Masaharu Tasaki

Isolation and characterization of a thermophilic benzoate-degrading, sulfate-reducing bacterium, Desulfotomaculum thermobenzoicum sp. nov.

A new thermophilic sulfate-reducing bacterium, strain TSB, that was spore-forming, rod-shaped, slightly motile and gram-positive, was isolated from a butyrate-containing enrichment culture inoculated with sludge of a thermophilic methane fermentation reactor. This isolate could oxidize benzoate completely. Strain TSB also oxidized some fatty acids and alcohols. SOinf4sup2-, SOinf3sup2-, S2Oinf3sup2-and NOinf3sup-were utilized as electron acceptors. With pyruvate or lactate the isolate grew without an external electron acceptor and produced acetate. The optimum temperature for growth was 62°C. The G+C content of DNA was 52.8 mol%. This isolate is described as a new species, Desulfotomaculum thermobenzoicum.

Methane production using a bio-reactor packed with pumice stone on an evaporator condensate of a kraft pulp mill

Abstract When an evaporator condensate stream from a kraft pulp mill was treated by anaerobic methane fermentation, the stream could not ferment continuously. Therefore, after the raw evaporator condensate was treated by various procedures, the treated samples were tested in a batch fermentation system. There seemed to be an inhibitor, an oily material, and the evaporator condensate could be fermented easily, after removal of the oily material, in a bio-reactor packed with pumice stone. In continuous operation, the minimum hydraulic retention time was 0.64 days, the maximum volumetric BOD removal rate was 11.47 kg/m3/d, and the maximum gas production rate for the theoretical volume was 97%. The efficiency of a bio-reactor using pumice stone was studied. The pumice stone has a large number of connected pores. The major pore sizes are 20–100 μm. The cell density of the pumice stone used in the bio-reactor was 18–19 g per liter.

Utilization of methoxylated benzoates and formation of intermediates by Desulfotomaculum thermobenzoicum in the presence or absence of sulfate.

Desulfotomaculum thermobenzoicum strain TSB (DSM 6193) was found to utilize some methoxylated benzoates as carbon and energy source with or without sulfate. 3- or 4-Methoxybenzoate, vanillate (4-hydroxy-3-methoxybenzoate), syringate (3,5-dimethoxy-4-hydroxybenzoate) and 3,4,5-trimethoxybenzoate were converted to corresponding hydroxybenzoates. However, neither 2-methoxybenzoate nor 2,6-dimethoxybenzoate was utilized. The organism grew acetogenically on each of the methoxylated benzoates in the absence of sulfate.3,4-Dihydroxy-5-methoxybenzoate was detected during conversion of syringate, and syringate and 3,4-dihydroxy-5-methoxybenzoate were detected during conversion of 3,4,5-trimethoxybenzoate as intermediates.These findings indicate that 4-methoxyl-group is most readily cleaved, whereas 2-methoxyl-group is not utilized by the organism.

Screening growth inhibitors of sulfate-reducing bacteria and their effects on methane fermentation

Abstract Growth inhibitors of sulfate-reducing bacteria (SRB) which did not significantly affect methanogenesis were screened, and their effects on methane fermentation were investigated. The screening stage was performed in vitro using two typical thermophilic anaerobic bacteria, Methanosarcina sp. (DSM 2906) as the methanogen and Desulfotomaculum nigrificans (DSM 574) as the sulfate reducer. Among eighty-eight substances tested, nine were found to be effective for inhibiting SRB growth with little or no effect on methanogenesis. Gentamicin and dodecylbenzene sulfonic acid (DBS) out of the nine effective substances were tested for their effect on the co-cultivation of two strains. These two substances were effective on co-cultivation in methane gas production. Furthermore, the effects on the methane fermentation process were investigated using a laboratory-scale membrane complex anaerobic fermentation unit with an effective volume of 20 l . In the fermentor study, DBS was found not to be effective in the suppression of sulfate reduction, whereas the addition of a small amount of gentamicin was effective for a long period.

Degradation of benzoate by an anaerobic consortium and some properties of a hydrogenotrophic methanogen and sulfate-reducing bacterium in the consortium

Abstract A highly simplified anaerobic consortium which was able to degrade benzoate under mesophilic conditions was obtained from digested sludge acclimatized with benzoate. It converted 5 mM benzoate to methane quantitatively within 3 weeks in the absence of any organic nutrients under an N 2 /CO 2 atmosphere. Degradation of benzoate was strictly inhibited by hydrogen. The consortium consisted of at least three microorganisms including an autofluorescent irregular coccus which was identified as Methanogenium sp., a short rod which did not autofluoresce and was considered to be a benzoate degrader, and a filamentous bacterium apparently classified as Methanothrix (= “Methanosaeta” . When sulfate was added to the medium, the methanogens were readily replaced by a sulfate-reducing bacterium, probably belonging to the genus Desulfovibrio , which had still remained in very low number in the consortium in the absence of sulfate, and benzoate was stoichiometrically converted to acetate without methanogenesis. Of various compounds which were expected to be intermediates in the benzoate degradation, only crotonate was degraded by concentrated cells of the consortium.

