Growth of probiotic bacteria and bifidobacteria in a soy yogurt formulation.

Soy beverage and cows' milk yogurts were produced with Steptococcus thermophilus (ATCC 4356) and Lactobacillus delbrueckii subsp. bulgaricus (IM 025). The drop in pH during fermentation was faster in the soy beverage than in cows' milk, but the final pH values were similar. Yogurts were prepared with a yogurt starter in conjunction with either the probiotic bacteria Lactobacillus johnsonii NCC533 (La-1), Lactobacillus rhamnosus ATCC 53103 (GG) or human derived bifidobacteria. The presence of the probiotic bacteria did not affect the growth of the yogurt strains. Approximately 2 log increases in both L. rhamnosus GG and L. johnsonii La-1 were observed when each was added with the yogurt strains in both cows' milk and the soy beverage. Two of the five bifidobacteria strains grew well in the cows' milk and soy beverage during fermentation with the yogurt bacteria. High pressure liquid chromatography (HPLC) analyses showed that the probiotic bacteria and the bifidobacteria were using different sugars to support their growth, depending on whether the bacteria were growing in cows' milk or soy beverage.

A dynamic model that simulates the human upper gastrointestinal tract for the study of probiotics.

A dynamic model of the human upper gastrointestinal (GI) tract was designed to better simulate conditions of ingestion and digestion, by including a food matrix as part of the model design. The dynamic model consisted of two reactors maintained at 37 degrees C, one simulating stomach conditions and the other simulating duodenum conditions. The model was tested by comparing survival of bacteria isolated from humans (Bifidobacterium infantis, Lactobacillus johnsonii, Lactobacillus rhamnosus, and Lactobacillus acidophilus) animals (Bifidobacterium animalis, 2 strains), and fermented dairy products (Bifidobacterium longum, Lactobacillus kefir, Lactobacillus kefirgranum, and Leuconostoc mesenteroides) with their survival as determined by conventional methods. Five strains were not able to survive (>3 log reduction) 15 min in a medium acidified at pH 2.0 using the conventional testing method, but survival was improved significantly for some strains in the dynamic model. Two strains (Bifidobacterium animalis ATCC 25527 and Lactobacillus johnsonii La-1 NCC 533) showed good survival with both methods. The dynamic model was shown to better represent the events during upper GI tract transit than the conventional methods, by incorporation of a food matrix to buffer the gastric acidity and therefore expose bacteria to pH levels found in vivo before, during, and after a meal.

Impact of a yogurt matrix and cell microencapsulation on the survival of Lactobacillus reuteri in three in vitro gastric digestion procedures.

The goal of this study was to assess the interaction between microencapsulation and a yogurt food matrix on the survival of Lactobacillus reuteri NCIMB 30242 in four different in vitro systems that simulate a gastric environment. The four systems were: United States Pharmacopeia (USP) solutions, a static two-step (STS) procedure which included simulated food ingredients, a constantly dynamic digestion procedure (IViDiS), as well a multi-step dynamic digestion scheme (S'IViDiS). The pH profiles of the various procedures varied between systems with acidity levels being: USP > STS > IViDiS = S'IVIDiS. Addition of a food matrix increased the pH in all systems except for the USP methodology. Microencapsulation in alginate-based gels was effective in protecting the cells in model solutions when no food ingredients were present. The stability of the probiotic culture in the in vitro gastric environments was enhanced when (1) yoghurt or simulated food ingredient were present in the medium in sufficient quantity, (2) pH was higher. The procedure-comparison data of this study will be helpful in interpreting the literature with respect to viable counts of probiotics obtained from different static or dynamic in vitro gastric systems.

The impact of meals on a probiotic during transit through a model of the human upper gastrointestinal tract.

Commercial literature on various probiotic products suggests that they can be taken before meals, during meals or after meals or even without meals. This has led to serious confusion for the industry and the consumer. The objective of our study was to examine the impact of the time of administration with respect to mealtime and the impact of the buffering capacity of the food on the survival of probiotic microbes during gastrointestinal transit. We used an in vitro Digestive System (IViDiS) model of the upper gastrointestinal tract to examine the survival of a commercial multi-strain probiotic, ProtecFlor®. This product, in a capsule form, contains four different microbes: two lactobacilli (Lactobacillus helveticus R0052 and Lactobacillus rhamnosus R0011), Bifidobacterium longum R0175 and Saccharomyces cerevisiae boulardii. Enumeration during and after transit of the stomach and duodenal models showed that survival of all the bacteria in the product was best when given with a meal or 30 minutes before a meal (cooked oatmeal with milk). Probiotics given 30 minutes after the meal did not survive in high numbers. Survival in milk with 1% milk fat and oatmeal-milk gruel were significantly better than apple juice or spring water. S. boulardii was not affected by time of meal or the buffering capacity of the meal. The protein content of the meal was probably not as important for the survival of the bacteria as the fat content. We conclude that ideally, non-enteric coated bacterial probiotic products should be taken with or just prior to a meal containing some fats.