Inhibition of ethanol-producing yeast and bacteria by degradation products produced during pre-treatment of biomass.

Klinke, H. B.; Thomsen, A. B.; Ahring, B. K.

An overview of the different inhibitors formed by pre-treatment of lignocellulosic materials and their inhibition of ethanol production in yeast and bacteria is given. Different high temperature physical pre-treatment methods are available to render the carbohydrates in lignocellulose accessible for ethanol fermentation. The resulting hydrolyzsates contain substances inhibitory to fermentation-depending on both the raw material (biomass) and the pre-treatment applied. An overview of the inhibitory effect on ethanol production by yeast and bacteria is presented. Apart from furans formed by sugar degradation, phenol monomers from lignin degradation are important co-factors in hydrolysate inhibition, and inhibitory effects of these aromatic compounds on different ethanol producing microorganisms is reviewed. The furans and phenols generally inhibited growth and ethanol production rate (QEtOH) but not the ethanol yields (YEtOH) inSaccharomyces cerevisiae. Within the same phenol functional group (aldehyde, ketone, and acid) the inhibition of volumetric ethanol productivity was found to depend on the amount of methoxyl substituents and hence hydrophobicity (logP). Many pentose-utilizing strainsEscherichia coli,Pichia stipititis, andZymomonas mobilisproduce ethanol in concentrated hemicellulose liquors but detoxification by overliming is needed.Thermoanaerobacter mathraniiA3M3 can grow on pentoses and produce ethanol in hydrolysate without any need for detoxification.

BIOTECHNOLOGY; YEAST; BACTERIA; ESCHERICHIA coli; SACCHAROMYCES

Applied Microbiology & Biotechnology, 2004, Vol 66, Issue 1, p10

0175-7598

Academic Journal

10.1007/s00253-004-1642-2