Real time intracellular pH dynamics in Listeria innocua under CO2 and N2O pressure
Real time intracellular pH dynamics in Listeria innocua under CO2 and N2O pressure
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DOI：
10.1016/j.supflu.2011.07.012
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发表时间：
2011-10-01
影响因子：
3.9
通讯作者：
Spilimbergo, Sara
中科院分区：
文献类型：
--
作者：
Giulitti, Stefano;Cinquemani, Claudio;Spilimbergo, Sara
本文研究了高压食品处理的失活机理，认为它是传统杀菌工艺的替代方法。我们的目标是确定在二氧化碳和N2O压力下细胞内pH的降低，到目前为止，这被认为是失活的主要原因之一。利用实验室规模的生物反应器，在温和的条件下-25℃，压力高达8兆帕-我们首次在加压期间监测到了基于荧光的pH敏感荧光团标记的无核李斯特菌的细胞质pH变化。我们发现，由于二氧化碳溶解到水相中，碳酸导致细胞质中的pH迅速下降，在1兆帕时达到pH 4.8，并低于指示剂荧光团的检测下限pH 4.0。这与在所调查的所有压力范围内的生存能力降低(低于90%)相关。相反，在N2O压力下处理会降低细胞存活率，而细胞内和细胞外液体在任何压力下都没有明显的pH下降。PH值保持在7到6之间，而在8 Mpa时可以达到80%以上的失活。我们的数据清楚地表明，当达到临界压力时，微生物失活的主要原因是压力诱导的膜渗透-也是由非酸化液刺激的，而不是迄今为止广泛争论的细胞质酸化。对压力下CO2/N2O引起的微生物失活机理的明确理解已经取得了显著进展。(C)2011爱思唯尔B.V.保留所有权利。
This article investigates the inactivation mechanism of high-pressure food treatment, considered as alternative to conventional biocidal processes. We aimed to determine intracellular pH decrease under CO2 and N2O pressure, so far postulated as one of the main causes of inactivation. Working with a lab-scale bioreactor in mild conditions - 25 degrees C and pressures up to 8 MPa - we monitored - for the first time during pressurization - cytoplasmic pH variations of Listeria innocua labeled with pH-sensitive fluorophores based on fluorescein.We show that carbonic acid, due to solubilization of CO2 into the aqueous phase, causes a rapid pH drop in the cytosol, reaching pH 4.8 at 1 MPa and falls below the detection limit of the indicator fluorophore of pH 4.0. This correlates with a reduced viability (below 90%) in all the pressure ranges investigated. Contrarily, treatment under N2O pressure reduces cell viability without significant pH-drop neither of intra- nor extra-cellular liquid at any pressure investigated. The pH value remains between 7 and 6 while an inactivation of more than 80% is achieved at 8 MPa.Our data clearly demonstrate that, as a critical pressure is achieved, microbial inactivation is mainly due to pressure-induced membrane permeation - stimulated by non-acidifying fluids as well, rather then cytoplasmic acidification, as widely argued so far. A definitive understanding of the microbial inactivation mechanism due to CO2/N2O under pressure has been advanced significantly. (C) 2011 Elsevier B.V. All rights reserved.