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Haffner F., Diab R., Girardon M., Fontanay S., Duval R., Pasc A.
SRSMC UMR 7565, CNRS-Université de Lorraine 54506 Vandoeuvre les Nancy, France

One way to reestablish the microbiota equilibrium is to administrate functional food containing probiotic cells (e.g. LGG). To insure protection of the living matter during food processing and gastrointestinal transit, encapsulation is oftentimes required. Herein we propose the use of silica- based hybrid carriers as new delivery systems of probiotics. Silica matrix should offer a chemical resistance to the gastric acidic environment and to bile salts in the small intestines, which is superior to that shown by commonly used bioadhesive polymers, such as alginate.

Alginate-silicate beads were obtained from food grade excipients through two easy and up scalable formulation methods, which enable a superior size and topology control of the resulting capsules. Synthesis: a) Emulsification: LGG-loaded beads were synthesized by silicalization of alginate with sodium silicate in a W/O emulsion containing Polyglycerol polyricinoleate (PGPR) and miglyol; b) Electrospraying: In a first step, LGG-loaded alginate beads were recovered in a Ca2+ aqueous solution by electrospraying. Secondly, the gelled beads were dispersed in an oily solution containing PGPR where they get coated by a silica layer upon addition of the silica precursors. Characterization: SEM, FTIR and NMR were used to characterize the structure and the morphology of the beads while CLSM and TEM allow the observation of the encapsulated LGG.

Two types of alginate-silicate beads containing LGG were obtained: hybrid beads in which the bacteria are surrounded by a mixture of alginate and silica; and core-shell beads in which the bacteria are embedded in an aqueous core of alginate and thus, less exposed to silica. In addition, according to the formulation method, emulsification or electrospraying, one can tune the size of the resulting beads in the range of tens to hundreds of micrometers. Via emulsification, the resulting beads have sizes smaller than 25 μm, which are sufficiently large to encapsulate suitable amount of probiotics, but small enough to remain undetected by humans during chewing. Via electrospraying the 230 μm beads hold a potential interest in adding a ‘crunchy appeal’ to the eventual food carrier.

The hybrid alginate-silicate carriers were synthesized with the aim of designing potential dry probiotic delivery systems. For the first time, carriers combining within the same matrix, a bio protective polymer, alginate, and a desiccant, amorphous silica, were obtained. The later is usually added to dried formulations in order to regulate the water activity, and to insure thus, a long-term storage of the living material. The viability of the bacteria, assessed by plate counting, gave some preliminary perspectives on the impact of inorganic, rigid matrix and synthesis conditions on the living matter. Interestingly, the core-shell beads show a selective response to pH conditions, i.e. they resist to acidic gastric conditions but disintegrate in duodenal pH conditions. This behavior is clearly related to the presence of the silica shell, which generates particular interest for probiotic oral delivery carriers that target a release in the intestines.
This study offers a proof of concept for the potential use of hybrid silica/biopolymer systems in oral delivery of probiotic bacteria.

Keywords: Microencapsulation, Emulsification, Electrospraying, L. rhamnosus GG, Hybrid beads, Probiotic

Haffner F., et al. (2016). Encapsulation of L. rhamnosus GG (LGG) in alginate-silicate hybrid beads. Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 27.). IPC2016

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