Effect of protectors on the viability of Lactobacillus acidophilus M92 in simulated gastrointestinal conditions.

Abstract

L. acidophilus has been considered to be among the predominant lactobacilli in the intestinal tract of healthy humans. The ability of L. acidophilus to survive and retain its viability through the gastrointestinal (GI) tract is one of the main characteristics desirable for probiotic activity. The influence of mucin and dietary constituents, such as casein, whey proteins concentrate (WPC) and skim milk, on survival of L. acidophilus M92 in the simulated GI conditions, was determined. A washed cell suspension was exposed to pepsin (3g/L) and sodium chloride (5g/L) at pH = 1.5, 2.0, 2.5 and 3.0, and to pancreatin (1g/L), sodium chloride (5g/L) and oxgall (1.5, 2.0, 3.0, 5.0 mg/mL) at pH = 8.0, mimicking the GI environment. Much greater tolerance to gastric and small intestinal juice was observed in the presence of mucin and milk proteins, especially with WPC. The influence of WPC, as the best protector, on the cell viability of L. acidophilus M92 in simulated gastric and small intestinal juice was confirmed by a mathematical model. Critical points, indicating GI conditions that L. acidophilus M92 can tolerate, were established. These observations showed that L. acidophilus M92 survives at pH = 1.99 in simulated gastric juice for 2 h and at 3.1 mg/mL oxgall in simulated small intestinal juice for 4 h, while in the presence of WPC it tolerates even lower pH (1.77) and higher concentration of oxgall (4.25 g/L). Furthermore, only 15 % of the L. acidophilus M92 cells survived the direct transit from simulated gastric to simulated small intestinal juice, but with added WPC, 45 % of the L. acidophilus M92 cells survived. These results suggested the addition of WPC as a protector in preparation of L. acidophilus M92 for probiotic use.