[Isolation and identification of the broad spectrum antimicrobial peptide AP311 produced by Lactobacillus...

The heat stable antimicrobial peptide (AP311) produced by Lactobacillus acidophilus was isolated and identified. The AP311 has broad spectrum of inhibition including many Gram-positive and Gram-negative bacteria. The inhibition activity of AP311 was lost upon treatment with trypsin, subtilisin, proteanase K, chymotrypsin and pepsin. Inhibition activity of AP311 was decreased with pH increasing. The AP311 is very stable at acidic condition (pH2-4) even if heating at 100 degrees C for 30 min. But it was inactivated at basic pH (pH12) and the activity was restored completely upon reversion to acidic. The AP311 was not precipitated and inactivated by various organic solvents, except n-butanol. When the precipitate was redissolved in 0.02 mol/L HC1, its activity was restored. Based on its proteinaceous nature, broad spectrum of inhibition, we propose that AP311 should be considered the broad spectrum antimicrobial peptide.