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The IIOAB Journal 2010
STRAIN IMPROVEMENT OF CANDIDA TROPICALIS OVC5 FOR XYLITOLPRODUCTION BY RANDOM MUTAGENESIS.Keywords: Candida tropicalis , MNNG , mutagenesis , strain improvement , UV , mutant Abstract: Candida tropicalis OVC 5 was subjected to ultraviolet (UV) rays and the mutants obtained were screened for xylitol production. One of the mutant strain CT-UV20, produced 0.78 g xylitol/ g xylose. To isolate high xylitol yielding, Xylitol de hydrogenase enzyme (XDH) defective mutant strain, CT-UV20 was further treated with N-methyl-N-nitro-N-nitroso guanidine (MNNG) and five mutants were selected based on difference in colony morphology. Xylitol production of these MNNG treated mutants were compared with UV treated mutant strain i.e. CT-UV20. In the present study the xylitol yield was found to be very low with five MNNG treated mutants (0.10, 0.23, 0.21, 0.24 and 0.19 g xylitol /g xylose, respectively) in comparison to UV treated mutant strain, CT-UV20 (0.78 g xylitol /g xylose).As we are looking for XDH defective strain by random mutagenesis, the less xylitol yielding MNNG treated mutant strain, CT-OVC5M1 was selected and further experiments were performed by adding 1.5% glycerol into the production medium. Xylitol production by the MNNG mutants increased to 0.59-0.89 g xylitol/g xylose when glycerol was added to the medium.
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