Degradation of the Cellulase of Ruminal Bacteria by the Protease of Coexisting Bacteria in vitro

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The degradation of cellulase by protease was examined by using the 3 major species of cellulolytic ruminal bacteria. In the culture of each of the cellulolytic bacteria, the coexistence of the 4 major species of proteolytic ruminal bacteria decreased the cellulolysis and cellulase activity. Liberated cellulase was much more readily degraded by the mixed protease from the 4 species of proteolytic bacteria than cell-bound cellulase. The activity of liberated cellulase was approximately 10 times higher than the cell-bound cellulase, suggesting that the degradation of cellulase is considerably large. In the co-culture of mixed cellulolytics with mixed proteolytics, cellulolysis was increased by the addition of insoluble soybean protein. Similarly, neutral detergent fiber (NDF) digestion was enhanced by insoluble protein in the continuous culture of the mixed microbiota from the rumen of a goat. These results could be explained by the binding of protease to insoluble protein, which decreased the binding of protease to cellulase. There was no significant difference between pH7.0 and 6.0 in the degradation of cellulase by mixed protease. However, the degradation in the presence of avicel was greater at pH6.0 than 7.0, probably indicating that avicel-bound cellulase is resistant to proteolysis and the binding to avicel decreases at pH6.0.
社団法人日本畜産学会の論文