Development of DLC and DLCA pretreatments with alkalis on rice straw for high titer microbial lipid production

Microbial lipid production from lignocellulosic biomass is largely impeded by unsatisfactory fermentation performance due to the presence of toxic degradation products generated by pretreatment. DLC (Densifying Lignocellulosic biomass with Chemicals) pretreatment completed at room temperature, generating fewer degradation products, showed great potentials for lignocellulosic biorefineries. This work developed DLC pretreatment with sodium hydroxide and calcium hydroxide on rice straw (RS) for microbial lipid production. Conditions for steam autoclave on DLC-RS (i.e. DLCA treatment) were optimized using response surface methodology. High solid loading enzymatic hydrolysis and lipid fermentations by Trichosporon dermatis 32,903 together with mass balances were performed. Lipid fermentations were successfully conducted, for the first time, on pretreated biomass at a solid loading as high as 35 wt.% without washing or detoxification. Lipid titers as high as 28.3 g/L and 29.5 g/L were achieved on DLC-RS and DLCA-RS, respectively, with lipid yields of 0.24 and 0.23 g/g consumed sugar.