ARS | Publication request: Critical cellulase and hemicellulase activities for hydrolysis of ionic liquid pretreated biomass

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 28, 2011
Publication Date: November 15, 2011
Citation: Barr, C.J., Mertens, J.A., Schall, C.A. 2012. Critical cellulase and hemicellulase activities for hydrolysis of ionic liquid pretreated biomass. Bioresource Technology. 104:480-485.

Interpretive Summary: Utilization of agricultural biomass will be required to meet future fuel and specialty chemical needs. Biomass residues are recalcitrant and are typically broken down by chemical pre-treatment and enzymes into useful simple sugars. While there are some issues associated with pretreatment processes, one of the more significant costs associated with biomass utilization is enzyme cost. This is due to the fact that there is not a full understanding of which component enzymes or how much enzyme is required to fully unlock the simple sugars from biomass. In this work we have determined the required enzyme activities and optimal enzyme quantity to maximize production of simple sugars from mildly pretreated switchgrass and poplar. This work leads to additional knowledge of the enzyme cocktails required for individual biomass sources and identifies useful enzyme species that will ultimately lead to a decrease in the cost of using agricultural crops for the production of high value products.

Technical Abstract: Critical cellulase and hemicellulase activities are identified for hydrolysis of ionic liquid (IL) pretreated poplar and switchgrass; hemicellulase rich substrates with amorphous cellulose. Enzymes from Aspergillus nidulans were expressed and purified: an endoglucanase (EG) a cellobiohydrolase (CBH), an endoxylanase (EX), and an acetylxylan esterase (AXE). ß-xylosidase (ßX) from Selenomonas ruminantium and a commercial ß-glucosidase (ßG) from Novozyme 188 were admixed with the A. nidulans enzymes. Statistical analysis indicates that ßG and ßX activities are significant for both glucose and xylose yields for the two substrates. EG is a significant factor for glucan hydrolysis while EX is significant for xylan hydrolysis of the substrates. The CBH, which has activity on crystalline cellulose and negligible activity on amorphous celluloase, was not a significant factor in glucan hydrolysis. EX is significant in glucan hydrolysis for poplar. The addition of AXE significantly improves xylan hydrolysis for poplar but not switchgrass.