Weusthuis R A, Luttik M A, Scheffers W A, van Dijken J P, Pronk J T
Department of Microbiology and Enzymology, Kluyver Laboratory of Biotechnology, Delft University of Technology, The Netherlands.
Microbiology (Reading). 1994 Jul;140 ( Pt 7):1723-9. doi: 10.1099/13500872-140-7-1723.
Candida utilis 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 C. utilis, 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 C. utilis CBS 621 and Debaryomyces castellii CBS 2923 in aerobic batch cultures on mixtures of sugars and ethanol.(ABSTRACT TRUNCATED AT 250 WORDS)
产朊假丝酵母CBS 621对麦芽糖表现出克鲁维效应，即这种酵母能够呼吸利用麦芽糖，并且能够发酵葡萄糖，但不能发酵麦芽糖。当向以麦芽糖为生长底物、处于氧气受限状态的恒化器培养的产朊假丝酵母中脉冲添加葡萄糖时，几乎瞬间就开始从葡萄糖形成乙醇，这表明酒精发酵所需的酶在以麦芽糖生长的细胞中是有表达的。然而，添加葡萄糖会抑制麦芽糖代谢。为了消除可能对麦芽糖代谢相关酶活性的分解代谢物抑制和/或阻遏作用，研究了在氧气受限、以麦芽糖生长的恒化器培养物中同时添加葡萄糖和麦芽糖的效果。在这种情况下，培养物中的葡萄糖浓度保持在0.1 mM以下，这使得葡萄糖分解代谢物阻遏不太可能发生。尽管如此，当培养物切换到混合进料时，麦芽糖代谢似乎停止了。基于混合底物研究的结果，推测克鲁维效应可能是由发酵性麦芽糖代谢产物乙醇对麦芽糖利用的反馈抑制引起的。如果乙醇抑制了不可发酵二糖的利用，这将为克鲁维效应的发生提供一个现象学解释：那么乙醇就不会积累，麦芽糖代谢速率将根据培养物的呼吸能力进行调节。通过研究产朊假丝酵母CBS 621和德巴利酵母CBS 2923在有氧分批培养中在糖和乙醇混合物上的生长情况来检验这一假设。（摘要截短至250字）
