Abstract: The effects of papain concentration,enzymolysis temperature and time on the deproteinization of extracellular polysaccharide from Rhizopusnigricans  in Enzyme-Sevag process were investigated by single-factor experiment combining with central composite design method of Box-Behnken.The optimal process parameters were determined based on the deproteinization rate and comprehensive index.After optimizing by response surface methodology,the optimal process parameters were confirmed as follows:papain concentration of 425 U/mL,enzymolysis temperature of 62  ℃ and time of 90 min.Following repeated experiments three times,the average deproteinization rateand comprehensive index were determined as 54.08 % and 2.07,respectively.

Key words: Rhizopusnigricans, exopolysaccharides, deproteinization, enzyme-sevag process, response surface methodology