Secretome analysis of Trichoderma reesei CICC41495 for degradation of arabinoxylan in malted barley

Abstract

Arabinoxylan, one of the major non-starch polysaccharides of the endosperm cell wall of barley, has a negative impact on the filterability of wort and beer. The addition of microbial xylanase would be an effective strategy to degrade arabinoxylan. In this study, the secretome of Trichoderma reesei CICC 41495 cultivated under submerged fermentation with wheat bran as a carbon source was characterised by two-dimensional electrophoresis combined with MALDI-TOF/TOF tandem mass spectrometry. A total of 24 proteins were identified in the culture supernatant, 23 of which were involved in non-starch polysaccharide degradation. The proteins belonged to 10 different families of glycoside hydrolases, including xyloglucanase, cellobiohydrolase I, cellobiohydrolase II, endoglucanase II, endo-1,4-β-glucanase VII, β-glucosidase, endo-1,4-β-xylanase I and II, endo-1,4-β-xylanase III, and α-l-arabinofuranosidase. Of these, four were correlated with arabinoxylan degradation. Supplementation of the secretome loading of 0.14 mg protein/g malt to mash resulted in the total degradation of high molecular weight arabinoxylan, a 90% increase in filtration rate and a 7.9% decrease in viscosity. The results suggest that T. reesei produces a tailored xylanolytic enzyme system that efficiently hydrolysed high molecular weight arabinoxylan. Accordingly, the secretome of this fungi has potential value in the brewing industry. © 2018 The Institute of Brewing & Distilling.