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Abstract

Lactic acid bacteria (LAB) constitute a heterogeneous group of bacteria that are traditionally used to produce fermented foods. The industrialization of food bio-transformations increased the economical importance of LAB, as they play a crucial role in the development of the organoleptique and hygienic quality of fermented products. Therefore, the reliability of starter strains in terms of quality and functional properties (important for the development of aroma and texture), but also in terms of growth performance and robustness has become essential. These strains should resist to adverse conditions encountered in industrial processes, for example during starter handling and storage (freeze-drying, freezing or spray-drying). The development of new applications such as life vaccines and probiotic foods reinforces the need for robust LAB since they may have to survive in the digestive tract, resist the intestinal flora, maybe colonize the digestive or uro-genital mucosa and express specific functions under conditions that are unfavorable to growth (for example, during stationary phase or storage). Also in nature, the ability to quickly respond to stress is essential for survival and it is now well established that LAB, like other bacteria, evolved defense mechanisms against stress that allow them to withstand harsh conditions and sudden environmental changes. While genes implicated in stress responses are numerous, in LAB the levels of characterization of their actual role and regulation differ widely between species. The functional conservation of several stress proteins (for example, HS proteins, Csp, etc) and of some of their regulators (for example, HrcA, CtsR) renders even more striking the differences that exist between LAB and the classical model micro-organisms. Among the differences observed between LAB species and B. subtilis, one of the most striking is the absence of a sigma B orthologue in L. lactis ssp. lactis as well as in at least two streptococci and probably E. faecalis. The overview of LAB stress responses also reveals common aspects of stress responses. As in other bacteria, adaptive responses appear to be a usual mode of stress protection in LAB. However, the cross-protection to other stress often induced by the expression of a given adaptive response, appears to vary between species. This observation suggests that the molecular bases of adaptive responses are, at least in part, species (or even subspecies) specific. A better understanding of the mechanisms of stress resistance should allow to understand the bases of the adaptive responses and cross protection, and to rationalize their exploitation to prepare LAB to industrial processes. Moreover, the identification of crucial stress related genes will reveal targets i) for specific manipulation (to promote or limit growth), ii) to develop tools to screen for tolerant or sensitive strains and iii) to evaluate the fitness and level of adaptation of a culture. In this context, future genome and transcriptome analyses will undoubtedly complement ...

Stress Physiology of Lactic Acid Bacteria

“…The latest review on the overall stress physiology of LAB was published by van de Guchte et al in 2002 (16). Here we present a detailed overview of the latest developments in the study of the stress behavior of LAB.…”

Identification and Probiotic Characteristics of Lactobacillus Strains Isolated From Traditional Domiati Cheese

“…(5) .Survival was calculated from the actual numbers (cfu ml -1 ). The two bacterial strains were tested for can be viable till 0. concentration (in 0.4 and 0.5%) there is no viable cell could grow [21].…”

Selection of Lactic Acid Bacteria as Probiotic Candidate for Chicken

“…Compared with previous study by Lin et al (2007), the survival ability of E5, E7, and E8 isolates were better than L. fermentum which decreased about 2-3 Log CFU/mL at pH 3.2 condition after 3 h incubation. The LAB isolates that were able to survive at low pH could be due to the physiological mechanisms that regulate intracellular pH homeostasis (Guchte et al, 2002). The viable cell of LAB isolates decreased significantly at pH 2 conditions.…”

“…The decrease of viable cell of LAB isolates was caused by oxidizing cell by acid. Hydrochloric acid (HCl) was secreted by stomach that can lead to oxidize cell components, damaging the membrane electron transport, decreased activity of various enzymes that are sensitive to acid (van de Guchte et al, 2002). The observation of survival ability of LAB isolates to bile salt showed that the survival rate of all LAB isolates were above 90% (Table 2 and 3).…”