Stress tolerance in Lactobacillus plantarum LMF6 isolated from human breast milk

Abstract

Lactobacillus plantarum is a lactic acid bacterium widely used in the food industry because of its beneficial effects on human health and its ability of adaptation to different stress conditions, hence the purpose of this work was to study the adaptation abilities of Lactobacillus plantarum LM6 and stress proteins involved during this adapta on. Lb. plantarum LMF6 was isolated from human breast milk and was exposed to acid, alkaline, thermal, oxidative, osmotic, detergent and nutritional stresses in order to determine their effects on growth, viability, tolerance and mortality. SDS-PAGE electrophoresis allowed us to compare the total proteins in the absence and in the presence of stress then the ImageJ® so ware analyzed the obtained pro les. The results show that Lb. plantarum LMF6 is highly tolerant to osmo c (at 9% NaCl, the UFC number is 3.4×1010 UFC/ml), alkaline (4.7×107UFC/ml at pH10), detergent (the UFC number is close to the control), oxydative (3.3×108 UFC/ml), nutri onnal (5.2×107 UFC/ml), acid (pH5, pH4 and pH3) and heat (40°C, 45°C and 50°C with 1.45×1011, 2.78×109 and 2.80×108UFC/ml respec vely) stresses, but sensi ve to extreme acid stress (pH1 and pH2 with mortality rate variable from 5log to 10log) and extreme heat stress (55°C and 60°C when mortality increases to 8log at 60°C). Comparison of proteins profiles allowed us to see quantitative and qualitative differences. Our results allowed to say that Lb. plantarum LMF6 showed interesting characteristics and could be used in food industry as probio c lactobacilli.