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

摘要

Tile methanogenic activity in tile presence of Entodinium caudatum and Epidinium ecaudatum was well preserved after long-term cultivation. Microscopic observation revealed that methane production in tile 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 surlacc and their intracellular activity. Methane production per protozoan cell of 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 tire total methane production in tile E. ecaudatum culture. Decrease of digestibility of substrates and differentes in the fermentation end products accompanied the inhibition of methanogenesis in both cultures by pcnicillin G. streptomycin, chloramphenicol. 2-bromoethanesulfonatc. and pyromellitic diimide. E. caudatum appeared to be more sensitive than E. ecaudatum to tile compounds tested Hydrogen recoveries based on both volatile fatty acids and methane production suggested that tile methanogenic population appeared not to be fully able to consume hydrogen produced in tire protozoan cultures. The culture conditions tested were found to be suitable lot experiments on the relationship between rumen ciliates and rumen bacteria.