Tipparat Hongpattarakere and Oraphan Riyaphan

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Abstract

Chitosan was prepared from black tiger shrimp carapace by deacetylation process performed in 50% NaOH at 100°C under vacuum, nitrogen and regular atmospheres. Each condition was maintained for 0.5, 1.0 and 2.0 h. Chitosan obtained from 1.0 h of deacetylation under regular atmosphere showed the lowest minimum inhibitory concentration (MIC) value of
625 ppm against Escherichia coli and Staphylococcus aureus, while Candida albicans was inhibited at MIC value of 312.5 ppm due to its higher degree of deacetylation (% DD) and lower molecular weight (MW) compared to chitosan deacetylated under vacuum and nitrogen atmospheres. Chitosan hydrolysates obtained from both chemical (H₂O₂
 in the presence of ferricions) and enzymatic (lysozyme) hydrolysis were not as inhibitory as the native one, except that from chemical hydrolysis,
which showed the elevation of the antifungal activity against C. albicans when longer hydrolysis was performed. However, antibacterial activity against E. coli decreased when the MW of hydrolyzed chitosan decreased.