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alpha-Glucosidase from baker's yeast was immobilized on macroporous copolymers of ethylene glycol dimethacrylate and glycidyl methacrylate, poly(GMA-co-EGDMA), with various surface characteristics and pore sizes ranging from 44 nm to 270 nm. Immobilization was done by glutaraldehyde on the copolymer previously modified with 1,2-diaminoethane. The specific activity of the obtained immobilized enzyme varied from 27 to 81 U/g depending on the employed copolymer. The half lives of the immobilized enzyme in cosolvents were influenced by the surface characteristics of the copolymer, ranging from 60 to 150 min in 35 % methanol and from 10 to 44 min in 45 % dimethyl sulphoxide (DMSO). The best stabilities were obtained when the enzyme was immobilized onto a copolymer having a pore size of 48 rim in methanol and 270 nm in DMSO. α-Glukozidaza izolovana iz pekarskog kvasca je imobilizovana na makroporoznim glicidil-metakrilatima različitih površinskih karakteristika i veličina pora od 44 do 270 nm. Imobilizacija je izvedena glutaraldehidom na polimeru prethodno modifikovanom sa 1,2-diaminoetanom. Specifična aktivnost dobijenog imobilizovanog enzima je varirala od 27 do 81U/g u zavisnosti od vrste korišćenog polimera. Poluživoti imobilizovanog enzima u korastvaračima su zavisili od površinskih karakteristika polimera i kretali su se u opsegu od 60 do 150 min u 35%(v/v) metanolu i od 10 do 44 min u 45 % (v/v) dimetilsufoksidu. Najveća stabilnost u metanolu je dobijena imobilizacijom enzima na polimeru sa veličinom pora od 48 nm a u dimetilsulfoksidu na polimeru sa veličinom pora od 270 nm.

Amyloglucosidase from A. niger was covalently immobilized onto poly(GMA-co-EGDMA) by the glutaraldehyde and periodate method. The immobilization of amyloglucosidase after periodate oxidation gave a preparate with the highest specific activity reported so far on similar polymers. The obtained immobilized preparates show the same pH optimum, but a higher temperature optimum compared with the soluble enzyme. The kinetic parameters for the hydrolysis of soluble starch by free and both immobilized enzymes were determined. Amiloglukozidaza iz A.niger je imobilizovana na poly(GMA-co-EGDMA) glutaraldehidnom i perjodatnom metodom. Imobilizacija amiloglukozidaze nakon perjodatne oksidacije daje preparat sa najvećom do sada objavljenom specifičnom aktivnosti na sličnim polimerima. Dobijeni imobilizovani preparat ima isti pH optimum ali povećani termooptimum u poređenju sa rastvornim enzimom. Određeni su i kinetički parametri za hidrolizu rastvornog skroba imobilizovanim kao i rastvornim enzimom.

Penicillin acylase (PAC) is an important industrial enzyme for the production of many β-lactam antibiotics. It is capable of catalyzing the hydrolysis of penicillin G (Pen G) to generate phenylacetic acid (PAA) and 6-aminopenicillanic acid (6-APA). In this paper, in order to prevent enzyme inactivation, an attempt of coupling enzyme modification and immobilization is presented. Chemical modification was promoted to introduce carbohydrate moiety into the PAC molecule, capable of being covalently linked to an amino support. This seems to provide a possibility to couple the enzyme without risking a reaction at the active site which might cause a loss of activity. PAC molecules were modified by cross-linking with polyaldehyde derivatives of alginate in order to add them new and useful functions. Immobilization of alginate-PAC on Sepabeads EC-HA was used as a model system in order to demonstrate the potential of this strategy. Optimal conditions for covalent immobilization of alginate-PAC from Escherichia coli on support Sepabeads EC-HA were investigated. The immobilized enzyme was then characterized by evaluating the potential effects of immobilization on its thermal stability, temperature and pH profile in comparison with native non-modified PAC and modified non-immobilized PAC. The maximum amount of the alginate-PAC coupled on the dry support of 99 mg/g was satisfactory. Deactivation rate constants at 50°C for free PAC, alginate-PAC and alginate-PAC immobilized on Sepabeads EC-HA were 2.32, 50.65 and 1.68 h-1, respectively. Alginate-PAC and alginate-PAC immobilized on Sepabeads EC-HA had the same pH and temperature optimum as the native non-modified PAC. U ovom radu započeto je sistematsko ispitivanje imobilizacije enzima modifikovanih derivatima alginata. Penicilin-acilaza (PAC) modifikovana je polialdehidnim derivatom alginata i zatim imobilisana na Sepabeads EC-HA nosač. Ispitani su optimalni uslovi za kovalentnu imobilizaciju modifikovane PAC i imobilisani enzim je okarakterisan u pogledu efekata imobilizacije na njegovu termalnu stabilnost, pH i temperaturni profil. Dodatno, imobilisani enzim je po pitanju ovih parametara upoređen kako sa nativnom tako i sa modifikovanom (alginat-PAC) formom enzima. Konstante brzine dezaktivacije za PAC, alginat-PAC i modifikovan enzim imobilisan na Sepabeads EC-HA (alginat-PAC-Sepabeads EC-HA) iznosile su redom 2,03, 36,48 i 1,23 h-1 na 40°C, odnosno 2,32, 50,65 i 1,68 h-1 na 50°C. Pokazano je da alginat-PAC i alginat-PAC-Sepabeads EC-HA imaju isti pH i temperaturni optimum kao i nativna PAC.