Effects of acetate, propionate, and butyrate on the thermophilic anaerobic degradation of propionate by methanogenic sludge and defined cultures

Abstract

The effects of acetate, propionate, and butyrate on the anaerobic thermophilic conversion of propionate by methanogenic sludge and by enriched propionate-oxidizing bacteria in syntrophy with Methanobacterium thermoautotrophicum AH were studied. The methanogenic sludge was cultivated in an upflow anaerobic sludge bed (UASB) reactor fed with propionate (35 mM) as the sole substrate for a period of 80 days. Propionate degradation was shown to be severely inhibited by the addition of 50 mM acetate to the influent of the UASB reactor. The inhibitory effect remained even when the acetate concentration in the effluent was below the level of detection. Recovery of propionate oxidation occurred only when acetate was omitted from the influent medium. Propionate degradation by the methanogenic sludge in the UASB reactor was not affected by the addition of an equimolar concentration (35 mM) of butyrate to the influent. However, butyrate had a strong inhibitory effect on the growth of the propionate-oxidizing enrichment culture. In that case, the conversion of propionate was almost completely inhibited at a butyrate concentration of 10 mM. However, addition of a butyrate-oxidizing enrichment culture abolished the inhibitory effect, and propionate oxidation was even stimulated. All experiments were conducted at pH 7.0 to 7.7. The thermophilic syntrophic culture showed a

High-Rate Anaerobic Treatment of Wastewater at Low Temperatures

“…Because acetate was accumulated during propionate degradation ( Fig. 4 and 6), and propionate oxidizers are sensitive to changes in environmental conditions (3), their growth might have been inhibited by acetate (24), due to the low activity of acetoclastic methanogens at low temperatures. Contrary to propionate oxidizers, the butyrate-oxidizing organisms grew very well, even in the first module.…”

Analysis of the Syntrophic Anaerobic Digestion of Volatile Fatty Acids Using Enriched Cultures in a Fixed‐Bed Reactor

“…The pH, concentration of volatile suspended solid (VSS), and concentration of total suspended solid (TSS) of the granular sludge were 7.4, 67.2 g/L, and 92.4 g/L, respectively. The minimal medium containing 0.6 g/L monopotassium phosphate (KH 2 PO 4 ), 1.33 g/L disodium hydrogen phosphate (Na 2 HPO 4 ), 0.3 g/L ammonium chloride (NH 4 Cl), 0.11 g/L calcium chloride and water (CaCl 2 ?H 2 O), 0.1 g/L magnesium chloride and water (MgCl 2 ?6H 2 O), 4.0 g/L sodium bicarbonate (NaHCO 3 ), 0.025 g/L sodium sulfide (Na 2 -S?9H 2 O), 0.45 g/L ferric chloride (FeCl 2 ), 0.04 g/L boric acid (H 3 BO 4 ), 0.032 g/L zinc chloride (ZnCl 2 ), 0.0063 g/L copper chloride (CuCl 2 ), 0.0295 g/L manganese chloride (MnCl 2 ), 0.0305 g/L phosgene (CoCl 2 ), 0.0062 g/L nickel chloride (NiCl 2 ), 0.05 g/L cysteine hydrochloride, and 0.05 g/L yeast extract was used to enrich the anaerobes (Stams et al, 1992;van Lier et al, 1993). The medium cultures were prepared with distilled water.…”

Syntrophism among Prokaryotes

“…Its impor tance may be even higher with, e.g., isovalerate degradation, since three molecules of acetate and only one hydrogen molecule are formed ( > Table 21.3). Indeed, inhibition by acetate accu mulations or by addition of acetate has been reported for syntrophic degradation of fatty acids and for benzoate (Ahring and Westermann 1988;Fukuzaki et al 1990;van Lier et al 1993;Warikoo et al 1996;Schöcke and Schink 1997).…”