To select plant-derived lactic acid bacteria with probiotic characteristics, 1000 strains of lactic acid bacteria (LAB) isolated from traditional fermented vegetables were evaluated for acid resistance, bile salt tolerance, bacteriostasis, in vitro antioxidant capacity, drug susceptibility, hemolytic activity and amino acid decarboxylase activity. Furthermore, the selected strains were identified by 16S rDNA gene sequencing. Totally 82 LAB strains were obtained by culturing in MRS medium at pH 3.0, and out of these, 49 strains were selected by culturing in MRS medium with pH 2.5, all of which were tolerant to 0.3% bile salt. Nineteen of the 49 strains were further selected based on their microscopic morphology and plant sources to evaluate their drug sensitivity, hemolytic activity, bacteriostatic effect, amino acid decarboxylase activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. Results showed that the 19 strains were susceptible to most of the 20 antibiotics tested with four of them being susceptible to all the antibiotics. All of the 19 strains had inhibitory activity against the tested pathogenic bacteria and had no hemolytic activity. As determined using a commercial amino acid decarboxylase activity kit and polymerase chain reaction (PCR), the 19 strains had no potential risk of producing bioamine, and the in vitro antioxidant capacity of five of these strains was higher than 40%, suggesting the 19 strains have probiotic properties. The results of identification showed that the 19 strains contained seven strains of Lactobacillus fermentorum, six strains of Lactobacillus plantarum, and one strain of Bacillus eneniensis, one strain of Lactococcus pentosus, one strain of Limoxibacter, one strain of Lactobacillus pentosus, one strain of Enterococcus faecium and one strain of Lactobacillus brevis.

A synthesized antimicrobial peptide (W3-2) from Lactiplantibacillus plantarum was found to have temperature, pH, proteases (papain, proteinase K, pepsin, trypsin, cellulase, and pectinase), and several chemical reagents (thylenediaminetetraacetic acid, urea, Tween, methanol, and ethanol). Its inhibitory effect against Staphylococcus aureus was investigated by determining the minimum inhibitory concentration (MIC) and bactericidal kinetics. The underlying mechanism was explored through measurement of extracellular K⁺ and ATP levels and nucleic acid and protein leakage, flow cytometry analysis, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. The results showed that W3-2 had strong inhibitory effects on both Gram-positive and Gram-negative bacteria. It inhibited the growth of S. aureus with an MIC of 0.425 mg/mL. W3-2 increased the permeability of the bacterial cell membrane, leading to K⁺ efflux and thereby disrupting the integrity of the cell membrane. This resulted in the leakage of intracellular macromolecular substances (nucleic acids, proteins, and ATP) and damage to both intracellular and extracellular structures, ultimately causing bacterial cell death. This study provides a scientific basis for the development and utilization of W3-2 as a novel antimicrobial agent.

To evaluate the flavor of fermented chopped peppers from different regions, free amino acids, organic acids, and volatile compounds were analyzed by high performance liquid chromatography (HPLC) and headspace solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), and taste and odor characteristics were detected using an electronic nose (E-nose) and an electronic tongue (E-tongue). Furthermore, radar plots were drawn based on the E-nose and E-tongue data, taste activity values (TAVs) and odor activity values (OAVs) were calculated, and principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were carried out. The results showed that the E-tongue was sensitive to the sweet and umami tastes but not to the salty, bitter, or sour tastes of fermented chopped peppers from different regions. HPLC identified a total of 24 free amino acids and 7 organic acids. The contents of sweet and umami amino acids in the samples were similar to the discrimination results of E-tongue sweet and umami taste sensors. The E-nose was sensitive to alcohols, aldehydes, phenols, and nitrogen-sulfur compounds in fermented chopped peppers from different regions, showing significant differences in the types and contents of alcohols and aldehydes among the samples. GC-MS analysis identified a total of 69 volatile compounds. Combining OAV and OPLS-DA differences were found in the key aroma components of fermented chopped peppers from different regions, and the OPLS-DA results were consistent with the PCA results of E-nose. These results indicated that the combination of GC-MS, HPLC, E-nose, and E-tongue can effectively evaluate the flavor quality of fermented chopped peppers from different regions, thereby providing technical support for the quality control and enhancement of fermented chopped pepper products.

To investigate the anti-allergic activity of lactic acid bacteria, lactic acid bacterial strains were obtained from fermented vegetables by the traditional isolation technique and screened for in vitro allergic activity by the degranulation inhibition assay against RBL-2H3 cells. The results showed that all four isolates exhibited good probiotic properties and safety and had a strong inhibitory effect on β-hexosaminidase released from RBL-2H3 cells after degranulation. Moreover, they showed significant down-regulation effects on the release of histamine, tumor necrosis factor-α and interleukin-4 from RBL-2H3 cell after degranulation, suggesting their potential as anti-allergic probiotics. The four strains were identified by 16S rDNA sequencing as two strains of Lactobacillus plantarum, one strain of L. fermentum and one strain of L. paracasei.