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Thursday, 22 February 2018
Bacterial Hydrogen Production PDF Print
*       Metabolic Flux Analysis as a Tool to Improve Hydrogen Production by a Genetic Modified Bacterium

Hydrogen is a strong candidate substitute for carbon based fuel. Hydrogen fuel cells are an excellent form of carbon dioxide reduction, but only if hydrogen is produced from renewed sources. However, great part of the hydrogen production today comes from fossils fuels, which liberate greenhouse effect gases to the atmosphere.

Biological hydrogen production is an alternative that is considered potentially promising, since it is carried out, in its majority, at ambient temperature, with good yields and of few undesirable byproducts.

Hydrogen can be produced by bacterial fermentative processes. Bacteria work as living machines that reproduce themselves. Bacteria produce hydrogen as a way to get rid of electrons generated during carbon compounds catabolism. Literature data suggests that Clostridium sp. present the best yield for hydrogen production. Hydrogen yields can be improved by metabolic engineering, redirecting the electron flux to the H2 production.

Our work considers a new biological pathway, of a genetically modified Clostridium butyricum based on metabolic flux analysis. Hydrogen production has been optimized in silico by using glycerol as substrate. Glycerol is an important byproduct of biodiesel production. It has been targeted for possible biological processing, such as glycerol degradation as a form to get interesting industrial products.

Clostridium butyricum produces large amounts of 1,3-propanodiol when it uses glycerol as a main carbon source. When glycerol dehydratase and 1,3-propanediol dehydrogenase enzymes are activated, glycerol is converted to 1,3-propanediol. However, our metabolic flux analysis showed surprisingly unexpected results. According to sensitivity analysis, the gene knockout of glycerol dehydratase enzyme, combined with glycerol feeding, is the best strategy for improving hydrogen production by the in silico genetically modified Clostridium. That does not mean that the actual performance under in vivo conditions will be as significant as the proposed metabolic route. On the other hand, as clearly pointed out by our results for hydrogen production, MFA is a powerful tool and may be used to try different strategies and alternatives before genetic manipulation is carried out.

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