The Screening of Alcohol Dehydrogenase (ADH) Mutant of Rhizopus oryzae

Abstract:

During L-lactic acid fermentation with Rhizopus oryzae,there existed a branch pathway by which pyruvate was transformed to eth- anol catalyzed by pyruvate decarboxylase(PDC)and alcohol dehydrogenase(ADH),thus decreasing the flux of pyruvate to lactic acid.In this study,the spores of Rhizopus oryzae AS3.3462 mutagenized with nitrosoguanidine(NTG),the appropriate dosage was 0.15 mg/mL and the lethal rate was 70%～80%.Two mutants,named mut-1 and mut-2,with decreased ADH activity were screened out by yeast peptone dextrose (YPD) agar medium containing allyl alcohol. These two mutants had decreased ADH activities of 41.63% and 50.29% compared with the parent strain. The fermentation behavior after 72h showed that the yields of ethanol produced by mut-1 and mut-2 were 4.87g/L and 6.56g/L respectively,while the wild type strain was 28.9g/L,and the lactate concentrations of mut-1 and mut-2 also increased from 40.31g/L to 54.45g/L and 44.07g/L,respectively. It is also found that mut-1 and mut-2 had a high reducing sugar consumption rate and biomass accumulation than its present strain

Key words:Rhizopus oryzae; ADH; Allyl alcohol; Ethanol; Biomass