Abstract:

A mannanase-producing bacterial strain F1-5 that isolated and preserved in our laboratory was identified as Bacillus subtilis (Genebank accession number FJ392725) according to the results of morphological observations, physiological and biochemical tests and 16S rDNA sequence homology analysis. The optimal fermentation conditions of F1-5 for producing mannanase were determined to be fermentation for 48 h at 35 ℃ with an inoculation size of 6% in a 250 ml flask with a shaking speed of 180 r/min containing 60 ml of culture medium consisting of 4.8% yeast cell wall as carbon source and 0.5% NH4NO3 as nitrogen source by one-factor-at-a-time and orthogonal array design methods. Under such conditions, the mannanase activity was up to 330 U/ml, which was 3.4 times higher than before the optimization. Furthermore, our 5 L fermentor experiments gave a mannanase activity as high as 582 U/ml. Therefore, these optimal conditions are reliable.

Key words: mannanase, 16S rDNA, Bacillus subtilis, fermentation condition