1887

Abstract

CBS 621 exhibits the Kluyver effect for maltose, i.e. this yeast can respire maltose and is able to ferment glucose, but is unable to ferment maltose. When glucose was pulsed to a maltose-grown, oxygen-limited chemostat culture of , ethanol formation from glucose started almost instantaneously, indicating that the enzymes needed for alcoholic fermentation are expressed in maltose-grown cells. However, the addition of glucose inhibited maltose metabolism. To eliminate a possible catabolite inhibition and/or repression of enzyme activities involved in maltose metabolism, the effect of simultaneously feeding glucose and maltose to an oxygen-limited, maltose-grown chemostat culture was studied. In this case, the glucose concentration in the culture remained below 0.1 mM, which makes glucose catabolite repression unlikely. Nevertheless, maltose metabolism appeared to cease when the culture was switched to the mixed feed. Based on the outcome of the mixed-substrate studies, it was postulated that the Kluyver effect may be caused by feedback inhibition of maltose utilization by ethanol, the product of fermentative maltose metabolism. If ethanol suppresses the utilization of non-fermentable disaccharides, this would provide a phenomenological explanation for the occurrence of the Kluyver effect: accumulation would then not occur and the rate of maltose metabolism would be tuned to the culture's respiratory capacity. This hypothesis was tested by studying growth of CBS 621 and CBS 2923 in aerobic batch cultures on mixtures of sugars and ethanol. With both yeasts diauxic growth was indeed observed on mixtures of ethanol and a disaccharide that gives rise to the Kluyver effect, with ethanol being the preferred substrate. In contrast, sugars which could be fermented were either utilized simultaneously with ethanol or preferred over this substrate.

Loading

Article metrics loading...

/content/journal/micro/10.1099/13500872-140-7-1723
1994-07-01
2019-12-07
Loading full text...

Full text loading...

http://instance.metastore.ingenta.com/content/journal/micro/10.1099/13500872-140-7-1723
Loading
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error