Isolation and characterization of a thermostable alkaline chitinase-producing Aeromonas strain and its potential in biodegradation of shrimp shell wastes

Chitinases are employed to the conversion of chitin and are produced by a wide range of bacteria. The objective of this study was to isolate chitinase-producing microorganisms with high chitinolytic activity. A thermostable alkaline chitinase producing isolate strain CQNU6-2 was obtained from soil samples and showed potential in biodegradation of shrimp shell wastes. The optimal culturing conditions of isolate CQNU6-2 is at 25°C and pH 7 for 24 h. The chitinase produced by strain CQNU6-2 exhibited maximum activity at pH 6.0 and 40°C and it could tolerate the treatment of high temperature (up to 80°C) and high pH (over 10). Taxonomic study, based on biochemical and morphological analysis and phylogenetic analysis of 16S rDNA, showed that strain CQNU6-2 was belongs to the genus Aeromonas sp. The isolate can effectively hydrolyze colloidal chitin with degradation rate of 100% and also can directly degrade the shrimp shells. Ammonium sulfate precipitation method can be used to preliminary purify the chitinase. In conclusion, strain CQNU6-2 had a promising potential for biodegradation of chitin under harsh pH or temperature conditions and could be employed to the comprehensive utilization of shrimp shell wastes.