Showing papers by "Roderick I. Mackie published in 1981"

Metabolic Activity of Fatty Acid-Oxidizing Bacteria and the Contribution of Acetate, Propionate, Butyrate, and CO2 to Methanogenesis in Cattle Waste at 40 and 60°C

Abstract: The quantitative contribution of fatty acids and CO2 to methanogenesis was studied by using stirred, 3-liter bench-top digestors fed on a semicontinuous basis with cattle waste The fermentations were carried out at 40 and 60°C under identical loading conditions (6 g of volatile solids per liter of reactor volume per day, 10-day retention time) In the thermophilic digestor, acetate turnover increased from a prefeeding level of 16 μM/min to a peak (49 μM/min) 1 h after feeding and then gradually decreased Acetate turnover in the mesophilic digestor increased from 15 to 40 μM/min Propionate turnover ranged from 2 to 52 and 15 to 45 μM/min in the thermophilic and mesophilic digestors, respectively Butyrate turnover (07 to 12 μM/min) was similar in both digestors The proportion of CH4 produced via the methyl group of acetate varied with time after feeding and ranged from 72 to 75% in the mesophilic digestor and 75 to 86% in the thermophilic digestor The contribution from CO2 reduction was 24 to 29% and 19 to 27%, respectively Propionate and butyrate turnover accounted for 20% of the total CH4 produced Acetate synthesis from CO2 was greatest shortly after feeding and was higher in the thermophilic digestor (05 to 24 μM/min) than the mesophilic digestor (03 to 05 μM/min) Counts of fatty acid-degrading bacteria were related to their turnover activity

Syntrophic association of a butyrate-degrading bacterium and methanosarcina enriched from bovine rumen fluid.

Abstract: An anaerobic butyrate-degrading bacterium, morphologically similar to Syntrophomonas wolfei, was isolated in coculture with Desulfovibrio strain G11 from an enrichment of bovine rumen fluid. A Methanosarcina species was the major H2-using organism in the enrichment. The results are discussed in relationship to the absence of Methanospirillum hungatei, the H2-using methanogen usually found in association with S. wolfei, and the finding of Methanosarcina rather than Methanobrevibacter ruminantium as the major H2-using bacterium in the enrichments. The finding of butyrate degraders in the rumen suggests that, if the retention time of the rumen contents becomes more prolonged, butyrate and longer-chained fatty acids might be significantly degraded.