The easily prepared polyanionic magnetic nanoparticle (MNP) was employed to recover a polycationic natural food preservative, epsilon-polylysine (E-PL) from fermentation broth of Streptomyces albulus. E-PL with a final concentration of 10g/L could be produced in a 5 day pH controlled two-stage fermentation of S. albulus. The polyanionic MNP was prepared by co-precipitating Fe(II)/Fe(III) solution in the presence of water soluble carboxymethyl cellulose (CMC) at pH 11. The Langmuir isotherm can well describe the adsorption behavior between CMC-conjugated MNP (CMC-MNP) and E-PL that 0.38g of E-PL could be captured by 1g of CMC-MNP at pH 5, 37 degrees C. Approximately, 80% of E-PL adsorbed on the freshly prepared CMC-MNP could be eluted by 0.1N HCl. The adsorption capacity of CMC-MNP remained at a constant level for at least 5 repeated adsorptions. The E-PL isolated by CMC-MNP not only demonstrated an improved purity but also its antimicrobial activity as compared with -polylysine against the bacterium E. coli.