Chitinase is produced by a number of organisms and it is one of the most important enzymes with industrial significance. In this study, we describe the optimization of medium composition with increased production of chitinase for Serratia marcescens strain JPP1. The strain was isolated from the peanut hulls in Jiangsu Province, China and exhibited antagonistic activity against aflatoxins and chitinolytic activity by producing chitinases. Medium composition was optimized using statistical experimental design: Plackett-Burman design was applied to find the key ingredients, and the five significant variables were peptone, glucose, ammonium sulfate, fructose and beef extract.