Bodzen Aurore, Jossier Audrey, Dupont Sébastien, Mousset Pierre-Yves, Beney Laurent, Lafay Sophie, Gervais Patrick
University of Burgundy, AgroSup Dijon, PAM UMR A 02.102, 21000 Dijon, France.
Indigo Therapeutics, 5 rue Salneuve, 75017 Paris, France.
Food Technol Biotechnol. 2021 Dec;59(4):443-453. doi: 10.17113/ftb.59.04.21.7076.
Freeze-drying is the most widely used dehydration process in the food industry for the stabilization of bacteria. Studies have shown the effectiveness of an acid prestress in increasing the resistance of lactic acid bacteria to freeze-drying. Adaptation of bacteria to an acid stress is based on maintaining the properties of the plasma membrane. Indeed, the fatty acid composition of the membrane of lactic acid bacteria is often changed after an acid prestress. However, few studies have measured membrane fluidity after an acid stress during lactic acid bacterial strain cultivation.
In order to use two pH profiles, the strains NCDO 712 and NZ9000 were cultivated in two media, without any pH control. The two pH profiles obtained were representative of the initial medium composition, medium buffering properties and strain metabolism. Absorbance at 600 nm and pH were measured during bacterial cultivation. Then, the two strains were freeze-dried and their survival rates determined. Membrane fluidity was evaluated by fluorescence anisotropy measurements using a spectrofluorometer.
Cultivation under more acidic conditions significantly increased the survival during freeze-drying (p<0.05, ANOVA) of both strains. Moreover, in both strains of , a more acidic condition during cultivation significantly increased membrane fluidity (p<0.05, ANOVA). Our results revealed that cultivation under such conditions, fluidifies the membrane and allows a better survival during freeze-drying of the two strains. A more fluid membrane can facilitate membrane deformation and lateral reorganization of membrane components, critical for the maintenance of cellular integrity during dehydration and rehydration.
A better understanding of the involvement of membrane properties, especially of membrane fluidity, in bacterial resistance to dehydration is provided in this study.
冷冻干燥是食品工业中用于细菌稳定化的最广泛使用的脱水工艺。研究表明，酸预处理在提高乳酸菌对冷冻干燥的抗性方面具有有效性。细菌对酸胁迫的适应基于维持质膜的特性。实际上，乳酸菌膜的脂肪酸组成在酸预处理后常常会发生变化。然而，在乳酸菌菌株培养过程中，很少有研究测量酸胁迫后的膜流动性。
为了使用两种pH曲线，将菌株NCDO 712和NZ9000在两种培养基中培养，不进行任何pH控制。获得的两种pH曲线代表了初始培养基组成、培养基缓冲特性和菌株代谢。在细菌培养过程中测量600 nm处的吸光度和pH值。然后，将这两种菌株进行冷冻干燥并测定其存活率。使用荧光分光光度计通过荧光各向异性测量来评估膜流动性。
在更酸性条件下培养显著提高了两种菌株冷冻干燥后的存活率（p<0.05，方差分析）。此外，在两种菌株中，培养期间更酸性的条件显著提高了膜流动性（p<0.05，方差分析）。我们的结果表明，在这种条件下培养可使膜液化，并使两种菌株在冷冻干燥过程中具有更好的存活率。流动性更高的膜可促进膜变形和膜成分的横向重组，这对于脱水和复水过程中维持细胞完整性至关重要。
本研究更好地理解了膜特性，尤其是膜流动性在细菌抗脱水能力中的作用。
