Adhesion analyses and comparative proteome to elucidate the interaction between the probiotic L.acidophilus NCFM and plant phenolics

Dietary phenolics are bioactive molecules that beneficially affect human health, due to their anti-oxidant, anti-inflammatory, cardio-protective and chemopreventive properties. They are absorbed in a very low percentage in the small intestine and reach the colon, where they are metabolized by the gut microbiota. In this context, firstly, differential proteomics was applied to reveal the influence of caffeic and ferulic acid on the surface and whole cell proteome of the probiotic bacterium Lactobacillus acidophilus NCFM. Then adhesion assays were performed in order to investigate the effect of the two phenolics on the adhesion potential of the probiotic to mucin and HT-29 cells. Caffeic and ferulic acids (at 500 µg/mL concentrations each) affected the abundance of different surface-associated proteins involved in adhesion and host interaction. They also modulate the abundance of intracellular proteins involved in general stress response mechanisms, carbohydrate and amino acid metabolism, protein synthesis and cell wall integrity. Phenolic acids showed an influence on probiotic adhesion strictly dependent on their concentration. Caffeic acid showed the best effect at the lowest concentration (100 µg/mL), increasing the adhesion to HT-29 cells, while ferulic acid was more effective at 250 µg/mL where it increased the adhesion to both mucin and HT-29 cells. These results have a great impact on the possibility to treat gastrointestinal inflammatory disorders by combining plant antioxidants with Lactobacilli.