7-26: The synergistic addition of accessory enzymes enhances the hydrolytic potential of a “cellulase complex” but is highly substrate specific

One way to reduce the overall cost/protein loading of the enzymatic hydrolysis step of a biomass-to-biofuels process is to formulate a more effective enzyme cocktail through the addition of so-called accessory enzymes (such as xylanases, GH61, “swelling factors”, etc.). We have shown that a 7-fold reduction in total protein loading could be achieved by optimizing the synergistic interaction of the enzymes present in a “cellulase” mixture during hydrolysis of steam pretreated corn stover while substantially increasing the glucan and xylan hydrolysis yields.  It was apparent that the interactions between the major cellulase monocomponents and family 10 and 11 endo-xylanases (GH10 EX and GH11 EX) and family 5 xyloglucanase (GH5 XG) played an important role during hydrolysis of various steam pretreated lignocellulosic substrates. The overall hydrolytic potential of the enzyme mixture could be substantially improved by the addition of small amounts of accessory enzymes such as Cel7A, Cel6A and Cel5A. When various “cocktails” were compared GH10 EX addition resulted in the greatest increase in the hydrolytic activity of the cellulase mixture when added to steam pretreated agriculture residues and hardwoods. Alternatively, GH5 XG addition resulted in greatest increases in hydrolysis of steam pretreated softwood. The further synergistic interaction between GH10 EX and GH5 XG was shown to enhance the hydrolytic activity of the cellulase complex when added to a range of pretreated lignocellulosic substrates. The possible mechanisms underlying the observed increase in the overall hydrolytic activity of cellulase complex by the addition of low concentrations of accessory enzymes will be discussed.