Enrichment of wheat bran by Rhodotorula gracilis through solid-state fermentation.

The potential oil-producing yeast Rhodotorula gracilis was found to produce higher yields of biomass (13.7 g/L) and lipids (20.3%) in a nitrogen-limited and economically cheaper medium (molasses without yeast extract) in a submerged fermentation system. But, when the yeast was grown on four different wheat bran media by solid-state fermentation technique, different media combinations affected the percent increase in biomass, protein, oil production, fatty acid profile and degree of saturation and unsaturation. The initial lipid content in the control medium was 3.5% while in a medium with wheat bran, molasses, and minerals it was 69.8%. The yeast did not produce alpha-amylase, amyloglucosidase and cellulolytic enzymes for the breakdown of wheat bran. The yeast produced red carotenoids, a precursor of vitamin B12 and some oligounsaturated fatty acids in the fermented product.