UMR STLO, INRAE, Agrocampus Ouest, 35042, Rennes, France.
Bioprox, 6 rue Barbès, 92532, Levallois-Perret, France.
Appl Microbiol Biotechnol. 2020 Apr;104(7):3145-3156. doi: 10.1007/s00253-020-10425-1. Epub 2020 Feb 19.
Propionibacterium freudenreichii is a beneficial bacterium widely used in food as a probiotic and as a cheese-ripening starter. In these different applications, it is produced, dried, and stored before being used. Both freeze-drying and spray-drying were considered for this purpose. Freeze-drying is a discontinuous process that is energy-consuming but that allows high cell survival. Spray-drying is a continuous process that is more energy-efficient but that can lead to massive bacterial death related to heat, osmotic, and oxidative stresses. We have shown that P. freudenreichii cultivated in hyperconcentrated rich media can be spray-dried with limited bacterial death. However, the general stress tolerance conferred by this hyperosmotic constraint remained a black box. In this study, we modulated P. freudenreichii growth conditions and monitored both osmoprotectant accumulation and stress tolerance acquisition. Changing the ratio between the carbohydrates provided and non-protein nitrogen during growth under osmotic constraint modulated osmoprotectant accumulation. This, in turn, was correlated with P. freudenreichii tolerance towards different stresses, on the one hand, and towards freeze-drying and spray-drying, on the other. Surprisingly, trehalose accumulation correlated with spray-drying survival and glycine betaine accumulation with freeze-drying. This first report showing the ability to modulate the trehalose/GB ratio in osmoprotectants accumulated by a probiotic bacterium opens new perspectives for the optimization of probiotics production.
丙酸杆菌是一种有益的细菌，广泛应用于食品中作为益生菌和奶酪成熟的起始剂。在这些不同的应用中，它在使用前被生产、干燥和储存。为此，考虑了冷冻干燥和喷雾干燥。冷冻干燥是一种连续的过程，消耗能量，但允许高细胞存活率。喷雾干燥是一种连续的过程，更节能，但可能导致与热、渗透和氧化应激相关的大量细菌死亡。我们已经表明，在高浓度丰富培养基中培养的丙酸杆菌可以通过喷雾干燥进行干燥，而细菌死亡有限。然而，这种高渗透压限制赋予的一般应激耐受性仍然是一个黑匣子。在这项研究中，我们调节了丙酸杆菌的生长条件，并监测了渗透保护剂的积累和应激耐受性的获得。在渗透压限制下改变生长过程中提供的碳水化合物与非蛋白氮的比例，调节渗透保护剂的积累。这反过来又与丙酸杆菌对不同压力的耐受性有关，一方面与冷冻干燥和喷雾干燥有关。令人惊讶的是，海藻糖的积累与喷雾干燥的存活率相关，甘氨酸甜菜碱的积累与冷冻干燥相关。这是第一个报告表明能够调节益生菌细菌积累的渗透保护剂中的海藻糖/GB 比例的报告，为优化益生菌生产开辟了新的前景。
