POLYPHENOLOXIDASES IMMOBILIZED IN ORGANIC GELS - PROPERTIES AND APPLICATIONS IN THE DETOXIFICATION OF AROMATIC-COMPOUNDS

Gelatine gels originate from water in oil microemulsions in which the ternary system consists of isooctane/sulfosuccinic acid bis [2-ethy/he xyl] ester/water; the solubilization of gelatin in the water pool of t hese microemulsions transforms them into viscous gels in which it is p ossible to cosolubilize various reactive molecules. These gels were us ed to immobilize two phenoloxidases, a laccase from Trametes versicolo r and a tyrosinase from mushroom. The best balance between gel retenti on and catalytic activity was reached at a gelatine concentration of 2 .5% (w/v) in the case of tyrosinase, while laccase immobilization was independent of gelatine concentration. Both enzymes kept the same opti mum pH as the corresponding soluble controls, while a partial loss of activity was observed when they were immobilized. Immobilized enzymes showed an increased stability when incubated for several days at 4 deg rees C with a very low release from the gels in the incubation solutio ns. The immobilization of tyrosinase and of laccase enhanced stability to thermal inactivation. Furthermore, gel-entrapped tyrosinase was al most completely preserved from proteolysis: more than 80% of the activ ity was maintained, while only 25% of the soluble control activity was detected after the same proteolytic treatments. A column packed with gel-immobilized tyrosinase was used to demonstrate that enzymes immobi lized with this technique may be reused several times in the same reac tion without loosing their efficiency. Finally, gel-entrapped tyrosina se and laccase were capable of removing naturally occurring and xenobi otic aromatic compounds from aqueous suspensions with different degree s of efficiency. (C) 1995 John Wiley & Sons, Inc.