Lipid production from corn stover by a cost-efficient system featuring ammonium carbonate-steam explosion and recirculating enzymatic hydrolysis

Abstract

A cost-efficient system was developed for the production of single cell oil from lignocellulosic biomass. The pretreatment of corn stover by ammonium carbonate-steam explosion was performed. A maximum lignin removal rate of 47.26% was observed and confirmed by SEM, XRD and FTIR. In the process of enzymatic hydrolysis, higher initial enzyme loadings were used to reduce the reaction time to 24 h. Under these conditions, the sugar conversion, sugar conversion rate and sugar yield of the pretreated corn stover were 74.84%, 2.00 g L-1 h-1 and 479.4 g kg-1 corn stover, respectively. The biomass production, lipid concentration and lipid content of Cryptococcus podzolicus SCTCC300292 were 10.56 g L-1, 5.03 g L-1 and 47.60%, respectively, in the fermentation of enzymatic hydrolysate. An improved cycling process of enzymatic hydrolysis was employed to reduce the enzyme loading by 40%. The sugar conversion increased to 80.17% and the sugar yield to 513.45 g kg-1 corn stover with a higher sugar release rate of 2.14 g L-1 h-1. Furthermore, the lipid yield reached 54.6 g kg-1 corn stover for the whole biorefinery process. These results indicated that the process of ammonium carbonate-steam explosion pretreatment and recirculated enzymatic hydrolysis would be a highly efficient path for converting lignocellulosic feedstocks into lipids.