EFFECT OF 2-BROMOETHANESULFONIC ACID AND PEPTOSTREPTOCOCCUS-PRODUCTUSATCC-35244 ADDITION ON STIMULATION OF REDUCTIVE ACETOGENESIS IN THE RUMINAL ECOSYSTEM BY SELECTIVE-INHIBITION OF METHANOGENESIS

Evidence is provided that reductive acetogenesis can be stimulated in ruminal samples during short-term (24-h) incubations when methanogenes is is inhibited selectively. While addition of the reductive acetogen Peptostreptococcus productus ATCC 35244 alone had no significant influ ence on CH4 and volatile fatty acid (VFA) production in ruminal sample s, the addition of this strain together with 2-bromoethanesulfonic aci d (BES) (final concentration, 0.01 or 0.03 mM) resulted in stimulation of acetic acid production and H-2 consumption. Since acetate producti on exceeded amounts that could be attributed to reductive acetogenesis , as measured by H-2 consumption, it was found that P. productus also fermented C-6 units (glucose and fructose) heterotrophically to mainly acetate (>99% of the total VFA). Using (CH3COOH)-C-14, we concluded t hat addition of BES and BES plus P. productus did not alter the consum ption of acetate in ruminal samples. The addition of P. productus to B ES-treated ruminal samples caused supplemental inhibition of CW, produ ction and stimulation of VFA production, representing a possible energ y gain of about 13 to 15%.