Synbiotic Matchmaking in Lactobacillus plantarum: Substrate Screening and Gene-Trait Matching To Characterize Strain-Specific Carbohydrate Utilization

Abstract

Synbiotics are food supplements that combine probiotics and prebiotics to synergistically elicit a health effect in humans. Lactobacillus plantarum exhibits a remarkable genetic and phenotypic diversity, in particular in strain-specific carbohydrate utilization capacities and several strains are marketed as probiotics. We have screened 77 L. plantarum strains for their capacity to utilize specific prebiotic fibers, revealing variable and strain-specific growth efficiencies on isomalto- and galacto-oligosaccharides. We identified a single strain within the screening panel that was able to effectively utilize inulin and FOS, which did not support efficient growth of the rest of the strains. In our panel tested, we did not find strains that could utilize arabinoxylo-oligosaccharides or sulfated fucoidan. The strain-specific growth phenotype on isomalto-oligosaccharides was further analyzed using high performance anion exchange chromatography and revealed distinct substrate utilization phenotypes within the strain panel. The strain-specific phenotypes could be linked to the strain's genotypes identifying gene clusters encoding for carbohydrate membrane transport systems that are predicted to be involved in the utilization of isomaltose and other (unidentified) oligosaccharides in the isomalto-oligosaccharide substrate. IMPORTANCE Synbiotics combine the concepts of prebiotics and probiotics to synergistically enhance the health benefits associated with these ingredients. Lactobacillus plantarum is encountered as a natural inhabitant of gastrointestinal tract and specific strains are marketed as a probiotic based on their strain-specific health-promoting activities. Strain-specific stimulation of growth through prebiotic substrates could enhance the persistence and/or activity of L. plantarum in situ. Our study establishes a high-throughput screening model for prebiotic substrate utilization by individual strains of bacteria, which can be readily employed for synbiotic match-making approaches that aim to enhance the intestinal delivery of probiotics through strain-specific, selective growth stimulation.

Phenotypic and genetic characterization of differential galacto-oligosaccharide utilization in Lactobacillus plantarum

“…In L. plantarum we detect only two distinctive GOS-utilization phenotypes, but this may be different in other species. In support of such possibilities, we have previously shown that the different degree of utilization of isomalto-oligosaccharides in L. plantarum coincides with multiple phenotype and corresponding genotype variations in specific strains of this species 16 . Finally, the results presented in this study offer opportunities for the design of strongly selective L. plantarum and HDP-GOS synbiotic products, aiming to synergistically enhance the health benefit to the consumer 45 , 46 , underpinning that deciphering the relationships between the chemical complexity of prebiotics and the selective stimulation of growth of probiotic strains by specific prebiotic constituents could enhance the health effects of synbiotics.…”

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Figure 1 L. plantarum strain-specific relative growth on GOS. The relative growth (OD 600 ) after 24 h of L. plantarum strains on ½ MRS-C supplemented with 0.5% GOS in comparison to their growth on ½ MRS-C supplemented with 0.5% glucose in batch growth experiments (OD 600 ; black bars, n = 1) and pH (grey bars, n = 1) and its congruency with the relative optical density (OD 600 ; white bars, n = 3) obtained in a previous reported in vitro screening 16 .

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“…Several strains of L. plantarum have demonstrated probiotic properties 37 – 40 , and their intrinsic genetic and phenotypic diversity in carbohydrate metabolism 17 , 18 , 41 offers opportunities for selective and strain-specific stimulation by prebiotics. The GOS preparation employed here supports the growth of a large amount of L. plantarum strains, although this growth stimulation displays a substantial degree of variability that is reflected by the strain-specific growth stimulation detected 16 . Notably, the GOS preparation employed here contains approximately 30% mono- and di- saccharides, which tend to reduce the selectivity of growth stimulation because most bacteria can utilize these sugars.…”

“…A panel of 21 L. plantarum strains with known genome sequences (Table 1 ) was selected from a larger panel of strains that was employed in an in vitro screening of strain-specific growth on Vivinal GOS containing media, to appropriately reflect the range of growth capacities observed in strains of this species 16 . These previously reported results illustrate that despite the significant variation in strain-specific growth on GOS, all L. plantarum strains grow relatively well on GOS-supplemented media, which was further confirmed in the present study by batch-growth experiments using optical density (OD 600 ) and pH as growth reflecting read-outs (Fig.…”

“…GOS and HMO compounds can facilitate the growth of several lactobacilli 13 , 14 , and various strains of different Lactobacillus species are marketed as probiotics, including strains of L. rhamnosus, L. reuteri, L. casei, L. acidophilus and L. plantarum 15 . Previously, we have analyzed the growth of 77 L. plantarum strains on a specific GOS substrate (Vivinal GOS), revealing that all strains could grow on this substrate but to a significantly different extent, indicating strain-specific variation of GOS-utilization within the L. plantarum species 16 . L. plantarum is found in a wide range of ecological habitats including silage, fermented and non-fermented food products and the gastro-intestinal tract of humans and animals, and displays a notable phenotypic and genotypic diversity, in particular in its carbohydrate metabolism repertoire 17 , 18 .…”