Survival and Impact on Microbial Diversity of Lacticaseibacillus paracasei DG in a Simulation of Human Intestinal Microbial Ecosystem.

Abstract

Background/Objectives: The probiotic Lacticaseibacillus paracasei DG (LpDG) has shown promising results for various gastrointestinal diseases. This study evaluated the survival, metabolic activity, and impact on colonic microbiota of LpDG in an in vitro gastrointestinal tract simulation. Methods: Encapsulated LpDG was tested under simulated fed, fasted, and shortened fasted conditions compared with a blank control in a modified Simulator of the Human Intestinal Microbial Ecosystem (SHIME^®) reactor. Capsule integrity, and cell culturability and viability were assessed at the end of each digestion phase. Metabolic activity (pH, total gas production, and concentrations of short-chain fatty acids, lactate, and ammonium) was assessed after a 24 h colonic incubation with a faecal inoculum. The impact of LpDG on the colonic microbial community was analysed by quantitative polymerase chain reaction and shallow shotgun sequencing. Results: The capsule was completely degraded at the end of the jejunum under all conditions. A low pH had a minimal impact on LpDG culturability and viability. Compared with blank control, LpDG remained metabolically active in the microbial community following a 24 h colonic incubation (LpDG [0-24 h] vs. blank control [0-24 h]: ΔpH, decreased [0.29-0.38 vs. 0.12-0.34]; Δlactic acid, decreased [1.52-1.69 mM vs. 0.13-0.21 mM]; and Δbutyrate, increased [7.49-10.52 mM vs. 5.19-7.76 mM]). Under fed conditions, treatment with LpDG compared with blank control significantly decreased levels of Escherichia coli and Blautia wexlerae and increased Clostridiaceae, Eubacteriaceae, and Lachnospiraceae. Conclusions: LpDG remains viable and metabolically active in the gastrointestinal tract, positively affecting intestinal microbiota and metabolite production.