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Chemostat study of xylitol production by Candida guilliermondii
- Granstrom, T., Ojamo, H., Leisola, M.
- Applied microbiology and biotechnology 2001 v.55 no.1 pp. 36-42
- Meyerozyma guilliermondii, NAD (coenzyme), acetates, aerobic conditions, agitation, enzyme activity, ethanol, glucose-6-phosphate 1-dehydrogenase, glucose-6-phosphate isomerase, glycerol, metabolites, oxygen, pentose phosphate cycle, xylitol, xylose
- The mechanism of production of xylitol from xylose by Candida guilliermondii was studied using chemostat cultures and enzymatic assays. The maximum dilution rate in aerobic conditions was 0.34 1/h. No xylitol was produced. Under oxygen-limited conditions xylose uptake was impaired and glycerol accumulated but no xylitol was detected. Under transient oxygen limitation, caused by a gradual decrease in the agitation rate, onset of xylitol, acetate and residual xylose accumulation occurred simultaneously when qo2 dropped below 25 mmol/C-mmol cell weight (CDW) per hour. Ethanol and glycerol started to accumulate when q02 dropped below 20 mmol/C-mmol CDW per hour. The highest in vitro enzyme activities were found at the lowest dilution rate studied (0.091/h) under aerobic conditions. The amount of active enzymes or cofactor availability did not limit the rate of xylose consumption. Our results confirm that a surplus of NADH during transient oxygen limitation inhibited the activity of xylitol dehydrogenase which resulted in xylitol accumulation. Phosphoglucoisomerase (E.C. 184.108.40.206.) and glucose-6-phosphate dehydrogenase (E.C. 220.127.116.11) activities suggest re-shuttling of the metabolites into the pentose phosphate pathway.