A novel antibacterial compound produced by Lactobacillus plantarum LJR13 isolated from rumen liquor of goat effectively controls multi-drug resistant human pathogens.

Probiotic lactobacilli have been implicated in the production of many low molecular weight bioactive molecules with tremendous potential to kill multidrug resistant human pathogens. The aim of the present study is to purify, characterise and evaluate a novel compound produced by a probiotic Lactobacillus plantarum LJR13 strain. The compound was purified employing silica gel column chromatography followed by RP-HPLC technique. The compound was identified as tert-butyl-4-(4-oxo-(2-((2-oxo-1- (p-tolyl) -2- (p-tolyloxy) ethyl) carbamoyl) pyrrolidin-1-yl) butanoyl) piperazine-carboxylate (BPBP) through various spectral techniques. Exhaustive literature search has revealed that the compound BPBP has not been reported from Lactobacillus species so far and ours is the first report describing its spectrum of activities against multidrug resistant human pathogens together with the morphological and physiological manifestations it brings about in the normal as well as human colon carcinoma cells. The MIC of BPBP for Listeria monocytogenes and Staphylococcus aureus was 15.62 µg/mL and 62.50 µg/mL respectively; however, for Acinetobacter baumannii the MIC was determined to be 31.25 µg/mL. Scanning electron microscopic studies of BPBP treated L. monocytogenes, S. aureus, and A. baumannii revealed the presence of blebs on the cell wall which represents the compromise in the cell wall integrity. While BPBP showed no significant cytotoxicity on mouse embryonic fibroblast cells, (NIH-3T3), marked discernible cytotoxic effect was observed on colorectal carcinoma cells, HCT-116, suggesting potential anti-cancer activity. Molecular docking studies displayed the interaction of BPBP with appropriate drug resistance associated proteins such as Penicillin binding proteins in gram positive L. monocytogenes and S. aureus and beta-lactamase in gram negative A. baumannii.

Characterization of purified antimicrobial peptide produced by Pediococcus pentosaceus LJR1, and its application in preservation of white leg shrimp.

The bacteriocinogenic lactic acid bacterium Pediococcus pentosaceus LJR1 isolated from rumen liquor of goat had strong anti-bacterial activity toward Listeria monocytogenes in vitro. This antibacterial activity was lost on treatment with protease indicating that the bacteriocin is proteinaceous in nature. The bacteriocin LJR1 produced by P. pentosaceus was purified following a three step procedure consisting of ammonium sulphate precipitation, gel filtration chromatography and reverse phase-high performance liquid chromatography. The molecular weight of purified bacteriocin was determined to be 4.6 kDa using Tricine SDS-PAGE. Further, we found that the proteinaceous bacteriocin was stable at 100 °C as well as 121 °C for 30 min and 15 min respectively and also at different pH ranging from 4 to 10 when stored for 15 min at 37 °C. Its minimum inhibitory concentration for S. typhi MTCC134 and L. monocytogenes MTCC 1143 was 7.81 µg/ml and 15.63 µg/ml respectively. Scanning electron microscopy analysis of the surface of S. typhi treated with the bacteriocin showed the presence of craters; while in the case of treated L. monocytogenes blebs were observed. The addition of the bacteriocin to shrimp (white leg shrimp) has led to reduction of about 1 log units of L. monocytogenes on day 1 and maintained for 7 days on storage at 4 °C. It is clear that the purified bacteriocin has good potential as a bio preservative for application in food industry.