Kinetic and Thermodynamic Study of Plantaricin IIA-1A5, a Bacteriocin Produced by Indonesian Probiotic Lactobacillus plantarum IIA-1A5

BACKGROUND

Plantaricin IIA-1A5 is a bacteriocin produced by Lactobacillus plantarum IIA-1A5, a locally isolated probiotic from Indonesia. Plantaricin IIA-1A5 exhibits antibacterial activity against wide spectrum of pathogenic bacteria, thus promising to be applied in various food products. Nevertheless, thermal stability of this bacteriocin remains to be fully investigated.

OBJECTIVE

This study aims to determine thermal stability of plantaricin IIA-1A5 through kinetic and thermodynamic parameters.

METHOD

To address, plantaricin IIA-1A5 was purified from Lactobacillus plantarum IIA-1A5, which was growth under whey media, using ammonium sulfate precipitation followed by ionexchange chromatography. Purified plantaricin IIA-IA5 was then subjected to analysis of its bacteriocin activity. The thermal inactivation of bacteriocin from L. plantarum IIA-1A5 was calculated by incubating the bacteriocin at different temperatures ranging from 60-80 °C for 30 to 90 min, which was then used to calculate its kinetic and thermodynamic parameters.

RESULTS

The result showed the inactivation rates (k-value) were ranging from 0.008 to 0.013 min-1. Heat resistance of plantaricin IIA-1A5 (D-value) at constant heating temperature of 60, 65, 70, 75, and 80 °C were 311.6, 305.9, 294.5, 198.9, and 180.2 min, which indicated a faster inactivation at higher temperatures. D-value sensitivity for temperature changes (z-value) was calculated to be 75.76 °C. Further, thermodynamic analysis suggested that plantaricin IIA-1A5 is thermostable, with activation energy (Ea) of 29.02 kJ mol-1.

CONCLUSION

This result showed that plantaricin IIA-1A5 is considerably more heat-stable than plantaricin members and promises to be applied in food industries where heat treatments are applied. Furthermore, a possible mechanism by which plantaricin IIA-1A5 maintains its stability was also discussed by referring to its thermodynamic parameters.

Antibacterial Activity and Mechanism of Lacidophilin From Lactobacillus pentosus Against Staphylococcus aureus and Escherichia coli

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.