Chitosan glutamate was obtained from Pronova (Drammen, Norway). It contained 42% glutamate and had a deacetylation
range of 75^85% (manufacturer’s data). Chitosan solutions were prepared in deionized water and autoclaved at 1211C for
20 min. The antimicrobial activity of chitosan was not a¡ected by autoclaving in laboratory media for up to 30 min (Roller and Covill 1999). All microbiological media and diluents were from Oxoid (Basingstoke, UK). All other chemicals were from Sigma Chemical Co (Poole, Dorset, UK), unless otherwise indicated.