Abstract: A facultative anaerobic lactic acid bacterium producing antibacterial substrates was isolated from the traditional fermentation pickle by clear-circle method and marked as A5. Its cell is short-rod, G+, motile. The results of physiological and biochemical research were obtained that amylolysis test was negative, while gelatin liquefaction, methyl red, glucose fermentation and cellulose decomposition tests were positive. By excluding the influence of acid inhibition and hydrogen peroxide, the supernatant still had better antibacterial activity. When the supernatant was treated with protease, its antibacterial activity largely decreased. All the results indicated strain A5 fermentation supernatant contained a type of proteinaceous antibacterial substance (bacteriocin). By adjusting the pH value of supernatant and measuring its antibacterial activity, the result showed supernatant had stronger antibacterial activity at pH 2, which meant these antibacterial substances had super tolerance to acid. Strain A5 has good inhibitory activity to gram-positive bacteria and gram-negative bacteria, meaning its broad-spectrum antibacterial activity, and higher tolerance to acid, which make it a potential application in bio-antibiotics field.

Key words: pickle, lactic acid bacterium(LAB), inhibitory circle, bacteriocin