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Publication date: 2003-06-30
Pol. J. Food Nutr. Sci. 2003;53(Special issue 2s):5-9
The products of fermentation of Bifidobacterium strains belonging to the 10 species were determined after incubation (37oC/48 h, anaerobic conditions) of the inoculated (106-107 cfu/mL) Garche’s medium containing 1% (w/w) lactose, glucose or fructooligosaccharides (FOS) (Wako, Japan). The study confirmed the presence of acetic and lactic acids as the main products of Bifidobacterium fermentation, and small amounts of ethanol were additionally determined. Concentration of total acetic and lactic acids (A+L) ranged from 90.4 to 231.8 μmol/mL (av. 140.9 μmol/mL) for lactose, and from 93.7 to 159.3 μmol/mL (av. 115.0 μmol/mL) for glucose. Lactic acid prevailed in the majority of cultures containing lactose or glucose as substrates of fermentation. The A+L concentrations in the cultures with FOS were lower. They ranged from 64.5 to 200.6 μmol/mL (av. 94.8 μmol/mL). Using that substrate, nine strains produced preferably acetic acid whereas fi ve strains produced higher amounts of lactic acid. The highest amounts of ethanol were produced as a result of FOS fermentation, ranging from 0.16 to 3.90 μmol/mL (av. 1.63 μmol/mL), lower from glucose - 0.67-3.55 μmol/mL (av. 1.46 μmol/mL), and the lowest from lactose – 0.33-2.12 μmol/mL (av. 0.84 μmol/mL). The pH level varied from 4.25-4.89 (av. 4.36), through 4.37-4.77 (av. 4.58) to 4.33-5.11 (av. 4.76) in cultures containing lactose, glucose or FOS, respectively. The application of 4% Carbowax 20M liquid phase on Carbopack B-DA 80/120 (Supelco) for gas chromatography enabled the direct parallel analysis of both acids, which made it possible to evaluate not only the concentration but also the proportion of the main products of fermentation. The results indicate middle or strong negative correlation between the acidity and the total amount of acetic and lactic acid, which confirms the usefulness and reliability of the assumed method for the determination of Bifidobacterium fermentation products in liquid cultures.
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