Microbial Lipid Production From Pectin-rich By-products From Sugar Industry By Oleaginous Yeasts

The shortage of fossil fuels and increasing environmental problems have drawn world wide attention to explore biodiesel as alternative fuels. Recently, microbial lipid has been widely suggested as an alternative feedstock for biodiesel production. It was necessary to use the low cost biomass for lipids production, since the input of feedstock has important effects on the economy of microbial lipid. As a complex polysaccharide, large amounts pectin are generated from industrial processing of fruits and vegetables. The hydrolysates of pectin are mainly composed of galacturonate and it also contains arabinose and glucose. Because both galacturonate and arabinose are not fermentable for Saccharomyces cerevisiae and Escherichia coli, pectin-rich biomass resources have not been applied in fermentation industry as raw materials. Therefore, this thesis intends to study the property of galacturonate for lipid fermentation by oleaginous yeasts, the results provide a scientific basis for pectin-rich biomass exploration.To explore the capability of microbial lipid production from pectin-rich biomass, 10 oleaginous yeast strains were evaluated using galacturonate as sole carbon sources. Trichosporon cutaneum AS 2.571,Trichosporon fermentans CICC 1368 and Cryptococcus curvatus ATCC 20509 were found to effectively convert galacturonate into lipid with lipid yields up to 0.12 g/g. When T. cutaneum AS 2.571 and T. fermentans CICC 1368 cells were cultured on model beet pulp hydrolysates contained galacturonate, arabinose and glucose, the lipid yield were above 0.15 g/g. Three strains were then tested for lipid production directly from real beet pulp hydrolysates, and cellular lipid content and lipid yield reached 43.6% and 0.14 g/g by C. curvatus ATCC 20509. Microbial lipid fatty acid profiles resembled that of vegetable oils. The results demonstrate pectin-rich biomass can be explored as feedstock for microbial lipid production.