Monday, May 4, 2009
5-29
Mechanistic Study of Enzymatic Cellulolysis Inhibitions
Ani Tejirian, Novozymes, 1445 Drew Avenue, Davis, CA 95618 and Feng Xu, BioFuels R&D, Novozymes North America, 77 Perry Chapel Church Rd, Franklinton, NC 27525.
Enzymatic conversion of cellulosic biomass materials to useful chemicals is prone to various interferences from non-cellulosic substances derived from biomass feedstock or upstream treatments. Understanding these cellulolysis-inhibitory or cellulase-inactivating reactions is of importance for the development of economically viable biorefinery technology. In this study, we investigated the mechanism under which oligomeric phenolics might inhibit cellulolysis. It was found that tannic acid, a representative oligomeric phenolics mimicking solubilized lignin, inactivated cellulases by reversibly complexing them. Individual cellulases showed different susceptibilities toward these inhibitions. Polyethylene glycol and tannase could bind and degrade tannic acid, respectively, and by doing so mitigate tannic acid’s inhibition on cellulolysis. We also investigated the mechanism under which redox-active metal ions might inhibit cellulolysis. A correlation between oxidation potential and inhibition efficacy indicated the oxidative nature of the inhibition. Strong iron ion chelators and polyethylene glycols might be used for effectively mitigation of the inhibition. Potential implication of the observed effect from the inhibitors and their prevention/mitigation in biomass research was discussed.