摘要 :
The anaerobic, photosynthetic bacterium Chlorobium thiosulfatophilum is able to convert H(sub 2)S and COS in synthesis gas to elemental sulfur. The bacterium grows on CO(sub 2) as its carbon source at 30(degrees)C. In the absence ...
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The anaerobic, photosynthetic bacterium Chlorobium thiosulfatophilum is able to convert H(sub 2)S and COS in synthesis gas to elemental sulfur. The bacterium grows on CO(sub 2) as its carbon source at 30(degrees)C. In the absence of sulfide, the formed elemental sulfur is converted to sulfate. Thus, bioreactor designs must incorporate sulfur removal as an integral part of the bioprocess. In this initial study, C. thiosulfatophilum was used to convert H(sub 2)S to elemental sulfur in a continuous stirred tank reactor with continuous gas and liquid feed. Sulfur removal was not part of this initial system design, but will be an added feature in future work. The gas used in this study contained 2.52 percent H(sub 2)S, 10.00 percent CO(sub 2), 14.99 percent CH(sub 4) and 72.49 percent He. The liquid flow rate to the 1380 mL reactor volume ranged from 10.8--23.6 mL/min and was a variable in the study. The initial gas flow rate was 11.6 standard mL/min, although it was also changed twice during the study. The temperature was maintained at 31(degrees)C and the agitation rate was held at 200 rpm in the Bioflo reactor. Cell density was monitored by the chlorophyl method and gas composition was monitored by gas-solid chromatography. Light at 2200 lux was supplied using two 40W tungsten light bulbs on the outside of the glass reactor vessel.
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This report presents results from the solvent selection, fermentation, and product recovery studies performed thus far in the development of a bench scale unit for the production of ethanol from coal-derived synthesis gas. Several...
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This report presents results from the solvent selection, fermentation, and product recovery studies performed thus far in the development of a bench scale unit for the production of ethanol from coal-derived synthesis gas. Several additional solvents have been compared for their ability to extract ethanol from aqueous solutions of ethanol in water and fermentation permeate. The solvent 2,6-dimethyl-4-heptanol still appears to be the solvent of choice. Liquid-liquid equilibrium data have been collected for ethanol and 2,6-dimethyl-4-heptanol.
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The purpose of this report is to present the results of culture selection studies for the removal of heteroatom compounds from coal liquids. A variety of pure cultures have been selected based upon a comprehensive literature revie...
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The purpose of this report is to present the results of culture selection studies for the removal of heteroatom compounds from coal liquids. A variety of pure cultures have been selected based upon a comprehensive literature review. In addition, cultures are being isolated from natural sources. Synthetic heteroatom compounds are presently being utilized in the degradation studies until the Environmental Assessment Questionnaire is approved. (VC)
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The purpose of this report is to present progress to date on the biological upgrading of coal liquids. This three-year study focuses on surveying of known microorganisms for S, N, and O removal and aromaticity reduction. Isolates ...
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The purpose of this report is to present progress to date on the biological upgrading of coal liquids. This three-year study focuses on surveying of known microorganisms for S, N, and O removal and aromaticity reduction. Isolates from natural sources will also be sought for these reactions. The performance of these cultures will be optimized and evaluated individually and as a mixed culture. The best cultures will be selected for performance evaluation in continuous submerged culture experiments in constant-stirring bioreactors. Reactor design and product removal processes will be projected and the economics of this technology compared with conventional methods. (VC)
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摘要 :
Research is continuing in attempting to increase both the ethanol concentration and product ratio (acetate to ethanol) from the C. ljungdahlii fermentation. Both batch and continuous reactors are being used for this purpose. The p...
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Research is continuing in attempting to increase both the ethanol concentration and product ratio (acetate to ethanol) from the C. ljungdahlii fermentation. Both batch and continuous reactors are being used for this purpose. The purpose of this report is four-fold. First, the data presented in PETC Report No. 2-4-91 (June--September, 1991) are analyzed and interpreted using normalized specific growth and production rates. This technique eliminates experimental variation due to differences in inoculum history. Secondly, the effects of the sulfur gases H(sub 2)S and COS on the performance of C. ljungdahlii are presented and discussed. Although these are preliminary results, they illustrate the tolerance of the bacterium to low levels of sulfur gases. Thirdly, the results of continuous stirred tank reactor studies are presented, where cell and product concentrations are shown as a function of agitation rate and gas flow rate. Finally, additional data are presented showing the performance of C. ljungdahlii in a CSTR with cell recycle.
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Widespread use and careless handling, storage and disposal practices, have lead to the dissemination of chlorinated short chain aliphatics into groundwater systems. These compounds are toxic and the presence of chlorinated ethenes...
