Denitrification with methane as electron donor in oxygen-limited bioreactors |
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Authors: | C Costa C Dijkema M Friedrich P García-Encina F Fernández-Polanco A J M Stams |
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Institution: | (1) University of Salamanca, Chemical Engineering Department, Plaza de la Merced s/n, 37008 Salamanca, Spain, ES;(2) Wageningen University, Laboratory of Molecular Physics, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands, NL;(3) Max-Planck-Institute for Terrestrial Microbiology, Karl-von-Frisch Strasse, 35043 Marburg, Germany, DE;(4) University of Valladolid, Chemical Engineering Department, Prado de la Magdalena s/n, 47005 Valladolid, Spain, ES;(5) Wageningen University, Laboratory of Microbiology, Hesselink van Suchtelenweg 4, 6703 CT Wageningen, The Netherlands e-mail: fons.stams@algemeen.micr.wau.nl Tel.: +31-317-483101 Fax: +31-317-483829, NL |
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Abstract: | The microbial population from a reactor using methane as electron donor for denitrification under microaerophilic conditions
was analyzed. High numbers of aerobic methanotrophic bacteria (3 107 cells/ml) and high numbers of acetate-utilizing denitrifying bacteria (2 107 cells/ml) were detected, but only very low numbers of methanol-degrading denitrifying bacteria (4 104 cells/ml) were counted. Two abundant acetate-degrading denitrifiers were isolated which, based on 16S rRNA analysis, were
closely related to Mesorhizobium plurifarium (98.4% sequence similarity) and a Stenotrophomonas sp. (99.1% sequence similarity). A methanol-degrading denitrifying bacterium isolated from the bioreactor morphologically
resembled Hyphomicrobium sp. and was moderately related to H. vulgare (93.5% sequence similarity). The initial characterization of the most abundant methanotrophic bacterium indicated that it
belongs to class II of the methanotrophs. “In vivo”13C-NMR with concentrated cell suspensions showed that this methanotroph produced acetate under oxygen limitation. The microbial
composition of reactor material together with the NMR experiments suggest that in the reactor methanotrophs excrete acetate,
which serves as the direct electron donor for denitrification.
Received: 19 October 1999 / Received revision: 11 January 2000 / Accepted: 14 January 2000 |
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