Enzymatic hydrolysis of autohydrolyzed barley husks

Abstract

BACKGROUND: Barley husks were subjected to non-isothermal autohydrolysis of different severities, yielding a liquid phase rich in hemicellulose-derived compounds and a solid phase, composed mainly of cellulose and lignin. This solid phase was subjected to enzymatic hydrolysis in order to assess the effects of severity on the susceptibility of substrates to enzymatic hydrolysis. The effects of the liquid to solid ratio (LSR, in the range 6 to 18 g g−1) and cellulase to substrate ratio (CSR, in the range 3.3 to 8.2 FPU g−1) on the enzymatic hydrolysis were assessed. RESULTS: Up to 25.8 g oligomers per 100 g raw material were present in liquors from the hydrothermal processing. Enzymatic hydrolysis of solid phases obtained under selected conditions (log Ro = 4.14, LSR = 6 g g−1 and CSR = 5.8 FPU g−1) yielded glucose concentrations up to 67 g L−1 (corresponding to cellulose to glucose conversions close to 100%). CONCLUSION: It was shown that autohydrolysis is an effective method for improving the enzymatic susceptibility of barley husks. High cellulose conversions resulting in high glucose yields were achieved by enzymatic hydrolysis at low LSR and CSR. The liquid fraction obtained upon autohydrolysis contained large amounts of hemicellulose-derived compounds. Copyright © 2010 Society of Chemical Industry