Methanogenesis in rumen ciliate cultures of Entodinium caudatum and Epidinium ecaudatum after long-term cultivation in a chemically defined medium

The methanogenic activity in the presence of Entodinium caudatum and Epidinium ecaudatum was well preserved after long-term cultivation Microscopic observation revealed that methane production in the presence of E. caudatum was probably caused by their intracellular methanogenic activity, while methane production in the presence of E. ecaudatum f. caudatum et ecaudatum could be atributed to both the methanogenic bacterial fraction of their external surface and their intracellular activity. Methane production per protozoan cell or E caudatum and E. ecaudatum was 2.1 nmol per cell per d and 6.0 nmol per cell per d, respectively E. caudatum, was responsible for almost the entire methane production in the culture, The activity of free methanogens constituted approximately 50 % of the total methane production ill the E, ecaudatum culture. Decrease of digestibility of substrates and differences in the ii fermentation end products accompanied the inhibition of methanogenesis in both cultures by penicillin G. streptomycin. chloramphenicol. 2-bromoethanesulfonate, and pyromellitic diimide E caudatum appeared to he more sensitive than E. ecaudatum to the compounds tested. Hydrogen recoveries based on both volatile fatty acids and methane production suggested that the methanogenic population appeared riot to be fully able to consume hydrogen produced in thr protozoan cultures The culture conditions tested were found to be suitable ibr experiments on thr relationship between rumen ciliates and rumen bacteria.