During the mashing process for brewing beer, incomplete degradation of arabinoxylan in barley malt may cause an intense filterability problem. The present study cloned a putative arabinofuranosidase (AnAbf), one of the debranching enzymes, from Aspergillus niger, to explore its application for improving filterability. Recombinant AnAbf (rAnAbf) showed activity towards both synthetic and natural substrates, such as 4-nitrophenyl α-l-arabinofuranoside (pNPαAraf) and malt water extractable arabinoxylan (WEAX), which was maximized at a temperature of 50 °C and pH of 5.5. Metal ions did not increase the activity of rAnAbf, indicating a difference in its C-terminal domain from that of type II GH43 family members. rAnAbf also exhibited a synergistic effect with β-xylanase against WEAX. The filtration rate of the wort increased by 12.8% after supplementing with rAnAbf during the initial stage of mashing. A slight decrease in viscosity and an unexpected increase in turbidity were observed.
Keywords: Aspergillus niger; Barley malt; Glycoside hydrolase; Wort filterability; α-l-arabinofuranosidase.
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