Preparation, characterization and antibacterial activity of oxidized κ-carrageenan

The oxidized kappa-carrageenans with different oxidation levels were prepared through the hydrogen peroxide and copper sulfate redox system. The oxidation level of oxidized kappa-carrageenan was successfully controlled by adjusting the dosage of hydrogen peroxide. The results showed that the microtopography of oxidized kappa-carrageenan changed from rough granules to smooth flakes, mainly resulting from the easily melting property of oxidized kappa-carrageenan induced by introduced carboxyl and aldehyde groups. Especially, the antibacterial activity of oxidized kappa-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 kappa-carrageenan could damage the bacterial cell wall and cytoplasmic membrane and suppress the growth of both Gram-positive and Gram-negative bacteria. The oxidized kappa-carrageenan possessed broad-spectrum antibacterial activity, which may be used as a new antibacterial agent. (C) 2017 Elsevier Ltd. All rights reserved.