Abstract:

Lactobacillin XH2 with antibacterial potency of 380.60 AU/mL was purified from the culture supernatant of
Lactobacillus acidophilus by ion-exchange chromatography. Its antibacterial mechanism on Escherichia coli (E. coli) was
investigated by examining its effects on mortality rate, cell membrane damage and leakage of intracellular contents from
E. coli cells. Most E. coli cells died in 3 h and their cell walls were partially damaged. The concentration of intracellular
K+ in E. coli decreased rapidly, which resulted in imbalance of the membrane potential. The leakage of large amounts of
macromolecules such as ultraviolet-absorbing substances, lactate dehydrogenase and intracellular ATP led to disruption of
the cellular structure and abnormal energy metabolism, causing the cells to die eventually. These observations indicate that
the pore formation theory could apply to Gram-negative bacteria E. coli.

Key words: Lactobacillus acidophilus, bacteriocin, Gram-negative bacteria, antibacterial mechanism