kluyver's contributions to microbiology and biochemistry 



covery, in Kluyver's laboratory, of a methane fermentation in which 

 ethanol, the only organic ingredient of the medium, was oxidized 

 quantitatively to acetic acid, while simultaneously methane was 

 formed, and an equivalent amount of carbon dioxide disappeared: 



2 CH 3 CH 2 OH+C0 2 -> 2CH 3 COOH+CH 4 



Later the origin of methane from carbon dioxide was established 

 quite unambiguously by Barker and collaborators [1940] in experi- 

 ments demonstrating that the methane formed by a pure culture of 

 the causative bacteria during the oxidation of ethanol in the presence 

 of n C0 2 was, indeed, n CH 4 . 



The rationale of Barker's use of ethanol as the oxidation substrate 

 for the study of methane production had its origin in yet another 

 application of the comparative biochemical approach. It was based 

 on the fact that various micro-organisms oxidize this substance only 

 as far as acetic acid; this applies, for instance, to the strictly aerobic 

 acetic acid bacteria, notably A. suboxydans, as well as to particular 

 representatives of the strictly anaerobic sulphate reducing bacteria, 

 as had been shown by Kluyver's collaborator, Baars [1930Tb], in his 

 extensive studies of this group of organisms. The advantage of such 

 an incomplete oxidation is, of course, that the initial substrate can 

 still be recognized in the oxidation product, which justifies the in- 

 ference that the substrate carbon cannot be implicated in the forma- 

 tion of methane. A comparable incomplete oxidation was later used by 

 Kluyver and Schnellen [Kluyver, 1939a; Schnellen, 1947Tb] to provide 

 additional evidence for the origin of methane from carbon dioxide, 

 before Barker had carried out his experiments with the radio-active 

 carbon isotope. They succeeded in inducing a methane fermentation 

 with isopropanol as the oxidizable substrate, and showed that the 

 latter was quantitatively oxidized to acetone, while simultaneously 

 carbon dioxide disappeared in an amount equivalent to that of the 

 methane generated, according to the equation: 



4CH 3 CHOHCH 3 +C0 2 -> 4CH 3 COCH 3 +CH 4 +2H 2 



During their studies on the methane fermentation Kluyver and 

 Schnellen [1947] also discovered two anaerobic bacterial species that 

 can produce methane in an environment that contains carbon mon- 

 oxide as the only oxidizable substrate [Schnellen, 1947TI1]. Appro- 



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