The characteristics of a new non-spore-forming cellulolytic mesophilic anaerobe strain CM126 isolated from municipal sewage sludge

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, β-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°C and at pH values 5·2–7·4 with optimal growth at 37–41·5°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°C for the endoglucanase and 50°C for the xylanase. Both enzyme activities were inhibited at 70°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.