Effect of Ethanol on Selected Enzymes of the Entner-Doudorff Pathway in Zymomonas mobilis

에탄올이 Zymomonas mobilis의 당대사 관련 효소에 미치는 영향

The aim of the presented paper was to elucidate the physiological background of ethanol inhibition on glucose uptake, ethanol production and cell growth in Z. mobilis. Data obtained from batch and continuous cultures showed that the rates of glucose uptake and ethanol production were not affected but growth rate was apparently reduced by ethanol produced. In order to know the effects of ethanol on the anabolism and the catabolism in Z. mobilis, enzyme activities of the Enter-Doudoroff pathway, viz. hexokinase, glucose 6-phosphate dehydrogenase, were analyzed with the cell grown at different concentration of ethanol produced. As results, it was found that the activities of the glucose kinase and the glucose 6-phosphate dehydrogenase were not affected greatly by the concentration of ethanol where the glucose uptake rates revealed a relatively constant value. However it was very interesting to note that transketolase, which is an essential enzyme to provide the important precursors for cell growth, was affected more apparently to reduce by increasing ethanol levels. Those results might suggest that the apparent reduction of growth rate at ethanol concentration above 20 g/$\ell$ would be caused by the reduction of the transketolase activity, which in turn provide less precursor for the cell growth.

발효생산된 에탄올의 농도가 Zymomonas mobilis 에서 당대사에 관련된 효소의 역가에 미치는 영향을 조사하였다. 그 결과, glucose kinase 및 glucose 6-phosphate dehydrogenase는 큰 영향을 받지 않았으나 transketolase 역가는 에탄을 농도가 증가함에 따라 심하게 저해됨을 알았다. 따라서 에탄을 농도의 증가에 따른 균성장속도의 감소는 transketolase에 의하여 영향을 받는 것으로 생각되었다.