In vitro stimulation of rumen microbial fermentation by a rumen anaerobic fungal culture

Cultures of the rumen anaerobic fungus, Piromyces communis strain 22 culture (AFC), filtered AFC and autoclaved AFC were evaluated for their ability to influence cumulative gas production, cellulose digestion, microbial population and enzyme activities by mixed ruminal microorganisms in vitro. The addition of AFC, filtered AFC and autoclaved AFC caused a marked increase in gas production, especially showing the significant (P<0.05) increase by 50, 29 and 32% after fermentation for 24 h, respectively, compared with control. The similar responses of the three treatments were seen in the cellulose digestion. The addition of AFC also significantly (P<0.05) increased not only the numbers of total bacteria, cellulolytic bacteria and anaerobic fungi but also the enzyme activities of avicelase, carboxymethyl cellulase (CMCase) and xylanase compared with the control treatment. Moreover, the addition of fungal fermentation end-products (filtered and autoclaved AFC) also had some stimulatory effects on mixed rumen microorganisms. There may be several mechanisms involved in the positive responses of the addition of rumen fungal cultures and their end-products on the rumen fermentation and ecosystem. It is suggested that the positive responses be caused by the high fibrolytic enzyme addition from the fungal cultures and increased microbial population despite of the antagonistic relationship of fiber break down by rumen fungi to rumen bacteria and unknown inhibitor factors in the rumen fluids.