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For patients with ulcerative colitis (UC), administration of the probiotic E. coli Nissle (EcN) holds promise for alleviation of disease symptoms. The mechanisms are unclear, but it has been hypothesised that a capacity of the probiotic to outcompete potentially detrimental UC-associated E. coli strains plays an important role. However, this could previously not be confirmed in a mouse model of competition between EcN and two UC-associated strains, as reported by Petersen et al. 2011. In the present study, we re-evaluated the idea, hypothesising that delivery of EcN by a micro device dosing system (microcontainers), designed for delivery into the intestinal mucus, could support colonisation and confer a competition advantage compared to classical oral dosing. Six groups of mice were pre-colonised with one of two UC-associated E. coli strains followed by oral delivery of EcN, either in capsules containing microcontainers with freeze-dried EcN powder, capsules containing freeze-dried EcN powder, or as a fresh sucrose suspension. Co-colonisation between the probiotic and the disease-associated strains was observed regardless of dosing method, and no competition advantages linked to microcontainer delivery were identified within this setup. Other approaches are thus needed if the competitive capacity of EcN in the gut should be improved.

Encapsulation of bacteria into a polymer matrix can potentially enhance the delivery of probiotics. In this study, we present a multilayer electrospun construct to facilitate enhanced delivery of probiotics, where the internal layer is loaded with bacterial cells and the external layers sandwich the internal layer for increased protection and potential mucoadhesion properties. In this proof of concept study, Lactobacillus rhamnosus GG (LGG), which is a robust and well-studied probiotic strain, was encapsulated into pullulan nanofibers, with two electrospun PLGA (Poly-lactic-co-glycolic acid) layers covering it. According to our in vitro study, there was a large decrease in the viability of LGG released from the monolayer sample (LGG:pullulan). However, the multilayer construct maintained excellent viability and an acceptable storage potential. Our in vivo competition study showed that LGG, delivered by multilayer construct, were able to survive intestinal transit and were recovered from all segments of the intestine. Not only did the multilayer construct perform as well as non-encapsulated spray-dried cells in terms of viability and establishment of LGG, but it also showed some cases of increased LGG colonization from fibers in jejunum and cecum compared to spray-dried LGG three days after dosage. We believe, the multilayer construct has the potential to enhance the delivery of the strains that require additional protection, and can benefit from mucus embedment with the help of the covering layers. Particularly, the use of electrospun fibers for the protection of next-generation probiotics sensitive to oxygen and/or gastric conditions could have major commercial interest.

Background: Probiotic microbes may confer a variety of positive health effects on the host. Until now, development of probiotic products has mainly focused on Lactobacillus and Bifidobacterium species, which generally tolerate the stresses encountered during processing, storage and delivery well. In recent years, newly-discovered gut microbes have gained attention due to their association with healthy host conditions. However, these microbes, designated next generation probiotics, are often oxygen-sensitive, do not tolerate the established product processing techniques, and need protection during delivery and gastric transit. Scope and approach: Here, we review the challenges related to development of next generation probiotic products. The applications of current microbial processing and delivery techniques for the oxygen-sensitive next generation probiotics are assessed, and putative process optimizations are discussed. Key findings and conclusions: Current microbial product processing techniques are not suited for next generation probiotics, thus optimizations or entirely novel processing approaches are needed. Freeze-drying is currently the only method that keeps cells viable during processing and storage, but optimization of the process for individual strains is required, e.g. by adding antioxidants to the drying solution. Oral delivery of live next generation probiotics is poorly investigated. The strains in question are often known to colonize primarily in the colon, and carriers, such as microparticles and microdevices, which have been verified for colon-targeted delivery of drugs, may represent a novel choice as delivery vehicle for next generation probiotics.

Oral administration of probiotics is beneficial for restoring the intestinal microbial balance and for the treatment of gastrointestinal (GI) tract-related disorders. In the current era characterized by the development of next-generation probiotic microorganisms, which are typically less robust toward environmental challenges than the classically applied lactic acid producing probiotics, we anticipate a need for delivery of live organisms directly to the site where they need to colonize. Here, we thus present, for the first time, a proof of concept for using micrometer-sized polymeric containers, for the engineered delivery of probiotics, using spray dried Lactobacillus rhamnosus GG (LGG), as a model probiotic microorganism. To achieve colon-specific delivery, microcontainers are loaded with LGG and sealed with an enzyme-sensitive coating. A genipin-cross-linked chitosan coating is developed that (i) is stable at gastric and intestinal pH; (ii) has tunable swelling; and (iii) is degradable by the colon-specific bacterial enzymes. The chitosan-genipin coated microcontainers are evaluated in vitro, ex vivo, as well as in vivo in a rat model. Our results confirm that the genipin-cross-linked chitosan coating enables an effective local delivery in the cecum and colon without any premature release in the small intestine. Our findings suggest that the integration of modified polysaccharides with ingestible microdevices has great potential for controlled and site-specific delivery of live microorganisms.