Abstract: A neomycin-resistant mutant NA-2,with the activity of F1-ATPase decreased roughly 86.82%,was obtained by synchrotron soft X-ray Nk mutagenesis based on analysis of energy metabolic pathway.The strain NA-2 was cultured in a flask containing L-lactic acid fermentation medium with 120 g/L glucose.It was found that compared with the fermentation characters of original Rhizopus oryza,the rates of glucose consumption and L-lactic acid production are higher with 25.17% and 32.57%,and the qs,qp and μ are higher 86.42%,128.13% and 60.0% respectively.The content of intracellular ATP decreases 18.99% in the mutant than in the origin.However,the change of intracellular energy charge is not obvious.The activities of key enzymes in glycoly ticpathway of the mutant and the origin were determined.Results showed that,compared with the original strain Rhizopus oryzae 3.819,the activities of key enzymes,phosphofructokinase,private kinas,glyceraldyde-3-phosphate dehydrogenase of the mutant NA-2 increase 58.34%,23.53% and 11.29%,respectively.The activity of LDH increase 42.27% while that of ADH decreases 32.11%.As a conclusion,the L-lactic acid productivity by Rhizopus oryza3.819 is enhanced when the activities of key enzymes in glycdytic pathway are regulated by decreasing the activity of F1 -ATPase.

Key words: Rhizopus oryzae, F1-ATPase, glycolytic pathway, L-lactic acid, neomycin-resistant, synchronous radiation