Application of the Combination of Soybean Lecithin and Whey Protein Concentrate 80 to Improve the Bile Salt and Acid Tolerance of Probiotics

In 2001, the Food and Agriculture Organization (FAO) and the World Health Organization (WHO) defined probiotics as "live microorganisms which when administered in adequate amounts confer a health benefit on the host." Probiotics are the most effective and accessible tools for modulating gut microbiota and thereby altering human health and diseases. Presently, lactic acid bacteria (LAB) and Bifidobacterium are used as traditional and universal probiotics in supplements or fermented foods. Probiotics demonstrate a range of effects, and gut microbiome dysbiosis is associated with gastrointestinal, autoimmune, neurological, and metabolic diseases [1]. The clinical efficacy of probiotics in some diseases, such as antibiotic-associated diarrhea [2], Clostridium difficileassociated diarrhea [3], and irritable bowel syndrome and inflammatory bowel disease [4] has been determined by manipulating the microbiota with probiotics. Additionally, the therapeutic success in some cancers is also associated with the diversity and composition of the gut microbiome [5]. To improve the bile salt and acid tolerance of probiotics against gastrointestinal stresses, we investigated the effects of soybean lecithin and whey protein concentrate (WPC) 80 on the bile salt tolerance of Lacticaseibacillus paracasei L9 using a single-factor methodology, which was optimized using response surface methodology (RSM). The survival rate of L. paracasei L9 treated with 0.3% (w/v) bile salt for 2.5 h, and combined with soybean lecithin or WPC 80, was lower than 1%. After optimization, the survival rate of L. paracasei L9 incubated in 0.3% bile salt for 2.5 h reached 52.5% at a ratio of 0.74% soybean lecithin and 2.54% WPC 80. Moreover, this optimized method improved the survival rate of L. paracasei L9 in low pH condition and can be applied to other lactic acid bacteria (LAB) strains. Conclusively, the combination of soybean lecithin and WPC 80 significantly improved the bile salt and acid tolerance of LAB. Our study provides a novel approach for enhancing the gastrointestinal tolerance of LAB by combining food-derived components that have different properties.