The effects of co-cultivation with the acetogen Acetitomaculum ruminis on the fermentative metabolism of the rumen fungi Neocallimastix patriciarum and Neocallimastix sp. strain L2

The effects of co-cultivation with the hydrogen-utilizing acetogenic bacterium Acetitomaculum ruminis on the fermentative activities of the rumen fungi Neoccallimastix patriciarum or Neocallimastix sp. L2 were investigated. In both co-cultures acetate production increased, making it the predominant fermentation product, as the accumulation of lactate, formate, ethanol, H₂ and (in the case of Neocallimastix sp. L2) succinate all decreased. The effects of co-cultivation with Methanobrevibacter smithii were more pronounced. Decreased activities of lactate dehydrogenase, alcohol dehydrogenase and (in the case of Neocallimastix sp. L2) fumarate reductase accompanied the shift in fermentation product formation. The rate of glucose utilization and the fungal biomass yield were also increased in the co-culture.