Comparison of Ethanol Degradation Pathways in Anoxic Freshwater Environments

Abstract

Pool sizes, turnover times and turnover rates of ethanol and acetate in anoxic sediments of Lake Mendota and Knaack Lake and in anoxic sewage digestor sludge were determined by gas chromatography-gas proportional counting techniques. Ethanol accounted for 6, 14 and 2.5 % of the total carbon flux to methane in these environments, respectively. The distribution of labelled carbon in the methane and carbon dioxide fractions obtained during incubation of the anoxic materials with C-1 and C-2 labelled acetate and ethanol revealed a significantly higher degree of randomization with ethanol than with acetate tracers, HPLC analysis of sediment pore water preparations revealed that labelled acetate and propionate were formed as intermediates of labelled ethanol degradation, whereas no labelled butyrate was detected. Addition of hydrogen to Knaack Lake sediment samples inhibited ethanol degradation drastically and led to a significant accumulation of labelled butyrate. The above findings together with the results of most probable number enumerations of anaerobic ethanol-degrading bacteria indicate that propionate-forming bacteria contributed significantly to ethanol degradation in Knaack Lake sediment and in sewage sludge.Abbretliation: MPN, most probable number. 0001-2015 0 1985 SGM

Development of monitoring and control technology based on trace gas monitoring. Final report

“…Formation of acetate and propionate was also observed in another study using an ethanolfermenting bacterium (Samain et al 1982). Addition of hydrogen inhibited ethanol degradation and resulted in an accumulation of 14C-labeled butyrate (Schink et al 1985). Fermentation of ethanol to acetate and propionate by Desulfobulbus was strongly inhibited by high hydrogen concentrations (Schink, et al 1987).…”

“…Propionate consumption via reactions 3 and 4 was energetically favorable during this period. Propionate could have been formed from acetate (reaction 6), propanol (reaction 7), or ethanol (Schink et al 1985).…”

“…As a result of this inhibition, more reduced products can build up as alternative electron sinks (Chung 1976;. CO is a metabolic intermediate involved in synthesis of carboxyl group of acetyl-coA and decarboxylation of acetate via CODH (Krzycki et al 1982;Stupperich et al 1983;Zeikus et al 1985;Eikmanns and Thauer 1984;Nelson and Ferry 1984;Krzycki and Zeikus 1984). Monitoring trace gases H2 and CO has attracted attention for anaerobic process monitoring due to the fact that they are relatively easy to measure, slightly soluble in water, sensitive, can be measured on-line, and have the potential of indicating metabolic status.…”

“…dreactions are referred to Acetate disproportionation to methane and C 0 2 can be described as a two-step reaction with CO as an intermediate: 1) acetate splitted to CO and CH,; 2) CO oxidized to CO, (Zeikus et al, 1985;Hickey et al 1987). Accumulation of CO could be the result of reversible equilibrium of CO between the liquid and gas phases.…”

Lab Testing and Field Implementation of Soil Flushing

“…In the ethanol-fed columns, most likely only bacteria in the first column had ethanol to utilize as an energy source with the next two columns having to use acetate, which is a potential ethanol metabolite ) that was not monitored in our study, or have no energy source. Previous research indicated that the predominant ethanol degradation pathway is through the production of propionate through succinate using the hydrogen released from the oxidation of acetate, which has a no net-yield of reducing equivalents Schink et al, 1985).…”