Fig. (4) Thermal stability at 50ÂșC and pH 8.0 for CRL immobilized on glyoxyl-agarose (absence and presence of PEG) in the reaction medium of p-NPP hydrolysis. Half-lives estimated by Sadana-Henley model [59]: absence of PEG (t1/2 = 11 min); presence of PEG (t1/2 = 30 min).