Comparison of different methods for release of Bifidobacterium longum Bb46 from the poly(vinylpyrrolidone)-poly(vinylacetate-co-crotonic acid) interpolymer complex matrix, and the effect of grinding on the microparticles

Bifidobacteria have been efficiently encapsulated in poly(vinylpyrrolidone)-poly(vinylacetate-co-crotonic acid) (PVP: PVAc-CA) interpolymer complex formed in scCO2. Research indicated that this method improves the stability of encapsulated bacteria in simulated gastrointestinal fluids in vitro. However, further analysis indicated release of lower numbers of encapsulated bacteria from the encapsulating matrix. The aims of this study were to determine a method that would release high numbers of bacteria from the PVP: PVAc-CA interpolymer complex matrix microparticles, and furthermore, to determine the effects of milling on the morphological properties of the microparticles. Three release methods, namely sonication, homogenization in a stomacher and incubation in simulated intestinal fluid were compared. Released viable bacteria were assayed using plate counts. Viable bacteria released using a stomacher were three orders of magnitude higher than those released by incubation and an order of magnitude higher than those released using sonication. SEM indicated no negative effects such as exposure of encapsulated bacteria on the matrix due to milling of product. Homogenization in a stomacher is the most efficient method for releasing bacteria from the PVP: PVAc-CA interpolymer complex matrix. Particle size of the PVP: PVAc-CA microparticles encapsulating bacteria can be reduced further by grinding, without exposing the enclosed bacteria.