Carbohydrate and energy-yielding metabolism in non-conventional yeasts

Sugars are excellent carbon sources for all yeasts. Since a vast amount of information is available on the components of the pathways of sugar utiliza tion in Saccharomyces cerevisiae it has been tacitly assumed that other yea sts use sugars in the same way. However, although the pathways of sugar uti lization follow the same theme in all yeasts, important biochemical and gen etic variations on it exist. Basically, in most non-conventional yeasts, in contrast to S, cerevisiae, respiration in the presence of oxygen is promin ent For the use of sugars. This review provides comparative information on the different steps of the Fundamental pathways of sugar utilization in non -conventional yeasts: glycolysis, fermentation, tricarboxylic acid cycle, p entose phosphate pathway and respiration. We consider also gluconeogenesis and, briefly, catabolite repression. We have centered our attention in the genera Kluyveromyces, Candida, Pichia, Yarrowia and Schizosaccharomyces, al though occasional reference to other genera is made. The review shows that basic knowledge is missing on many components of these pathways and also th at studies on regulation of critical steps are scarce. Information on these points would be important to generate genetically engineered yeast strains for certain industrial uses. (C) 2000 Federation of European Microbiologic al Societies. Published by Elsevier Science B.V. All rights reserved.