Production of Xylitol from d -Xylose by a Xylitol Dehydrogenase Gene-Disrupted Mutant of Candida tropicalis

Abstract

Xylitol dehydrogenase (XDH) is one of the key enzymes in D-xylose metabolism, catalyzing the oxidation of xylitol to D-xylulose. Two copies of the XYL2 gene encoding XDH in the diploid yeast Candida tropicalis were sequentially disrupted using the Ura-blasting method. The XYL2-disrupted mutant, BSXDH-3, did not grow on a minimal medium containing D-xylose as a sole carbon source. An enzyme assay experiment indicated that BSXDH-3 lost apparently all XDH activity. Xylitol production by BSXDH-3 was evaluated using a xylitol fermentation medium with glucose as a cosubstrate. As glucose was found to be an insufficient cosubstrate, various carbon sources were screened for efficient cofactor regeneration, and glycerol was found to be the best cosubstrate. BSXDH-3 produced xylitol with a volumetric productivity of 3.23 g liter ؊1 h ؊1 , a specific productivity of 0.76 g g ؊1 h ؊1 , and a xylitol yield of 98%. This is the first report of gene disruption of C. tropicalis for enhancing the efficiency of xylitol production.

Ethanol and xylitol production from glucose and xylose at high temperature by Kluyveromyces sp. IIPE453

“…A number of yeasts and molds can produce xylitol from xylose because they possess the enzyme xylose reductase. Candida guilliermondii [10], Candida tropicalis [14,16], Candida boidinii [31], Candida magnoliae [29], Debaryomyces hansenii [26], and Pichia stipitis [13] are some of the yeasts with xylitol production capability.…”

Enhancement of xylitol production in Candida tropicalis by co-expression of two genes involved in pentose phosphate pathway

“…The first constructed cassette was composed of 5 0 HisF1, glutamic acid (glu), uracil marker (URA3), glutamic acid (glu), GAPDH promoter (P GAPDH ), zwf, GAPDH terminator (T GAPDH ), and 3 0 HisR1. The cassette contained two DNA fragments 5 0 HisF1 and 3 0 HisR1 flanking the first target hisG region, and was transformed into C. tropicalis L10 by homologous recombination system using lithium acetate method [12]. A gnd expression cassette was constructed by similar procedure.…”

“…We screened various carbon sources for xylitol production by this mutant strain, termed BSXDH-3, and found that glycerol was the best co-substrate for cell maintenance and NADPH regeneration [12]. In micro-organisms, NADPH is produced mainly via the pentose phosphate pathway (PPP), as a co-factor of two enzymes: (1) glucose-6-phosphate…”

Simultaneous Production of Xylitol and Ethanol from Different Hemicellulose Waste Substrates by Candida tropicalis Strain Ly15

“…High substrate concentration is imperative for the production of xylitol in a cost-effective way for scale up process. Significant steps towards the strain improvement for xylitol-production have been assumed [8][9][10].…”