O-18 Simultaneous saccharification and fermentation of lignocellulosic biomass for phenyllactate production by recombinant Escherichia coli

Abstract

Sorghum bagasse pretreated with diluted acid, which was predominantly composed of glucan (59%) and xylan (7.2%), was used as a lignocellulosic feedstock to produce D-phenyllactic acid (PhLA) by a recombinant Escherichia coli strain expressing phenylpyruvate reductase from Wickerhamia fluorescens. Compared to filter paper hydrolysate, the PhLA yield was reduced by 35% during fermentation with enzymatic hydrolysate of sorghum bagasse as a carbon source, and metabolomics analysis revealed that intracellular levels of erythrose-4-phosphate and phosphoenolpyruvate and NAD(P)H regeneration for PhLA production from glucose markedly reduced. Compared to the separate hydrolysis and fermentation (SHF) with sorghum bagasse hydrolysate, simultaneous saccharification and fermentation (SSF) of sorghum bagasse under glucose limitation conditions yielded 4.8-fold more PhLA with less accumulation of eluted components of p-coumaric acid and aldehydes, which inhibited PhLA fermentation. These results suggest that gradual hydrolysis of sorghum bagasse during SSF reduces the accumulation of both glucose and fermentation inhibitors, collectively leading to increased PhLA yield.