Intracellular pH and Metabolic Activity of Long-Chain Dicarboxylic Acid-Producing Yeast Candida tropicalis

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概要

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• The intracellular pH (pH_i) of α,ω-dicarboxylic acid producing Candida tropicalis was determined by a fluorescence technique using the pH-sensitive fluorescent probe 5(6)-carboxyfluores-cein diacetate. Fermentations with n-tridecane substrate to produce α,ω-tridecanedioic acid were carried out in a 5-l bioreactor in which growth and production were separated. During the growth phase, the measured pH_i, values were varied from 5.65 to 6.15 in all the experiments performed under different constant pH-operating conditions. The specific rates of growth, sucrose consumption, CO_2 production, and O_2 consumption were correlated with pH_i. Cytochrome P450 monooxy-genase (P450), which catalyzes n-alkane hydroxylation, was only slightly expressed during the growth phase. During the first 6 h of the production phase, P450 activity was induced rapidly accompanying higher pH_i. A much higher level of P450 activity was observed at pH_i of 6.55±0.15 for all the fermentations, with maximum productivity (1.919 g/l/h) occurring when using an optimal pH-control strategy. However, P450 activity, tridecanedioic acid productivity, and pH_i, decreased progressively during the latter part of the production phase, as a consequence of the metabolic activity changes of the cells. Even though culture pH has only a slight influence on pH_i the metabolic activity of C. tropicalis is sensitive to the variations in pH_i. The measured pH_i, varied from 6.1 to 6.7 during the production phase for all the fermentations. Thus, both tridecanedioic acid productivity and P450 activity are correlated with pH_i, or pH gradients across the cell membrane.

• 社団法人日本生物工学会の論文
• 2003-10-25

著者

• LI CHUN

  Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences

• Xie Langyi

  Institute Of Marine Biotechnology Department Of Biological Sciences And Biotechnology Tsinghua Unive

• Cao Zhu'an

  Institute Of Biochemical Engineering Department Of Chemical Engineering Tsinghua University

• LIU SHUCHEN

  Institute of Biochemical Engineering, Department of Chemical Engineering Tsinghua University

• Liu S

  Sichuan Univ. Chengdu Chn

• Li Chun

  Institute Of Biochemical Engineering Department Of Chemical Engineering Tsinghua University

• Xie Langyi

  Institute Of Biochemical Engineering Department Of Chemical Engineering Tsinghua University

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