BIOCHEMICAL PROPERTIES AND VIABILITY OF TWO THERMOPHILIC LACTIC ACID BACTERIA IN A SINGLE CHAMBER GASTROINTESTINAL TRACT SIMULATOR-GIS1: PARTIAL CHARACTERIZATIONS
The viability of the thermophilic probiotic bacteria Lactobacillus plantarum BS1 and BS3 was determined in a in vitro unicameral system (www.gissystems.ro). The bacterial cells were isolated by centrifugation at 5000 x g for 10 min, washed three times and freeze-dried in a Martin Christ Alpha 1-2 LD plus freeze dryer. The unicameral system GIS1 consists of 1 Duran bottle with removable screw cap, of 1,000-mL capacity, made of borosilicate glass. The Duran bottle screw cap has 4 entry points. The operating conditions for in vitro simulation depend mainly on pH values for each segment of the colon. Results proved that the two thermophilic strains had a good survival capacity (CFU/mL) after the gastric and small intestine transit. The synthesis of exopolysaccharides and viscosity, as major biochemical parameters, were determined. The exopolysaccharides quantity decreased during the GIS1 transit, generally not directly correlated to viscosity. It results that viscosity increase and viability loss in the GIS1 system was proportional, especially in the small intestine. It was also observed that the viscosity increased with the stationary time spent in each simulated segment. The current model is one of the most significant in vitro simulation systems, due to the correlation between physiologica, and microbiological effects, with a good biochemical stability during in vitro simulation.
Key words: exopolysaccharides, Lactobacillus, probiotic, GIS1 system