Characterization of Grass Degrading Bacteria Active on β-1,3-1,4-D-glucans from Bacillus subtilis GN156 Potential Use for Grass Silage-Making

Abstract

One hundred and sixty-one bacterial isolates were screened for (i) the stability of CM-cellulase at high temperature of 60°C as primary screening, (ii) the stability of pH and temperature of 3-7 and 30-60°C, respectively and (iii) the activities of pH and temperature range following stability study. The
isolate GN156 showed high stability of CM-cellulase activity at the pH and temperature of 3.7 - 7.2 and 30 – 70°C, respectively. Based on physical and biochemical properties, this isolate was identified as Bacillus subtilis. The enzyme system study revealed various hydrolytic enzymes of CM-cellulase,
dextrinase, cellobiase, xylanase, polygalacturonase, polymethylgalacturonase, but, β-1,3-1,4-glucanase was the most effective enzyme. Therefore, optimum pH and temperature of β-1,3-1,4-glucanase were further studied. Interestingly, its activities appeared at wide range of pH and  temperature of 5.5-9 and 40-60°C, respectively. The profile of growth and enzyme production indicated that β-1,3-1,4-glucanase produced by B. subtilis GN156 was associated with cell growth. Induction of β-1,3-1,4-glucanase production by 1% of CM-cellulose, pectin and xylan revealed an increment of activities of 47, 41 and 11-folds, respectively. When various concentrations of CMC were taken into account, the CMC concentration of 0.8% (w/v) provided the maximum β-1,3-1,4-glucanase production.