PRINT ISSN 2285-5718, CD-ROM ISSN 2285-5726, ISSN ONLINE 2286-0126, ISSN-L 2285-5718


Published in AgroLife Scientific Journal, Volume 5, Number 2
Written by Silvia-Simona GROSU-TUDOR, Iulia-Roxana ȘTEFAN, Medana ZAMFIR

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 other species. Also, a high resistance to low pH values and in the presence of bile salts is necessary for probiotic strains, in order to survive in the stomach and intestine, or even to compete with other bacterial groups in this environment and to colonize the gastrointestinal tract (GIT) of the host. The purpose of the present work was to evaluate the growth/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°C and 37°C, with a viability between 1010-1014 CFU/ml. Three strains grew well at 50°C reaching a viability of 108-109 CFU/ml. Four strains were resistant to pH 3.5 and 4.5, after 24 h of incubation reaching a viability of 1010 CFU/ml and 1014 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 high resistance to a concentration of 0.3% (w/v), reaching a cell viability of 107-109 CFU/ml after 24 h of incubation. After 3 h of exposure to 0.5% (w/v) of bile salts, the viability of Lb. brevis FV530 was about 1010 CFU/ml. Six of the selected strains had a high resistance to NaCl (up to 7%) reaching a viability of 109 CFU/ml after 48 h of incubation.

[Read full article] [Citation]

The publisher is not responsible for the opinions published in the Volume. They represent the authors’ point of view.

© 2019 AgroLife Scientific Journal. All Rights Reserved. To be cited: AgroLife Scientific Journal.

Powered by INTELIDEV