An aptly industrialized bioprocess for lactic acid production from corn stover using thermotolerant microbial consortia.

Abstract

Chemical pretreatment of lignocellulosic biomass is a critical step in the conversion of lignocellulose to biofuels and biochemical. The main drawback of this pretreatment process is the formation of inhibitors which exhibit combined toxicity to microorganisms and result to low product concentrations and yields. In this study, the selection of microbial consortia by enrichment on hydrolysate of H2SO4-pretreated corn stover (pre-CS) without detoxification has been investigated as an efficient way to develop new strategies for lignocellulose utilization. The analysis of cattle stomach-dervied microbial consortia domesticated to degrade hydrolysate of pre-CS to produce lactic acid (LA) at different temperatures was investigated. Bacterial 16S rRNA gene amplicon sequencing analyses indicated that the three microbial consortia were taxonomically distinct and Enterococcus became dominant at high temperature. The highest glucose consumption rate was observed at 45°C, while the three microbial consortia showed similar consumption rates of xylose and arabinose. The selected microbial consortia DUT37, DUT45 and DUT47 showed preferable resistances to inhibitors in hydrolysate of pre-CS and abilities of xylose utilization. A batch simultaneous saccharification and fermentation (SSF) process was developed by microbial consortium DUT47 at 47°C to produce LA from pre-CS under non-detoxified and non-sterile conditions. The LA concentration and yield were 43.73g/L and 0.50g/g-corn stover (CS), respectively. Microbial consortium DUT47 has been shown to be suitable for LA production from H2SO4-pretreated corn stover without detoxification due to its thermophilic growth characteristics, robust tolerance of inhibitors, and the simultaneous utilization of glucose and xylose.