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Title: Pathway of Fermentative Hydrogen Production by Sulfate-reducing Bacteria

Abstract

Biofuels are a promising source of sustainable energy. Such biofuels are intermediate products of microbial metabolism of renewable substrates, in particular, plant biomass. Not only are alcohols and solvents produced in this degradative process but energy-rich hydrogen as well. Non photosynthetic microbial hydrogen generation from compounds other than sugars has not been fully explored. We propose to examine the capacity of the abundant soil anaerobes, sulfate-reducing bacteria, for hydrogen generation from organic acids. These apparently simple pathways have yet to be clearly established. Information obtained may facilitate the exploitation of other microbes not yet readily examined by molecular tools. Identification of the flexibility of the metabolic processes to channel reductant to hydrogen will be useful in consideration of practical applications. Because the tools for genetic and molecular manipulation of sulfate-reducing bacteria of the genus Desulfovibrio are developed, our efforts will focus on two strains, D. vulgaris Hildenborough and Desulfovibrio G20.Therefore total metabolism, flux through the pathways, and regulation are likely to be limiting factors which we can elucidate in the following experiments.

Authors:
 [1]
  1. Univ. of Missouri, Columbia, MO (United States)
Publication Date:
Research Org.:
Univ. of Missouri, Columbia, MO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1170223
Report Number(s):
DOE/UMissouri-08ER64691
DOE Contract Number:
FG02-08ER64691
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; Hydrogenase mutants; cytochrome c3; Desulfovibrio

Citation Formats

Wall, Judy D. Pathway of Fermentative Hydrogen Production by Sulfate-reducing Bacteria. United States: N. p., 2015. Web. doi:10.2172/1170223.
Wall, Judy D. Pathway of Fermentative Hydrogen Production by Sulfate-reducing Bacteria. United States. doi:10.2172/1170223.
Wall, Judy D. 2015. "Pathway of Fermentative Hydrogen Production by Sulfate-reducing Bacteria". United States. doi:10.2172/1170223. https://www.osti.gov/servlets/purl/1170223.
@article{osti_1170223,
title = {Pathway of Fermentative Hydrogen Production by Sulfate-reducing Bacteria},
author = {Wall, Judy D.},
abstractNote = {Biofuels are a promising source of sustainable energy. Such biofuels are intermediate products of microbial metabolism of renewable substrates, in particular, plant biomass. Not only are alcohols and solvents produced in this degradative process but energy-rich hydrogen as well. Non photosynthetic microbial hydrogen generation from compounds other than sugars has not been fully explored. We propose to examine the capacity of the abundant soil anaerobes, sulfate-reducing bacteria, for hydrogen generation from organic acids. These apparently simple pathways have yet to be clearly established. Information obtained may facilitate the exploitation of other microbes not yet readily examined by molecular tools. Identification of the flexibility of the metabolic processes to channel reductant to hydrogen will be useful in consideration of practical applications. Because the tools for genetic and molecular manipulation of sulfate-reducing bacteria of the genus Desulfovibrio are developed, our efforts will focus on two strains, D. vulgaris Hildenborough and Desulfovibrio G20.Therefore total metabolism, flux through the pathways, and regulation are likely to be limiting factors which we can elucidate in the following experiments.},
doi = {10.2172/1170223},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2015,
month = 2
}

Technical Report:

