Transcriptional repression of ADH2-regulated β-xylanase production by ethanol in recombinant strains of Saccharomyces cerevisiae

The regulation of endo-β-(1,4)-xylanase production by two different strains of Saccharomyces cerevisiae, each transformed with the XYN2gene from Trichoderma reeseiunder control of the promoter of the alcohol dehydrogenase II ( ADH2) gene of S. cerevisiae, was investigated. In batch culture, the rate of xylanase production was severely reduced by the pulse addition of 390 mmol ethanol l −1. Pulses of 190–630 mmol ethanol l −1into aerobic glucose-limited steady-state continuous cultures reduced the xylanase activity about five-fold and showed that ethanol repressed the ADH2promoter, as was evident from Northern blot analyses. Derepression of the ADH2-regulated xylanase gene occurred at ethanol concentrations below approximately 50 mmol l −1.