Van Vleet Jennifer Headman, Jeffries Thomas W, Olsson Lisbeth
Center for Microbial Biotechnology, Technical University of Denmark, Biocentrum-DTU, Building 223, DK-2800 Kgs. Lyngby, Denmark.
Metab Eng. 2008 Nov;10(6):360-9. doi: 10.1016/j.ymben.2007.12.002. Epub 2007 Dec 27.
Overexpression of D-xylulokinase in Saccharomyces cerevisiae engineered for assimilation of xylose results in growth inhibition that is more pronounced at higher xylose concentrations. Mutants deficient in the para-nitrophenyl phosphatase, PHO13, resist growth inhibition on xylose. We studied this inhibition under aerobic growth conditions in well-controlled bioreactors using engineered S. cerevisiae CEN.PK. Growth on glucose was not significantly affected in pho13Delta mutants, but acetate production increased by 75%. Cell growth, ethanol production, and xylose consumption all increased markedly in pho13Delta mutants. The specific growth rate and rate of specific xylose uptake were approximately 1.5 times higher in the deletion strain than in the parental strain when growing on glucose-xylose mixtures and up to 10-fold higher when growing on xylose alone. In addition to showing higher acetate levels, pho13Delta mutants also produced less glycerol on xylose, suggesting that deletion of Pho13p could improve growth by altering redox levels when cells are grown on xylose.
在经工程改造用于木糖同化的酿酒酵母中，D-木酮糖激酶的过表达会导致生长抑制，这种抑制在较高木糖浓度下更为明显。对硝基苯磷酸酶PHO13缺陷的突变体对木糖上的生长抑制具有抗性。我们在使用工程改造的酿酒酵母CEN.PK的、控制良好的生物反应器中，研究了有氧生长条件下的这种抑制作用。pho13Δ突变体在葡萄糖上的生长没有受到显著影响，但乙酸盐产量增加了75%。pho13Δ突变体的细胞生长、乙醇产量和木糖消耗均显著增加。当在葡萄糖-木糖混合物上生长时，缺失菌株的比生长速率和比木糖摄取速率比亲本菌株高约1.5倍，而在单独木糖上生长时则高达10倍。除了显示出较高的乙酸盐水平外，pho13Δ突变体在木糖上产生时产生的甘油也较少，这表明当细胞在木糖上生长时，缺失Pho13p可能通过改变氧化还原水平来改善生长。
