Effect of Fiber Concentration on the Growth of Lactobacillus rhamnosus
Authors: Santos Amanda B. , Gillen Craig , Santos Fernanda B.O. , Santos Anael A. 
Published: June 2021

The use of probiotics and prebiotics has become widely accepted as beneficial for intestinal health. In addition to the enhanced intestinal function, probiotics and prebiotics are being recognized for their capacity to modulate the immune system, and their effectiveness and safety in diseases, such as diabetes, cancer and heart disease. The best known probiotic bacteria are those belonging to the genera Lactobacillus and Bifidobacterium. The most common prebiotics are fibers, also known as dietary fibers, which have the potential to stimulate the growth of commensal bacteria residing in the intestinal tract. Gaining insight on how fibers can modulate or enhance the growth of probiotics is of great importance. Therefore, this study aims to evaluate the effect of different fiber sources and different concentrations of these fibers on in vitro bacterial growth. It is hypothesized that higher concentration of fiber will result in higher microbial populations.

Lactobacillus rhamnosus, 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 about 108 CFU/ml. Lactobacillus culture media, MRS broth, was supplemented with different fibers at different concentrations to evaluate the effect of these different nutrients and their concentration on bacterial growth. Three different fibers were used in the study, which were inulin, fructooligosaccharides (FOS), and psyllium. To test the concentration effect, three different concentrations were used, 1%, 2% and 4%.

In a previous study, we have proven the beneficial effect of the addition of fiber to the growth media. The present study results agree with those findings. In addition, based on the current results, the hypothesis that higher concentration of the fibers enhances bacterial growth was proven correct for psyllium (8.7, 9.0, 9.3 log CFU/ml for 1, 2, 4% respectively, p<0.05), but not for the other fibers used in this study. Psyllium supplemented at 2% provided a greater bacterial growth than the other fibers (9.0 vs. 8.7 log CFU/ml, p=0.01). The highest bacterial growth observed with psyllium supplementation compared to the other treatments was achieved at 4% supplementation (9.3 vs 8.7 log CFU/ml, p<0.001).

In conclusion, Lactobacillus rhamnosus growth can be differently affected by the different fibers. Psyllium resulted in the highest population growth, and its effect increased as concentration increased. Distinct probiotics are influenced by different types of prebiotic at different concentrations, which is correlated to the growth needs of the bacterial cells. Therefore, the present study findings add important information regarding the complex interaction between probiotic bacteria and prebiotics; however, more research is needed to better understand these intricate relationships.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.