Papers by Zorica Knežević-Jugović
Biotechnology progress, Jan 6, 2015
The use of penicillin G acylase (PGA) covalently linked to insoluble carrier is expected to produ... more The use of penicillin G acylase (PGA) covalently linked to insoluble carrier is expected to produce major advances in pharmaceutical processing industry and the enzyme stability enhancement is still a significant challenge. The objective of this study was to improve catalytic performances of the covalently immobilized PGA on an potential industrial carrier, macroporous poly(glycidylmethacrylate-co-ethyleneglycoldimethacrylate) [poly(GMA-co-EGDMA)], by optimizing the copolymerization process and the enzyme attachment procedure. This synthetic copolymer could be very promising alternative for the development of low-cost, easy to prepare and stable biocatalyst compared to expensive commercially available epoxy-carriers such as Eupergit or Sepabeads. The PGA immobilized on poly(GMA-co-EGDMA) in the shape of microbeads obtained by suspension copolymerization appeared to have higher activity yield compare to copolymerization in a cast. Optimal conditions for the immobilization of PGA on p...
Journal of biomaterials applications, Jan 5, 2015
Chitosan-glutaraldehyde microparticles were produced by emulsion crosslinking method to be used a... more Chitosan-glutaraldehyde microparticles were produced by emulsion crosslinking method to be used as drug delivery system for polyphenols from Thymus serpyllum L. aqueous extract. The effect of preparation conditions, chitosan concentration (1.5-3% w/v), and glutaraldehyde/chitosan (GA/Ch) mass ratio (0.15-1.20) on water and polyphenols transport properties was investigated. Swelling ratio of dry particles (68-230 µm) in water ranged from 280% to 530%, depending on the formulation. The decrease in swelling was observed with increased GA/Ch mass ratio (i.e. crosslinking degree) at the same chitosan concentration, or with increased chitosan concentration at the same GA/Ch mass ratio. The increase in GA/Ch mass ratio was also manifested by increased particle compactness i.e. decreased size and reduced surface roughness. The sorption capacity for polyphenols seems to be a complex interplay of swelling behaviour and interactions chitosan-glutaraldehyde-polyphenols identified by Fourier tra...
Hemijska industrija, 2008
Hemijska industrija, 2008
U radu je ispitana imobilizacija lipaze iz Candida rugosa u pH-i temperaturno-osetljive hidrogelo... more U radu je ispitana imobilizacija lipaze iz Candida rugosa u pH-i temperaturno-osetljive hidrogelove N-izopropilakrilamida i itakonske kiseline različitog sastava i pod različitim uslovima. Aktivnost imobilisanog enzima je ispitana standardnom metodom na emulziji maslinovog ulja. Praćena je kinetika otpuštanja enzima iz hidrogelova. Utvrđeno je da na aktivnost imobilisane lipaze utiče način imobilizacije i sastav hidrogelova. Značajan uticaj ima i temperatura na kojoj se izvodi imobilizacija, tako da se sa promenom temperature menja i masa imobilisane lipaze kao i njena specifična aktivnost. Ispitana su mehanička svojstva i morfologija sintetisanih hidrogelova.
Journal of the Serbian Chemical Society, 2006
In this study, the feasibility of the synthesis of various flavor esters catalyzed by a commercia... more In this study, the feasibility of the synthesis of various flavor esters catalyzed by a commercial lipase from Candida rugosa was investigated and the process parameters were optimized. Lipase from C. rugosa successfully catalyzed the synthesis of 19 esters. The highest yields, of more than 90 % after 20 h, were observed in the synthesis of short-chain esters, pentyl propanoate, isopentyl butanoate, and butyl butanoate. Increasing the number of carbon atoms of both substrates above 8 caused a significant decrease of the initial reaction rates and the final yields. The enzyme showed surprisingly low affinity towards pentanoic acid and hexanoic acid, compared with the higher homologues, octanoic acid and decanoic acid. In addition to the number of carbon atoms, the structure of the substrates had a significant influence on the enzyme activity. Namely, the activity of the enzyme towards isopropanol was significantly lower compared with n-propanol. Additionally, cis-9-octadecenoic acid was a better substrate than octadecanoic acid, its saturated analogue.
Journal of the Serbian Chemical Society, 2007
A wild yeast strain isolated from spoiled soybean oil and identified as Candida utilis initially ... more A wild yeast strain isolated from spoiled soybean oil and identified as Candida utilis initially presented rather low lipase activity (approximately 4 IU dm -3 ) in submerged culture in a universal yeast medium containing 2 % malt extract. Studies were undertaken to improve the lipase production. The best yields of lipase were obtained with a medium supplemented with caprylic and oleic acids as inducers, but higher concentrations of the former (> 0.5 %) had a negative effect on the lipase production and cell growth. The type of nitrogen source seemed also to be very important. The highest lipolytic activity of 284 IU dm -3 was achieved after 5 days of fermentation in a medium containing oleic acid and hydrolyzed casein as carbon and nitrogen sources, respectively, and supplemented with Tween 80 ® . It was shown that optimization of the fermentation conditions can lead to a significant improvement in the lipase production (more than 70-fold higher compared to the initial value obtained in the non-optimized medium).
