Abstract.From anaerobic digestor sludge of a waste water treatment plant, a gram-negative, strictly anaerobic sulfate-reducing bacterium was isolated with acetone as sole organic substrate. The bacterium was characterized as a new species, Desulfocoecus biacutus. The strain grew with acetone with doubling times of 72 h to 120 h; the growth yield was 12.0 (+_2.1) g . [ m o l acetone] -1. Acetone was oxidized completely, and no isopropanol was formed. In labelling studies with 14CO2, cell lipids (including approx. 50% PHB) of acetone-grown cells became labelled 7 times as high as those of 3-hydroxybutyrate-grown cells. Enzyme studies indicated that acetone was degraded via acetoacetyl-CoA, and that acetone was channeled into the intermediary metabolism after condensation with carbon dioxide to a C4-compound, possibly free acetoacetate. Acetoacetyl-CoA is cleaved by a thiolase reaction to acetyl-CoA which is completely oxidized through the carbon monoxide dehydrogenase pathway. Strain K M R A c t S was deposited with the Deutsche Sammlung yon Mikroorganismen, Braunschweig, under the number DSM 5651.
A new mesophilic anaerobic cellulolytic bacterium, CM126, was isolated from an anaerobic sewage sludge digester. The organism was non-spore-forming, rod-shaped, Gram-negative and motile with peritrichous flagella. It fermented microcrystalline Avicel cellulose, xylan, Solka floc cellulose, filter paper, L-arabinose, D-xylose, beta-methyl xyloside, D-glucose, cellobiose and xylitol and produced indole. The % G + C content was 36. Acetic acid, ethanol, lactic acid, pyruvic acid, carbon dioxide and hydrogen were produced as metabolic products. This strain could grow at 20-44.5 degrees C and at pH values 5.2-7.4 with optimal growth at 37-41.5 degrees C and pH 7. Both endoglucanase and xylanase were detected in the supernatant fluid of a culture grown on medium containing Avicel cellulose and cellobiose. Exoglucanase could not be found in either supernatant fluid or the cell lysate. When cellulose and cellobiose fermentation were compared, the enzyme production rate in cellobiose fermentation was higher than in cellulose fermentation. The optimum pH for both enzyme activities was 5.0, the optimum temperature was 40 degrees C for the endoglucanase and 50 degrees C for the xylanase. Both enzyme activities were inhibited at 70 degrees C Co-culture of this organism with a Methanosarcina sp. (A145) had no effect on cellulose degradation and both endoglucanase and xylanase were stable in the co-culture.
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