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Schlagwörter:
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Zusammenfassung:
Anaerobic digestion is a widely applied technology for sewage sludge
treatment. Hydrogen and CO2 are important degradation products, which
serve as substrates for both hydrogenotrophic methanogenesis and
chemolithotrophic acetogenesis. In order to understand the competition
between these processes for H-2/CO2, sludge samples were incubated under
H-2/CO2 headspace at different temperatures, and analyzed with respect
to turnover of H-2, CO2, CH4 and acetate including their delta C-13
values. At 15 degrees C, C-13-depleted acetate (delta C-13 of -41 to -43
parts per thousand) and transient acetate accumulation were observed
under H-2/CO2, and CH4 accumulated with delta C-13 values increasing
from -53 to -33 parts per thousand. The copy numbers of the fhs gene,
which is characteristic for acetogenic bacteria, were at 15 degrees C
one order of magnitude higher in the H-2/CO2 incubations than the N-2
control. At 30 degrees C, however, acetate did not accumulate in the
H-2/CO2 incubation and the delta C-13 of CH4 was very low (-100 to -77
parts per thousand). At 50 degrees C, isotopically enriched acetate was
transiently formed and subsequently consumed followed by the production
of C-13-depleted CH4. Collectively, the results indicate a high
contribution of chemolithotrophic acetogenesis to H-2/CO2 utilization at
15 degrees C and 50 degrees C, while H-2/CO2 was mainly consumed by
hydrogenotrophic methanogenesis at 30 degrees C. Fermentative production
and methanogenic consumption of acetate were active at 50 degrees C.