Journal of the Serbian Chemical Society, 2008
Response surface methodology was used for the evaluation of the effects of various factors on the... more Response surface methodology was used for the evaluation of the effects of various factors on the synthesis of biodiesel catalyzed with immobilized lipase from Rhizomucor miehei in a solvent-free system. The production of biodiesel was optimized and model response equations were obtained, enabling the prediction of biodiesel production from the values of the four main factors. It would seem that the reaction temperature and the amount of water predominantly determined the conversion process while the methanol/oil molar ratio had no significant influence on the reaction rate. The temperature and amount of water showed negative interactive effects on the observed reaction rate per amount of enzyme. However, there were no significant interactions among the other variables according to the test of statistical significance. The highest yield of 10.15 mol kg -1 enzyme was observed at 45 °C with a 6:1 methanol to oil molar ratio and with no added water in the system.
Journal of Molecular Catalysis B: Enzymatic, 2007
The aim of this study was to compare activities of commercial lipases in synthesis of various est... more The aim of this study was to compare activities of commercial lipases in synthesis of various esters in solvent-free system and in isooctane. Moreover, the effect of substrate polarity (expressed as log P) on solvent-free synthesis was investigated. The decrease of yields of esters of butanoic acid in absence of organic solvent was observed, while similarly high yields were noticed in synthesis of esters of octanoic acid in both systems (solvent-free and organic solvent). The kinetic analysis has shown that ester synthesis can be described with Ping-pong bi-bi kinetics. In a case of esterification of butanoic acid in solvent-free system additional term, which represents enzyme inactivation by acid substrate, must be included. It was found out that log P of initial substrate mixture was in linear correlation with kcat of ester synthesis, while final yields depend only on type of acid substrate. Each of the examined lipases showed similar properties, although immobilized lipase from Rhizomucor miehei was slightly more resistant to harmful influence of butanoic acid. Finally, it was also shown that detrimental influence of butanoic acid could be circumvented by two-step addition of acid substrate in reaction catalyzed with immobilized lipase from R. miehei.
Journal of Molecular Catalysis B: Enzymatic, 2006
... The same model was proposed by Hazarika et al. for synthesis of ethyl oleate with porcine pan... more ... The same model was proposed by Hazarika et al. for synthesis of ethyl oleate with porcine pancreatic lipase [15] and by Yadav and Lathi for synthesis of butyl isobutyrate with the commercial immobilized lipase from Candida antarctica [16]. ...
Journal of Chemical Technology & Biotechnology, 2009
BACKGROUND: Immobilization of lipase (triacylglycerol acylhydrolase EC 3.1.1.3) from Candida rugo... more BACKGROUND: Immobilization of lipase (triacylglycerol acylhydrolase EC 3.1.1.3) from Candida rugosa on Eupergit C and Eupergit C 250L was performed under microwave irradiation in order to reduce immobilization time. Lipase loading, hydrolytic activity, esterification activity and operational stability in organic solvent of immobilized lipase preparation were determined.
Enzyme and Microbial Technology, 1998
Lipase from Candida cylindracea immobilized on hydrophobic zeolite type Y was used to hydrolyze p... more Lipase from Candida cylindracea immobilized on hydrophobic zeolite type Y was used to hydrolyze palm oil in (I microaqueous two-phase reaction system containing isooctane as organic medium and lecithin as su$actant. The lipase was immobiliced to zeolite by adsorption. The maximum amount of bound protein at 8.2 mg g-l and an immobilization eficiency of 33% were achieved under optimum conditions. The kinetics of lipase binding to zeolite were assessed by using the general model of topochemical reaction. Based on the values of the specific kinetic model parameters, we propose that the adsorption process is controlled by surface kinetics that was later experimentally conjirmed. The activation energy for lipase adsorption on zeolite was 43 kJ mol K'. The lipase immobilized on zeolite had 35% of the activir); of the free enzyme. After the seventh cycle. immobilized lipase retained 10% of the initial activity in palm oil hydrolysis. 0 1998 Elsevier Science Inc.
površinski aktivnih materija. Pri sintezi je varirana vrsta i sadržaj površinski aktivnih materij... more površinski aktivnih materija. Pri sintezi je varirana vrsta i sadržaj površinski aktivnih materija. Ispitana su mehanička svojstva sintetisanih hidrogelova i urađena je FT-IR analiza. Imobilizacija lipaze je izvedena bubrenjem prethodno sintetisanih hidrogelova u rastvoru lipaze, a zatim je ispitan uticaj dodatka površinski aktivnih materija pri sintezi nosača na kapacitet uklapanja lipaze u hidrogel i na aktivnost tako uklopljene lipaze. Imobilisana lipaza iz Candida rugosa je pokazala umanjenu hidrolitičku aktivnost, kako u odnosu na aktivnost slobodne lipaze, što je i očekivano, tako i u odnosu na aktivnost lipaze imobilisane u referentni hidrogel, sintetisan bez prisustva površinski aktivnih materija.
