Monday, April 30, 2007 - 11:10 AM

Enzymatic hydrolysis of wheat arabinoxylan by a recombinant "minimal" enzyme cocktail containing ▀-xylosidase, endo-1,4-▀-xylanase, and novel α-L-arabinofuranosidase activities

Hanne Risbjerg S°rensen, Starch, Novozymes A/S, Laurentsvej 51-53, BagsvŠrd, 2880, Denmark

Hydrolysis of arabinoxylan is an important prerequisite for improved utilization of wheat hemicellulose in the ethanol fermentation industry. This study describes the identification of the key enzyme activities required in an enzyme cocktail able to catalyze hydrolysis of both water soluble and water insoluble wheat arabinoxylan, and whole vinasse, a fermentation effluent resulting from industrial ethanol manufacture of wheat. The optimal arabinose-releasing and xylan depolymerizing enzyme activities were selected from data obtained when selected, recombinant enzymes were systematically supplemented to the different arabinoxylan substrates in mixtures; this examination revealed two novel α-L-arabinofuranosidase activities: i) one GH51 enzyme from Meripilus giganteus, able to catalyze arabinose release from singly substituted xylose; ii) one GH43 enzyme from H. insolens able to catalyze the release of arabinose from doubly substituted xylose. Treatment of soluble and insoluble wheat arabinoxylan with an enzyme cocktail containing a 20:20:20:40 mixture and a 25:25:25:25 mixture, respectively, of the GH43 α-L-arabinofuranosidase from H. insolens (Abf II), the GH51 α-L-arabinofuranosidase from M. giganteus (Abf III), a GH10 endo-1,4-β-xylanase from H. insolens (Xyl III), and a GH3 β-xylosidase from Trichoderma reesei (β-xyl) released 322 mg arabinose and 512 mg xylose per g of soluble wheat arabinoxylan dry matter and 150 mg arabinose and 266 mg xylose per g of insoluble wheat arabinoxylan dry matter after 24 hours at pH 5, 50º. A 10:40:50 mixture of Abf II, Abf III, and β-xyl released 56 mg arabinose and 91 mg xylose per g of vinasse dry matter after 24 hours at pH 5, 50º.