Kinetics of Phenol Biodegradation by an Immobilized Methanogenic Consortium

Abstract

A phenol-degrading methanogenic enrichment was successfully immobilzed in agar as shown by the stoichiometric conversion of phenol to CH4 and CO2. The enrichment contained members of three physiological groups necessary for the syntrophic mineralization of phenol: a phenol-oxidizing bacterium, a Methanothrixlike bacterium, and an H2-utilizing methanogen. The immobilization technique resulted in the cells being embedded in a long, thin agar strand (1 mm in diameter by 2 to 50 cm in length) that resembled spaghetti. Immobilization had three effects as shown by a comparative kinetic analysis of phenol degradation by free versus immobilized cells. (i) The maximum rate of degradation was reduced from 14.8 to 10.0 ,ug of phenol per h; (ii) the apparent Km for the overall reaction was reduced from 90 to 46 ,ug of phenol per ml, probably because of the retention of acetate, H2 and CO2 in the proximity of immobilized methanogens; and (iii) the cells were protected from substrate inhibition caused by high concentrations of phenol, which increased the apparent Ki value from 900 to 1,725 ,ug of phenol per ml. Estimates for the kinetic parameters Ki, Ki, and Vmax were used in a modified substrate inhibition model that simulated rates of phenol degradation for given phenol concentrations. The simulated rates were in close agreement with experimentally derived rates for both stimulatory and inhibitory concentrations of phenol.

Kinetics of Phenol Degradation in an Anaerobic Fixed‐Biofilm Process

“…Phenol-utilizing bacteria (PUB) are responsible for converting phenol to acetate and H 2 . In addition, two types of methane-producing bacteria (MPB) complete the process: A methanothrix-like organism converts acetate to CH 4 and CO 2 ; and a Methano bacterium formicicum grows on H 2 and CO 2 to produce methane (Dwyer et al, 1986).…”

“…The enrichments of PUB and MPB were grown at 358C under stationary conditions. Every 2 days, approximately 2 mM of phenol was added to the enrichment of PUB and 2 mM of acetate was added to the enrichment of MPB (Dwyer et al, 1986). There was no gas production during the enrichment of phenol-utilizing bacteria.…”

Utilizing pyrolysis GC-MS to characterize organic matter quality in relation to methane production in a thermokarst lake sediment core

“…While anaerobic mineralization of phenolic compounds has not been observed in these natural aquatic ecosystems, anaerobic microbial processing of phenols to CO2 and CH4 has been documented in wastewater treatment studies (e.g. Dwyer et al, 1986;Young and Rivera, 1985;Fang and Zhou, 1999). Since methanogens do not directly metabolize phenolic compounds (Wolfe, 1971), anaerobic conversion of phenolic compounds to CH4 requires a multistep process.…”

“…Phenolic compounds are initially converted to benzoate (C7H5O2 -), which is subsequently converted into intermediate fatty acids, then acetate (C2H3O2 -) and H2, and finally CH4 (Fang and Zhou, 1999). This process requires syntrophic association between phenol-oxidizing bacteria, Methanothrix-like bacteria and H2utilizing methanogens (Dwyer et al, 1986).…”

Effects of bioaugmentation strategies in UASB reactors with a methanogenic consortium for removal of phenolic compounds

“…These reactors initially contained 500 mL of supplemented Boyd's medium and were inoculated with 60 mL of the consortium described previously (Tawfiki et al, 1999). A volume of 200 mL of the supplemented Boyd's medium containing 150 mg/L of phenol, 150 mg/L of p-cresol, and 100 mg/L of o-cresol was added to the reactors every 5 d. The transfer of the medium and harvesting of the cells were made under anaerobic conditions with anaerobic gases as described by Dwyer et al (1986). Typically, 5 L of the culture were centrifuged at 6000g for 15 min.…”