Poly-(vinylpyrrolidone)-poly-(vinylacetate-co-crotonic acid) (PVP : PVAc-CA) interpolymer complex microparticles encapsulating a Bifidobacterium lactis Bb12 probiotic strain: microparticle characterization and effect on viability of encapsulated probiotic cells

Dissertation (MSc)--University of Pretoria, 2012.

Microorganisms have been known to play a major role in human health since early times. The ingestion of microorganisms as probiotics to restore and/or maintain health is a widely accepted and common practice. The challenge in industry is to ensure viability of probiotics until their ingestion to their site of action, the colon, for health benefits to be realised. Microencapsulation is one of the techniques used to protect probiotic bacteria and ensure viability. A method that does not involve the use of extreme temperatures and/or solvents which would otherwise adversely affect viable cells was developed and patented. The method is solventless and is based on complexation of Food and Drug Administration-approved polymers, poly (vinylpyrrolidone) and poly (vinylacetate-co-crotonic acid) in supercritical carbon dioxide. The use of this method of encapsulation was found to be suitable in target release in earlier studies. Microparticles produced were found to have pH-dependent swellability, protecting bioactives, in this case probiotic bifidobacteria, in acid (simulated gastric acid) and only releasing them in an alkaline environment (simulated intestinal fluid). Further studies were, however, needed to investigate the suitability of the microparticles for food and pharmaceutical applications. The current study therefore aimed to characterize these microparticles in terms of size range, distribution of bacteria within the microparticles, and particle size distribution. The average size of the Bifidobacterium lactis Bb12-encapsulating microparticles was found to be within the acceptable size in food applications. High encapsulation efficiency was obtained, with live bacteria distributed evenly within the microparticles, demonstrating the potential of the microparticles to deliver high numbers of probiotic cultures as required for this type of microorganisms to deliver purpoted benefits to the consumer. Probiotic products are normally kept under refrigerated storage, yet the viability of bacterial cells still decreases. An additional benefit of encapsulation within microparticles would be protection of the encapsulated probiotics from the detrimental factors to which the probiotic products are exposed during storage. In order to investigate this for the microparticles in this study, the shelf life of encapsulated B. lactis Bb 12 powder stored in glass vials was investigated. High temperatures were used for accelerated shelf life studies. Encapsulated B. lactis Bb 12 maintained the viable levels above the therapeutic minimum for the duration of the study (12 weeks), which was 7 weeks more than was the case with unencapsulated probiotic. Thus the microparticles provided protection to the probiotic cultures at temperatures much higher than those normally used for storage of probiotic products. These results further indicate the possibility for storage of the B. lactis Bb12 encapsulated in the tested microparticles, at ambient temperatures for at least two months, without drastic loss of culture viability. Research has recently focused on the development of probiotic foods other than dairy and dairy-based foods. This has been necessitated by increasing vegetarian lifestyle and concerns of allergenicity. A maize-based traditional fermented beverage, mageu, was investigated for use as a vehicle for probiotic delivery. Although no significant difference was noted between survival of encapsulated and unencapsulated probiotic was noted, pH decrease in mageu with encapsulated B. lactis Bb 12 was less than with unencapsulated cells. This suggested that encapsulation would ensure that metabolites produced by encapsulated probiotics, if any, would not negatively affect a product in which they are incorporated. Further studies may be needed for investigation of the effect of the encapsulating microparticles in traditional fermented non-dairy products, using more acid-sensitive probiotic strains as the test strain used in the current study is well-known for its inherent resistance to acidity. This study filled gaps in knowledge in terms of the characteristics of microparticles produced using supercritical technology. The main highlights of the research findings were that the microparticles were suitable for food applications, improved probiotic viability under nonrefrigerated temperatures, and delayed browning of the probiotic powder and minimized drop in pH of the fermented product containing the probiotic encapsulated within. The results showed that microparticles encapsulating B. lactis Bb 12 are appropriate to consumers in areas where refrigeration is absent. Furthermore, the study showed that mageu is a suitable alternative vehicle to dairy-based products, for delivery of probiotic B. lactis Bb 12. This possibility extends accessibility of probiotic products to consumers who do not take dairy products for various reasons. There is also a potential increase of probiotic products on the market. Copyright

Microbiology and Plant Pathology

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