Synergistic degradation of arabinoxylan with α-L-arabinofuranosidase, xylanase and β-xylosidase from soy sauce koji mold, Aspergillus oryzae, in high salt condition

This study addresses induction and some properties of alpha-L-arabinofuranosidase from a soy sauce koji mold, Aspergillus oryzae HL15, cultured on solid and liquid media. alpha-L-Arabinofuranosidase was induced by soybean polysaccharide and secreted into media on solid cultivation; the enzyme was associated with mycelium as a cell-wall-bound form in liquid cultivation. A major alpha-L-arabinofuranosidase, which was purified homogeneously on SDS-PAGE, showed highest activity in the presence of 10% of NaCl; also, somewhat higher activity was observed even in 25% NaCl than in the absence of NaCl. Arabinoxylan was synergistically degraded by xylanase, beta-xylosidase, and alpha-L-arabinofuranosidase from A. oryzae HL15 in the condition of imitative pH 5.0 and 15% NaCl concentration of the soy sauce moromi mash. These results suggest that arabinose and xylose, which are closely related to melanoidin formation, can be released by synergistic action of these enzymes in soy sauce moromi mash.