Isolation of extracellular 28- and 42-kilodalton beta-1,3-glucanases and comparison of three beta-1,3-glucanases produced by Bacillus circulans IAM1165.

Bacillus circulans IAM1165 produces three major extracellular beta-1,3-glucanases (molecular masses, 28, 42, and 91 kDa) during the stationary phase of growth. The 28- and 42-kDa enzymes were purified to homogeneity from the culture supernatant in this study. The properties of these two enzymes were examined, together with those of the 91-kDa enzyme previously isolated. The enzymatic properties of the 28- and 42-kDa beta-1,3-glucanases closely resemble each other. The enzymes belong to a category of endo type 1,3-beta-D-glucan glucanohydrolases. The enzymes were active at pH 4.0 to 7.0. The optimum temperature of the reactions was 60 degrees C when laminarin (a soluble beta-1,3-glucan) was used as the substrate at pH 7.0. The enzymes hydrolyzed barley glucan and lichenan (beta-1,3-1,4-glucans) more effectively than laminarin. Of the three enzymes, the 42-kDa enzyme lysed fungal cell walls the most effectively.