Abstract
The main purpose of this study was to explore the antibacterial activity and mechanism of lacidophilin from Lactobacillus pentosus against Staphylococcus aureus and Escherichia coli. The effects of temperature, enzyme, metal ions, and pH on the antibacterial activity of L. pentosus were evaluated. The result showed that lacidophilin had good thermal stability and could be decomposed by trypsin completely. The antibacterial ability was affected by high concentration of metal ions, and the best antibacterial ability was acquired under acidic conditions. The antibacterial mechanism of lacidophilin was explored through studying cytomembrane injury, phosphorus metabolism, protein changes, and oxidative stress response of the indicator bacteria. It was shown that lacidophilin destroyed the cytomembrane of the bacteria and increased the cytomembrane permeability, which resulted in the leak of proteins, nucleic acids, and electrolytes. In addition, it further restrained phosphorus metabolism, caused changes of some protein contents, and increased cytomembrane lipid peroxidation and cell oxidative damage. All these might inhibit the growth of bacteria and even cause their death. This study identified a natural biological preservative with strong antibacterial activity against both Gram-positive and Gram-negative foodborne pathogens. The high antibacterial activity against the two types of bacteria reflected its potential in food preservation used as a natural food preservative.
Highlights
The food industry has made significant progress in food standards, food processing, and food testing, but health and safety concerns still persist
No antibacterial effect against E. coli and S. aureus was observed in the negative control (MRS medium alone) (Table 1), which eliminated the interference of the medium to the antibacterial effect
The diameters of inhibition zones around the Oxford cup against E. coli and S. aureus were 19.83 and 18.46, respectively (Table 1), which indicated that the lacidophilin from L. pentosus had high activity against the two strains
Summary
The food industry has made significant progress in food standards, food processing, and food testing, but health and safety concerns still persist. It was estimated that about one-third of food is wasted due to spoilage each year (Gills et al, 2015). Some physical and chemical methods have been adopted to extend the shelf life of foods, among which, the addition of chemical preservatives is the most effective way. Long-term intake of chemical preservatives has adverse effects on human health (Yang et al, 2014). More attention has been paid to natural preservatives for their safe and non-polluting character. Bacteriocins have been widely used in foods as natural preservatives because of their wide sources and diverse structures, which have high efficiency in killing various foodborne pathogens and spoilage bacteria (Lv et al, 2018)
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