Fermentation of Glucose, Fructose, and Xylose by Clostridium thermoaceticum : Effect of Metals on Growth Yield, Enzymes, and the Synthesis of Acetate from CO ₂

Abstract

Clostridium thermoaceticum ferments xylose, fructose, and glucose with acetate as the only product. In fermentations with mixtures of the sugars, xylose is first fermented, then fructose, and last, glucose. Fructose inhibits the fermentation of glucose, and this inhibition appears to be due to a repression of the synthesis of an enzyme needed for glucose utilization. Addition of metals to the culture medium increases the cell yield drastically from about 7 to 18 g per liter, and Y(glucose) values between 40 and 50 are obtained. According to the postulated pathways of the fermentation of glucose and synthesis of acetate from CO2 by C. thermoaceticum, 3 mol of ATP are available as energy for growth. Thus a Y(adenosine 5'-triphosphate) of 13 to 16 is obtained. Because the normal Y(ATP) value is 10.5, this could mean that an additional source of ATP is available by an unknown mechanism. The addition of metals also increases the nicotinamide adenine dinucleotide phosphate-dependent formate dehydrogenase activity, the overall reaction ("CO2-p acetate), and the incorporation of the

Tungsten, the Surprisingly Positively Acting Heavy Metal Element for Prokaryotes

“…Instead of obtaining a strong inhibitory effect of tungstate, as Jane Pinsent had found in 1954 for the FDH of Escherichia coli, 16 we could reproducibly show that tungsten, instead of molybdenum, is a positively acting element besides selenium for the nicotinamide adenine dinucleotide phosphate (NADP)-dependent FDH of Moorella thermoacetica, even by growing the organism in the very complex medium used in those days. 42,43 These results stood in sharp contrast to studies using E. coli that showed a strict requirement for molybdate and selenite to express an active FDH if the organism is grown in a defined medium, whereas addition of tungstate is a strong antagonist for FDH activity. 16,44 Until that time, tungstate was supposed to act only as an inhibitor for molybdoenzymes, such as nitrate reductase, xanthine dehydrogenase, aldehyde oxidase, and sulfite oxidase.…”

Using gas mixtures of CO, CO2 and H2 as microbial substrates: the do's and don'ts of successful technology transfer from laboratory to production scale

“…Andreesen et al, 1973;Daniel et al, 1990;Parekh and Cheryan, 1991;G€ oßner et al, 1999;Bengelsdorf et al, 2015a;Poehlein et al, 2015a) …”

The Eastern and Western branches of the Wood/Ljungdahl pathway: how the East and West were won

“…Elucidation of the first step in this Eastern Branch became a controversial topic. This led to the discovery of the first tungsten enzyme, formate dehydrogenase [21,22]. There were many who fought Lars Ljungdahl and dismissed the possibilities that tungsten could possibly be a component of an enzyme and that NADPH could effect the reduction of CO 2 to formate.…”

“…Lars used a combination of biochemistry and microbial physiology to definitively prove his case. The formate dehydrogenase from C. thermoaceticum was shown to be an α 2 β 2 enzyme (M r = 340,000) containing, per αβ dimer, one tungsten, one selenium, and about 18 iron and about 25 inorganic acid-labile sulfides in the form of iron-sulfur clusters [23] and NADP + /NADPH was shown to indeed couple to the CO 2 /HCOOH half-reaction [21][22][23][24]. The tungsten was found to be part of a tungstopterin prosthetic group, like the molybdopterin found in xanthine oxidase, sulfite oxidase, and nitrate reductase and the Mo-containing formate dehydrogenases of other organisms [25].…”