Factors affecting the cellulolytic activity of rumen contents.

The cellulolytic activity of rumen contents was assayed by measuring losses in weight and tensile strength of cotton yarn incubated in rumen contents in the presence of dietary additives (barley, tallow) and at different pH values. The addition of barley depressed cellulolysis and the titer of filter paper-degrading bacteria only if the pH was allowed to fall. Lowering the pH from 7.0 to 6.0 by addition of HCl almost completely inhibited attack of cotton and greatly reduced the titer of filter paper-degrading bacteria. The layering of tallow on cotton inhibited attack of cotton but did not decrease the titer of filter paper-degrading bacteria. The results are discussed with special reference to the importance of the study of cellulosic substrates, which require a known enzyme or mixture of enzymes for attack.