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Microbial conversion of wastewater from butanol fermentation to microbial oil and biomass by oleaginous yeasts

Four oleaginous yeasts (Trichosporon coremiiforme, Trichosporon dermatis, Cryptococcus albidus, and Trichosporon cutaneum) were used for treatment of the wastewater after butanol fermentation. The wastewater containing high COD value (33.70 g L−1) and total sugar concentration (13.07 g L−1) could satisfy the requirement of cellular growth. Among the four strains, the highest cell accumulation of 9.82 g L−1 was produced by T. cutaneum, and the maximum biomass (9.76 g L−1) of T. dermatis was also obtained after four days fermentation, followed by T. coremiiforme (7.90 g L−1) and C. albidus (7.59 g L−1). However, T. coremiiforme achieved the highest lipid content (34.35%) and yield (2.38 g L−1) after four days' fermentation. The lipid content of T. dermatis, C. albidus and T. cutaneum increased up to 15.69%, 10.25%, and 15.39%, respectively. Meanwhile, after five days' fermentation, the conversion yields of lipid/COD (%, g L−1/g L−1) by T. coremiiforme, T. dermatis, C. albidus, and T. cutaneum were 7.47%, 3.72%, 3.18%, and 3.03%, respectively. Results showed that T. coremiiforme had the highest yield (1635.4 mg L−1) of the fatty acids composition (C18:1 and C18:2), followed by T. dermatis (978.9 mg L−1) and T. cutaneum (998.4 mg L−1). Comparison among the four oleaginous yeasts, T. coremiiforme gave the best bioconversion for lipid content, lipid yield and conversion yields using the wastewater after butanol fermentation as the growth medium oleaginous yeasts. The results suggested that T. Coremiiforme had a great potential to be a candidate for biodiesel feedstock. This bioconversion of wastewater from butanol fermentation to microbial oil and biomass by oleaginous yeasts could both solve the environmental problem and offer lipid production with low cost. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1220–1226, 2018