A comparison of mining methods to extract novel bacteriocins from Lactiplantibacillus plantarum NWAFU-BIO-BS29.

One of the most important challenges in the field of food safety is producing natural and safe substances that act against pathogens in food. Bacteriocins and antimicrobial peptides (AMPs) have an anti-pathogens effect for both Gram-negative and positive bacteria. The aim of this study was to isolate and characterize safe lactic acid bacteria from traditional Chinese fermented milk that can produce anti-bacterial molecule compounds and does not harm for humans and animals. Lactiplantibacillus plantarum NWAFU-BIO-BS29 was found to be safe, lacking 16 genes for virulence factors, biogenic amine production and antibiotic resistance, and no hemolysis activity was observed. In contrast, it has ability to produce a novel potential bacteriocin of Plantaricin Bio-LP1. Precipitation of bacteriocin by Ethyl-acetate proved to be a suitable method for the extraction the bacteriocin. Whilst, the purification steps were performed as follows: the protein purification system (AKTA-Purifier equipped with HiTrap (gel column)), followed by reversed phase high-performance liquid chromatography (RP-HPLC) equipped with C18 column. In addition, LC-MS-MS and MALDI-TOF were used to identify the peptide sequences and estimate the molecular weight, respectively. Notably, among the eight peptide sequences considered, a couple of sequences have been announced as uncharacterized in protein database (FDYYFFDKK and KEIDDNSIAVK) with a molecular mass less than 1.3 kDa. The MIC was 0.552 mg/ml and exhibited high stability under various temperature, pH, and enzymes conditions. The best activity was found at temperature and pH of 4 °C and 6 °C, respectively, which are the optimal conditions for preservation of most foods. We concluded that, the described method can arouse a growing interest in mining novel bacteriocins. Plantaricin Bio-LP1 is a potentially unique bacteriocin that is effective as a bio-preservative and could make a promising contribution in food and animal feed industries or in the medical field with further clinical studies.

Lactic acid bacteria isolated from Chinese traditional fermented milk as novel probiotic strains and their potential therapeutic applications.

Lactic acid bacteria (LAB) are believed to have health-promoting properties to the host and can be used in therapeutics interventions; intriguingly, they have the property to produce bio-preservatives substances. Therefore, this study aimed to mine probiotics and evaluate their safety, functional properties, and cholesterol-lowering capability. Seven potential probiotic strains were compared from 56 LAB strains isolated from traditional Chinese fermented milk. The results showed that all tested strains are tolerant to gastric acidity (45.5-83.26) and bile salts (11.92-92.91%) and have antibacterial activity against Staphylococcus aureus ATCC25923 and Escherichia coli ATCC25922. Likewise, it lowered the cholesterol levels in vitro by live cells (26.57-45.76%) and dead cells (29.53-50.97%) with remarkable aggregation ability (13.8-43.71%). Antioxidant properties and produce short chain fatty acids (SCFAs) were strain-dependent features. Upon assessment of the safety, Enterococcus faecium NWAFU-BIO-AS14 exhibited virulence factors genes (VFs) of (mur-2ed, odc, and tet(K)) and + hemolysis activity. While Enterococcus faecium NWAFU-BIO-A-B24 and Limosilactobacillus fermentum NWAFU-BIO-B-S6 have VFs of (odc, vanC2, and ant(6)-Ia). Limosilactobacillus fermentum NWAFU-BIO-D-B2 has only (odc). Thus, they are not considered as safe probiotics. In contrast, Lactiplantibacillus plantarum NWAFU-BIO-BS29, Companilactobacillus crustorum NWAFU-BIO-AS16, and Lactobacillus gallinarum NWAFU-BIO-D-S7 are the safest and best strains, respectively, due to the absence of 16 VFs and their sensitivity to antibiotics such as kanamycin, erythromycin, tetracycline, gentamycin, vancomycin, streptomycin, chloramphenicol, and ampicillin. Accordingly, these strains have a high potentiality to be used as starter cultures or safely applied as perfect probiotics in functionals food and feed. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-022-03403-z.