Preparation, characterization and antibacterial activity of oxidized κ-carrageenan

The oxidized κ -carrageenans with different oxidation levels were prepared through the hydrogen peroxide and copper sulfate redox system. The oxidation level of oxidized κ -carrageenan was successfully controlled by adjusting the dosage of hydrogen peroxide. The results showed that the microtopography of oxidized κ -carrageenan changed from rough granules to smooth flakes, mainly resulting from the easily melting property of oxidized κ -carrageenan induced by introduced carboxyl and aldehyde groups. Especially, the antibacterial activity of oxidized κ -carrageenans against Gram-positive bacteria ( Staphylococcus aureus and Listeria monocytogenes ) and Gram-negative bacteria ( Escherichia coli and Pseudomonas aeruginosa ) was systematically investigated. The results showed that the oxidized κ -carrageenan could damage the bacterial cell wall and cytoplasmic membrane and suppress the growth of both Gram-positive and Gram-negative bacteria. The oxidized κ -carrageenan possessed broad-spectrum antibacterial activity, which may be used as a new antibacterial agent.