Abstract: The purpose of this study was the optimization of the papain-catalyzed deproteinization conditions of polysaccharide from Portulaca oleracea L. (POP) by response surface methodology (RSM). Polysaccharide loss and the rate of protein removal were investigated with respect to four variables: enzyme to sample ratio, hydrolysis time, hydrolysis temperature and pH. The optimum operating conditions were obtained as follows: enzyme to sample ratio 0.2:1, hydrolysis time 60 ℃, hydrolysis temperature 3 h and pH 6. Under the optimized conditions, the deproteinization efficiency was as high as 78.22% with only 10.39% loss of the polysaccharide. Monosaccharide composition?analysis by high performance liquid chromatography (HPLC) showed that the purified polysaccharide was composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose and arabinose in a molar ratio of 5.3:5.9:1.3:27.6:1:18.8:14.6.

Key words: Portulaca oleracea L., polysaccharide, papain, response surface methodology, deproteinization