A Comparison of Hydrogen Production from Sugars and Formic Acid by Normal and Variant Strains of Escherichia coli

Abstract

It is common knowledge that the gases formed by members of the colon-typhoid group of bacteria consist of mixtures of hydro-gen and carbon dioxide. Pakes and Jollyman (1901) showed that pure cultures of organisms of this group produced mixtures of hydrogen and carbon dioxide from formic acid. Since they also produced these gases from glucose, Pakes and Jollyman concluded that the gas from glucose came from intermediately-formed formic acid. Harden (1901) showed that the most striking difference in the fermentation reactions of Escherichia coli and Eberthella typhosa is that the latter is unable to decom-pose formic acid to hydrogen and carbon dioxide. He made the further observation that increased pressure decreased the pro-duction of hydrogen and carbon dioxide and increased the amount of formic acid in the fermentation of glucose by Escherichia coli. The latter observation suggested the reversibility of the re-action, later demonstrated by Woods (1936). It has generally been believed by most investigators of fermen-tations by the colon-typhoid group that the hydrogen formed during fermentation comes from intermediate formic acid. Most fermentation schemes, therefore, (e.g. Kluyver, 1931), designate formic acid as the precursor of the hydrogen formed. However, Stephenson and Stickland (1932) and Stephenson (1937) present evidence that hydrogen may be produced by Escherichia coli from glucose and other carbohydrates, otherwise than from preliminarily-formed formic acid. Tasman and Pot (1935) could not confirm these findings. Quastel and Whetham (1925), using the Thunberg methylene-blue technique, showed that Escherichia coli, which produces hydrogen and carbon dioxide from glucose, is able to reduce methylene blue in the presence of formic acid. Early studies in this investigation showed that certain strains of Escherichia coli, which had lost the ability to produce gas from sugars and sodium formate, had also lost the ability to reduce methylene blue with formic acid. This observation supported the suggestion that formic acid is the precursor of hydrogen and carbon dioxide in the fermentation of glucose by Escherichia coli. However, Stickland (1929) showed that Eberthella typhosa which does not produce gas from glucose, is able to reduce methyl-ene blue in the presence of formic acid. Consequently, factors other than the activation of formic acid must be operative in order that carbon dioxide and hydrogen be produced. Since the work of Quastel, various investigators have studied the enzymes of bacteria of the colon-typhoid group which liberate gases from sugars and formic acid. Quastel (1925) described one of these as formic dehydrogenase, catalysing the reaction HCOOH + R =± RH2 + CO2 where R is methylene blue or some other hydrogen acceptor. Another enzyme, hydrogenase, was studied by Tauss and Donath (1930) and Stephenson and Stickland (1931). Green and Stickland (1934) have shown that hydro-genase catalyses the reaction H2 =-2H+ + 2(e) in a perfectly reversible manner. Stephenson and Stickland (1932) have given the name "formic hydrogenlyase" to an enzyme which liberates hydrogen and carbon dioxide from formic acid, catalysing the reaction HCOOH = H2 + CO2. They are of the opinion that formic