ARS | Publication request: Hemicellulolytic enzymes from the maize endophyte Acremonium zeae

Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: May 6, 2009
Publication Date: May 6, 2009
Citation: Bischoff, K.M., Jordan, D.B., De Rezende, S.T., Rich, J.O. 2009. Hemicellulolytic enzymes from the maize endophyte Acremonium zeae [abstract]. Biotechnology for Fuels and Chemicals.

Technical Abstract: Despite recent advances in cellulase development, there is still a need for efficient enzyme systems for the economical depolymerization of lignocellulosic feedstocks to fermentable sugars. In particular, the varying and heterogeneous structure of the hemicellulose fraction requires a complex suite of enzymatic activities for complete hydrolysis. Acremonium zeae is one of the most prevalent fungal colonists of preharvest maize, producing symptomless infections of seeds and inhabiting the stalks of mature plants. When cultured on artificial media, A. zeae grows most vigorously on medium containing corn cob xylan, suggesting that A. zeae might be a source of hemicellulolytic enzymes uniquely adapted for the utilization of corn cell wall components. An examination of A. zeae grown on corn fiber found that it possesses a full complement of hemicellulolytic enzymes including xylanases, xylosidases, and arabinofuranosidases capable of releasing greater than 90% of xylose and arabinose from corn cob and wheat arabinoxylans. A 30 kDa arabinofuranosidase (AF30) and a 47 kDa arabinofuranosidase (AF47) were purified from the cell-free culture supernatant by ion-exchange and hydrophobic interaction chromatography. AF30, which does not bind to the anion exchange support at pH 6.5, has a Km for 4-nitrophenyl-alpha-L-arabinofuranoside (4NPA) of 8.6 mM and Vmax of 3.2 U/mg. Temperature and pH optima are 45°C and pH 4.5. TLC analysis of the hydrolysis products indicated that AF30 releases primarily arabinose and some xylobiose from corn fiber arabinoxylan. AF47, which binds to the anion-exchange support, has a Km for 4NPA of 4.4 mM and Vmax of 1.7 U/mg. Temperature and pH optima were 32°C and pH 6.0. The enzymes produced by A. zeae may have industrial application for the hydrolyisis of recalcitrant lignocellulosic biomass such as corn fiber.