Selection and identification of oleaginous yeast isolated from soil, animal feed and ruminal fluid for use as feed supplement in dairy cattle

摘要

The purpose of this study was to select oleaginous yeast for microbial lipid production. Sixty-four yeast isolates were obtained from soil (GSY1-12), animal feeds (FDY1-21), and ruminal fluid (RMY1-31) using yeast extract peptone dextrose (YPD) agar. The cultivation of these isolates on nitrogen limitedmedium revealed that GSY2 to GSY6, GSY10, FDY2, FDY12 and FDY14 accumulated lipid over 20% of dry biomass. Therefore, they were preliminarily classified as oleaginous yeast. In subsequent experiment, an 8 9 3 factorial in completely randomized design was conducted to examine the effect of eight oleaginous yeast strains and three nitrogen sources (peptone, (NH4)(2)SO4, urea) on lipid accumulation when using molasses as substrate. The result illustrated that only GSY3 and GSY10 accumulated lipid over 20% of biomass when using peptone or (NH4)(2)SO4 but urea did not. However, GSY10 gave higher biomass and lipid yield than GSY3 (P 0.05). Identification of GSY10 using 26S rDNA illustrated that GSY10 belongs to Trichosporon asahii. Fatty acid profiles of this strain contained unsaturated fats up to 62.5% of which oleic acid (C-18:1) was predominant. In conclusion, T. asahii GSY10 was the most promising oleaginous yeast for microbial lipid production from molasses.