A rare sugar xylitol.: Part I:: the biochemistry and biosynthesis of xylitol

The rare sugar xylitol is a five-carbon polyol (pentitol) that has beneficial health effects. Xylitol has global markets and, therefore, it represents an alternative to current dominant sweeteners. The research on microbial reduction of D-xylose to xylitol has been focused on metabolically engineered Saccharomycess cerevisiae and Candida strains. The Candida strains have an advantage over the metabolically engineered S. cerevisiae in terms of D-xylose uptake and maintenance of the intracellular redox balance. Due to the current industrial scale production of xylitol, it has become an inexpensive starting material for the production of other rare sugar. The first part of this mini-review concentrates on the biochemistry of xylitol biosynthesis and the problems related to intracellular redox balance. almost the same sweetness as sucrose, but with an energy value of only 2.4 cal/g compared to the 4 cal/g of sucrose. Xylitol has a negative heat of solution and good solubility in water, causing a cooling sensation when consumed orally. Due to its beneficial health effects, xylitol has become a global sweetener. It is mainly used as a sweetener in chewing gums, mints, sweets and toothpaste.