Pathways of propionate degradation by enriched methanogenic cultures.

A mixed methanogenic culture was highly enriched in a growth medium containing propionate as the sole organic carbon and energy source. With this culture, the pathways of propionate degradation were studied by use of C-radiotracers. Propionate was first metabolized to acetate, carbon dioxide, and hydrogen by nonmethanogenic organisms.

The influence of the sulphonic group on the biodegradability of n-alkylbenzene sulphonates.

1. Model compounds of the type p-n-alkylbenzene sulphonates, p-n-alkylbenzoic acids and phenylcarboxylic acids were tested for biodegradability. Bioassays were performed with unadapted mixed cultures (soil suspensions) using the Organization for Economic Cooperation and Development (OECD) screening test.

Characterization of an acetate-decarboxylating, non-hydrogen-oxidizing methane bacterium.

A methanogenic bacterium, commonly seen in digested sludge and referred to as the "fat rod" or Methanobacterium soehngenii, has been enriched to a monoculture and is characterized. Cells are gramnegative, non-motile and appear as straight rods with flat ends. They form filaments which can grow to great lengths.

Kinetic parameters and relative turnovers of some important catabolic reactions in digesting sludge.

The kinetics of propionate degradation, acetate splitting, and hydrogen consumption in digesting sludge were investigated in a lab-scale digester. At natural steady-state conditions, the acetate-splitting systems in well-digested sludge were about half saturated. Propionate-degrading systems were saturated to only 10 to 15%, and hydrogen removal was less than 1% of the maximum possible rate.

Influence of sulfide compounds on the metabolism of Methanobacterium strain AZ.

Various organic sulfides and inorganic sulfide were studied in respect to their effect on growth and methane production of Methanobacterium strain AZ. In mineral, sulfide-free medium, cysteine regulated the specific rate of methane production (optimum concentration = 5-10(-4) mole/1). A supplement of sulfide (10(-4) mole/1) caused an additional stimulation.