Roca C, Haack M B, Olsson L
Centre for Process Biotechnology, BioCentrum-DTU, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
Appl Microbiol Biotechnol. 2004 Feb;63(5):578-83. doi: 10.1007/s00253-003-1408-2. Epub 2003 Aug 19.
Two xylose-fermenting glucose-derepressed Saccharomyces cerevisiae strains were constructed in order to investigate the influence of carbon catabolite repression on xylose metabolism. S. cerevisiae CPB.CR2 (Delta mig1, XYL1, XYL2, XKS1) and CPB.MBH2 (Delta mig1, Delta mig2, XYL1, XYL2, XKS1) were analysed for changes in xylose consumption rate and ethanol production rate during anaerobic batch and chemostat cultivations on a mixture of 20 g l(-1) glucose and 50 g l(-1) xylose, and their characteristics were compared to the parental strain S. cerevisiae TMB3001 ( XYL1, XYL2, XKS1). Improvement of xylose utilisation was limited during batch cultivations for the constructed strains compared to the parental strain. However, a 25% and 12% increased xylose consumption rate during chemostat cultivation was achieved for CPB.CR2 and CPB.MBH2, respectively. Furthermore, during chemostat cultivations of CPB.CR2, where the cells are assumed to grow under non-repressive conditions as they sense almost no glucose, invertase activity was lower during growth on xylose and glucose than on glucose only. The 3-fold reduction in invertase activity could only be attributed to the presence of xylose, suggesting that xylose is a repressive sugar for S. cerevisiae.
构建了两株木糖发酵且葡萄糖去阻遏的酿酒酵母菌株，以研究碳代谢物阻遏对木糖代谢的影响。分析了酿酒酵母CPB.CR2（Δmig1，XYL1，XYL2，XKS1）和CPB.MBH2（Δmig1，Δmig2，XYL1，XYL2，XKS1）在含有20 g l(-1)葡萄糖和50 g l(-1)木糖的混合物上进行厌氧分批培养和恒化培养期间木糖消耗率和乙醇产率的变化，并将它们的特性与亲本菌株酿酒酵母TMB3001（XYL1，XYL2，XKS1）进行比较。与亲本菌株相比，在分批培养期间构建菌株的木糖利用率提高有限。然而，在恒化培养期间，CPB.CR2和CPB.MBH2的木糖消耗率分别提高了25%和12%。此外，在CPB.CR2的恒化培养过程中，由于细胞在几乎检测不到葡萄糖的情况下被认为是在非阻遏条件下生长，因此在木糖和葡萄糖上生长时的转化酶活性低于仅在葡萄糖上生长时。转化酶活性降低3倍只能归因于木糖的存在，这表明木糖对酿酒酵母是一种阻遏性糖类。
