Simultaneous Liquid-Liquid Extraction and Fermentation: A General Method to Reduce Microbial Inhibition by Hydroxycinnamic Acids Derived From Biomass Pretreatment

Production of biofuels involves the formation of bioethanol from lignocellulosic biomass.  Three main steps are involved in the transformation of biomass into ethanol: (1) pretreatment, (2) enzymatic hydrolysis and (3) fermentation.  Pretreatment is needed to make polysaccharides accessible for enzymatic hydrolysis and subsequent fermentation.  A number of pretreatment technologies have been developed using a diverse range of pH, temperatures, oxidants, and solvents.  All of these pretreatments have unique positive attributes but have a common problem: the generation of hydroxycinnamic acid inhibitor compounds from lignin degradation.  To test the tolerance of E. coli KO11 and S. cerevisiae BY 4710 to these inhibitors, growth experiments using minimal media were prepared using varying concentrations of ferulic acid, p-coumaric acid and their decarboxylase derivatives.  Two-phase organic fermentation using alkanes and higher alcohols was conducted to test the removal of these inhibitors.  After finding conditions in which the decarboxylase derivatives of these hydroxycinnamic acids are less toxic, enzyme purification and design will be used to improve the catalytic conversion of these acids to their derivatives.