Bifidin I – A new bacteriocin produced by Bifidobacterium infantis BCRC 14602: Purification and partial amino acid sequence

A three-step purification protocol has been applied for purification of a new bacteriocin, bifidin I, from Bifidobacterium infantis BCRC 14602. The purification protocol resulted in a purification fold of 1390 with a specific activity of 365714 AU mg−1 and a yield of 25.6%. Bifidin I was recovered by adsorption–desorption onto/from silicic acid (ADSA). The adsorption of the bifidin I from B. infantis BCRC 14602 to silicic acid (5%) was strongly affected by the pH of the broth culture of which 100% adsorption occurs between pH 5.0 and 7.0, whereas at pH values below 5.0 and above 7.0, the adsorption ratio decreased to values 67–45% respectively. Mass spectrometry analysis showed the mass of bifidin I to be approximately 2879.7 Da. Only a partial NH2-terminal amino acid sequence was obtained comprising of 8 amino acid residues; NH2 – Lys-Tyr-Gly-Ser-Val-Pro-Leu-Gly. The strong antilisterial activity of bifidin I and its ability of inhibiting the growth of many other Gram-positive and Gram-negative bacteria which can cause food spoilage and food borne diseases have great applications in food safety. Curing experiments which resulted in Bif¯ variants incapable of producing bifidin I but retaining immunity showed that production of bifidin I is plasmid associated.