Xylitol production is increased by expression of codon-optimized Neurospora crassa xylose reductase gene in Candida tropicalis

• Published in: Bioprocess and biosystems engineering Vol. 35; no. 1-2; pp. 191 - 198
• Main Authors: Jeon, Woo Young, Yoon, Byoung Hoon, Ko, Byoung Sam, Shim, Woo Yong, Kim, Jung Hoe
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.01.2012; Springer; Springer Nature B.V
• Subjects: Aldehyde Reductase - genetics; Aldehyde Reductase - metabolism; Biological and medical sciences; Biotechnology; Candida tropicalis - enzymology; Candida tropicalis - genetics; Chemistry; Chemistry and Materials Science; Codon - genetics; Dehydrogenase; Energy sources; Environmental Engineering/Biotechnology; Fermentation; Food Science; Fundamental and applied biological sciences. Psychology; Gene expression; Genetic Enhancement - methods; Industrial and Production Engineering; Industrial Chemistry/Chemical Engineering; Neurospora crassa - genetics; Neurospora crassa - metabolism; Optimization techniques; Original Paper; Transfection; Xylitol - biosynthesis; Xylitol - isolation & purification; Xylose - metabolism; Yeast; Yeasts; Xylitol; Glucose repression; Xylose reductase; Codon optimization; Ascomycota; Yeast; Enzyme; Glucose; Repression; Optimization; Fungi; Xylose; Codon; Gene; Production; Candida tropicalis; Neurospora crassa; Fungi Imperfecti; Oxidoreductases; Reductase
• ISSN: 1615-7591; 1615-7605
• DOI: 10.1007/s00449-011-0618-8

Xylose reductase (XR) is the first enzyme in d -xylose metabolism, catalyzing the reduction of d -xylose to xylitol. Formation of XR in the yeast Candida tropicalis is significantly repressed in cells grown on medium that contains glucose as carbon and energy source, because of the repressive effect of glucose. This is one reason why glucose is not a suitable co-substrate for cell growth in industrial xylitol production. XR from the ascomycete Neurospora crassa (NcXR) has high catalytic efficiency; however, NcXR is not expressed in C . tropicalis because of difference in codon usage between the two species. In this study, NcXR codons were changed to those preferred in C . tropicalis . This codon-optimized NcXR gene (termed NXRG) was placed under control of a constitutive glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter derived from C . tropicalis , and integrated into the genome of xylitol dehydrogenase gene ( XYL2 )-disrupted C . tropicalis . High expression level of NXRG was confirmed by determining XR activity in cells grown on glucose medium. The resulting recombinant strain, LNG2, showed high XR activity (2.86 U (mg of protein) −1 ), whereas parent strain BSXDH-3 showed no activity. In xylitol fermentation using glucose as a co-substrate with xylose, LNG2 showed xylitol production rate 1.44 g L −1  h −1 and xylitol yield of 96% at 44 h, which were 73 and 62%, respectively, higher than corresponding values for BSXDH-3 (rate 0.83 g L −1  h −1 ; yield 59%).