When yeast (C. tropicalis ) inoculated to the glucose and xylose medium at 2% rate separately it utilizes the sugars into ethanol and xylatol respectively at 12h but when the sugars are combine in a certain proportion in fermentation broth the yeast was unable to convert the xylose to xylatol but the glucose is conversion to ethanol is efficient one. But in the same fermentation condition the yeast utilize the xylose to xylatol after a long incubation period (more than 144h) but the efficiency was very poor. So can anybody suggest what will be the reason for the yeast behaves like this? What should be done to utilize both sugars in to their respective products efficiently in combined form?
I never work with this type of yeast. But I assume the enzymes required for xylose metabolism are repressed when glucose present in the media. In other word, the yeast prefer glucose to be metabolized than xylose. Once the glucose exhausted it start to use xylose as their carbon source, but then it is already a long period of incubation, which mean that the yeast already started to loose its viability. Therefore the efficiency that you observed was also poor.
I will follow this discussion to get other answers..
Cheers...
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