Previous Article | Next Article ![]()
Journal of Bacteriology, February 2002, p. 672-678, Vol. 184, No. 3
0021-9193/01/$04.00+0 DOI: 10.1128/JB.184.3.672-678.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
-Gluconolactone in the Yeast Saccharomyces bulderi
Kluyver Laboratory of Biotechnology, Delft University of Technology, 2628 BC Delft,1 Laboratorium voor Microbiologie, Wageningen University, 6700 EJ Wageningen, The Netherlands2
Received 1 July 2001/ Accepted 6 November 2001
Under anaerobic conditions, the yeast Saccharomyces bulderi rapidly ferments
-gluconolactone to ethanol and carbon dioxide. We propose that a novel pathway for
-gluconolactone fermentation operates in this yeast. In this pathway,
-gluconolactone is first reduced to glucose via an NADPH-dependent glucose dehydrogenase (EC 1.1.1.47). After phosphorylation, half of the glucose is metabolized via the pentose phosphate pathway, yielding the NADPH required for the glucose-dehydrogenase reaction. The remaining half of the glucose is dissimilated via glycolysis. Involvement of this novel pathway in
-gluconolactone fermentation in S. bulderi is supported by several experimental observations. (i) Fermentation of
-gluconolactone and gluconate occurred only at low pH values, at which a substantial fraction of the substrate is present as
-gluconolactone. Unlike gluconate, the latter compound is a substrate for glucose dehydrogenase. (ii) High activities of an NADP+-dependent glucose dehydrogenase were detected in cell extracts of anaerobic,
-gluconolactone-grown cultures, but activity of this enzyme was not detected in glucose-grown cells. Gluconate kinase activity in cell extracts was negligible. (iii) During anaerobic growth on
-gluconolactone, CO2 production exceeded ethanol production by 35%, indicating that pyruvate decarboxylation was not the sole source of CO2. (iv) Levels of the pentose phosphate pathway enzymes were 10-fold higher in
-gluconolactone-grown anaerobic cultures than in glucose-grown cultures, consistent with the proposed involvement of this pathway as a primary dissimilatory route in
-gluconolactone metabolism.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»