Chitosan, produced by thermochemical deacetylation of chitin, is a unique polymer. This chemical process causes insoluble and impure chitin/chitosan derivates. Therefore, the methods such as enzymatic bioconversion have recently been investigated for the yielding of novel polymers. It is aimed to purification and biochemical characterization of chitin deacetylases from Bacillus cereus in the marine environment. In this research, the biochemical characterization of the crude chitin deacetylase supernatant from Bacillus cereus was analyzed. The specific activity was calculated as 0.274 U/mg. The optimum activity of supernatant was determined at 50 degrees C and pH 7.0. After the pre-incubation of enzyme at 50 degrees C for 20 min, the activity increased up to 115%. Acetic acid (105%), glycerol (123%), CoCl2 (113%), NaCl (137%) and CaCl2 (102%) in 5 mM concentration stimulated to the enzyme activity. EDTA (81.12%) and Triton X-100 (75.5%) behaved as the inhibitory agent on activity. In the presence of SDS, 2-mercaptoethanol, MgCl2 and MnCl2, this activity preserved as 97, 89, 64 and 83% respectively. In SDS-PAGE analysis, two protein bands in 39 and 29.60 kDa molecular weight belonging to chitin deacetylase were estimated. According to our biochemical results, the crude CDA supernatant can suggested to use in several potential applications such as biological control of fungal diseases in human, plant pathogens, some pest insects and food protection.