Screening of Xylanase-producing Bacillus sp. and Optimization of Fermentation Process

Selective medium for xylanase was used in screening the xylanase producing Bacillus strains.Thirtyseven of the 120 Bacillus strains tested were found to form transparent circles on the plates.After a secondary screening with the enzyme fermentation medium, B.safensis FJAT-14260 was determined to be the most desirable strain for the xylanase production.A single factor and an orthogonal experiment were used to optimize the fermentation conditions.The results showed the substrate concentration to be the most important factor relating to the medium, and temperature, the most critical condition for the fermentation process.In all, the best medium for the enzyme production consisted of carbon source (yeast extract) at 7g·L-1, nitrogen source (peptone) at 9g·L-1, and substrate (xylan) at 10g·L-1.And, the optimal fermentation temperature was 30℃, initial pH at 8.0, and liquid volume at 30mL/250 mL.Under these conditions, after allowing FJAT-14260 to ferment for 32 h, the xylanase activity could reach as high as 113 585.78U·mL-1, which was 4.62 times of what was without the optimization.