using environmental waste as substrate

Micro-organisms such as bacteria, yeasts, molds and algae that accumulate lipid more than 20 % of their biomass are called oleaginous. Microbial lipid has high similarity to the oil obtained from plants and animals. Microbial lipids are renewable sources that can be used for different purposes such as biodiesel production. Production of oil from yeasts has more advantages than that from plants. Accordingly, isolation of oleaginous yeasts with high ability of lipid production is very valuable. In this study we isolated 176 yeasts from 34 soil samples, from which 68 could produce lipid. The strains were screened by an enrichment technique in glycerol and then Sudan black B staining. After lipid extraction by Bligh and Dyer method, the best strain, Rodotorula 110, was selected. This strain proved to comprise lipid, dry biomass and lipid productivity at levels of 8.9 g/l, 15.29 g/l and 58.2 % in optimized conditions, respectively. Then lipid production by the selected strain was evaluated on corn stalk and wheat straw hydrolysate as sole carbon sources. Lipid content on these media was 38.9 % and 43.4%, respectively. The extracted lipid was analyzed by thin layer chromatography and FTIR spectroscopy