Jeppsson H, Yu S, Hahn-Hägerdal B
Department of Applied Microbiology, Lund Institute of Technology/University of Lund, Sweden.
Appl Environ Microbiol. 1996 May;62(5):1705-9. doi: 10.1128/aem.62.5.1705-1709.1996.
Saccharomyces cerevisiae ATCC 24860 was cultivated in chemostat culture under anoxic conditions with 111.1 mmol of glucose liter-1 alone or with a mixture of 66.7 mmol of xylulose liter-1 and 111.1 mmol of glucose liter-1. The substrate consumption rate was 5.4 mmol g of cells-1 h-1 for glucose, whereas for xylulose it was 1.0 mmol g of cells-1 h-1. The ethanol yield decreased from 0.52 carbon mole of ethanol produced per carbon mole of sugar consumed during the utilization of glucose alone to 0.49 carbon mole produced per carbon mole consumed during the simultaneous utilization of xylulose and glucose, while cell biomass was maintained at 2.04 to 2.10 g liter-1. Xylulose coutilization was accompanied by a shift in product formation from ethanol to acetate and arabinitol. Xylulokinase activity was absent during glucose metabolism but detectable during simultaneous utilization of xylulose and glucose. Xylulose cometabolism resulted in increased in vitro activity of pyruvate decarboxylase and an increased concentration of the intracellular metabolite fructose 1,6-diphosphate without significant changes in the concentrations of 6-phosphogluconate and pyruvate. The results are discussed in relation to (i) altered enzyme activities and (ii) the redox flux of the cell.
酿酒酵母ATCC 24860在恒化器培养中于缺氧条件下，单独以111.1 mmol/L的葡萄糖或66.7 mmol/L的木酮糖与111.1 mmol/L的葡萄糖混合物进行培养。葡萄糖的底物消耗速率为5.4 mmol/（g细胞·h），而木酮糖的底物消耗速率为1.0 mmol/（g细胞·h）。乙醇产量从单独利用葡萄糖时每消耗1碳摩尔糖产生0.52碳摩尔乙醇，降至同时利用木酮糖和葡萄糖时每消耗1碳摩尔糖产生0.49碳摩尔乙醇，而细胞生物量维持在2.04至2.10 g/L。木酮糖的共利用伴随着产物形成从乙醇向乙酸盐和阿拉伯糖醇的转变。在葡萄糖代谢期间不存在木酮糖激酶活性，但在同时利用木酮糖和葡萄糖期间可检测到。木酮糖共代谢导致丙酮酸脱羧酶的体外活性增加以及细胞内代谢物果糖1,6 - 二磷酸的浓度增加，而6 - 磷酸葡萄糖酸和丙酮酸的浓度没有显著变化。结合（i）酶活性的改变和（ii）细胞的氧化还原通量对结果进行了讨论。
