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The microalgal-based industries are facing a number of important challenges that in turn affect their economic viability. Arguably the most important of these are associated with the high costs of harvesting and dewatering of the microalgal cells, the costs and sustainability of nutrient supplies and costly methods for large scale oil extraction. Existing harvesting technologies, which can account for up to 50% of the total cost, are not economically feasible because of either requiring too much energy or the addition of chemicals. Fungal-assisted flocculation is currently receiving increased attention because of its high harvesting efficiency. Moreover, some of fungal and microalgal strains are well known for their ability to treat wastewater, generating biomass which represents a renewable and sustainable feedstock for bioenergy production.
We screened 33 fungal strains, isolated from compost, straws and soil for their lipid content and flocculation efficiencies against representatives of microalgae commercially used for biodiesel production, namely the heterotrophic freshwater microalgae Chlorella protothecoides and the marine microalgae Tetraselmis suecica. Lipid levels and composition were analyzed in fungal-algal pellets grown on media containing alternative carbon, nitrogen and phosphorus sources from wheat straw and swine wastewater, respectively. The biomass of fungal-algal pellets grown on swine wastewater was used as feedstock for the production of value-added chemicals, biogas, bio-solids and liquid petrochemicals through pyrolysis. Co-cultivation of microalgae and filamentous fungus increased total biomass production, lipid yield and wastewater bioremediation efficiency.
Fungal-assisted microalgal flocculation shows significant potential for solving the major challenges facing the commercialization of microalgal biotechnology, namely (i) the efficient and cost-effective harvesting of freshwater and seawater algal strains; (ii) enhancement of total oil production and optimization of its composition; (iii) nutrient supply through recovering of the primary nutrients, nitrogen and phosphates and microelements from wastewater. The biomass generated was thermochemically converted into biogas, bio-solids and a range of liquid petrochemicals including straight-chain C12 to C21 alkanes which can be directly used as a glycerine-free component of biodiesel. Pyrolysis represents an efficient alternative strategy for biofuel production from species with tough cell walls such as fungi and fungal-algal pellets.
For further details log on website :
http://www.ncbi.nlm.nih.gov/pubmed/25763102
Biotechnol Biofuels. 2015 Feb 15;8:24. doi: 10.1186/s13068-015-0210-6. eCollection 2015.
Title
Fungal-assisted algal flocculation: application in wastewater treatment and biofuel production.
Author
Muradov N1, Taha M2, Miranda AF2, Wrede D2, Kadali K2, Gujar A1, Stevenson T2, Ball AS2, Mouradov A2.
Author information
- 1Florida Solar Energy Centre, University of Central Florida, 1679 Clearlake Road, 32922 Cocoa, FL USA.
- 2School of Applied Sciences, Royal Melbourne Institute of Technology University, 3083 Bundoora, Melbourne, VIC Australia.
Abstract
BACKGROUND:
RESULTS:
CONCLUSION:
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Published online 2015 Feb 15. doi: 10.1186/s13068-015-0210-6
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Figure 1
Lipid production in fungal isolates. (A) The lipid concentrations in cultured fungal strains; (B) microscopic analysis of oil bodies accumulation in A. fumigatus (a, c) and M. circinelloides (b, d) using Nile red (a, b) and Sudan black (c, d).
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Published online 2015 Feb 15. doi: 10.1186/s13068-015-0210-6
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Figure 2
Flocculation of C. protothecoides and T. suecica by 15 fungal strains. (A) 12-well microtitre plate experiment: fungal pellets were mixed with suspensions of C. protothecoides (left wells) and T. suecica (right wells) for 24 h. Controls: microalgal suspensions grown without fungi (top wells); fungal cultures grown alone (middle wells). (B) Flocculation efficiency measured by reduction in optical densities, cell numbers and chlorophyll concentrations of uncaptured algal cells after 24 h of co-cultivation.
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Published online 2015 Feb 15. doi: 10.1186/s13068-015-0210-6
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Figure 3
Flocculation of microalgal strains by A. fumigatus . (A) Flocculation of C. protothecoides: A. fumigatus culture (left); mixotrophically grown C. protothecoides culture (middle); A. fumigatus/C. protothecoides pellets (right). (B) Flocculation of T. suecica: autotrophically grown T. suecica culture (left); A. fumigatus/T. suecica pellets (right). (C) T. suecica culture mixed with A. fumigatuspellets, time = 0 (left); 24 h later (right). (D, E) A. fumugatus pellets grown PDB (left) and 1% TWS (right). (F) Flocculation of T. suecica: A. fumigatus/PDB-T. suecica pellets (left); original T. suecica culture (middle); A. fumigatus/TWS-T. suecica pellets (right).
| PMC full text: |
Published online 2015 Feb 15. doi: 10.1186/s13068-015-0210-6
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Figure 4
Flocculation efficiency of algal strains by A. fumigatus. Flocculation of C. protothecoides by A. fumigatus/PDB (1) and A. fumigatus/TWS pellets (3); flocculation of T. suecica by A. fumigatus/PDB pellets (2) and A. fumigatus/ TWS pellets (4).
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| PMC full text: |
Published online 2015 Feb 15. doi: 10.1186/s13068-015-0210-6
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Figure 5
Fatty acid composition of A. fumigatus, C. protothecoides, T. suecica and fungal-algal pellets. 1) A. fumigatus/TWS pellets; 2) A. fumigatus/PDB pellets; 3) algal strains; 4) A. fumigatus/TWS-algal pellets; 5) A. fumigatus/PDB-algal pellets.
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For further details log on website :
http://www.ncbi.nlm.nih.gov/pubmed/25763102
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