Immobilisation of bifidobacteria in biodegradable food-grade microparticles

The present research features a natural polymer that can be used for immobilisation of bifidobacteria as well as a method of immobilisation. We described a modified method of microencapsulation of probiotics using sodium alginate. The experiment studied the effect of encapsulation on probiotic stability and involved an in vitro model of human digestive tract. The test sample of microencapsulated Bifidobacterium bifidunt 791 showed a decrease in the activity from 3.0x10(7) to 2.2x10(5) CFU/ml in a mouse model with pH 1.2. By contrast, the control sample, unprotected by biodegradable polymer microcapsules, demonstrated a higher death rate of bifidobacteria: from 2.6x10(8) CFU/ml to 5.0x10(3) CFU/ml. The control sample demonstrated the same downward trend in in vitro gastrointestinal models with pH values of 4.5, 6.8, 7.2, and 5.8. Because the total plate count fell down to 4.01 g CFU/ml in acidity gradients, the titres of the initial microencapsulated biomass had to be increased up to > 10(9) CFU/ml. According to the results of scanning electron microscopy, the new type of microcapsules obtained by using a resistant starch had a closed surface. Prebiotics increased the resistance of bacteria to low pH and bile salts. Bifidobacteria encapsulated with natural biodegradable polymers proved to be well-tolerated and harmless for mice. The experiment revealed that biodegradable polymer microcapsules did not cause any chronic or acute toxicity when administered orally at 2x10(7) CFU per 1 gram of animal mass. The microcapsules demonstrated neither dermonecrotic properties nor any irritant effect on the ocular mucosa and, thus, can be used for food enforcement.