species, by adding agar to inhibit pellet formation. The most promising waste stream for yeast/fungal growth was cheese whey (Whey). Pellet inhibition (i.e., filamentous growth) resulted in increased metabolic activity of cells in the confectionary bakery waste stream with agar but decreased metabolic activity in Whey with agar. The best-growing species, Geotrichum candidum, has potential commercial value as a producer of enzymes, biochemicals and lipids and could provide added value while improving the circularity of water and nutrients in food production.
Supplementary Information
The online version contains supplementary material available at 10.1186/s12866-023-03083-6.
... They also produce many industrially important enzymes and have a balanced amino acid pro le making it potentially nutritious [6, 18]. Additionally, lamentous fungi can be used for various speci c purposes like occulating microalgae [19], providing a cheap alternative for microalgal harvesting, which is currently an expensive process [20]. Fungal cultivation in FPWS for various applications increases sustainability and develops the circular economy of food processing plants, furthering the EU's SDG 12. ...
... Based on these factors and the fact that some species had similar metabolic rates in CWS and Whey, namely P. ostreatus, L. tigrinus and T. versicolor, CWS's potential as growth media cannot be disregarded. Mixing speed coupled with its non-speci c formulation may explain L. tigrinus' lack of growth in YMB as in our previous study [19], L. tigrinus grew in YMB at a slower RPM (90) and it grows slower than the other species when maintained in YMB. ...
Food production produces large amounts of nutrient-rich waste streams which are disposed of - a wasted opportunity given nutrients such as phosphorus and nitrogen are in short supply. A more circular approach would be to reuse these waste streams. Fungi and yeasts are possible candidates as they require lots of organic carbon (which is especially high in food production waste streams) for growth, producing value-added biomass. Here, we determined the growth of seven fungi and three yeasts in five different food production waste streams. Initial tests were done to find the most appropriate waste stream for growth. All species were then cultured in the waste stream best suited for growth. Oxygen uptake was measured to gauge metabolic activity and as a proxy for growth rate. Pelletization’s effect on metabolic rates was tested on the most pellet-forming species, by adding agar to inhibit pellet formation. The most promising waste stream for yeast/fungal growth was cheese whey (Whey). Pellet inhibition (i.e., filamentous growth) resulted in increased metabolism in the confectionary bakery waste stream but decreased metabolism in Whey. The best growing species, Geotrichum candidum , has potential commercial value as a producer of enzymes, biochemicals and lipids and could provide added value while improving the circularity of water and nutrients in food production.
... It has been postulated that the mechanism for bio-flocculation depends on the neutralization of the negative surface charge of microalgae with EPS, as well as the direct interaction with the flocculate (Li et al., 2020). Some fungi, in particular, are intriguing as bio-flocculates owing to their high flocculation efficiency, as well as their naturally high lipid content, and valuable fatty acid profile (Bansfield et al., 2022;Du et al., 2018a;Liber et al., 2020). In such cases, fungal biomass contributes to the overall pool of lipids for use in biofuels or functional foods. ...
Microalgae are promising sources of valuable bioproducts such as biofuels, food, and nutraceuticals. However, harvesting microalgae is challenging due to their small size and low biomass concentrations. To address this challenge, bio-flocculation of starchless mutants of Chlamydomonas reinhardtii (sta6/sta7) was investigated with Mortierella alpina, an oleaginous fungus with high concentrations of arachidonic acid (ARA). Triacylglycerides (TAG) reached 85 % of total lipids in sta6 and sta7 through a nitrogen regime. Scanning electron microscopy determined cell-wall attachment and extra polymeric substances (EPS) to be responsible for flocculation. An algal-fungal biomass ratio around 1:1 (three membranes) was optimal for bio-flocculation (80-85 % flocculation efficiency in 24 h). Nitrogen-deprived sta6/sta7 were flocculated with strains of M. alpina (NVP17b, NVP47, and NVP153) with aggregates exhibiting fatty acid profiles similar to C. reinhardtii, with ARA (3-10 % of total fatty acids). This study showcases M. alpina as a strong bio-flocculation candidate for microalgae and advances a mechanistic understanding of algal-fungal interaction.
... The production yield and metabolite composition also depend on the factors such as operation modes, aeration, and nutrient feeding strategies (Ochsenreither et al., 2016). Downstream processing significantly affects the production cost because the extraction and purification steps accounts for 60 % (Grima et al., 2003), and harvesting for 20-30 % of the production cost (Bansfield et al., 2022). Increasing the efficiency of downstream processes can improve the economics of biofuel production (Kim et al., 2013). ...
