Microencapsulated Lactiplantibacillus plantarum ZGP-Lpl.19 modulates growth and virulence gene expression of Shigella flexneri ATCC 12022 in vitro

Abstract

Encapsulation of Lactiplantibacillus plantarum (L. plantarum) ZGP-Lpl.19 in alginate-pectin-chitosan microcapsules significantly improved its survival under simulated gastrointestinal conditions and attenuated Shigella flexneri (S. flexneri) growth and pathogenicity through downregulation of the mdoH and IcsA virulence genes. Microencapsulation was achieved via extrusion using a polysaccharide blend, yielding an encapsulation efficiency of 98.44. Structural integrity of the microcapsules was confirmed by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Encapsulation markedly enhanced probiotic survivability, with viable counts of 5.37 log CFU/mL after 60 min in gastric fluid and 120 min in intestinal fluid, compared with 2.25 log CFU/mL for free cells. Both encapsulated and free L. plantarum ZGP-Lpl.19 demonstrated potent antimicrobial activity against S. flexneri ATCC 12022, with comparable antimicrobial metabolite production. The minimum inhibitory concentration (MIC) of cell-free supernatants from both forms was 1/8 of the original concentration. Importantly, real-time PCR analysis confirmed that both encapsulated and free cells significantly downregulated mdoH and IcsA expression. Overall, these findings demonstrate that alginate-pectin-chitosan microencapsulation provides effective protection for L. plantarum and enhances its functional delivery, positioning encapsulated L. plantarum as a promising therapeutic strategy to mitigate S. flexneri infections.