Production of xylitol from D‐xylose by candida tropicalis: Optimization of production rate

Abstract

The effect of culture conditions on xylitol production rate was investigated using Candida tropicalis IFO 0618. From the variance analysis of xylitol production rate, it was found that initial yeast extract concentration was highly significant (99%), while the interaction between D-xylose concentration and aeration rate was significant (95%). These results show the importance of initial yeast extract concentration and of the balance between D-xylose concentration and aeration in the production of xylitol. It was also clearly shown that C. tropicalis needed more yeast extract concentration for efficient xylitol production than for its growth. In order to enhance xylitol production rate, culture conditions were optimized by the Box-Wilson method. In this respect, initial D-xylose concentration, yeast extract concentration, and K(L)a were chosen as the independent factors in 2(3)-factorial experimental design. As the result of experiments, a maximum xylitol production rate of 2.67 g/L . h was obtained when initial D-xylose concentration and yeast extract concentration were 172.0 and 21.0 g/L, respectively, and K(L)a was 451.50 h(-1) by 90% oxygen gas.

Structure of xylose reductase bound to NAD+ and the basis for single and dual co-substrate specificity in family 2 aldo-keto reductases

“…There is conflicting information, however, regarding XR from Candida tropicalis (AKR2B4). One report suggests that it is specific for NADPH [26], whereas others show dual specificity [27,28]. Since a key determinant for NADH specificity appears to be Glu 227 in C. tenuis XR, we examined this position in the other XRs.…”

“…Based upon the structure of the AKR1C9 ternary complex with NADP + and testosterone [30], the shorter side chain of the aspartate residue and slightly different placement position of the nearest carboxylate oxygen is 8.99 Å from the adenosine O3 compared with 3.66 Å for the analogous distance of the glutamate residue side chain in the XR complex with NADP + . The Asp 224 side chain is also engaged in a hydrogen bond with the main-chain amide nitrogen of Glu 27 . Glu 227 in XR makes no such interactions which may facilitate it making interactions with the adenosine ribose.…”

Biotechnical modification of carbohydrates

“…Yeast species such as Pachysolen tannophilus, Pichia stipitis and Candida guilliermondii are most cited as useful microorganisms. Xylitol conversion yields of 50-76% are obtained [14].…”

Molecular Cloning and Characterization of NAD+‐Dependent Xylitol Dehydrogenase from Candida tropicalis ATCC 20913

“…The yeast's ability to utilize n-alkanes and fatty acids as carbon sources has been exploited to produce dicarboxylic acid, the starting material for the preparation of perfumes, polymers, adhesives, and macrolide antibiotics, by metabolic engineering of peroxisomal -oxidation enzymes (1,2). Furthermore, C. tropicalis has recently attracted an attention because of its production of xylitol from D-xylose as a result of its high xyloseassimilating activity (3,4).…”

“…As a result of these benefits, the use of xylitol in the food industry is growing rapidly. Xylitol is produced by natural xylose-assimilating yeasts and fungi, such as Pachysolen tannophilus, Petromyces albertensis, C. guilliermondii, C. parapsilosis, and C. tropicalis (3,(15)(16)(17)(18). In addition, genetically engineered S. cereVisiae harboring the XR gene from P. stipitis was reported to produce xylitol (19).…”