Isolation of a peptide fraction from honeybee royal jelly as a potential antifoulbrood factor

Abstract

A peptide fraction was isolated from honeybee royal jelly (RJ) using dual dialysis under acidic conditions. The N-terminal amino acid sequence of the major peptide within the fraction was V-T-C-D-L-L-S-F-K-G. This sequence corresponds to the honeybee defensin royalisin of MW 5523 Da which has been shown to exert antibacterial activity against some Gram-positive bacteria. Diffusion tests on agar plates showed that the peptide fraction had an inhibitory effect against the honeybee pathogen Paenibacillus larvae larvae, the primary pathogen of Amerìcan foulbrood disease, as well as against other Gram-positive bacteria such as Bacillus subtilis and Sarcina lutea. Moreover, the peptide fraction was shown also to have antifungal effect against the model fungus Botrytis cinerea. It is the first evidence of an antibiotic effect of royalisin against a honeybee pathogen. The procedure described is very simple and does not require application of complicated separation techniques. It is based on dialysis of RJ using membranes with different pore sizes, which enable to separate the compounds having molecular weight below 2 kDa, between 2 kDa and 10 kDa, and over 10 kDa.