Methanogenesis in a thermophilic (58/sup 0/C) anaerobic digestor: methanothrix sp. as an important aceticlastic methanogen

Journal Article · Sun Apr 01 04:00:00 EST 1984 · Appl. Environ. Microbiol.; (United States)

OSTI ID:6432213

Zinder, S H; Cardwell, S C; Anguish, T; Lee, M; Koch, M

Aceticlastic methanogens and other microbial groups were enumerated in a 58/sup 0/c laboratory-scale anaerobic-digestor which was fed air-classified municipal refuse, a lignocellulosic waste. Two week after start-up, Methanosarcina sp. was present in high numbers (10/sup 5/ to 10/sup 6/ CFU/ml) and autofluorescent Methanosarcina like clumps were abundant in sludge examined by using epifluorescence microscopy. After about 4 months of digestor operation, numbers of Methanosarcina sp. dropped 2 to 3 orders of magnitude and large numbers of a thermophilic aceticlastic methanogen morphologically resembling Methanothrix sp. were found. Methanothrix sp. had apparently displaced Methanosarcina sp. as the dominant, aceticlastic methanogen in the digestor. During the perid when Methanothrix sp. was apparently dominant, acetate concentration varied between 0.3 and 1.5 ..mu..mol/ml during the daily feeding cycle, and acetate was the precursor of 63 to 66% of the methane produced during peak digestor methanogenesis. The apparent K/sub m/ value obtained for methanogenesis from acetate, 0.3 ..mu..mol/ml, indicated that the aceticlastic methanogens were nearly saturated for substrate during most of the digestor cycle. CO/sub 2/-reducing methanogens were capable of methanogenesis at rates more than 12 times greater than those usually found in the digestor. Added propionate (4.5 ..mu..mol/ml) was metabolized slowly by the digestor populations and slightly inhibited methanogenesis. Added n-butyrate, isobutyrate, or n-valerate (4.5 ..mu..mol/ml each) were broken down within 24 h. Isobutyrate was oxidized to acetate, a novel reaction possibly involving isomerization to n-butyrate. The rapid growth rate and versatile metabolism of Methanosarcina sp. make it a likely organism to be involved in start-up whereas the low K/sub m/ value of Methanothrix sp. for acetate may cause it to be favored in stable digestors operated with long retention times. 49 references.

• Research Organization: Cornell Univ., Ithaca, NY
• DOE Contract Number: AC02-81ER10872
• OSTI ID: 6432213
• Journal Information: Appl. Environ. Microbiol.; (United States), Journal Name: Appl. Environ. Microbiol.; (United States) Vol. 47:4; ISSN AEMID
• Country of Publication: United States
• Language: English

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ACETATES
ANAEROBIC DIGESTION
BACTERIA
BIOCONVERSION
CARBOXYLIC ACID SALTS
DIGESTION
GROWTH
KINETICS
MANAGEMENT
METABOLISM
METHANOGENIC BACTERIA
MICROORGANISMS
MUNICIPAL WASTES
PROCESSING
THERMOPHILIC CONDITIONS
WASTE MANAGEMENT
WASTE PROCESSING
WASTES