English

Abstract

  This study explored a strategy to convert agricultural and forestry residues into microbial lipid, which could be further transformed into biodiesel. Among the 250 yeast strains screened for xylose assimilating capacity, eight oleaginous yeasts were selected by Sudan Black B test. The lipid content of these 8 strains was determined by soxhlet extraction method. One strain (T216) was found to produce lipids up to 36.6%, and it was identified as Rhodotorula glutinis. The optimal fermentation conditions were obtained as follows: glucose as carbon source 100 g/L; yeast extract and peptone as nitrogen sources at, respectively, 8 and 3 g/L; initial pH of 5.0; inoculation volume of 5%; temperature at 28oC, shaking speed of 180 r/min, cultivated for 96 h. Under these conditions, R. glutinis accumulated lipids up to 49.25% on a cellular biomass basis and the corresponding lipid productivity reached 14.66 g/L. Experiments with a 5-L bioreactor under the optimal culture conditions showed that R. glutinis accumulated lipids up to 60.69%, resulting in 23.41 g/L in lipid productivity. More encouraging results were observed for the lipid production with alternative carbon sources. Corn stalk and Populus euramevicana leaves hydrolysate could be used to substitute glucose. Chemical analysis indicated that biodiesel obtained by transesterification possessed similar composition to that from vegetable oil, one of the widely used feedstock for biodiesel.   Key words: Oleaginous yeast, Rhodotorula glutinis, culture optimization biodiesel.