Isolation Of A Cellulase-producing Fungus And Optimization Of Fermentation Condition For Enzyme Production

Cellulase has been widely used in the paper industry, textile industry, food industry and feed industry, etc. Cellulose-decomposing strain is one of the most effective ways in cellulase production. There are many problems in production process, although the existing cellulase-producing strains provide plenty of cellulase resources, such as the low activity of β-glucosidase in Trichoderma reesei. Moreover, low production of enzyme, enzyme instability and high cost also limit the cellulase application. The high demand of cellulase makes the work that screening efficient cellulase-producing strain of great significance.A cellulose-decomposing strain was isolated from more than 20 soil samples from Dalian surrounding region. The strain was identified as Penicillium oxalicum by analyzing its 18SrDNA gene sequence, named the strains of Penicillium oxalicum JG.Basic growth characters of JG were studied. It can achieve the maximum enzyme production at 7th days. The optimal initial fermentation pH is about 2, demonstrated the resistance to acid of JG. Optimal carbon source, nitrogen source, metal ions was optimized by using single factor method, and the optimum component in shaking flask fermentation medium for JG is wheat bran as carbon source, soybean meal as nitrogen source, and adding a certain amount of K+.Furthermore, optimized the fermentation medium composition of JG using the response surface method (RSM), Filter paper activity (FPA)was employed as response value, three factors(carbon sources, nitrogen sources and pH) and 3 levels experiment were carried out. Based on the prediction of medium components, the optimum for maximum enzyme production are as followed:wheat bran 46.9 g/L, soybean meal 6.33 g/L, pH 1.5, measured actual FPA is 0.366 IU/mL.Effects of different kinds of surfactants on the enzyme production were carried out. The results showed that the lecithin has a great promoting action on the yield of cellulase. And using lecithin pretreatment wheat bran under acid condition, the reducing sugar yield can be greatly improved.Capacity of enzyme production from JG was verified in 5 L fermentation tank by liquid fermentation. Enlarged fermentation can shorten the enzyme production time from 7 days to 3 days. And compared with shaking flask fermentation, cellulase activity CBH, FPA, CMCase and BGL were improved 12%,37.3%,5.6%,20.3% respectively. Adding lecithin in fermentation tank increased cellulase activity of CBH, FPA, CMCase and BGL by 33.5%, 63%,8.3%,38.9% respectively, compared with no adding,. This is the evidence that the lecithin can be used as a Penicillium oxalicum JG optimal surfactant. The cellulase components was analyzed by SDS-PAGE, JG was producing acidic cellulase after preliminary judgment.