Effects of p-coumaric acid on probiotic properties of Lactobacillus acidophilus LA-5 and lacticaseibacillus rhamnosus GG

Abstract

Probiotics are defined as "live microorganisms that provide health benefits to the host when administered in adequate amounts." Probiotics have beneficial effects on human health, including antibacterial activity against intestinal pathogens, regulation of blood cholesterol levels, reduction of colitis and inflammation incidence, regulation of the immune system, and prevention of colon cancer. In addition to probiotic bacteria, some phenolic compounds found in foods we consume (both food and beverages) have positive effects on human health. p-coumaric acid (p-CA) is one of the most abundant phenolic compounds in nature and human diet. The interactions between these two different food components (phenolics and probiotics), resulting in more beneficial combinations called synbiotics, are not well understood in terms of how they will affect the gut microbiota by promoting the probiotic properties and growth of probiotic bacteria. Thus, this study aimed to investigate synbiotic relationship between p-CA and Lactobacillus acidophilus LA-5 (LA-5), Lacticaseibacillus rhamnosus GG (LGG). Probiotic bacteria were grown in the presence of p-CA at different concentrations, and the effects of p-CA on probiotic properties, as well as its in vitro effects on AChE and BChE activities, were investigated. Additionally, Surface analysis was conducted using FTIR. The results showed that treatment with p-CA at different concentrations did not exhibit any inhibitory effect on the growth kinetics of LA-5 and LGG probiotic bacteria. Additionally, both probiotic bacteria demonstrated high levels of antibacterial properties. It showed that it increased the auto-aggregation of both probiotics. While p-CA increased co-aggregation of LA-5 and LGG against Escherichia coli, it decreased co-aggregation against Staphylococcus aureus. Probiotics grown with p-CA were more resistant to pepsin. While p-CA increased the resistance of LA-5 to bile salt, it decreased the resistance of LGG. The combinations of bacteria and p-CA efficiently suppressed AChE and BChE with inhibition (%) 11.04-68.43 and 13.20-65.72, respectively. Furthermore, surface analysis was conducted using FTIR to investigate the interaction of p-coumaric acid with LA-5 and LGG, and changes in cell components on the bacterial surface were analyzed. The results, recorded in range of 4000 -600 cm^-1 with resolution of 4 cm^-1, demonstrated that p-CA significantly affected only the phosphate/CH ratio for both bacteria. These results indicate the addition of p-CA to the probiotic growth may enhance the probiotic properties of bacteria.

Keywords: Cholinesterase; Enzyme inhibition; Phenolic compound; Probiotic bacteria; Synbiotics; p-Coumaric acid.