Efficient lipid production from herbal extraction residue hydrolysate by the oleaginous yeast Cutaneotrichosporon oleaginosum for biodiesel production

Tremendous amounts of herbal extraction residues (HERs) derived from the traditional Chinese herb medicine industry are routinely generated annually. However, HERs are generally treated by landfill or incineration, resulting in a great waste of resources and serious environmental issues. Here, the residue of the production of Xuanmai Ganjie Capsule (XGCR) was described for lipid production. Part of the sugar polymers (44.0%) contained in the raw XGCR could be directly hydrolyzed using a fed-batch hydrolysis process at 54% solids loading. More interestingly, sugar yield approached the theoretical maximal value when the residue was pretreated by 1% (w/w) dilute sulfuric acid before enzymatic hydrolysis. Cutaneotrichosporon oleaginosum exhibited high oleaginicity with lipid titer, content, and yield of 8.5 g/L, 40.7%, and 80.2 g/kg of residue supplied, respectively. The fatty acid profiles and the prediction of biodiesel parameters indicated the microbial lipid prepared from the XGCR was a suitable feedstock for biodiesel industry. This study strongly supported that the XGCR-to-lipid route can be a promising way for turning HERs into treasure.