Enhanced microencapsulation for probiotic strains reported
With the probiotic segment of the market enjoying growth on both sides of the Atlantic, the list of food products that can be used as vehicles for the gut health-boosting bacteria continues to grow.
According to the FAO, probiotics are defined as live microorganisms which when administered in adequate amount confer a health benefit on the host, and this means passing through the gastrointestinal tract alive, and in sufficient numbers.
Microencapsulation has been explored by numerous companies as a way of enhancing gastrointestinal transit of specific strains, and for prolonging the shelf-life of strains in certain foods.
According to findings published in the Journal of Food Science, coating potentially probiotic bacterial strains with alginate, and then applying an extra coating of palm oil and poly-L-lysine (POPL), significant improvements may be achieved in the viability of the bacteria.
While this may support the potential viability of these strains under such conditions, trials of these strains in humans would be required to confirm if the strains are truly ‘probiotic’.
Study details
Researchers from Victoria University in Australia looked at the new encapsulation method on the viability of eight strains of bacteria including Lactobacillus rhamnosus, Bifidobacterium longum, L. salivarius, L. plantarum, L. acidophilus, L. paracasei, and B. lactis types Bl-O4 and Bi-07.
All of the strains underwent alginate encapsulation alone or alginate with POPL. Additional coating with POPL increased the overall size of the capsules about three micrometres, said the researchers. Electron microscopy revealed that these POPL capsules had smoother surface textures.
A model gastrointestinal system was used to assess the viability of the strains under conditions of low pH (pH 2.0) and in the presence of two bile salts, oxgall bile salt and taurocholic acid.
The ‘model gut’ tests revealed an improved average viability of more than 1 log CFU/mL for the strains encapsulated in both alginate and POLP, compared to alginate alone, under the acidic conditions.
However, similar counts were observed between both encapsulation techniques when exposed to the bile salts, added the Melbourne-based researchers.
“This suggests that an extra coating of POPL could be readily broken down by bile salts that are commonly found in the lower gastrointestinal tract (GIT),” they wrote.
Such an observation may have potential for controlled release of the strains, they added, noting: “Future studies could explore the role of bile as an effective release mechanism to help free encapsulated probiotic bacteria so that they may act in the lower gastrointestinal tract.”
Holding on
A final set of experiments using the encapsulation techniques and the water-soluble fluorescent dye, 6-carboxyflourescin, was performed to investigate how well the capsule could retain the contents. These porosity tests revealed that the alginate plus POPL microcapsules retained 52 per cent more of the dye over a six-week period than the alginate-only microcapsules.
“Coating of microcapsules may improve an already well-established technique for improving the viability of probiotic organisms in functional foods,” wrote the researchers.
“Moreover, the positive results of our study may encourage other researchers to investigate other novel coating materials,” they concluded.
Source: Journal of Food Science Published online ahead of print, doi: 10.1111/j.1750-3841.2008.01030.x“An Improved Method of Microencapsulation of Probiotic Bacteria for Their Stability in Acidic and Bile Conditions during Storage” Authors: W.K. Ding, N.P. Shah
