Presence in rumen bacterial and protozoal populations of enzymes capable of degrading fungal cell walls.

Abstract

Ruminal bacteria and protozoa, and cell-free rumen fluid, were tested for the presence of enzymes involved in the degradation of the fungal cell wall. Protozoal homogenate obtained by ultrasonication showed chitinase (EC 3.2.1.14) and N-acetyl-beta-glucosaminidase (EC 3.2.1.52) activities when assayed with fluorogenic 4-methylumbelliferyl substrates. The chitinase activity was predominantly of the 'exo'-type. Lysozyme (EC 3.2.1.17) and 1,3-beta-glucanase (EC 3.2.1.39) activities were also present in this fraction. All these activities, except lysozyme activity, were recovered mainly in the supernatant fraction of the homogenate (approximately 85% of the total activity). Lysozyme showed the same amount of activity in the precipitate and supernatant fractions. Bacterial homogenates had N-acetyl-beta-glucosaminidase activity in both supernatant and precipitate fractions. The specific activity was one-third that of the protozoa. Bacteria able to grow in a medium with chitin as the sole carbon source were recognized and counted. Cell-free rumen fluid was unable to degrade any of the substrates tested.