ENTRAPMENT OF PARATHION HYDROLASE FROM PSEUDOMONAS SPP IN SOL-GEL GLASS

The present work reports on the entrapment of parathion hydrolase from Pseudomonas spp. into the sol-gel glass matrix. Enzyme entrapment was studied in the range of 0.01-0.25 U, and compared with the activity o f the free, non-immobilized enzyme. The reaction catalyzed by the entr apped enzyme was almost two orders of magnitude slower than with the f ree enzyme. Addition of surfactants slightly increased the parathion h ydrolysis rate, and the addition of ethanol almost doubled it. However , this increase of reaction rate cannot by itself explain the decrease of activity, suggesting that irreversible damage to the enzyme during gelation, rather than diffusion limitation throughout the,eel-glass s tructure, is the main cause for the decrease of activity. Regardless o f damage to the enzyme during gelation, the remaining entrapped active fraction displayed stability even after eleven days, during successiv e cycles of the same entrapped enzyme batch, each for 24 h. The sol-ge l entrapped enzyme retained relatively good activity for several month s when stored as a dry powder, and over a year when kept in buffer sol ution, at ambient conditions. The results obtained may give a rise to the use of entrapped parathion hydrolase for simple on-field bio-detec tion of organophosphates.