Papain can be immobilized on sand by cross-linking method, using melamine and glutaraldehyde as activator and cross-linking agent. In the presence of 20 mM Cystein, 10 mM EDTA and 1 mg/ml papain solution pH 8.5 for 150 minutes at room temperature, the immobilized papain contains 0.59-0.63 mg protein/g sand and the activity is 40-50 CDU/g sand. Using casein as substrate, the optimum pH of immobilized papain is 6.5 with pH stability in the range of 8-9, which is higher than free papain, but the stability to temperature is only 40°c, lower than free papain (60°c). The Km value of immobilized papain is 4.319 mg/ml, which is slightly higher than free papain (3.770 mg/ml), but its storage stability at 4°c as moist cake is longer than in buffer solution pH 9. Immobilized papain packed in a column is able to digest casein (1%) continuously for 7 days without loss of activity, but in the batch system immobilized papain lost 50% of its activity after 3 repeated uses. When natural rubber latex 25% DRC is used as substrate for immobilized papain 200 CDU/20 ml latex at optimum pH 8.5, temperature 45°c and reaction time 4 hrs. Immobilized papain can reduce protein in natural rubber latex assayed as the reduction of nitrogen content (% protein content = 6.25 x % nitrogen content) down to 0.37%. When the natural rubber latex was centrifuged and diluted to 10% DRC before adding immobilized papain, the nitrogen content can be reduced to 0.15% with the same amount of enzyme. However immobilized papain still has lower deproteinization efficiency than free papain. At equal amount of 200 CDU, immobilized papain can reduce nitrogen content from 0.67% to 0.37%, where free papain can reduce nitrogen content to 0.29%. The deproteinized natural rubber (DPNR) produced by immobilized papain shows similar raw rubber properties, and other non-rubber contaminants at the same level as DPNR produced by free papain. The stability of immobilized papain decreased 50 %, after 2 repeated uses for latex deproteinization in the batch system, therefore immobilized papain is still not valid for natural rubber latex deproteinization, because the operating cost for papain immobilization is 40 fold of using free papain