Fermentation of soluble sugars by anaerobic holotrich ciliate protozoa of the genera Isotricha and Dasytricha

Abstract

Suspensions of virtually bacteria-free and starved holotrich ciliates separated from sheep''s rumen contents, containing I. prostoma, I. intestinalis and D. ruminantium, produced acids and gas at a rapid rate under anaerobic conditions from the following soluble carbohydrates: glucose, fructose, sucrose, raffinose, inulin, rye-grass levan and, to a much lesser degree, cellobiose. No other soluble carbohydrate was attacked. Glucose was not attacked in presence of 02. The relatively high concn. of streptomycin used to kill bacteria associated with the protozoa had little effect upon the viability or fermentative activity of the latter. The fermentation products from glucose were lactic, acetic, propionic (traces) and butyric acids, CO2 and H2. Soluble nitrogenous compounds, which were not ammonia, urea or amino acids, were also produced. In the first 3 hrs. the starved ciliates stored more glucose as polysaccharide than was fermented to acids. The endogenous fermentative activity of the ciliates containing storage glucosan yielded lactic, acetic and butyric acids. Glucose fermentation did not extensively suppress the endogenous fermentation of storage polysaccharide. The use of CO2 instead of N2 in the gas phase had little apparent effect upon the protozoan glucose fermentation. The importance of these ciliates as fermentative agents in the rumen is dis-cussed.