Screening, Characterization Of Cellulase Producer And Optimization Of Cellulase Production

Cellulosic enzymes have important applications in various fields including food processing; feed industry and biofuel production, therefore, development of efficient producer strains and cellulase production have attracted the attention of researchers worldwide.In this study, filamentous fungi and Strepotmycete strains were isolated from corn stover compost in Shanxi and marine sediment samples in Dalian, one of which showed superior cellulosic enzyme activity and was named M20. ITS sequence analysis showed that M20 the highest identity to that of Trichoderma viride. Fermentation broth of M20 exhibited good hydrolytic activities against not only filter paper, sodium carboxyl methyl cellulose, and cotton fiber, but also corn stover, lawn grass, fallen leaves, and Jerusalem artichoke stalk. The properties of the cellulosic enzymes were studied, and the cellulase production conditions were further optimized, the main results were listed below:The best elicitor of cellulase in M20 is microcrystalline cellulose, and the optimum final concentration is 0.5%. The best nitrogen source in replace of amino acid is peptone. At 28℃and when the initial pH value was 6, Filter Paper Activity (FPA) reached 9.2 IU/ml within 7 days. The optimum media composition was obtained by orthogonal design, and the highest FPA attained 9.89 IU/ml, with 12% increase comparing with the control. The optimum pH for enzyme reaction was 4.8 and the optimum temperature 50℃. The activity of the cellulase did not change significantly at 50℃within 2 weeks, while the enzyme activity was lowered significantly under the temperatures higher than 60℃.Next, celluase production was tested in a 5L fermentor. The results showed that FPA reached the highest value of 8 IU/ml within 6 days. Optimum operation condition was proved to be first cultivating at pH 4.8, after 2.5 days, changing the pH value to 6, and adding 5 g/L (final concentration) of microcrystalline cellulose on the 3rd day. Under this condition, the FPA reached the highest activity of 8 IU/ml in the 5th day.Hydrolysis of different lignocellulosic materials was carried out using the broth of M20, and the sugar release was investigated by HPLC. The results showed that corn stover contains highest amount of glucose and xylose, lawn grass released more glucose than Jerusalem artichoke stalks and fallen leaves. On the other hand, Jerusalem artichoke stalks released more xylose than fallen leaves and lawn grass.