Hydrolysis of oleuropein by recombinant beta-glycosidase from hyperthermophilic archaeon Sulfolobus solfataricus immobilised on chitosan matrix

The recombinant beta-glycosidase (EcS beta gly) from Sulfolobus solfataricu s was immobilised on chitosan to perform the enzymatic hydrolysis of commer cial oleuropein (heterosidic ester of elenolic acid and 3,4-dihydroxy-pheny lethanol (hydroxytyrosol)) at two temperatures (60 and 70 degrees C). Inter estingly, on the basis of the reasonable assumption that the enzyme hydroly ses only the sugar linkage, the biotransformation produces unstable aglycon e species formed by oleuropein hydrolysis that, differently from some comme rcially available beta-glucosidases tested, give rise to the formation of h ydroxytyrosol, at the operative temperatures of the bioreactor. The results of the biotrasformation at 70 degrees C showed that the main products are hydroxytyrosol, and glucose, being the oleuropein aglycone present in low a mount at the end of reaction. Both in single step approach or in recycle ap proach the amounts of glucose and oleuropein aglycone were lightly dependen t from flow rate. The amount of hydroxytyrosol, increased on decreasing the flow rate of bioreactor in recycle approach, following a non-linear trend and obtaining the highest value at a flow rate of 15 ml h(-1) while in the single step approach the 3,4-dihydroxy-phenylethanol was at its maximum at higher flow rate (16 mi h(-1)). For the hydrolysis of the oleuropein by bio reactor at 60 degrees C we used lower molar ratio oleuropein/enzyme only by the single step approach. In these conditions it is possible to obtain hig h amounts of only two products (glucose and hydroxytyrosol) in short time ( 2 h). The stability of the bioreactor at the operative temperatures showed a t(1/2) of 30 days at 70 degrees C and a t(1/2) of 56 days at 60 degrees C . (C) 2000 Elsevier Science B.V. All rights reserved.