Encapsulation of Probiotic Cells in Alginate Beads

Alginate beads were prepared by mixing 2 g sodium alginate in 100 ml culture medium 2 × stock solution (6 g·l⁻¹ yeast extract, 16 g·l⁻¹ soybean peptone, 0.04 g·l⁻¹ MnSO₄, 3 g·l⁻¹ KH₂PO₄, 3 g·l⁻¹ K₂HPO₄, and pH = 6.8) and sterilizing the mixture at 121°C for 20 min. We then mixed 50 ml of the cooled 2% sodium alginate medium with 0.5 ml pre-culture of probiotic bacterium and extruded the cell-containing sodium alginate solution through a 25G sterile cannula (inner diameter = 0.32 mm) in the form of droplets into 150 ml of 100 mM sterile CaCl₂, while stirring at 100 rpm to form the beads. After 1 h, the hardened beads were rinsed with sterile sugar-free culture medium to remove free cells and CaCl₂. The beads were then added to the diluted FOS solution at a 1:1 ratio, and incubated at 40°C for 24 h to evaluate the efficiency of FOS purification.