Influence of pH on methane and sulfide production from methanol

Abstract To investigate the influence of pH on methane and sulfide production, continuous cultures were done using a bio-reactor packed with pumice stone. Sulfate (1 g SO42−·l−1) in a methanol defined medium (10 g·l−1) was almost completely reduced to sulfide at pHs between 7.0 and 7.5 in methane fermentation, but at pHs between 6.2 and 6.8, sulfate reduction to sulfide was suppressed up to 40%. In addition, methane fermentation was not inhibited by 10 g sulfate·l−1.

Propionate formation from alcohols or aldehydes by Desulfobulbus propionicus in the absence of sulfate

Abstract Fermentative degradation of alcohols and aldehydes in the absence of sulfate was investigated using a propionate-oxidizing, sulfate-reducing bacterium, Desulfobulbus propionicus strain MUD (DSM 6523). The organism converted ethanol plus CO 2 to acetate and propionate. The conversion was not affected by the presence of hydrogen. Strain MUD converted propanol plus acetate to propionate. Acetaldehyde and propionaldehyde were also converted with a dismutation reaction in the absence of sulfate. The products were propionate and acetate from acetaldehyde, and propionate from propionaldehyde plus acetate.

Polymer flood produced water treatment trials

Summary Polymer-enhanced-oil-recovery (EOR) operation has been implemented for the production of oil from difficult mature oil fields in Oman. The polymer used to sweep oil toward production wells in this EOR technique is resulting in the generation of polymer-flood produced water (PFPW) of increasing viscosity. Current methods of treating oilfield produced water must be reconsidered for the effective treatment of PFPW of such changing quality. In a previous study, the use of polyaluminum chloride (PAC) was proposed for the coagulation of oil in produced water to be separated by flotation and filtration. As such, laboratory tests were conducted to evaluate the applicability of PAC and other chemicals for treatment of PFPW with higher viscosity than ordinary oilfield-produced water. These tests indicated clearly that aluminum sulfate (AS) was more effective for treatment of such higherviscosity water. A pilot plant developed during the earlier study was used to conduct coagulation/flocculation-, flotation-, filtration-, and adsorption-treatment trials for PFPW from an oil field at which polymer EOR was under way. For the final trial, the inlet PFPW viscosity was 1.4 cp at 40°C and oil concentration was greater than 200 mg/L. AS was applied for the coagulation/flocculation and flotation stages, and was found to be effective in reducing oil concentration to 1 mg/L. Filtration and adsorption stages resulted in further improvement of water quality. Most of the polymer used for EOR was believed to have been removed along with oil and suspended solids.

Isolation of a Propionate-Using, Sulfate-Reducing Bacterium

Propionate is one of the most important intermediates in the anaerobic digestion process because propionate accumulation may inhibit methanogenesis, reducing the efficiency of anaerobic treatment. Subsequently, propionate degrading bacteria have received increasing attention because of their important role in maintaining digester efficiency. This report describes the isolation and characterization of a propionate-using, sulfate-reducing bacterium, named strain MUD.

Flotation, Filtration, and Adsorption Pilot Trials for Oilfield Produced Water Treatment

Summary As an oil field matures, it produces larger quantities of produced water. Appropriate treatment levels and technologies depend on a number of factors, such as disposal methods or usage aims, environmental impacts, and economics. In this study, a pilot plant with a capacity of 50 m3/d was used to conduct flotation, filtration, and adsorption trials for producedwater treatment at a crude-oil gathering facility. The flexible design of the plant allows for the testing of different combinations of these processes on the basis of the requirements of the water to be treated. The subject water during this study was a complex and changing mixture of brine and oil from different oil fields. Induced-gas-flotation (IGF) trials were conducted, with different coagulant [polyaluminum chloride (PAC)] -addition rates from 0 to 820 mg⋅L–1. Inlet-dispersed oil-in-water (OIW) concentrations were quite varied during the trials, ranging from 39 to 279 mg⋅L–1 (fluorescence-analysis method). Turbidity also varied, ranging from 85 to 279 FTU. Through coagulation/flocculation and flotation, dispersed oils were removed from the water. PAC addition ranging from 60 to 185 mg⋅L–1 resulted in the reduction of the dispersed-oil concentration to less than 50 mg⋅L–1 in treated water; and PAC addition ranging from 101 to 200 mg⋅L–1 resulted in the reduction of the dispersed-oil concentration to less than 15 mg⋅L–1 in treated water. Turbidity was also reduced through flotation, with trial average reductions ranging from 57 to 78%. Filtration further reduced turbidity at rates greater than 80% through the removal of any suspended solids remaining from flotation. Activated-carbon adsorption reduced OIW concentrations of flotation-/filtrationtreated water to 5 mg⋅L–1 (infrared-analysis method) through the removal of dissolved oil remaining in the water. Results confirmed that such adsorption treatment would be more practical for water with lower chemical-oxygen-demand (COD) concentration because high-COD concentrations in water reduce the lifetime of activated carbon dramatically.