Screening of allyl alcohol resistant mutant of Rhizopus oryzae and its fermentation characterization

  • Z Zheng
  • S Luo
  • X Li
  • X Wu
  • L Pan
  • S Jiang
Keywords: Alcohol dehydrogenase, ethanol, L-lactic acid, Rhizopus oryzae.

Abstract

Ethanol is a main by-product in the fermentation broth of Rhizopus oryzae during the production of high-optical purity L-lactic acid. By screening the lower activity of alcohol dehydrogenase (ADH) mutant, thus decreasing the flux of pyruvic acid to ethanol may be a virtual method for increasing the conversion rate of glucose to L-lactic acid. Mutagenesis of R. oryzae As3.3461 was conducted in this study, and a high-producing lactic acid mutant HBF-12 was screened out with selective medium of Yeast-Peptone-Dextrose (YPD) containing allyl alcohol. This mutant showed higher conversion rate of 88.4 g/l to lactate in a 7 L bioreactor, which was an increase of 30.1% compared to original strain of 67.95 g/l, and the conversion rate to ethanol decreased 73.6%. The zymological analysis indicated HBF-12 had a lower ADH specific activity, but an appreciably higher lactate dehydrogenase (LDH) specific activity. The HBF-12 mutant also had a higher consumption rate of glucose and higher biomass
collection.
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eISSN: 1684-5315