Simultaneous saccharification and co-fermentation of dilute acid co-pretreated corn straw and tapioca starch with low enzyme dosage for enhanced lipid production by Cutaneotrichosporon oleaginosum

Due to the structural recalcitrance and relatively high nitrogen content of corn straw, the supplementation of additional carbon sources is probably meaningful to alleviate sugar limitation during the simultaneous saccharification and co-fermentation (SSCF) and increase the carbon-to-nitrogen ratio beneficial for lipid overproduction by oleaginous yeasts. Here, the dilute sulfuric acid co-pretreatment of a corn straw and tapioca starch mixture as co-substrates, followed by direct SSCF without detoxification, was first described for lipid production by Cutaneotrichosporon oleaginosum. Tapioca starch was almost completely degraded into fermentable sugars via the dilute acid co-pretreatment, which provided sufficient initial sugars for microorganisms. The combination of co-pretreatment with the SSCF using a mixed substrate of 40 g/L corn straw and 40 g/L tapioca starch allowed an extremely low enzyme dosage of 1 FPU/g for lipid production, resulting in 12.7 g/L of lipid and 0.11 g/L/h of lipid productivity. The biodiesel parameters of the lipids produced by C. oleaginosum matched those of the European and U.S. biodiesel standards. This study provides a novel combination strategy to simplify the process, reduce enzyme input, and improve lipid production, which is valuable for the commercial viability of lipid technology.