... Harvesting is the recovery of microalgal biomass from cultivation media. The harvesting process of microalgal biomass accounts for 20-30 % of production costs and also has an environmental impact (Bansfield et al., 2022). To harvest microalgal biomass, filtration, centrifugation, flocculation, flotation, gravity sedimentation, electrical processes, and magnetic separation methods have been used (Table 4). ...
... Additionally, fungal bioflocculation can be used as a lowcost and eco-friendly method. Ganoderma lucidum, Pleurotus ostreatus, and Penicillium restrictum showed 62-75 % recovery of E. gracilis biomass without damage, with an optimal fungus to algae ratio of 1:2 (Bansfield et al., 2022). ...
Sustainable aviation fuels (SAFs) can contribute reduce greenhouse gas emissions compared to conventional fuel. With the increasing SAFs demand, various generations of resources have been shifted from the 1st generation (oil crops), the 2nd generation (agricultural waste), to the 3rd generation (microalgae). Microalgae are the most suitable feedstock for jet biofuel production than other resources because of their productivity and capability to capture carbon dioxide. However, microalgae-based biofuel has a limitation of high freezing point. Recently, a jet biofuel derived from Euglena wax ester has been paying attention due to its low freezing point. Challenges still remain to enhance production yields in both upstream and downstream processes. Studies on downstream processes as well as techno-economic analysis on biofuel production using Euglena are highly limited to date. Economic aspects for the biofuel production will be ensured via valorization of industrial byproducts such as food wastes.
... Co-cultivation of microalgae with filamentous fungi is currently considered as a superior method for accumulation and harvesting efficient amount of biomass for biofuel production or production of other biotechnologically important products (Alam et al., 2016;Chu et al., 2021). Three fungal species, Ganoderma lucidum, Pleurotus ostreatus, and Penicillium restrictum, have been recently shown to reliably flocculate and harvest 62-75% of E. gracilis cells while leaving it unharmed (Bansfield et al., 2022). The separation of dense clusters of algae and fungi decrease operational cost of harvesting process of microalgal biomass (Gultom and Hu, 2013;Zhao et al., 2019). ...
Euglena gracilis is a freshwater flagellate possessing secondary chloroplast of green algal origin. This protist has numerous biotechnological applications such as production of biofuels and pharmaceuticals, and it can be also used for bioremediation of polluted water and wastewater. One of the highest limitations for its large-scale cultivation is that it cannot synthesize vitamins B1 and B12 which are expensive and they have to be added to media. This study revealed that E. gracilis can be grown for long time periods without the addition of vitamins B1 and B12 in the co-culture containing filamentous fungus Cladosporium westerdijkiae, and bacteria Lysinibacillus boronitolerans and Pseudobacillus badius. Growing of E. gracilis in such co-cultures without the addition of vitamins can dramatically reduce large scale cultivation costs. Moreover, C. westerdijkiae could be used in biotechnology for immobilization and effective harvesting of E. gracilis from big cultivation containers by bioflocculation.
Although microalgae are often studied for their biochemical extracts, utilizing them in a viable state opens new avenues for sustainable oxygenation in various systems. This study addresses the challenges of maintaining system homeostasis and presents an effective method for immobilizing live microalgae within poly(vinyl alcohol) (PVA) nanofibers using electrospinning technology. Characterization techniques, including scanning electron microscopy (SEM), fluorescence microscopy, Fourier‐transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC), were used to validate successful immobilization. Rheological studies were performed to investigate the influence of microalgae on the fiber morphology. Changing the PVA concentration, the fiber diameter could be regulated between 150 and 650 nm in the spinnable range. The addition of microalgae to the solution increased the viscosity of the prepared solution and reduced the resulting fiber diameter by approximately 2/3. Our results show that PVA nanofibers effectively encapsulate living microalgae and allow for sustained transport of nutrients and metabolites. The photosynthetic efficacy of the encapsulated microalgae was evaluated using dissolved oxygen measurements and showed two times higher rates of oxygen production and consumption compared with a film‐based approach. Our results show that PVA nanofibers effectively encapsulated living microalgae and allowed for the sustained transport of nutrients and metabolites. This innovative methodology provides a robust platform for immobilizing living microorganisms, with broad implications for applications ranging from regenerative medicine to sustainable agriculture.
