Screening Of Anaerobic Fungi For Production Of Fiber-Degrading Enzymes And Characterization Of The Crude Enzymes

Twelve anaerobic fungal strains were isolated and screened for xylanase and CMCase production. Effect of medium components on enzyme production and characterization of anaerobic fungal crude enzymes were also investigated. This thesis was described in the following three sections.In the first section, twelve anaerobic fungal strains isolated from rumen and faeces of ruminants were screened for xylanase and CMCase production. Isolate A4 identified as a Neocallimastix sp. had the highest activities of xylanase and CMCase among all isolates. With rice straw as fermentation substrates, the maximum activities of xylanase and CMCase by A4 were 13.54 U·mL-1, 0.25 U·mL-1, respectively. The dry matter loss of rice straw by A4 was 46.56%.In the second section, the effect of growth substrates and main components of the conventional medium on enzyme production by an anaerobic fungus A4 were investigated. With rice straw, corn straw, peanut straw and filter paper as fermentation substrates, the activities of xylanase by A4 were14.31 U·mL-1, 11.39 U·mL-1, 6.99 U·mL-1, 13.38 U·mL-1, respectively. The activities of CMCase by A4 were 0.25 U·mL-1, 0.15 U·mL-1, 0.13 U·rnL-1, 0.27 U·mL-1, respectively. The reduced level of cell-free rumen fluid had no significant effect on xylanase production, but had significant effect on the CMCase activity. Without cell-free rumen fluid, the high concentration level of yeast extract could improve xylanase and CMCase production.In the third section, crude enzymes produced by anaerobic fungus A4 was extracted, and their characteristics of the crude enzyme was also investigated. The optimal saturation of (NHU) 2SO4 for enzymes extraction was 70% at 20℃. After extraction and drying at 45℃, the specific activities of xylanase and CMCase were 7562 U·g-protein-1, 37.6 U·g-protein-1, respectively. The optimal temperature for xylanase activity was 50℃ and optimal pH in the range of 5.0-6.0. Xylanase activity was stable at 37℃-50℃ and at the range pH 4.0 to pH 11.0. The optimal temperature for CMCase activity was 50℃ and optimal pH was 6.0. CMCase activity was stable at 37℃-50℃ and in the range pH 5.0 to pH 11.0.