Hemicellulases of Bacillus species: preliminary comparative studies on production and properties of mannanases and galactanases

Abstract

A range of Bacillus subtilis strains and other Bacillus species were screened for mannanase, beta-mannosidase and galactanase activities. Maximum mannanase activity, 106.2 units/ml, was produced by B. subtilis NRRL 356. beta-Mannosidase and galactanase activities from all strains were relatively low. The effect of carbon and nitrogen source on mannanase and galactanase production by B. brevis ATCC 8186, B. licheniformis ATCC 27811, B. polymyxa NRRL 842 and B. subtilis NRRL 356 was investigated. Highest mannanase production was observed in the four strains tested when the mannan substrate, locust bean gum, was used as carbon source. Induction was most dramatic in the case of B. subtilis NRRL 356 where only basal enzyme levels were produced in the presence of other carbon sources. beta-Mannosidase was induced in the four Bacillus cultures by locust bean gum. Results indicated that galactose acted as an inducer for production of galactanase. Organic and inorganic nitrogen sources resulted in induction of high mannanase titres in B. subtilis. Highest galactanase activity was produced by each organism in media containing sodium nitrate as nitrogen source. Mannanases from B. brevis, B. licheniformis, B. polymyxa and B. subtilis retained 100% residual activity after a 3 h incubation at 65 degrees C, 65 degrees C, 60 degrees C and 55 degrees C respectively. Galactanases retained more than 95% activity at 55 degrees C after 3 h. The pH optima of mannanases ranged from 6.5-6.8 whereas galactanases ranged from 5.1 in the case of B. brevis to 7.0 for B. polymyxa.