The aim of this study was to assess the germination, survival and metabolic activity of the probiotic Bacillus coagulans GBI-30, 6086 [GanedenBC30] (BC30) in a dynamic, computer controlled in vitro model of the gastrointestinal (GI) tract, simulating human adults. Experiments were performed in the presence of a meal to maximise germination, due to the presence of germination-triggers. Both an upper GI tract (stomach and small intestine; TIM-1) and a colon model (TIM-2) were used, where material exiting TIM-1 was added to TIM-2. Spores of BC30 were introduced in the gastric compartment of TIM-1 and samples were taken immediately after the pylorus. Moreover, for 6 h, every hour the ileal efflux was collected and a subsample was plated for viable counts (spores and germinated cells). The remainder of the sample was fed to TIM-2, and after 24 h another sample was taken and tested for viable counts. In addition, samples were taken from the dialysates of the model and analysed using LC-MS/MS to determine bacterial metabolites and digestion products. Survival after transit through the gastric compartment was high (97%) and most cells were still in the spore form (76%). Survival after transit through TIM-1 was on average 51%, meaning that on average half of the orally provided spores was found back as cfu on the agar plates. Of these on average 93% were germinated cells and only 7% were spores. 24 h after the start of the experiments germination had increased in TIM-2 to 97% vegetative cells, and only 3% spores. No further loss of viability was observed in TIM-2. In terms of metabolic activity, increased levels of amino acids, dipeptides and citric acid cycle metabolites were found compared to experiments in the absence of BC30. In conclusion, BC30 spores germinate to a large extent (>90%) in the presence of germination triggers in the small intestine in a model that closely mimics the physiological conditions of human adults. Of the oral dose, as much as half of the cells survived transit through the upper GI tract, and based on the metabolite profile, these cells were metabolically active. Either these cells or the enzymes released from the dead cells aided in digestion of the meal. These insights help explain some of the observations in previous experiments, and support the understanding of the mechanism of action of the probiotic BC30.
Keywords: gastrointestinal model; germination; metabolic activity; probiotic; survival.