Abstract: In order to improve the capacity of Serratia marcescens strain S68-CM5 producing chitinase,the fermentation conditions of enzyme production were optimized. Using Plackett-Burman design and response surface method,the conditions of medium and fermentation were explored. The results showed that the optimal enzyme production medium：1.5% colloidal chitin,beef extract 7 g/L,yeast extract 2 g/L,glucose 8 g/L,NaCl 3.5 g/L,peptone 2 g/L,and hydrogen phosphate dehydrate potassium 3.5 g/L;the optimal culture conditions for enzyme production：pH6.88,temperature 27.32℃,shakers revolutions 155.82 r/min,incubation time 60 h,and inoculums size 1% liquid volume 50 mL/250 mL. After optimization,the enzyme production reached 7.131 U/mL,and 1.43 folds of that before optimization.

Key words: Serratia marcescens, medium optimization, response surface