Antibacterial activity of chitin, chitosan and its oligomers prepared from shrimp shell waste

The antimicrobial activities of chito-oligosaccharides against four Gram-positive and seven Gram-negative bacteria were compared to chitosan and chitin with an emphasis on the effects of biopolymer molecular weight (Mv) and degree of deacetylation (DD). Chitin was isolated from shrimp (Parapenaeus longirostris) shell waste by sequential chemical treatments. Chitosan and its oligomers N-acetyl chito-oligosaccharides and chito-oligosaccharides were prepared by deacetylation and chemical hydrolysis, respectively. Chitin exhibited a bacteriostatic effect on Gram-negative bacteria, Escherichia coli ATCC 25922, Vibrio cholerae, Shigella dysenteriae, and Bacteroides fragilis. Chitosan exhibited a bacteriostatic effect on all bacteria tested, except Salmonella typhimurium. The oligomers exhibited a bactericidal effect on all bacteria tested.