Production and some properties of salt-tolerant β-xylosidases from a Shoyu Koji Mold, Aspergillus oryzae in solid and liquid cultures

β-Xylosidase production from a shoyu (soy sauce) koji mold, Aspergillus oryzae HL15, cultured in solid and liquid media was examined and some properties of the enzymes were studied. Three β-xylosidases (Xy11, Xy12 and Xy13) were easily extracted with 0.5% NaCl from a solid medium and purified homogeneously on SDS-PAGE by chromatography. On the other hand, in a liquid medium, A. oryzae HL15 produced mainly cell-wall-bound β-xylosidases which could not be extracted with 0.5% NaCl or any detergent. Cell-wall-bound β-xylosidases, Xy11-CB and Xy12-CB, were liberated by digestion of mycelia with Yatalase and purified to a homogeneous state on SDS-PAGE by HPLC column chromatography. Four β-xylosidases (Xy11, Xy12, Xy11-CB and Xy12-CB) exhibited not only high activity at high NaCl concentrations, but also similar properties; on the other hand, Xy13 differed in terms of thermostability and halophilic properties. The salt tolerance of β-xylosidases in A. oryzae suggests that these enzymes are highly active and involved in releasing xylose in shoyu moromi mash.