Bacillus Circulans Wxy-producing ¦Â-mannanase Fermentation Conditions And Preliminary Application

β-mannanase, a kind of biological enzyme secreted by many microorganisms such as Bacillus circulans, can hydrolyze galactomannan, galactoglucomannan or glucomannan into oligosaccharide. It's widely used in feed additive for degrading vegetable gum into manna-oligosaccharide to deal with anti-nutrition agents.Under the selective pressure of locust bean gum and high temperature, a strain of Bacillus circulans, termed WXY-100, was isolated and identified with producing neutral β-mannanase. The culture ingredients and conditions were optimized with the orthonormal table L₉(3⁴) method. Studies showed that the culture components for optimization of β-mannanase production were yeast extract 20 g/L, Konjak powder 20 g/L, (NH₄)₂SO₄ 2 g/L, KH₂PO₄ 1 g/L and MgSO₄ · 7H₂O 1 g/L; and the optimal culture conditions were seed incubation time 8-12 h, inoculation ratio 6%, culture volume 25 mL, pH 7.5, fermentation temperature 40 ℃ and fermentation time 25 h. The highest enzyme activity was 1002.25 u/ml when provided with the above culture ingredients and conditions. Then, β-mannanase was purified by centrifugation, deposition, dialysis and concentration. Characterization of purified β-mannanase were investigated. Results showed that the enzyme was stable between pH 4 to pH 8 and below 60 ℃, the optimal pH and temperature for enzyme activity were 5.0 and 60 ℃ respectively. Cu²⁺ and Co²⁺ had a remarkable influence on improving the activity of β-mannanase, while Hg²⁺ was the opposite.The fermentation maganification of β-mannanase produced by Bacillus circulans WXY-100 in fermentor was investigated. All operating parameters and indexes in the fermentation process were screened and optimized in a 50 L fermentor. As a result, the optimal fermentation process for Bacillus circulans WXY-100 with producing β-mannanase was achieved. This fermentation process will be very helpful for producing β-mannanase on industrialization.Finally, the possible application of fermentative products of Bacillus circulans WXY-100 as feed additives was studied. Body weight uniformity and anti-infection ability were used for evaluation of the effects of fermentative products. Studies showed that fermentative products had a significantly effect on improving body weight uniformity with about 25%, at the same time reducing mortality and improving feed efficiency accordingly. The results indicate that fermentative products of Bacillus circulans WXY-100 have a promising application as feed additive.