Chemical Mutagenesis of Bacillus subtilis for Improved Mannanase Biosynthesis

The aim of the present study was to isolate bacterial associated with abattoir waste water, compost saw dust, soil and water samples from Ilaje Lake, Ondo State, Nigeria. The microbial isolates were identified using standard microbiological method. The bacterial isolates were screened for mannanase production. Mannanase activity was determined by dinitrosalicylic acid (DNSA) method while protein concentration in the fermentation broth was quantified by Lowry’s method. Isolate designated 2k tentatively identified as Bacillus subtilis had the highest mannanase activity. The isolate with highest mannolytic activity was then subjected to different mutagens. The mutants of Bacillus subtilis generated were screened for mannanase production in comparison with the wild type in submerged state fermentation. All the mutant strains generated from B. subtilis had their mannolytic activities repressed in comparison with the wild strain. Out of mutants screened, mutant designated CH017 have the highest mannolytic activity 1.20 U/mg. The mannanase activity produced by CH017 was approximately 44% lower than the wild strain. The pretreatment of B. subtilis with nitrous acid caused enzyme repression. Therefore, another chemical mutagen should be worked upon whether it would result in appreciable yield of mannanase.