Weak-acid preservatives: pH and proton movements in the yeast Saccharomyces cerevisiae.
Weak-acid preservatives: pH and proton movements in the yeast Saccharomyces cerevisiae.
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DOI：
10.1016/j.ijfoodmicro.2012.12.013
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发表时间：
2013-02
影响因子：
5.4
通讯作者：
M. Stratford;G. Nebe-von-Caron;H. Steels;M. Novodvorska;J. Ueckert;D. Archer
中科院分区：
文献类型：
--
作者：
M. Stratford;G. Nebe-von-Caron;H. Steels;M. Novodvorska;J. Ueckert;D. Archer
通常用于防止低pH值食品真菌腐败的弱酸性防腐剂包括山梨酸和乙酸。“经典弱酸理论”提出，弱酸通过未解离的酸通过膜扩散、在细胞内解离成质子和阴离子以及随后的细胞质酸化来抑制腐败生物。来自25株酿酒酵母的结果证实了乙酸在摩尔浓度比山梨酸高42倍时的抑制作用，这与弱酸理论相矛盾，即所有相同pKash的酸都能在等摩尔浓度下抑制。流式细胞仪显示，在生长抑制浓度的乙酸下，细胞内pH值下降至pH4.7，而在抑制浓度的山梨酸下，pH值仅下降至pH6.3。细胞膜H+-ATP酶质子泵（Pma 1 p）在生长抑制浓度下被山梨酸强烈抑制，而被乙酸激活。H+-ATP酶也被抑制较低的山梨酸浓度，但后来显示恢复和升高的活性，如果山梨酸被删除。PMA 1转录水平短暂增加山梨酸后，但很快恢复到正常水平。乙酸对S.酿酒酵母的发酵是由于细胞内酸化所致，符合“经典弱酸理论”的雅阁。然而，山梨酸似乎是一种膜活性抗菌化合物，质膜H+-ATP酶质子泵是抑制的主要靶点。了解山梨酸的作用机制将有望改进食品保存方法。
Weak-acid preservatives commonly used to prevent fungal spoilage of low pH foods include sorbic and acetic acids. The “classical weak-acid theory” proposes that weak acids inhibit spoilage organisms by diffusion of undissociated acids through the membrane, dissociation within the cell to protons and anions, and consequent acidification of the cytoplasm. Results from 25 strains of Saccharomyces cerevisiae confirmed inhibition by acetic acid at a molar concentration 42 times higher than sorbic acid, in contradiction of the weak-acid theory where all acids of equal pKashould inhibit at equimolar concentrations. Flow cytometry showed that the intracellular pH fell to pH4.7 at the growth-inhibitory concentration of acetic acid, whereas at the inhibitory concentration of sorbic acid, the pH only fell to pH6.3. The plasma membrane H+-ATPase proton pump (Pma1p) was strongly inhibited by sorbic acid at the growth-inhibitory concentration, but was stimulated by acetic acid. The H+-ATPase was also inhibited by lower sorbic acid concentrations, but later showed recovery and elevated activity if the sorbic acid was removed. Levels of PMA1 transcripts increased briefly following sorbic acid addition, but soon returned to normal levels. It was concluded that acetic acid inhibition of S. cerevisiae was due to intracellular acidification, in accord with the “classical weak-acid theory”. Sorbic acid, however, appeared to be a membrane-active antimicrobial compound, with the plasma membrane H+-ATPase proton pump being a primary target of inhibition. Understanding the mechanism of action of sorbic acid will hopefully lead to improved methods of food preservation.