Abstract
Abstract Identification, characterization and assessment of novel bacteriocins for their potential use as biopreservatives continue to be highlighted in LAB research from past to present. A bacteriocin-producing Lactobacillus casei TN-2 strain was isolated from fermented camel milk (Shubat) of Xinjiang Uygur Autonomous region, China, after which the bacteriocin (designated as caseicin TN-2) was purified by performing ammonium sulfate precipitation, gel filtration, anion exchange chromatography and reversed-phase HPLC separation. According to MS spectrum, the molecular mass of caseicin TN-2 was 6352 Da, which was significantly different from previous reported bacteriocins produced by L. casei strains. Antibacterial activity of caseicin TN-2 was retained over a wide pH range and survived a heat treatment of 121 °C for 20 min. It was sensitive to proteases, such as trypsin and papain. Caseicin TN-2 exhibited a broad antimicrobial spectrum against Gram-positive and Gram-negative food-borne pathogenic strains including some antibiotic-resistant strains. It was found that the minimum inhibitory concentration of caseicin TN-2 to Escherichia coli ATCC25922 and Staphylococcus aureus ATCC25923 was 2.5 mg/mL and 5 mg/mL respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses were carried out to investigate the effect of caseicin TN-2 on the target cells, where it was demonstrated that the bacteriocidal mode of action was pore formation in the cytoplasmic membrane.
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