Purification and antibacterial mechanism of fish-borne bacteriocin and its application in shrimp (Penaeus vannamei) for inhibiting Vibrio parahaemolyticus

Vibrio parahaemolyticus: is recognized as the main cause of gastroenteritis associated with consumption of seafood. Bacteriocin-producing Lactobacillus plantarum FGC-12 isolated from golden carp intestine had strong antibacterial activity toward V. parahaemolyticus. The fish-borne bacteriocin was purified by a three-step procedure consisting of ethyl acetate extraction, gel filtration chromatography and high performance liquid chromatography. Its molecular weight was estimated at 4.1 kDa using SDS-PAGE. The fish-borne bacteriocin reached the maximum production at stationary phase after 20 h. It was heatstable (30 min at 121 degrees C) and remained active at pH range from 3.0 to 5.5, but was sensitive to nutrasin, papain and pepsin. Its minimum inhibitory concentration for V. parahaemolyticus was 6.0 mg/ml. Scanning electron microscopy analysis showed that the fish-borne bacteriocin disrupted cell wall of V. parahaemolyticus. The antibacterial mechanism of the fish-borne bacteriocin against V. parahaemolyticus might be described as action on membrane integrity in terms of the leakage of electrolytes, the losses of -Na+ K+-ATPase, AKP and proteins. The addition of the fish-borne bacteriocin to shrimps leaded V. parahaemolyticus to reduce 1.3 log units at 4 degrees C storage for 6 day. Moreover, a marked decline in total volatile base nitrogen and total viable counts was observed in bacteriocin treated samples than the control. It is clear that this fish-borne bacteriocin has promising potential as biopreservation for the control of V. parahaemolyticus in aquatic products.