Arabinoxylans (AXs) from wheat malts potentially affect beer quality and production. β-D-Xylosidase is a key enzyme that degrades the main chains of AXs to produce xylose. This study performed a partial characterization of β-D-xylosidase from wheat malts. The optimal temperature was 70°C and the enzyme exhibited excellent thermostability, that is, residual activities were 92.6% at 60°C for 1 h. The enzyme was stable over a pH range of 3.0-6.0 and showed optimum activity at pH 3.5 and 4.5. Kinetic parameters K m and V max of wheat malt β-D-xylosidase against p-nitrophenyl-xyloside were 1.74 mmol L À1 and 0.76 mM min À1 , respectively. The enzyme activity was severely inhibited by Cu 2+ , moderately inhibited by Mn 2+ , Mg 2+ , Al 3+ , Ca 2+ , Ba 2+ and Na + and mildly inhibited by Fe 3+ and Fe 2+ . The partial enzymatic characterization achieved in this study can be used as a theoretical basis for purifying β-D-xylosidase from wheat malts.

In this paper the arabinoxylanase activities and the content of water-extractable arabinoxylans (WEAXs) including their degradation products in wheat Yannong 24 during the malting process were studied. The results showed that the endo-β-1,4-xylanase activity had a large increase during the steeping process, endo-β-1,4-xylanase and α-L-arabinofuranosidase achieved the highest activity on day 4 of germination. During malt kilning, endo-β-1,4-xylanase and α-L- arabinofuranosidase were not heat stable, and the activity decline rate were 65.88% and 69.58%; whereas malt β-D-xylosidase was resistant to heat and it’s activity decline rate was only 18.74%. It is during steeping and the first day of germination that the content of WEAXs and it’s degradation products (WEAXs+DP) dramatically increased, and this corresponded to the greater improvement of endo-β-1,4-xylanase activity in the same phase. The WEAXs+DP content has a very significant positive correlation with the endo-β-1,4-xylanase activity (0.892, p<0.01). It can be indicated that endo-β-1,4-xylanase is the main degrading enzyme in the degradation of WUAXs and the increase of the WEAXs content during steeping and the first day of wheat germination.