Biofloc Technology (BFT) is proven to be the fulcrum of sustainable recirculating aquaculture system especially under zero water discharge condition. The efficiency of BFT system is reinforced by an unswerving microbial community in the system. Several researchers have made copious reports on the microorganisms in BFT and identified heterotrophic bacteria predominant in the microbial composition. A summary of these researches considers these microorganisms playing the role of chemo-photosynthetic autotrophs, organic detoxifiers, probiotic, decomposers/bioflocculants, bio-leachers and pathogens. Although these functional roles are well identified, the reports have failed to sufficiently illustrate the borderline at which these microbial communities fail to serve their beneficial roles in BFT system. This review paper firstly presents a snapshot of some indispensable water quality conditions and zootechnical variables aided by the microbial community in floc as well as the amphibolic process that synthesizes nutrient from the organic deposit in BFT. Furthermore, information on the microbial community in BFT is evaluated to have Bacillus sp., Lecane sp. and Pseudomonas sp. serving all-encompassing role in BFT while Vibrio sp. and Enterobacter sp. are pathogenic under unsuitable water quality conditions. Functional characterisation of the commonly reported microorganisms in BFT categorised 21.95 % as most critical, whose abundance indicates an efficient BFT.
Background
Synthetic algal–fungal and algal–bacterial cultures have been investigated as a means to enhance the technological applications of the algae. This inclusion of other microbes has enhanced growth and improved stress tolerance of the algal culture. The goal of the current study was to investigate natural microbial consortia to gain an understanding of the occurrence and benefits of these associations in nature. The photosynthetic protist Euglena mutabilis is often found in association with other microbes in acidic environments with high heavy metal (HM) concentrations. This may suggest that microbial interactions are essential for the protist’s ability to tolerate these extreme environments. Our study assessed the Cd tolerance of a natural fungal–algal–bacterial (FAB) association whereby the algae is E. mutabilis.
Results
This study provides the first assessment of antibiotic and antimycotic agents on an E. mutabilis culture. The results indicate that antibiotic and antimycotic applications significantly decreased the viability of E. mutabilis cells when they were also exposed to Cd. Similar antibiotic treatments of E. gracilis cultures had variable or non-significant impacts on Cd tolerance. E. gracilis also recovered better after pre-treatment with antibiotics and Cd than did E. mutabilis. The recoveries were assessed by heterotrophic growth without antibiotics or Cd. In contrast, both Euglena species displayed increased chlorophyll production upon Cd exposure. PacBio full-length amplicon sequencing and targeted Sanger sequencing identified the microbial species present in the E. mutabilis culture to be the fungus Talaromyces sp. and the bacterium Acidiphilium acidophilum.
Conclusion
This study uncovers a possible fungal, algal, and bacterial relationship, what we refer to as a FAB consortium. The members of this consortium interact to enhance the response to Cd exposure. This results in a E. mutabilis culture that has a higher tolerance to Cd than the axenic E. gracilis. The description of this interaction provides a basis for explore the benefits of natural interactions. This will provide knowledge and direction for use when creating or maintaining FAB interactions for biotechnological purposes, including bioremediation.
Background
Synthetic algal-fungal and algal-bacterial cultures have been investigated for technological applications because the microbe interactions enhance growth and improve stress tolerance of the co-cultures. Yet these studies often disregarded natural consortia due to the complexity of environmental samples. The protist Euglena mutabilis is found in association with other microbes in acidic environments with high heavy metal (HM) concentrations. This may suggest that microbial interactions are essential for the alga’s ability to tolerate these extreme environments. Our study assessed the Cd tolerance of a natural fungal-algal-bacterial (FAB) association where the algae is replaced by the photosynthetic protist E. mutabilis.
Results
This study provides the first assessment of antimycotic and antibiotic agents on E. mutabilis. Our results indicate that suppression of associated fungal and bacterial partners significantly decreases the number of viable E. mutabilis cells upon Cd exposure. However, axenic Euglena gracilis recovered and grew well following antibiotic treatments. Interestingly, both Euglena species displayed increased chlorophyll production upon Cd exposure. Finally, the constituent organisms in the E. mutabilis FAB consortia were identified using PacBio sequencing to be a Talaromyces sp and Acidiphilium acidophilum.
Conclusion
This study uncovers a possible tripartite symbiotic relationship, a FAB consortia, that withstands exposure to high concentrations of HM. This unique fungus, bacterium, and E. mutabilis interaction strengthens the photobiont’s resistance to Cd and provides a model for the types of FAB interactions that could be used to create a self-sustaining bioremediation technology.
