MICROBIAL CATALYSTS TO PRODUCE FUEL ETHANOL AND VALUE ADDED PRODUCTS
Location: National Center for Agricultural Utilization Research
Title: Extracellular Hemicellulolytic Enzymes from the Maize Endophyte Acremonium zeae
Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 25, 2008
Publication Date: January 31, 2009
Citation: Bischoff, K.M., Wicklow, D.T., Jordan, D.B., De Rezende, S.T., Liu, S., Hughes, S.R., Rich, J.O. 2009. Extracellular hemicellulolytic enzymes from the maize endophyte Acremonium zeae. Current Microbiology. 58:499-503.
Interpretive Summary: New enzymes that can degrade cellulose and hemicellulose are needed to help overcome some of the technical barriers to using agricultural residues as feedstocks for fuel ethanol production. Fungal micro-organisms that colonize corn plants need to degrade cellulose and hemicellulose during the infection process, and therefore may be a source of new enzymes. In the present study, a fungus called Acremonium zeae was examined for enzyme activity. The organism was found to produce a full range of enzymes that can degrade hemicellulose and release greater than 80% of the total sugars from select hemicellulose substrates. Results will be valuable to researchers developing new enzymes to serve as biocatalysts in the conversion of agricultural residues to fermentable sugars.
The maize endophyte Acremonium zeae was examined for production of extracellular enzymes that hydrolyze cellulose and hemicellulose. The most prominent enzyme activity in cell-free culture media from A. zeae NRRL 6415 was xylanase, with a specific activity of 60 U/mg from cultures grown on crude corn fiber. Zymogram analysis following SDS-PAGE indicated six functional xylanase polypeptides ranging in mass from 20 to 50 kDa. Xylosidase, arabinofuranosidase, endoglucanase, cellobiohydrolase, and beta-glucosidase activities were also detected. In combination with exogenously added xylosidase, A. zeae enzymes were able to release greater than 90% of the xylose and 80% of the arabinose from corn cob and wheat arabinoxylans. A. zeae NRRL 6415 possesses a full complement of hemicellulolytic enzymes that may be developed for industrial application in the biofuels industry.