The Synergistic Effect of Fiber Blends on Lactobacillus rhamnosus
Authors: Johnson Amanda K. , Adams Victoria R. , Walker Brittany B. , Santos Fernanda B.O. , Santos Anael A 
Published: June 2021

The combination of prebiotics with probiotic microorganisms has been shown to improve gastrointestinal health. Previous studies have demonstrated the beneficial effect of psyllium supplementation on the growth of probiotic bacteria. However, little is known about the synergistic effect of fiber blends. Thus, the main objective of this study was to evaluate the effect of the combination of different fibers with psyllium on the growth of Lactobacillus rhamnosus.

Lactobacillus rhamnosus (ATCC® 7469™), a Gram‐positive bacterium with demonstrated probiotic activity, was the bacterial species used in this study. The bacterial inoculum was prepared by growing the bacteria in MRS (De Man, Rogosa and Sharpe) broth for 24 hours under microaerophilic condition (5% CO2) at 37°C, yielding approximately 108 CFU/mL. The Lactobacillus culture media, MRS broth, was supplemented with different combinations of fibers to evaluate their effect on bacterial growth. Three different fibers, psyllium, inulin, and fructooligosaccharides (FOS), were used in the study. To test the combined effect, the fibers were combined with each other at a concentration of 0.5% each and then altogether. The inoculum was grown in an un‐supplemented broth following the same conditions as the fiber‐supplemented broths, to be used as a negative control. Positive controls of psyllium supplemented at 0.5%, 1.0%, and 1.5% were included to test against different treatment concentrations. Each inoculated broth supplemented with each fiber blend were incubated in duplicate. Colony forming units (CFU) were measured on plates in duplicate. The CFU data was converted to a base‐10 algorithm before statistical analysis was performed. All data were analyzed using the general linear model procedure for analysis of variance (ANOVA) and Pearson correlation analysis.

The presence of fiber in the growth media, regardless of concentration, improved bacterial growth significantly when compared to the control containing 0% of fiber (9.11 vs 8.57 log CFU/mL, respectively, p<0.005). Bacterial growth increased as the concentration of psyllium increased (r=0.8, p<0.01). This result agrees with earlier studies presented by our team. Treatments containing psyllium supplementation demonstrated significantly better growth than treatments without psyllium (9.14 vs 8.80 log CFU/mL, respectively, p<0.001). The psyllium supplementation at 0.5% concentration, in all blends, exhibited similar growth with no significant differences between treatments. Treatment supplemented with psyllium at 1.5% was similar to the treatment containing a combination of all fibers (psyllium, inulin, and FOS at 0.5% each) (9.22 vs 9.07 log CFU/mL, respectively, p>0.05).

In conclusion, no synergistic effect on the growth of Lactobacillus rhamnosus was observed from the blending of fibers. However, the addition of prebiotic fibers to the growth media caused an increase in probiotic bacteria growth. More research is needed to understand if combinations of prebiotics can produce synergistic effects at higher concentrations and with different fiber blends.

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.