Kluyver effect

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The Kluyver effect , named after the Dutch biochemist and microbiologist Albert Jan Kluyver , describes a phenomenon of yeast metabolism , according to which some types of yeast utilize certain sugars only under aerobic conditions (i.e. in the presence of oxygen ), but not anaerobically (i.e. with the exclusion of oxygen) can.

Yeasts that are capable of sugar such as maltose , galactose , raffinose , lactose and the like under aerobic conditions . a. to utilize, can subsequently no longer grow if the respiration (breathing) z. B. is prevented by certain mutations or an inhibitor . Yeast strains that are "breath-dependent" for a certain sugar are therefore called the "Kluyver effect positive".

Background and possible causes

Since its discovery in 1940 , the cause of the Kluyver effect has largely remained in the dark. In the course of time different explanations have been developed:

  • Breathability may be essential to enable the selective transport of certain sugars into the cell.
  • The Kluyver effect could be an extreme case of the Pasteur effect ; H. the fermentation is inhibited by the respiration.
  • the concentration of key enzymes (e.g. pyruvate decarboxylase ) may be too low to keep cells growing.
  • direct product inhibition

All of the above hypotheses imply an indirect explanation of the Kluyver effect. Since this is sugar-specific in any case, the first hypothesis in particular has received increased attention in many scientific papers. Recent research appears to support this fact. Kluyveromyces lactis strains u. a. are positive for galactose Kluyver effect, can no longer utilize this sugar if respiration is inhibited. Under these conditions, the activity of the host's own galactose transporter (protein which the galactose smuggles into the cell) does not seem to be sufficient to enable growth in a galactose-containing nutrient medium. It was only when galactose transporters that were foreign to the organism were smuggled in using genetic engineering to reverse the Kluyver effect. K. lactis strains, which are normally positive for the galactose Kluyver effect, could therefore also be cultivated with inhibited respiration.

Importance of the Kluyver effect in biotechnology

The occurrence of the Kluyver effect could definitely offer advantages for many biotechnological fermentation processes , especially for high-density fermentations . When facultative fermenting yeasts grow , an unwanted oxygen limitation inevitably leads to alcoholic fermentation. This in turn limits the overall yield of the fermentation process considerably. In particular, nutrient media containing glucose therefore require precise control of the process conditions, in particular the dissolved oxygen concentration. Yeasts that are positive for certain sugars, the Kluyver effect, also do not use alcoholic fermentation under anaerobic conditions. The use of these yeasts would make the control of fermentation processes much easier and measures to prevent fermentation processes would largely minimize.

Examples of Kluyver effect positive yeast strains

Footnotes

  1. ↑ Kluyver, AJ and Custers, MTJ (1940) The suitability of disaccharides as respiratory and assimilation substrates for yeasts which do not ferment these sugars. Antonie van Leeuwenhoek 6, 121-162.
  2. ^ Barnett JA The utilization of sugars by yeasts. Adv Carbohydr Chem Biochem. 1976; 32: 125-234.
  3. ↑ Weusthuis RA, Luttik MA, Scheffers WA, van Dijken JP, Pronk JT. Is the Kluyver effect in yeasts caused by product inhibition? Microbiology. 1994 Jul; 140 (Pt 7): 1723-9
  4. ^ Fukuhara H. (2003) The Kluyver effect revisited. FEMS Yeast Research 3,327-331
  5. ↑ Goffrini, P., Ferrero, I. and Donnini, C. (2002) Respiration-dependent utilization of sugars in yeasts: a determinant role of sugar transporters. J. Bacteriol. 184, 427-432
  6. ↑ Castrillo JI, Kaliterna J., Weusthuis RA, van Dijken JP, Pronk JT; High-Cell-Density Cultivation of Yeasts on Disaccharides in Oxygen-Limited Batch Cultures. (1996) Biotechnology and Bioengineering, 49, 621-628

further reading

Zimmerman FK, Entian K.-D. (1997) Yeast Sugar Metabolism: Biochemistry, Genetics, Biotechnology, and Applications. CRC Press ISBN 1-56676-466-1