Antimicrobial activity of shrimp chitin and chitosan from different treatments and applications of fish preservation英文电子书.pdf

FISHERIES SCIENCE 2002; 68: 170–177 Original Article Antimicrobial activity of shrimp chitin and chitosan from different treatments and applications of fish preservation Guo-Jane TSAI,* Wen-Huey SU, Hsing-Chen CHEN AND Chorng-Laing PAN Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan 202 ABSTRACT: The effects of the deacetylation degree (DD) and preparation methods for chitosan on antimicrobial activity were evaluated. Chemically prepared chitin (CH-chitin) and microbiologically prepared chitin (MO-chitin) were obtained from shrimp shells. The CH-chitin and MO-chitin were further chemically deacetylated to obtain various chitosan products of which their DD ranged from low (47–53%) through medium DD (74–76%) to high (95–98%). In addition, MO-chitin was deacety- lated also by various proteases. The antimicrobial activities of these products were evaluated in medium with pH 6.0. Neither the CH-chitin, MO-chitin nor protease-deacetylated chitinous products showed any antimicrobial activity. For chitosan, antimicrobial activity increased with increasing DD, and was stronger against bacteria than against fungi. The minimal lethal concentrations (MLC) of chitosan with a high DD against Bacillus cereus, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Shigella dysenteriae, Staphylococcus aureus, Vibrio cholerae, and V. parahaemolyticus were all in the range of 50–200 p.p.m., whereas the MLC against Candida albi- cans and Fusarium oxysporum were 200 p.p.m. and 500 p.p.m., respectively. No antifungal activity was found at 2000 p.p.m. against Aspergillus fumigatus or A. parasiticus. Pretreatment of fish fil