Investigation into the possible use of cryptococcus albidus for lipid accumulation using volatile fatty acids as sole carbon source for biodiesel production

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Owing to rising global population and associated competition for food of which some serve as feedstock for biodiesel, especially the vegetable oils, it is necessary to identify alternative sources of lipids. The concept of using volatile fatty acids as sole carbon source for microbial lipids accumulation was investigated in flask cultures of Crypotoccus albidus. C.albidus was cultivated at a temperature of 25oC, pH of 6.0 and pure VFA concentration of 5g/l.The hexane/ isopropanol alcohol/ distilled water solvent extraction method using a soxhlet apparatus was used for possible lipids extraction. Pure volatile fatty acids mixtures (acetic, propionic and butyric acids) of different ratios as well as volatile fatty acids from anaerobic digestion of faecal sludge were used. It was observed that Crypotoccus albidus could not grow well on volatile fatty acids as there were decreases in optical density from an initial 0.228 to 0.184 when pure VFAs were used with ammonium chloride as nitrogen source. When cells were grown on VFAs from faecal sludge also, there was no growth as a similar decrease in optical density was observed from 0.098 to -0.009. The effect of different nitrogen sources on the growth of Crypotoccus albidus was also investigated. It was observed that yeast extract which is an organic source of nitrogen gave the highest growth of cells with an optical density of 0.110 from 0.052. No lipid was extracted in this study as C. albidus could not grow on VFAs thereby not metabolizing the VFAs into lipids accumulated in its cells for extraction.
A thesis submitted to the Chemical Engineering Department, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the degree of Master of Science, 2014