Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Industrial Microbiology Key Laboratory, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, People's Republic of China.
J Ind Microbiol Biotechnol. 2013 Apr;40(3-4):353-63. doi: 10.1007/s10295-012-1227-5. Epub 2013 Jan 24.
Two lactose-consuming diploid Saccharomyces cerevisiae strains, AY-51024A and AY-51024M, were constructed by expressing the LAC4 and LAC12 genes of Kluyveromyces marxianus in the host strain AY-5. In AY-51024A, both genes were targeted to the ATH1 and NTH1 gene-encoding regions to abolish the activity of acid/neutral trehalase. In AY-51024M, both genes were respectively integrated into the MIG1 and NTH1 gene-encoding regions to relieve glucose repression. Physiologic studies of the two transformants under anaerobic cultivations in glucose and galactose media indicated that the expression of both LAC genes did not physiologically burden the cells, except for AY-51024A in glucose medium. Galactose consumption was initiated at higher glucose concentrations in the MIG1 deletion strain AY-51024M than in the corresponding wild-type strain and AY-51024A, wherein galactose was consumed until glucose was completely depleted in the mixture. In lactose medium, the Sp. growth rates of AY-51024A and AY-51024M under anaerobic shake-flasks were 0.025 and 0.067 h(-1), respectively. The specific lactose uptake rate and ethanol production of AY-51024M were 2.50 g lactose g CDW(-1) h(-1) and 23.4 g l(-1), respectively, whereas those of AY-51024A were 0.98 g lactose g CDW(-1) h(-1) and 24.3 g lactose g CDW(-1) h(-1), respectively. In concentrated cheese whey powder solutions, AY-51024M produced 63.3 g l(-1) ethanol from approximately 150 g l(-1) initial lactose in 120 h, conversely, AY-51024A consumed 63.7 % of the initial lactose and produced 35.9 g l(-1) ethanol. Therefore, relieving glucose repression is an effective strategy for constructing lactose-consuming S. cerevisiae.
构建了两株能消耗乳糖的二倍体酿酒酵母 AY-51024A 和 AY-51024M，它们通过在宿主菌株 AY-5 中表达克鲁维酵母 LAC4 和 LAC12 基因而产生。在 AY-51024A 中，这两个基因都被靶向到 ATH1 和 NTH1 基因编码区，以消除酸性/中性海藻糖酶的活性。在 AY-51024M 中，这两个基因分别被整合到 MIG1 和 NTH1 基因编码区，以解除葡萄糖的抑制作用。在厌氧培养葡萄糖和半乳糖培养基中对两种转化体的生理研究表明，除 AY-51024A 在葡萄糖培养基中外，这两个 LAC 基因的表达并没有给细胞带来生理负担。在缺失 MIG1 的菌株 AY-51024M 中，半乳糖的消耗起始于更高的葡萄糖浓度，而在相应的野生型菌株和 AY-51024A 中，半乳糖的消耗一直持续到混合物中葡萄糖完全耗尽。在乳糖培养基中，在厌氧摇瓶中，AY-51024A 和 AY-51024M 的 Sp. 生长速率分别为 0.025 和 0.067 h(-1)。AY-51024M 的特定乳糖摄取率和乙醇产量分别为 2.50 g 乳糖 g CDW(-1) h(-1)和 23.4 g l(-1)，而 AY-51024A 的分别为 0.98 g 乳糖 g CDW(-1) h(-1)和 24.3 g 乳糖 g CDW(-1) h(-1)。在浓缩奶酪乳清粉溶液中，AY-51024M 在 120 h 内从约 150 g l(-1)初始乳糖中产生了 63.3 g l(-1)乙醇，相反，AY-51024A 消耗了 63.7%的初始乳糖，产生了 35.9 g l(-1)乙醇。因此，解除葡萄糖的抑制作用是构建能消耗乳糖的酿酒酵母的有效策略。
