Sodium alginate

Two grams of sodium alginate (Carl Roth, Germany) were dissolved in 100 mL of demineralized water. This alginate solution was mixed with an equal volume of KHV-T P78 suspension, to achieve a final concentration of one percent sodium alginate. Additionally, the colour of the capsules was adjusted to the colour of the regular food with food colouring. Finally, the alginate-KHV-solution was dropped into 1 M CaCl₂-solution (Carl Roth, Germany), with a mean drop volume of 50 µL. The resulting capsules were rinsed once with isotonic sodium chloride and used for vaccination trials.

All the chemicals (cephalexin (Cayman Chemical, Tallinn, Estonia), sodium hydroxide (Chempur, Piekary Śląskie, Poland), hydrochloride acid (Chemical Company, Iași, Romania), sodium alginate (Carl Roth, Karlsruhe, Germany), calcium chloride (Chempur, Piekary Śląskie, Poland), sodium chloride (Chemical Company, Iași, Romania), ethanol (Chemical Company, Iași, Romania)) required in the experiments were of analytical purity and were used without further purification.
Yeast strain of Saccharomyces cerevisiae was kindly donated by Rompak Company (Pașcani, Romania).
A stock solution of cephalexin (Figure 1) with a concentration of 500 mg/L was prepared by dissolving the reagent in distilled water and kept at 4 °C in a closed vessel.
For the calibration curve, 0.02, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mL of CPX stock solution were placed in a series of volumetric flasks and the volumes were adjusted to 10 mL in order to obtain concentrations ranging between 1 mg/L and 30 mg/L. The samples absorbance was acquired at 260 nm with the help of a UV1280 spectrophotometer (Shimadzu, Tokyo, Japan). A calibration graph (absorbance vs. concentration) was plotted and a linear regression equation was recovered.
The other work solutions were obtained by appropriate dilutions. When necessary, NaOH (0.1 M) or HCl (0.1 M) were used to adjust the pH.