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.

Detection and study of the experimental infection of Aeromonas strain in the common carp (Cyprinus carpio L.)

The aim of this study was to isolate motile aeromonad strain of common carp (Cyprinus carpio) which was obtained from farms around Baghdad and identification of the isolate by using Analytical profile index API20E. Experimental infection was carried out by intramusculer injecting LD50 does 0.3× 108.66 cell/fish into common carp Cyprinus carpio L. Infected fish after 14 days of injection showed hemorrhage and ulceration on the body surface, eye abnormalities and accumulation of red-colored ascetic fluid . Macroscopically pale liver with hemorrhagic and necrotic spots was seen and kidney showed liquefaction. Microscopically severe necrotic changes in muscular structure and internal organs with intense polymorphonuclear cell. Infiltration characterized by of pyknosis of nuclei with presence of cellular detritus were seen.