An ecological and physiological study on acetogenesis as an alternative to methanogenesis in the rumen

Paolo Boccazzi, Purdue University

Abstract

Methanogenesis is a predominant fermentation reaction in the gut ecosystem of ruminants. A functional replacement of methanogenesis with acetogenesis in the rumen could potentially decrease energy losses and increase the efficiency of ruminant production. Hydrogen limited continuous cultures, at pH 6.0, were used to isolate over 40 potentially acetogenic bacteria from ruminal contents of a fistulated dairy cow. The dairy cow was at mid-lactation, consuming a 56% hay and 44% corn silage-concentrate diet. Eight bacterial isolates had the ability to grow on CO$\sb2$ and H$\sb2$ as their sole carbon and energy source producing acetate as the main end product. Batch and continuous cultures were used to study acetogenesis as a functional alternative to methanogenesis in the rumen. In batch culture experiments, acetogen strains G1.5a, G2.4a, G3.2a, A10, and 3H were able to reduce H$\sb2$ concentrations in ruminal contents in the presence of BES, an inhibitor of methanogenesis. In two continuous culture experiments, the acetogen strains G3.2a and/or A10 did not reduce H$\sb2$ concentrations in ruminal contents in the presence of BES. Batch culture studies indicated that acetogens could function as an alternative electron sink to methanogens under some conditions. However, continuous culture studies indicated that not all factors affecting the ability of acetogens to functionally replace methanogens are understood in vitro and much less in vivo.

Degree

Ph.D.

Advisors

Patterson, Purdue University.

Subject Area

Microbiology|Livestock

COinS