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Widespread use and careless handling, storage and disposal practices, have lead to the dissemination of chlorinated short chain aliphatics into groundwater systems. These compounds are toxic and the presence of chlorinated ethenes and chlorinated propanes in the environment is of public concern. Halorespiration is a newly recognized anaerobic process by which certain bacteria use chlorinated compounds as terminal electron acceptors in their energy metabolism. In contrast to co-metabolic dechlorination, which is fortuitous, slow, and without benefit to the organisms, halorespiration, characterized by high dechlorination rates, is a specific metabolic process beneficial to the organism. The goals are to isolate and characterize organisms which use chlorinated ethenes (including tetrachloroethene (PCE), trichloroethene (TCE), cis-dichloroethene (cis-DCE), and vinyl chloride (VC), or 1,2-dichloropropane (1,2-D)) as electron acceptors in their energy metabolism. Better understanding of the physiology and phylogeny of the halorespiring organisms as well as the biochemistry of the dehalogenating enzyme systems, will greatly enhance the authors knowledge of how these organisms can successfully be employed in the bioremediation of contaminated sites. This report summarizes the results of 1.5 years of a 2-year project. Anaerobic microcosms were established using a variety of geographically distinct sediments. In several microcosms complete dechlorination of PCE to ethene (ETH), and 1,2-D to propene was observed. Upon subsequent transfers to anaerobic medium, four sediment-free, methanogenic enrichment cultures were obtained that dechlorinated PCE to ETH, and two cultures that dechlorinated 1,2- D to propene. 2-Bromoethanesulfonate (BES), a well known inhibitor of methanogens, did not inhibit the dechlorination of 1,2-D to propene or the dechlorination of PCE to cis-DCE. However, the complete dechlorination of PCE to VC and ETH was severely inhibited. They could also show that BES inhibited the dechlorination of chloroethenes in cultures without methanogens. Therefore, BES should not be used to attribute dechlorination activities to methanogens.'
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摘要 :
Widespread use and careless handling, storage and disposal practices, have lead to the dissemination of chlorinated short chain aliphatics into groundwater systems. These compounds are toxic and the presence of chlorinated ethenes...
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Widespread use and careless handling, storage and disposal practices, have lead to the dissemination of chlorinated short chain aliphatics into groundwater systems. These compounds are toxic and the presence of chlorinated ethenes and chlorinated propanes in the environment is of public concern. Halorespiration is a newly recognized anaerobic process by which certain bacteria use chlorinated compounds as terminal electron acceptors in their energy metabolism. In contrast to co-metabolic dechlorination, which is fortuitous, slow, and without benefit to the organisms, halorespiration, characterized by high dechlorination rates, is a specific metabolic process beneficial to the organism. The goals are to isolate and characterize organisms which use chlorinated ethenes (including tetrachloroethene (PCE), trichloroethene (TCE), cis-dichloroethene (cis-DCE), and vinyl chloride (VC), or 1,2-dichloropropane (1,2-D)) as electron acceptors in their energy metabolism. Better understanding of the physiology and phylogeny of the halorespiring organisms as well as the biochemistry of the dehalogenating enzyme systems, will greatly enhance the authors knowledge of how these organisms can successfully be employed in the bioremediation of contaminated sites. This report summarizes the results of 1.5 years of a 2-year project. Anaerobic microcosms were established using a variety of geographically distinct sediments. In several microcosms complete dechlorination of PCE to ethene (ETH), and 1,2-D to propene was observed. Upon subsequent transfers to anaerobic medium, four sediment-free, methanogenic enrichment cultures were obtained that dechlorinated PCE to ETH, and two cultures that dechlorinated 1,2- D to propene. 2-Bromoethanesulfonate (BES), a well known inhibitor of methanogens, did not inhibit the dechlorination of 1,2-D to propene or the dechlorination of PCE to cis-DCE. However, the complete dechlorination of PCE to VC and ETH was severely inhibited. They could also show that BES inhibited the dechlorination of chloroethenes in cultures without methanogens. Therefore, BES should not be used to attribute dechlorination activities to methanogens.'
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摘要 :
The objectives of this study are to: (1) determine the biochemical pathways for reductive dehalogenation of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC), including identification of the enzymes involved, (2) determine the...
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The objectives of this study are to: (1) determine the biochemical pathways for reductive dehalogenation of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC), including identification of the enzymes involved, (2) determine the chemical requirements, especially the type and quantity of electron donors needed by the microorganisms for reductive dehalogenation, and (3) evaluate the kinetics of the process with respect to the concentration of both the electron donors and the electron acceptors (cDCE and VC). Progress has been made under each of the three primary objectives. One manuscript related to the first objective has been published. Manuscripts related to the other two objectives have been submitted for publication. Findings related to the three objectives are summarized.'
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