Optimization of cultural conditions for thermostable beta-1,3-1 ,4-glucanase production by Bacillus subtilis ZJF-1A5

摘要

The optimization of cultural conditions for beta- glucanase production by Bacillus subtilis ZJF-1A5 was investigated in flask trials. Temperature had great effect on beta-glucanase production which maximized at optimal temperature of 37 deg C and decreased significantly when temperature was over 37 deg C. Charge quantity affected beta-glucanase production significantly. Adding oxygen vector N-dodecane or acetic ether benefited beta-glucanase production, but it depended on the concentration and charge quantity. The results of fractional factorial design showed that age and size of inoculum and shaking speed were the key factors affecting beta-glucanase production and the cultivation time span to reach the highest beta-glucanase activity. The optimal cultural conditions for P-glucanase production obtained with CCD were as follows: inoculum age and size (16 h, 3.82 percent (v/v)), shaking speed 210 r/min, charge quantity of 30 mL in 250 mL flask and initial pH 7.0, cultured at 37 deg C for 50 h. Repeated experimental results accorded with those predicted by a second-order polynomial model. The amount of beta-glucanase, alpha-amylase and neutral protease produced by B subtilis ZJF-1A5 was associated partially with cell growth. Those three enzymes' activities increased following the cell growth and increased significantly when cells entered the stationary phase.