Enhanced gut microbiota delivery of a model probiotic (Faecalibacterium prausnitzii): Layer-by-layer encapsulation using riboflavin-conjugated sodium alginate and glycol chitosan

Faecalibacterium prausnitzii (F. prausnitzii) exhibits a variety of biological functions that make it suitable for use as a next-generation probiotic. However, its high sensitivity to oxygen and digestive fluids currently limits its application. Riboflavin is known to support the growth of F. prausnitzii in oxygen environments, but it is important that it is in close proximity to the probiotics. Layer-by-layer assembly can be used to form protective coatings around probiotics, which can protect them from adverse environmental conditions. Moreover, riboflavin can be conjugated to these coatings, thereby increasing its efficacy by bringing it close to probiotic surfaces. In this study, we therefore evaluated the potential of electrostatic layer-by-layer assembly to protect F. prausnitzii by coating them with riboflavin-alginate and glycol-chitosan layers. Initially, we showed that riboflavin could be successfully conjugated to alginate, with a grafting ratio of around 4.35%. Then, the layer-by-layer method was used to coat F. prausnitzii using cationic glycol chitosan and anionic riboflavin-alginate. The coating formed was found to have a thickness of approximately 18.5 nm. Encapsulation did not adversely affect the growth of F. prausnitzii, but it significantly enhanced its resistance to oxygen and digestive fluids. The encapsulated probiotic was shown to have enhanced mucoadhesive properties using an in vitro intestinal monolayer model. Furthermore, the encapsulated probiotics colonized the colons of rats for longer than nonencapsulated ones. These results show that coating F. prausnitzii with riboflavin-rich biopolymer layers improves its resistance to oxygen and digestive fluids, and enhances its mucoadhesion and colonization properties, which should enhance its potential as an orally administered probiotic.