Enzymes of carbohydrate metabolism of mycelial fungi from marine environments.: β-1,3-glucanase of the marine fungus Chaetomium indicum

Thirty samples of fungi belonging to 17 species living in marine environments were studied for their ability to produce extracellular enzymes. In the culture fluids, a variety of glycosidases (beta -glucosidases, N-acetyl-beta -glucosaminidase, beta -galactosidases, and alpha -mannosidases) and glucanases (amylases and beta -1,3-glucanases) were found. Several cultures were found that could be used as efficient producers of either individual enzymes or a whole complement of enzymes degrading carbohydrate-containing compounds. Optimal growth conditions for the fungus Chaetomium indicum and beta -1,S-glucanase biosynthesis were developed. beta -1,3-Glucanase was isolated by a combination of ion-exchange chromatography, ultrafiltration, and gel chromatography. The molecular mass of the enzyme determined by gel-filtration was 54 kD. The enzyme was stable at temperatures below 50 degreesC, had a temperature optimum for activity at 60 degreesC, and retained activity between pH 4.5 and 7.5. The pH dependence of the beta -1,3-glucanase activity showed two maxima, at pH 4.4 and 5.6; this suggested the existence of two forms of the enzyme. Analysis of the products of enzymatic hydrolysis of laminaran, transglycosylating ability, and the effect of a specific natural inhibitor indicates that both forms are exo-beta -1,3-glucanases.