Effects of nitrogen oxides and denitrification by Pseudomonas stutzeri on acetotrophic methanogenesis by Methanosarcina mazei

Abstract

Nitrate and its reduced forms produced during denitrification, nitrite and nitrous oxide, were studied for their influence on methane production from acetate by Methanosarcina mazei. While 0.18 mM nitrite and 0.8% nitrous oxide in the gas phase completely suppressed methane production, 71.4 mM nitrate resulted in only 83.3% inhibition. Co-culture experiments showed that M. mazei growing with 15 mM nitrate produced methane from acetate until the denitrifying bacterium Pseudomonas stutzeri was inoculated and nitrate denitrification began. The presence of nitrous oxide in the gas phase after cessation of denitrification activity by P. stutzeri in co-cultures flasks prevented M. mazei resuming methane production. Nitrous oxide, instead of dinitrogen, was the end product of denitrification by P. stutzeri either in pure cultures or in co-cultures with M. mazei, probably because of the highly reduced culture conditions that were used. This study strongly suggests that acetatedependent methane production by M. mazei was inhibited by reduced nitrogen forms produced during bacterial nitrate denitrification, rather than by competition for acetate between denitrifying and methanogenic bacteria. These results are consistent with previous studies with H P /CO P methanogens. z 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V.

Simultaneous phosphorus, nitrogen and dinitrotoluene removals in batch anaerobic/anoxic/aerobic sequentials

“…This may be due to the competition for nitrate by denitrification by the presence of non-Poly-P denitrifiers. Also denitrifying phosphorus bacteria can use organic substrate directly for growth and nitrate as electron acceptor instead of PO 4 -P. This result agreed with the results obtained by Clarens et al [30], in which they reported that acetate decreased the P uptake and increased the denitrification. However, Ng et al [25] found that a net phosphorus uptake still occurred, which seemed to suggest that the influence of anoxic acetate was not very significant and high COD concentrations decreased the P uptake rates.…”

“…The feasibility of denitrification in an anaerobic digester has been established to be strongly dependent on the COD/NO 3 -N ratio and the nature of the carbon source [27]. Attempts to carry out denitrification and methane production in a completely mixed reactor have not proved very effective because nitrogen oxides are known to inhibit the methanogenic activity of bacteria [28][29][30]. The biofilter reactor system developed by Akunna et al [31] exhibits a denitrification activity at the bottom and methane production in the upper part, where NO 3 -N had been totally removed.…”

Toxicity of nitrite toward mesophilic and thermophilic sulphate-reducing, methanogenic and syntrophic populations in anaerobic sludge

“…Following the apparent suppression of SRB activity by nitrite at 50 ppm, effluent acetate levels decreased and effluent propionate and butyrate concentrations were reduced to non-detectable levels [16]. There was no indication, in this study, of inhibition of the syntrophic or methanogenic populations by nitrite, but toxic effects of nitrous oxides have been reported by other authors [2,8,9,17,19]. Kluber and Conrad [8] found that the addition of 5 mM (230 mg L À1 ) nitrite in batch tests on anoxic rice field soil resulted in complete inhibition of methanogenesis with concurrent elevated levels of acetate and propionate, for at least 24 days.…”

The roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of biomass to methane: a review

“…Several investigations have already been reported, which have covered the activity and the behaviour of the microbial communities in anaerobic biogas reactors running on various kind of substrates (Petersen and Ahring 1991;Hedrick et al 1992;Angelidaki and Ahring 1993;Raskin et al 1995;Ahring 1995;Chanakya et al 1997;Clarens et al 1998;Vavilin et al 1998;Oude Elferink et al 1998;Hansen et al 1999). In the following sections of this paper, the roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of particulate biomass to methane will be discussed, respectively, in view of the works recently published in literature.…”