Abstract
To purify and to characterize the antimicrobial compound cerein 8A. Cerein 8A was isolated by ammonium sulfate precipitation, 1-butanol extraction and ion-exchange chromatography. Direct activity on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was observed. The purified substance corresponded to a 26 kDa peptide band. The native protein eluted at the void volume of Sephadex G-100, but within the included volume when a 1.5 mol l(-1) NaCl buffer was used, indicating that cerein 8A aggregates extracellularly. The antimicrobial activity was lost by treatment with proteases and heat. The ultraviolet spectrum was typical of a polypeptide and the infrared spectrum indicates that the peptide contains acyl group(s) in its structure. Intact Bacillus cereus spores were sensitive to cerein 8A at 1600 AU ml(-1). Cerein 8A show distinct properties from other antimicrobial peptides of B. cereus, and has a significant inhibitory effect on spores. The characterization of a substance active against important pathogens addresses an important aspect of food safety.
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