Effect of the carbohydrate growth substrate on polysaccharolytic enzyme formation by anaerobic fungi isolated from the foregut and hindgut of nonruminant herbivores and the forestomach of ruminants

The effect of the carbohydrate growth substrate on polysaccharide-degrading enzyme formation by anaerobic fungi was examined using four strains of Piromyces isolated from hindgut fermenters, three Piromyces isolates from the pre-peptic forestomach of macropodid marsupials, and two ruminal isolates of Neocallimastix spp. The range of enzymes formed by the nine isolates was similar although, under the growth conditions examined, one hindgut isolate did not form amylolytic enzymes. The cellulolytic and xylanolytic enzyme profiles were the same: inter-strain differences in the levels of enzymic activity were apparent, but they were not related to either the genus or intestinal origin of the isolates. Pectin degrading enzymes were not detected in any of the isolates. The cellulolytic and xylanolytic enzymes were formed constitutively during growth on mono-, di- and polysaccharidic carbohydrates but the specific activities were both strain-and substrate-dependent. The activities were considerably lower in glucose-grown preparations of three of the fungi (one each from the hindgut, foregut and rumen) indicating that enzyme synthesis was repressed by glucose; enzyme formation by the other isolates studied was not controlled by catabolite regulatory mechanisms.