Low-moisture food matrices as probiotic carriers.

To exert a beneficial effect on the host, adequate doses of probiotics must be administered and maintaining their viability until consumption is thus essential. Dehydrated probiotics exhibit enhanced long-term viability and can be incorporated into low-moisture food matrices, which also possess high stability at refrigeration and ambient temperature. However, several factors associated with the desiccation process, the physicochemical properties of the matrix and the storage conditions can affect probiotic survival. In the near future, an increased demand for probiotics based on functionally dominant members of the gut microbiome ('next-generation probiotics', NGP) is expected. NGPs are very sensitive to oxygen and efficient encapsulation protocols are needed. Strategies to improve the viability of traditional probiotics and particularly of NGPs involve the selection of a suitable carrier as well as proper desiccation and protection techniques. Dehydrated probiotic microcapsules may constitute an alternative to improve the microbial viability during not only storage but also upper gastrointestinal tract passage. Here we review the main dehydration techniques that are applied in the industry as well as the potential stresses associated with the desiccation process and storage. Finally, low- or intermediate-moisture food matrices suitable as carriers of traditional as well as NGPs will be discussed.

Dark chocolate as a stable carrier of microencapsulated Akkermansia muciniphila and Lactobacillus casei.

The viability of probiotics is affected by several factors during manufacturing, storage and gastrointestinal tract passage. Protecting the probiotics from harmful conditions is particularly critical for oxygen sensitive species like Akkermansia muciniphila, a bacterium which recently has been proposed as a next-generation probiotic candidate. Previously, we have developed a protocol for microencapsulating A. muciniphila in a xanthan/gellan gum matrix. Here, we report the enhanced survival during storage and in vitro gastric passage of microencapsulated A. muciniphila embedded in dark chocolate. Lactobacillus casei, as a representative species of traditional probiotics, was included in order to compare its behavior with that of A. muciniphila. For A. muciniphila we observed a 0.63 and 0.87 log CFU g-1 reduction during 60 days storage at 4°C or 15°C, respectively. The viability of L. casei remained stable during the same period. During simulated gastric transit (pH 3), microencapsulated A. muciniphila embedded in chocolate showed 1.80 log CFU mL-1 better survival than naked cells, while for L. casei survival was improved with 0.8 log CFU mL-1. In a hedonic sensory test, dark chocolate containing microcapsules were not significantly different from two commercially available chocolates. The developed protocol constitutes a promising approach for A. muciniphila dosage.

Viability of microencapsulated Akkermansia muciniphila and Lactobacillus plantarum during freeze-drying, storage and in vitro simulated upper gastrointestinal tract passage.

Akkermansia muciniphila, an abundant member of the human gut microbiota, has been suggested as a potential next-generation probiotic. However, its high sensitivity to oxygen limits the development of dosage protocols. Here, we describe microencapsulation, in a xanthan and gellan gum matrix, and a subsequent freeze-drying protocol for A. muciniphila DSM22959. For comparison Lactobacillus plantarum subsp. plantarum ATCC14917 was microencapsulated and freeze-dried using similar protocols. Four different mixtures were tested for cryoprotective properties: sucrose 5% plus trehalose 5%; agave syrup 10%; skim milk 10%, glucose 1%, yeast extract 0.5%, and mannitol 2.5%; as well as peptone 0.1% plus sorbitol 1.2%. Milli-Q-water served as control. Only cryoprotectant solutions with high sugar or protein content significantly improved the survival of both strains during freeze-drying. Microencapsulated cells were stored aerobically or anaerobically for 1 month at 4 °C or 25 °C. Survival of A. muciniphila was significantly better when stored anaerobically at 4 °C. The survival of microencapsulated L. plantarum, was relatively stable at both temperatures under anaerobic conditions. Survival of microencapsulated cells was compared with that of free cells during in vitro simulated upper gastrointestinal tract (GIT) transit at fasted and fed state. During in vitro simulated stomach passage, encapsulation significantly improved survival and viable cells remained at relevant levels after the entire simulated upper GIT transit. In conclusion, we here report a protocol for encapsulating A. muciniphila giving acceptable storage stability and enhancing survival during in vitro simulated upper GIT transit and thus constitutes an important step towards enabling future use of this important member of the human colonic microbiota as a probiotic.