Development of oil-producing microbiota and its application in fermenting distiller's grains to obtain microbial oil and ruminant feed

Abstract

With the depletion of global fossil energy, it is a good choice to produce biodiesel (renewable energy) from waste biomass resources. We tried to domesticate microbiota with distiller's grains as medium, and obtained genetically stable and acid-resistant microbiota JQY1, which could convert lignocellulose into microbial oil. Amplicon sequencing results showed that Proteobacteria (94.05 %) and ascomycetes (100 %) were the main phyla, and Rhizobiaceae_unclassified (41.19 %) and Pseudomonas (24.47 %) were the dominant genera, The fungi are Wickerhamomyces and Meyerozyma, and their abundance accounts for 70.8 % and 26.32 % respectively. Using external carbon sources in the microbial body one-step fermentation of distiller's grains by microbiota JQY1 can yield a microbial oil content of 2.52 g/L. The fatty acid composition, including palmitic acid, stearic acid, oleic acid, and linoleic acid, conforms to the specifications for biodiesel raw materials set by the American ASTM. The contents of distiller's grains after fermentation were detected, in which the crude protein increased by 6.19 % and the crude fiber decreased by 10.18 %. Microbial cooperation can effectively degrade lignocellulose and transform it into microbial oil. In addition, the distiller's grains after fermentation have higher value as ruminant feed. Through one-step fermentation, we can achieve a win-win strategy of efficiently harvesting biodiesel and improving the nutritional components of distiller's grains to feed animals, which not only reduces the production cost of microbial oil, but also solves the final destination problem of distiller's grains and makes important contributions to promoting the circular economy of distiller's grains.