Influence of growth conditions and the food matrix on the functionality of Bifidobacterium animalis subsp. lactis INL1

VINDEROLA CG; BOCKELMANN W; NEVE H; ZACARIAS MF; REINHEIMER, J.; HELLER H

Buenos Aires

Congreso; XII Congreso Argentino de Microbiología.; 2010

AAM

Introduction: Bifidobacterium animalis subsp. lactis INL1 is a probiotic strain isolated from human breast milk with the capacity of enhancing the gut defences through the increase of the number of IgA+ cells in the small and large intestine of mice. Recent studies suggest that cell viability might not always be a full indicator of cell functionality when strains undergo technological treatments like biomass production and drying for storage. Aim: To study as a criterion of cell functionality the influence of growth conditions and storage in different food matrixes of Bifidobacterium animalis subsp. lactis INL1 on its resistance to simulated gastric digestion. Materials and Methods: The strain was grown in MRS broth in a biofermentor at 37ºC at pH 6.5 and 5 for 12 and 22 h with the influx of CO2. Cells were harvested, washed twice with PBS buffer, resuspended in 10% lactose and freeze-dried for 22 h in a Christ Beta 2-16 freeze-drier. Scanning electron microscopy studies were carried out for the freeze-dried cultures obtained. Freeze-dried cultures were added (ca. 108 CFU/ml) to six different commercial dairy and non-dairy food products: orange juice (1), banana-carrot juice (2), mixed-fruits juice + fiber (3), vanilla milk drink (4), apple-banana puree (5) and apple-peach puree (6). Samples were kept at 5ºC for 4 weeks. Cell viability and resistance to simulated gastric digestion (pH 2 + 0.5% NaCl + 0.3% pepsin, 37ºC for 90 min) was assessed at time 0 and at the end of the storage period. Results: No significant differences were observed in cell viability for cultures grown for 12 or 22 h at pH 6.5 or 5. However, cell losses after 90 min of exposure to simulated gastric acidity were higher than 4 log cycles for cultures grown at pH 6.8 compared to the negligible cell losses observed for cultures grown at pH 5. Scanning electron microscopy studies showed that only cultures grown at pH 6.5 for 22 h presented an exopolysaccharide-like matrix around freeze-dried cells. No significant differences in cell counts were observed among food products after 4 weeks of storage compared to counts at zero time. However, resistance to simulated gastric digestion differed among the commercial food products analysed. After 90 min of gastric digestion, reductions in cell counts were negligible for products 2 and 4. For products 3 and 6, cell losses were around 1 log order, whereas for products 5 and 1, cell losses were 2 and 3 log orders, respectively. Conclusions: For the development of functional foods, conditions appropriate for biomass production and food matrix must be carefully chosen to preserve not only viability but also cell functionality of probiotic strains.