초록
<P><B>Abstract</B></P><P><B>Aims: </B> A major problem in industrial fermentation of organic acids with micro‐organisms is to ensure a suitable pH in the culture broth. To circumvent this problem, we investigated the effect of citrate, which is a widely used auxiliary energy co‐substrate, on cell growth, organic acid production and pH homeostasis among extracellular environment, cytoplasm and vacuole, in the pyruvic acid production by <I>Candida glabrata</I> CCTCC M202019 under different pH conditions.</P><P><B>Methods and Results: </B> Analysis of intracellular ATP regeneration, cytoplasmic and vacuolar pH values under different culture conditions points towards a relief of stress when <I>C.？glabrata</I> is exposed to lower pH, if citrate is added. When 50 mmol l<SUP>−1</SUP> citrate was added to the culture medium, the intracellular ATP concentrations increased by 20·5% (pH 5·5), 20·4% (pH 5·0) and 39·3% (pH 4·5), and higher pH gradients among the culture broth, cell cytoplasm and vacuoles resulted. As a consequence, the cell growth and pyruvic acid production of <I>C.？glabrata</I> CCTCC M202019 were significantly improved under pH 5·0 and 4·5.</P><P><B>Conclusions: </B> The acid tolerance of yeast can be improved by enhancing the ATP supply, which helps to maintain higher pH gradients in the system.</P><P><B>Significance and Impact of the Study: </B> The results presented here expand our understanding of the physiological characteristics in eukaryotic micro‐organisms under low pH conditions and provide a potential route for the further improvement of organic acids production process by process optimization or metabolic engineering.</P>