Abstract: Megasphaera elsdenii is one of dominant bacteria in the rumen. In according to the characteristic of energy metabolism for the ruminant, that is energy supply through the volatile fatty acids such as acetate, propionate, butyrate generated by fermentation of microorganism in rumen, and the theory of ruminal fermentated regulation, which is mainly to regulate the degradation of lactate and the production of propionate. Primary substrates (lactic acid and pyruvate) were cocultured with H6 and TnH6 for 48 h, respectively, in order to observe the fermentation of ruminal fluid in vitro. Culture fluid was sampled for analysis of pH and VFA. The results showed that the lactate in the culture fluid was utilized by the strains of H6 and TnH6. Compared to strains H6, the acetate concentrations and the ratio of acetate to propionate were obviously reduced in the culture fluid of the strain TnH6, even though the concentration of propionate was slightly reduced. The results suggested that the transponed engineering bacteria TnH6 belonged to a deleted strain of acetic acid-producing gene and it could lay a foundation of developing a new micro ecosystem preparation for prevention and control of the diseases in periparturient dairy cows.

Key words: Megasphaera elsdenii; lactic fermentation; metabolic characteristics