Hu Chun-Keng, Bai Feng-Wu, An Li-Jia
Department of Bioengineering, Huaqiao University, Quanzhou 362011, China.
Sheng Wu Gong Cheng Xue Bao. 2005 Jan;21(1):123-8.
Investigation was undertaken for the purpose of examining any possible correlation between flocculence of a self-flocculating fusant of Schizosaccharomyces pombe mutant and Saccharomyces cerevisiae mutant (called fusant SPSC for short) and the tolerance of this strain to ethanol. When exposed to 18% (V/V) ethanol for 7 h at 30 degrees C, 52%, 37% and 9% of viability levels remained for the cells of fusant SPSC and its two parental strains, Sch. pombe mutant and S. cerevisiae mutant respectively. Analysis of phospholipid fatty acid composition of plasma membrane showed that the content of palmitic acid of each flocculating yeast (fusant SPSC or Sch. pombe mutant) was around 2-fold higher than that of free S. cerevisiae mutant, with remarkably lower contents of palmitoleic and oleic acids than the latter. When 0.1 mol/L sodium citrate was initially included in the medium in which cells of each flocculating yeast were grown, free cells rather than aggregates were finally obtained. Furthermore, the content of palmitic acid in the phospholipid fatty acid composition of the plasma membranes of the free cells of each flocculating yeast was found to decrease significantly, with a marked increase in the contents of palmitoleic and oleic acids. As a result, the characteristics of the phospholipid fatty acid composition of the plasma membranes of the free cells of each flocculating yeast were similar to those of S. cerevisiae mutant. Meanwhile, the disappearance of flocculence of each flocculating yeast caused by the action of sodium citrate brought about a steeply decreased tolerance of the free cells to ethanol, thus being equivalent to that of S. cerevisiae mutant. These data suggest that the stronger ethanol tolerance of each flocculating yeast is related to the higher content of palmitic acid in the phospholipid fatty acid composition of the plasma membranes. Thus, the enhancement by flocculence on the tolerance of yeast cells to ethanol as well as its mechanism are first reported in this work.
为了研究粟酒裂殖酵母突变体与酿酒酵母突变体的自絮凝融合体（简称融合体SPSC）的絮凝性与其对乙醇的耐受性之间是否存在任何可能的相关性，开展了此项研究。当在30℃下将融合体SPSC及其两个亲本菌株粟酒裂殖酵母突变体和酿酒酵母突变体暴露于18%（V/V）乙醇中7小时后，融合体SPSC及其两个亲本菌株的细胞活力水平分别剩余52%、37%和9%。对质膜磷脂脂肪酸组成的分析表明，每种絮凝酵母（融合体SPSC或粟酒裂殖酵母突变体）的棕榈酸含量比游离的酿酒酵母突变体高约2倍，棕榈油酸和油酸的含量则显著低于后者。当在每种絮凝酵母细胞生长的培养基中最初加入0.1 mol/L柠檬酸钠时，最终获得的是游离细胞而非聚集体。此外，发现每种絮凝酵母游离细胞质膜的磷脂脂肪酸组成中的棕榈酸含量显著降低，棕榈油酸和油酸的含量显著增加。结果，每种絮凝酵母游离细胞质膜的磷脂脂肪酸组成特征与酿酒酵母突变体相似。同时，柠檬酸钠作用导致每种絮凝酵母絮凝性消失，使得游离细胞对乙醇的耐受性急剧下降，与酿酒酵母突变体相当。这些数据表明，每种絮凝酵母较强的乙醇耐受性与质膜磷脂脂肪酸组成中较高的棕榈酸含量有关。因此，本研究首次报道了絮凝对酵母细胞乙醇耐受性的增强作用及其机制。
