Anaerobic degradation of acetone by Desulfococcus biacutus spec. nov.

Abstract

Abstract.From anaerobic digestor sludge of a waste water treatment plant, a gram-negative, strictly anaerobic sulfate-reducing bacterium was isolated with acetone as sole organic substrate. The bacterium was characterized as a new species, Desulfocoecus biacutus. The strain grew with acetone with doubling times of 72 h to 120 h; the growth yield was 12.0 (+_2.1) g . [ m o l acetone] -1. Acetone was oxidized completely, and no isopropanol was formed. In labelling studies with 14CO2, cell lipids (including approx. 50% PHB) of acetone-grown cells became labelled 7 times as high as those of 3-hydroxybutyrate-grown cells. Enzyme studies indicated that acetone was degraded via acetoacetyl-CoA, and that acetone was channeled into the intermediary metabolism after condensation with carbon dioxide to a C4-compound, possibly free acetoacetate. Acetoacetyl-CoA is cleaved by a thiolase reaction to acetyl-CoA which is completely oxidized through the carbon monoxide dehydrogenase pathway. Strain K M R A c t S was deposited with the Deutsche Sammlung yon Mikroorganismen, Braunschweig, under the number DSM 5651.

Molecular characterization of mesophilic and thermophilic sulfate reducing microbial communities in expanded granular sludge bed (EGSB) reactors

“…Average substrate removal by the MR exceeded 95% during the various periods of operation with ethanol alone or with a mixture of citric acid, isopropanol (IPA) and polyethylene glycol (PEG, M n 300), with the exception of IPA which was partially degraded to acetone. This finding is in agreement with studies reporting the ability of a number of sulfate-reducing bacteria (Janssen and Schink 1995b;Platen et al 1990) and methanogenic archaea (Garcia 1990) to oxidize IPA to acetone. IPA (Davies and Stephenson 1941; Widdel 1986) and acetone (Ensign et al 1998;Platen et al 1990;Schink 1987, 1989) can serve as growth-supporting substrates for a number of diverse anaerobic microorganisms.…”

“…This finding is in agreement with studies reporting the ability of a number of sulfate-reducing bacteria (Janssen and Schink 1995b;Platen et al 1990) and methanogenic archaea (Garcia 1990) to oxidize IPA to acetone. IPA (Davies and Stephenson 1941; Widdel 1986) and acetone (Ensign et al 1998;Platen et al 1990;Schink 1987, 1989) can serve as growth-supporting substrates for a number of diverse anaerobic microorganisms. The factors responsible for the poor removal of both compounds by the microbiota in the sulfate-reducing bioreactor are unclear.…”

“…lienii is a moderately thermophilic bacterium with a fermentative type of metabolism, which can reduce elemental sulfur to sulfide (Dahle and Birkeland 2006). Sequences of sulfate reducers such as Desulfococcus biacutus and Desulfobacterium cetonicum which are able to oxidize acetone to CO 2 (Janssen and Schink 1995a, b;Platen et al 1990) or other microorganisms in those genera were not detected in the clone libraries, which is in agreement with the observed accumulation of acetone in the MR. Within the class Proteobacteria, clones were only found in the delta (d) sub-division.…”

Desulfatirhabdium butyrativorans gen. nov., sp. nov., a butyrate-oxidizing, sulfate-reducing bacterium isolated from an anaerobic bioreactor

“…Acetate and butyrate are important intermediates in the anaerobic degradation of wastewaters. Some bacteria in the family Desulfobacteraceae are able to oxidize butyrate either incompletely to acetate or completely to carbon dioxide with concomitant reduction of sulfate to sulfide (Stieb & Schink, 1989;Platen et al, 1990;Brandt et al, 1999).…”

“…Desulfatirhabdium butyrativorans gen. nov., sp. nov. Data for reference species were obtained from Widdel (1980), Bak & Widdel (1986) and Platen et al (1990 …”