GROWTH/SURVIVAL OF SOME FUNCTIONAL LACTIC ACID BACTERIA UNDER DIFFERENT STRESS CONDITIONS

摘要

Lactic acid bacteria (LAB) used as starter cultures in food industry must survive under several stress conditions,including low pH, low water activity, high and low temperatures, oxidative stress, starvation and competition with otherspecies. Also, a high resistance to low pH values and in the presence of bile salts is necessary for probiotic strains, inorder to survive in the stomach and intestine, or even to compete with other bacterial groups in this environment and tocolonize the gastrointestinal tract (GIT) of the host. The purpose of the present work was to evaluate thegrowth/survival of 19 LAB strains with biotechnological applications (production of bacteriocins, exopolysaccharides,S-layer proteins) under different stress conditions. The strains were investigated for tolerance to acidity (pH 2.0, 3.5,4.5 and 5.5), bile salts (0.05%, 0.1%, 0.2%, 0.3% and 0.5%), different temperatures (15°C, 20°C, 28°C, 37°C, 42°C,47°C, and 50°C), and different concentrations of NaCl (1%, 3%, 5%, and 7%). All 19 tested strains grew well at 28°Cand 37°C, with a viability between 1010-1014 CFU/ml. Three strains grew well at 50°C reaching a viability of 108-109CFU/ml. Four strains were resistant to pH 3.5 and 4.5, after 24 h of incubation reaching a viability of 1010 CFU/ml and1014 CFU/ml, respectively. After 3 h of exposure to pH 2.0, two strains, namely Lb. brevis FV403 and Lb. brevis FV530,maintained a viability of 102-103 CFU/ml. Concerning the bile salt resistance, all tested strains showed a highresistance to a concentration of 0.3% (w/v), reaching a cell viability of 107-109 CFU/ml after 24 h of incubation. After 3h of exposure to 0.5% (w/v) of bile salts, the viability of Lb. brevis FV530 was about 1010 CFU/ml. Six of the selectedstrains had a high resistance to NaCl (up to 7%) reaching a viability of 109 CFU/ml after 48 h of incubation.