Methane fermentation of an apple pomace: Characteristics of a pectin.xylan degrading-anaerobic bacterium isolated from methane fermentation sludges
2006
Takeda, K.(Hirosaki Univ., Aomori (Japan). Faculty of Agriculture and Life Science) | Suda, I. | Tonouchi, A.
Methane fermentation was carried out with an upflow-anaerobic sludge blanket reactor. The sludge was made by acclimatizing paddy soil added as a seed culture with an apple pomace. Granulated sludge composed of coccoid, rods and filamentous bacteria was formed after 3 months incubation. Pectin. xylan degrading-anaerobic bacteria, strain AP81 was isolated from the methane fermentation sludge, which was acclimatized with apple pomace. The strain was motile with lateral flagella, Gram-negative, spore-forming strict anaerobes. The strain used a wide range of sugars containing glucose and xylose in addition to pectin and xylan and produced formate, acetate, lactate, ethanol, carbon dioxide and hydrogen as fermentation products. The GC content of DNA was 42 mol%. The 16S rDNA similarity of strain AP81 to Cl. aerotolerans was 97.9%. The strain is considered to be closely related to Cl. aerotolerans on the basis of its cell morphology and the phenotypic and phylogenetic characteristics. Strain AP81 used a wide range of sugars containing glucose or arabinose in addition to pectin and xylan, and produced a large amount of hydrogen in addition to ethanol and acetate as the main fermentation products. The growth of the strain was not suppressed by hydrogen produced by degrading of pectin and xylan. The production of ethanol, however, decreased, while that of acetate increased by the dual culture with a hydrogen-utilizing methanogen. It is suggested that the energy metabolism has an advantageous effect on the strain AP81 by the association with hydrogen-utilizing methanogens.
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