Exploring the potential of the glycerol-3-phosphate dehydrogenase 2 (GPD2) promoter for recombinant gene expression in .

A control point for keeping redox homeostasis in during fermentative growth is the dynamic regulation of transcription for the glycerol-3-phosphate dehydrogenase 2 () gene. In this study, the possibility to steer the activity of the promoter was investigated by placing it in strains with different ability to reoxidise NADH, and applying different environmental conditions. Flow cytometric analysis of reporter strains expressing green fluorescent protein () under the control of the promoter was used to determine the promoter activity at the single-cell level When placed in a strain background, the promoter displayed a 2-fold higher activity as compared to the strong constitutive glyceraldehyde-3-phosphate dehydrogenase (). In contrast, the promoter was found to be inactive when cells were cultivated in continuous mode at a growth rate of 0.3 h and in conditions with excess oxygen (i.e. with an aeration of 2.5 vvm, and a stirring of 800 rpm). In addition, a clear window of operation where the strain can be grown with the same efficiency as wild type yeast was identified. In conclusion, the flow cytometry mapping revealed conditions where the promoter was either completely inactive or hyperactive, which has implications for its implementation in future biotechnological applications such as for process control of heterologous gene expression.