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  • The work proposed to be accomplished in the previous funding period was to develop a procedure for genetic exchange based on conjugation mediated by broad host-range plasmids. Such a system has recently been identified that employs IncQ group plasmids and a Desulfovibrio desulfuricans G100A derivative as recipient. During the search for conjugation, we also identified a defective bacteriophage capable of generalized transduction of fragments of chromosomal DNA between mutants of Desulfovibrio desulfuricans. Some of the factors influencing the production and transduction by this defective phage have been investigated. A curious observation was made concerning the response of colonies of thesemore » sulfate-reducing bacteria upon exposure to air. All the cells of a colony do not die. Some survive, most likely by producing sulfide at a rate sufficient to provide an anaerobic environment. Dramatic colony morphological changes occur and these have been documented by scanning and transmission electron microscopy. Finally a small endogenous plasmid has been isolated from Desulfovibrio desulfuricans G100A. It has been stably subcloned into a sequencing vector, and nested deletions of this plasmid are being prepared. This plasmid may be useful for the development of a shuttle cloning vector that could be used in more diverse Desulfovibrio. Many of the techniques now to be used in the mutant analysis of hydrogenase genes in the sulfate-reducing bacteria have been successfully applied in an analysis of hydrogenase functions of Rhodobacter capsulatus. 8 figs., 2 tabs.« less
  • The degradation of our environment and the depletion of fossil fuels make the exploration of alternative fuels evermore imperative. Among the alternatives is biohydrogen which has high energy content by weight and produces only water when combusted. Considerable effort is being expended to develop photosynthetic systems -- algae, cyanobacteria, and anaerobic phototrophs -- for sustainable H 2 production. While promising, this approach also has hurdles such as the harvesting of light in densely pigmented cultures that requires costly constant mixing and large areas for exposure to sunlight. Little attention is given to fermentative H 2 generation. Thus understanding the microbialmore » pathways to H 2 evolution and metabolic processes competing for electrons is an essential foundation that may expand the variety of fuels that can be generated or provide alternative substrates for fine chemical production. We studied a widely found soil anaerobe of the class Deltaproteobacteria, a sulfate-reducing bacterium to determine the electron pathways used during the oxidation of substrates and the potential for hydrogen production.« less
  • Studies aimed at developing methods to exploit the genetics and molecular biology of the sulfate-reducing bacteria are described. The long-term goal of these studies is to examine the H/sub 2/ metabolism of Desulfovibrio desulfuricans. We recently observed transduction mediated by an apparently defective bacteriophage. The requirements for transduction, the efficiency of cultures as donors or recipients and the kinetics of production of the phage have been examined. Since it is sometimes necessary to manipulate the bacterial cultures outside the anaerobic chamber, it seemed pertinent to establish the oxygen tolerance of the D. desulfuricans cultures. We observed dramatic morphological responses ofmore » colonies upon exposure to air. The development of a genetic exchange process was predicated on the facility of handling these bacteria during standard microbiological procedures. Experience with these bacteria has revealed that for D. desulfuricans ATCC 27774, the doubling time in the standard lactate/sulfate based medium at 31 C is 6 to 9 hours and that 7 to 9 days is required to observe good colony formation.« less
  • In anaerobic digestors and natural environments, the sulfate-reducing bacteria (SRB) play a pivotal role in methane generation, either providing hydrogen and acetate for methane formation or competing with the methanogens for those same substrates. The SRB are also the primary culprits in causing environmental metal corrosion costing millions of dollars each year and in producing poisonous sulfide sometimes costing lives. Key factors controlling the interactions of the SRB with other microorganisms in their environment are hydrogen metabolism and their tolerance of exposures to oxygen. The number of enzymes capable of producing or consuming hydrogen in the SRB and their physiologicalmore » functions remain obscure. Our laboratory is developing the genetics and molecular biology of the SRB with the aim of examining the hydrogen metabolism. Desulfovibrio desulfuricans ATCC 27774 has been found to be amenable to classical genetic manipulation, antibiotic resistant mutants as well as mutants altered in sulfate and hydrogen metabolism have been isolated. Most excitingly, this strain has been found to produce a defective bacteriophage capable of generalized transduction. This strain as well as G100A have been found to be capable of genetic exchange with Escherichia coli via conjugation involving Q-incompatibility group plasmids. Detailed examination of the metabolic properties of these bacteria is now possible.« less
  • Anaerobic corrosion by sulfate-reducing bacteria appears to be caused by a highly active volatile phosphorus compound, which reacts with bulk iron to form iron phosphide. Preliminary evidence also indicates that the phosphorus compound may also be produced by the direct action of bacterially produced hydrogen sulfide on inorganic phosphorus compounds. Accordingly, any organism that produces hydrogen sulfide, under anaerobic conditions, in the presence of certain phosphorus compounds should stimulate the anaerobic corrosion of iron, providing the iron does not have a film of iron sulfide present. In addition to formation of the phosphorus compound and the metabolic production of hydrogenmore » sulfide by sulfate-reducing organisms, methylmercaptan and dimethyldisulfide are produced. These compounds were relatively non-corrosive to iron.« less