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Recycle of fermentation process water through mitigation of inhibitors in dilute-acid corn stover hydrolysate

Nancy N. Nichols, Jeffrey A. Mertens, Bruce S. Dien, Ronald E. Hector, Sarah E. Frazer
Bioresource technology reports 2020 v.9 no. pp. 100349
Coniochaeta ligniaria, Escherichia coli, biofuels, biomass, corn stover, ethanol, fermentation, hydrolysates, recycling
Water consumption is an important consideration for production of advanced biofuels and chemicals. Recycling process water to reduce water consumption concentrates inhibitors formed during biomass pretreatment processes. To lessen their impact, Coniochaeta ligniaria NRRL 30616 was used to biologically abate inhibitors in dilute-acid pretreated corn stover hydrolysate. Biological abatement of inhibitors enabled recombinant ethanologenic E. coli FBR5 to complete fermentation before cultures using untreated hydrolysate emerged from the lag phase. Biological abatement allowed 50% reuse of the liquor in subsequent fermentations, and hydrolysate could be recycled five times. Although growth of E. coli FBR5 was variable in fermentations using recycled hydrolysate, ethanol productivity was essentially the same as in single-use hydrolysate. In contrast to biological abatement, overliming did not adequately eliminate inhibitors and led to unsatisfactory fermentation results. Bioabatement also enabled recovery of failed fermentations and allowed recycling of spent liquor for use as process water in a corn stover pretreatment process.