Studies on Immobilisation of Papain on Powdered Resin after Isolation and Purification from Indigenous Papaya Latex

Isolation and purification of papain from indigenous papaya latex was carried out according to the method of Baines et al and the purity of the papain thus obtained was verified by disc-gel electrophoresis. The half-life periods of the purified papain solution maintained at different pH values were determined. It was found that the aqueous solution of the purified papain was most stable at 30° C in the pH range 5 to 6. Studies on the effect of different activators on the activity of papain showed that cysteine and dithiol compounds activate the purified enzyme to a greater extent. The optimum concentration of both the cysteine and dithiol compounds for obtaining maximum activity of the purified papain was 0.05M. Studies on the immobilisation of papain on phenol formaldehyde resin using glutaraldehyde as cross-linking agent showed that for eliminating the external mass transfer resistance during reaction of immobilised enzyme, the optimum stirrer speed was 800 r.p.m and that pore-diffusional limitation was practically absent. Investigation on the evaluation of different parameters of reaction of papain and immobilised papain showed that the values of Michaeles-Menten constant and maximum reaction rate were very close in both the cases while the values of optimum pH of reaction, optimum temperature of reaction and activation energy were the same in both the cases of free and immobilised enzyme. Comparative studies on immobilisation of papain and mercuripapain performed separately on phenol-formaldehyde resin indicated that immobilised papain showed only 68.5% of the activity of immobilised mercuripapain.