Kronberg M F, Nikel P I, Cerrutti P, Galvagno M A
Instituto de Investigaciones Biotecnológicas, IIB-CONICET, Universidad Nacional de San Martín, Buenos Aires, Argentina.
J Appl Microbiol. 2008 Mar;104(3):716-27. doi: 10.1111/j.1365-2672.2007.03588.x. Epub 2007 Oct 9.
To study the effect of prestress conditions on the freezing and thawing (FT) response of two baker's yeast strains and the use of statistical analysis to optimize resistance to freezing.
Tolerance to FT of industrial strains of Saccharomyces cerevisiae was associated to their osmosensitivity and growth phase. Pretreatments with sublethal stresses [40 degrees C, 0.5 mol l(-1) NaCl, 1.0 mol l(-1) sorbitol or 5% (v/v) ethanol] increased freeze tolerance. Temperature or hyperosmotic prestresses increased trehalose contents, nevertheless no clear correlation was found with improved FT tolerance. Plackett-Burman design and response surface methodology were applied to improve freeze tolerance of the more osmotolerant strain. Optimal prestress conditions found were: 0.779 mol l(-1) NaCl, 0.693% (v/v) ethanol and 32.15 degrees C.
Ethanol, saline, osmotic or heat prestresses increased freezing tolerance of two phenotypically distinct baker's yeast strains. A relationship among prestresses, survival and trehalose content was not clear. It was possible to statistically find optimal combined prestress conditions to increase FT tolerance of the osmotolerant strain.
Statistically designed combination of prestress conditions that can be applied during the production of baker's yeast could represent a useful tool to increase baker's yeast FT resistance.
研究预应力条件对两种面包酵母菌株冻融（FT）反应的影响，并利用统计分析优化其抗冻性。
酿酒酵母工业菌株对FT的耐受性与其渗透敏感性和生长阶段有关。用亚致死应激（40℃、0.5 mol l⁻¹ NaCl、1.0 mol l⁻¹ 山梨醇或5%（v/v）乙醇）预处理可提高耐冻性。温度或高渗预应力增加了海藻糖含量，但未发现与改善的FT耐受性有明显相关性。采用Plackett-Burman设计和响应面方法来提高渗透耐受性更强的菌株的耐冻性。发现的最佳预应力条件为：0.779 mol l⁻¹ NaCl、0.693%（v/v）乙醇和32.15℃。
乙醇、盐、渗透或热预应力提高了两种表型不同的面包酵母菌株的耐冻性。预应力、存活率和海藻糖含量之间的关系不明确。通过统计学方法可以找到最佳的组合预应力条件，以提高渗透耐受性菌株的FT耐受性。
在面包酵母生产过程中应用经统计学设计的预应力条件组合，可能是提高面包酵母FT抗性的一种有用工具。
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