Microencapsulation of Lactobacillus acidophilus in zein-alginate core-shell microcapsules via electrospraying

Survival of probiotic bacteria, namely, Lactobacillus acidophilus, in gastric fluid was enhanced by embedding the bacterial cells in alginate microcapsules, which were formed by electrospraying; the resultant microcapsules were then coated with citric acid-modified zein and dried at ambient temperature. The effects of citric acid concentration (0.10-0.15%, w/v) as well as electrospraying condition (applied voltage) on morphology of the obtained core-shell microcapsules, encapsulated cell count and survival cell number after incubating in simulated gastric fluid (SGF) were investigated. The results showed that an increase in the citric acid concentration did not affect the microcapsules size; nevertheless, the survival cell number significantly decreased due to an increase in the zein solution acidity. The size of the microcapsules was significantly reduced from 543 ± 88 to 312 ± 69 and 259 ± 62 μm when being produced at 4, 6 and 10 kV, respectively. Microcapsule surface wrinkles were significantly reduced as the applied voltage increased. After 2 h-incubation in SGF at pH 1.2 with pepsin, the encapsulated L. acidophilus suffered only 1-log reduction, whilst the number of the non-encapsulated bacteria was reduced by about 5-log cycles.