EFFECT OF THE ADDITION OF PEPTOSTREPTOCOCCUS PRODUCTUS ATCC-35244 ON REDUCTIVE ACETOGENESIS IN THE RUMINAL ECOSYSTEM AFTER INHIBITION OF METHANOGENESIS BY CELL-FREE SUPERNATANT OF LACTOBACILLUS-PLANTARUM-80

The addition of the cell-free supernatant of Lactobacillus plantarum 8 0 (LP80) to ruminal samples during short-term batch experiments (24 h) led to significant increases in volatile fatty acid (VFA) production (5-30%) and to significant decreases in CH4 production (5-15%), accomp anied by H-2 accumulation. The supplemental addition of the reductive acetogen Peptostreptococcus productus ATCC35244 gave rise to an additi onal increase in VFA production, while CH4 production was decreased fu rther (p < 0.01) and H-2 accumulation was abolished. The addition of P . productus without the addition of supernatant had no effect on the f ermentation patterns. The utilization of H-2, the lowering of the H-2 recovery (2Hr) value and the high acetate production observed in the e xperiment indicated that both the addition of either the supernatant o r the addition of the supernatant and P. productus stimulated reductiv e acetogenesis. The persistence of the obtained effects was further ev aluated in vitro by incubation of rumen contents under pH control (6.4 -6.6) during 72 h, Compared to short-term batch experiments, the stimu lation of VFA production was lower (8-15%), while inhibition of CH4 pr oduction was higher (18-30%). These effects became manifest during the first 24 h of incubation and persisted during the 72 h incubation per iod. Infusion of both supernatant of LP80 and P. productus in the rume n of two rumen fistulated rams revealed that during the first days of administration, the addition of supernatant and P. productus decreased methanogenesis much more strongly than was observed in vitro (80%), w hereas no clear effect on fermentation rate or patterns was observed. However, the effect was only transient, since at the sixth day of the administration period methanogenesis was again at the same level as du ring the control period. These results indicate that the supernatant o f LP80 contains compounds which inhibit methanogenesis in the rumen, b ut that either resistance to the compound, or stimulation of rumen mic robial breakdown of these compounds had occurred. Also, the ability to stimulate reductive acetogenesis by additional introduction of P. pro ductus was only important during short-term incubations, while the eff ect diminished during long-term in vitro incubations or disappeared in vivo. (C) 1998 Elsevier Science B.V.