Optimization of β-Mannanase Production from Bacillus licheniformis TJ-101 Using Response Surface Methodology

Plackett-Burman design, central composite design and response surface analysis were carried out with the aim of optimizing culture conditions for β-mannanase production from Bacillus licheniformis TJ-101. Screening experiments of Plackett-Burman design were firstly employed to evaluate the effects of 16 variables on β-mannanase production. The four identified significant variables, i.e. the concentration of Na 2 HPO 4 , the concentration of KH 2 PO 4 , initial pH and medium volume, were further optimized by central composite design and response surface analysis. The optimum values of four critical variables were determined as Na 2 HPO 4 6.4 g L -1 , KH 2 PO 4 0.36 g L -1 , initial pH 7.7 and medium volume V = 30.1 mL. Under these conditions, the β-mannanase activity can experimentally reach a = 523.1±5.9 U mL -1 (127.7 % increase compared with the enzyme activity before optimization) at the flask level. Moreover, oxygen limitation and initial pH remarkably affected β-mannanase production from Bacillus licheniformis TJ-101 as revealed by response surface analysis. Maximum β-mannanase activity increased by 73.7 % in a 6.6 L fermenter using the optimized medium and dissolved oxygen at 20 % saturation.