Abstract: Caseicin A is an antimicrobial peptide （ABP） generated through the bacterial fermentation of sodium caseinate， and on the basis of previous studies， it is active against many Gram-negative pathogens and Gram-positive organisms. In order to obtain more active ABP， the amino acid sequence of Caseicin A was rearranged. Our results showed that the changes of amino acid sequence would cause the alteration of antimicrobial activity， but the influence was different on different tested bacteria.

Key words: casein, caseicin A, antimicrobial activity, minimum antibacterial concentrations