Effect of microencapsulation on oxygen toxicity in probiotic bacteria

Abstract

Microencapsulation was tested for its protective role against oxygen toxicity in probiotic bacteria. Two strains of Bifidobacterium lactis and one strain of Lactobacillus acidophilus were encapsulated in calcium alginate and grown aerobically in reconstituted skim milk broth for 24 h. Counts of encapsulated cells in all three strains were one log higher than corresponding free cell counts. The encapsulated cell count (log 10 cfu/mL) of B. lactis 920 was 9.12 as against 8.66 of free cells whereas L. acidophilus 2409 when encapsulated, demonstrated a cell count (log 10 cfu/mL) of 7.84 as compared to a free cell count of 6.67. In a follow-up study, the protective effect of microencapsulation was also tested in yogurt. Twelve strains of L. acidophilus and Bifidobacterium spp. were encapsulated and incorporated in yogurt for 24 h maintained aerobically at 6°C. Interestingly, while microencapsulation was found to significantly increase viability in six strains, no significant difference was observed between encapsulated cell counts and free cell counts in the other six strains. Preliminary evidence therefore suggests that although microencapsulation can offer protection to probiotic bacteria against oxygen toxicity in broth culture, further optimisation studies are needed before its application in yogurt.