Nanocevi poseduju veliki potencijal primene u raznim oblastima nauke i inženjerstva. Velika mehan... more Nanocevi poseduju veliki potencijal primene u raznim oblastima nauke i inženjerstva. Velika mehanička čvrstoća, odlična termička i električna provodljivost, veliki odnos površine prema zapremini i minimalna difuziona ograničenja čine ih idealnim nosačima za imobilizaciju biomolekula kao što su proteini, antigeni, antitela, vitamini, hormoni, antibiotici i dr. U ovom radu opisane su tehnika adsorpcije i kovalentnog vezivanja enzima na nemodifikovane, oksidovane i amino funkcionalizovane ugljenične nanocevi. Takođe je opisan uticaj površine ugljeničnih nanocevi na strukturne promene enzima, kao i na promene u pogledu aktivnosti i stabilnosti.
American Journal of Applied Sciences, 2009
... Nurul Aini, AR Ruwaida, MS Shalyda, A. Ideris, AS Rozaimi, JH Sharifuddin and NIA Ahamad Nord... more ... Nurul Aini, AR Ruwaida, MS Shalyda, A. Ideris, AS Rozaimi, JH Sharifuddin and NIA Ahamad Nordin Faculty of Chemical and Natural Resources Engineering, Universiti Malaysia Pahang, Lebuhraya Tun Razak, 26300 Kuantan, Pahang Darul Makmur, Malaysia Abstract: This ...
Acta periodica technologica, 2007
Escherichia coli on sepabeads EC-EP, an epoxy-activated polymethacrylic carrier and kinetic prope... more Escherichia coli on sepabeads EC-EP, an epoxy-activated polymethacrylic carrier and kinetic properties of the immobilized enzyme. The selected enzyme belongs to a class of biocatalysts whose industrial interest is due to their versatility to mediate hydrolysis of penicillins and semi-synthetic E-lactam antibiotics synthesis reactions.
Acta periodica technologica, 2004
Attractive features of lipase systems include versatility, substrate selectivity, regioselectivit... more Attractive features of lipase systems include versatility, substrate selectivity, regioselectivity, enantioselectivity and catalysis at ambient temperatures and pressures. To fully exploit the technical and economical advantages of lipases, it is recommended to use them in an immobilized form to reduce the cost and the poor stability of the free lipase. This paper summarizes various methods of lipases immobilization including covalent attachment to or adsorption on solid supports, encapsulation and entrapment within the membrane and in polymeric matrices. The effects of immobilization conditions on lipase properties and stability of biocatalysts are considered. Applications of immobilized lipases in the feasible reaction system as well as probable future trends in lipase catalyzed process are discussed.
Acta periodica technologica, 2008
Biodiesel is an alternative fuel for diesel engine that is environmentally acceptable. Convention... more Biodiesel is an alternative fuel for diesel engine that is environmentally acceptable. Conventionally, biodiesel is produced by transesterification of triglycerides and short alcohols in the presence of an acid or an alkaline catalyst. There are several problems associated with this kind of production that can be resolved by using lipase as the biocatalyst. The aim of the present work was to investigate novel acyl acceptors for biodiesel production. 2-Propanol and n-butanol have a less negative effect on lipase stability, and they also improve low temperature properties of the fuel. However, excess alcohol leads to inactivation of the enzyme, and glycerol, a major byproduct, can block the immobilized enzyme, resulting in low enzymatic activity. This problem was solved by using methyl acetate as acyl acceptor. Triacetylglycerol is produced instead of glycerol, and it has no negative effect on the activity of the lipase.
Acta periodica technologica, 2005
An approach is presented for the stable covalent immobilization of lipase from Candida rugosa on ... more An approach is presented for the stable covalent immobilization of lipase from Candida rugosa on Eupergit ® with a high retention of hydrolytic activity. It comprises covalent bonding via lipase carbohydrate moiety previously modified by periodate oxidation, allowing a reduction in the involvement of the enzyme functional groups that are probably important in the catalytic mechanism. The hydrolytic activities of the lipase immobilized on Eupergit ® by two conventional methods (via oxirane group and via glutaraldehyde) and with periodate method were compared. Results of lipase assays suggest that periodate method is superior for lipase immobilization on Eupergit ® among methods applied in this study with respect to both, yield of immobilization and hydrolytic activity of the immobilized enzyme.
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Papers by Zorica Knežević-Jugović