The amylase activity of 14 species of entodiniomorphid protozoa and the distribution of amylase in rumen digesta fractions of sheep containing no protozoa or one of seven different protozoal populations

Abstract

The amylolytic activity of the cytoplasmic fraction prepared from 14 single species of rumen ciliate protozoa and two natural mixed populations has been determined using five different assays. All the protozoa contained an a-amylase and the major product of amylose digestion was maltose. The highest activities were found in Eremoplastron bovis, Diploplastron affine, Ophryoscolex caudatus and Polyplastron multivesiculatum grown in vitro on grass and wholemeal flour and the lowest in Ostracodinium obtusum bilobum and Diplodinium pentacanthum under all growth conditions and in cultured Entodinium bursa and E. caudatum. The maximum activities depended on the substrate and with Eremoplastron bovis varied from 2·3 (with starch grains) to 48·8 (with amylose) μtmol maltose produced/mg protein per h.The distribution of amylase between various rumen fractions has been determined at three times after feeding in sheep containing no ciliate protozoa or seven different protozoal populations. A method to give maximal release of the enzyme from mixed rumen bacteria was devised and three different assay methods were compared. The total rumen amylase varied by up to 2·6 times and was highest in animals that contained only Entodinium caudatum or natural A- or B-type populations. The distribution of amylase activity between rumen fractions varied considerably with the various protozoal populations, that in the protozoal cytoplasm being highest in animals containing Epidinium ecaudatum caudatum (46–53%) and the natural A- and B-type populations (35–57 %) and lowest in the animals containing no protozoa (3–11 %) or only Ostra-codinium obtusum bilobum (6–21%). The reverse was true for the activity in the bacterial fraction which contained little activity in animals with natural A- and B-type populations and over 58% of the total activity in an animal containing only Entodinium caudatum. The lowest activities in all fractions were obtained 1·5 h after feeding. Comparatively little activity was found in the plant debris or clarified rumen fluid fractions from any animal. Using results obtained previously the ratios of carboxymethylcellulase to amylase activities have been calculated and shown to be highest in the protozoal cyto-plasmic fraction of Diplodinium pentacanthum and Ostracodinium obtusum bilobum and lowest in Entodinium spp., Diploplastron affine and Eremoplastron bovis.