Development of a synbiotic potential score as a quantitative approach for selecting putative synergistic strain-prebiotic candidates
A 2026 in vitro study published in the Journal of Applied Microbiology introduced a Synbiotic Potential Score (SPS), a developed method for identifying which beneficial bacteria species can use a given prebiotic and/or fiber. The motivation was a real flaw in the current gold standard approach, called the Prebiotic Activity Score, or PAS. The PAS counts bacterial cells at a single time point (e.g. 24 or 48 hours), which the authors argue can be misleading due to different growth timelines between various strains. A slow-growing strain, for example, might look weak at 24 hours simply because it hasn’t peaked yet. SPS adjusts for this by using continuous growth curve data, that tracks bacterial density every 20 minutes and calculates the difference between the highest and lowest readings.
Researchers tested 8 probiotic strains on short-chain fructooligosaccharides (scFOS), resistant maltodextrin (RM), and a scFOS/RM combination, first in a standard nutrient-rich growth medium (MRS), then in a stripped-down minimal version (minMRS).
scFOS results were significant, showing that L. plantarum, B. breve, B. longum, and B. adolescentis all scored well, with B. longum and B. adolescentis exceeding a score of 1 (showing better growth on scFOS than with glucose). RM showed a more challenging picture. In MRS, most strains showed near-zero SPS on RM, but the authors note the problem was with MRS itself. MRS supplies enough nutrients to sustain bacterial growth even without added fiber, masking if any prebiotic ingredient is actually being used. Switching to minMRS changed the picture. RM scores jumped across all four selected strains, with L. plantarum showing the most pronounced increase, followed by B. breve, B. adolescentis, and B. longum. L. rhamnosusserved as a negative control and showed no growth change on RM in either medium, confirming it can’t metabolize RM. Viable cell counts verified that none of the strains multiplied in minMRS without an added carbon source, ruling out background growth as the explanation.
For synbiotic formulators, the practical takeaway is the SPS scoring shows L. plantarum, B. breve, B. adolescentis, and B. longum are the strongest pairings for RM-based synbiotic formulations. The authors are upfront that in vitro growth on a prebiotic doesn’t guarantee in vivo benefit, and only one strain per species was tested, so strain-level variation within each species remains unknown. Follow-up work should test strain combinations in co-culture (cooperative degradation may unlock better RM metabolism than any single strain achieves alone) and validate findings in animal or human models.
