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Tonova, K.; Lazarova, Z.; Nemestothy, N.; Gubicza, L.; Belafi-Bako, K.
Chemical Industry & Chemical Engineering Quarterly, 2006, Volume: 12, Issue: 3Journal Article
In this work, the lipase-catalyzed synthesis of i-amyl oleate was performed in a reversed micellar system of a cationic surfactant, CPC. The influence of the RM-system constituents on the biocatalysis characteristics (initial esterification rate and conversion extent) was studied and discussed in terms of the RM-structure. The initial water content in the RM-system (the water to surfactant mole ratio, Wo), affected both reaction parameters in a bell-shaped manner, with the maximum depending on the alcohol amount. In general the optimal Wo-values remained between 34 ?40 for a wide range of the initial substrate ratio. The polarity (logP) and the structure of the organic solvent used as the RM-continuum strongly affected the kinetic parameters. A linear function of the initial rate on arg(logP) was established for the alkanes up to n-C1O. The highest rates were measured using a medium of cycle or branched alkanes. The esterification under inhibiting concentrations of the substrates could be intensified by a small change in the initial Wo, thus improving the enzyme RM-accommodation and manipulating the effective concentrations of both substrates around the lipase. In the studied RM-system of 0.115 mol dm-3 CPC, the maximal initial rate of the lipase-catalyzed i-amyl oleate synthesis was found to be limited at ~340 ?mol min-1 g-1. U radu je proucavana sinteza i-amil oleata u sistemu sa reverznim micelama (RM) koriscenjem katjonske povrsinski aktivne materije (KPAM). Uticaj osnovnih konstituenata RM sistema na biokataliticku aktivnost lipaze (pocetna brzina esterifikacije, stepen konverzije) analizirana je i diskutovan? u svetlu RM strukture. Pocetni udeo vode u RM sistemu (odnos vode i povrsinski aktivne amterije, Wo) utice na parametre brzine reakcije (princip zastitnog zvona) sa maksimumom koji zavisi od prisutne kolicine (udela u reakcionoj smesi) alkohola. Utvrdjeno je da je optimalan odnos Wo oko 34 do 40 za sve ispitivane odnose supstrata. Polarnost i struktura organskog rastvaraca (log P), koji je kontinualna faza u RM sistemu ima velikog uticaja na kineticke parametre. Pokazano je da postoji linearna zavisnost izmedju pocetne brzine i alkana (sve do n-C10). Najvece izmerene brzine su u slucaju primene medijuma zasnovanog na ciklo ili racvastim alkanima. Esterifikacija koja je inhibirana prisustvom supstrata moze se ubrzati malim promenama odnosa Wo cime se povecava adaptacija enzima u RM sistemu i stvarno uvecava koncentracija oba supstrata u blizini lipaze. Maksimalna brzina esterifikacije i-amil oleata katalizovane lipazom je ogranicena na oko 340 mmol/g.min kada je koncentracija dodate KPAM 0,115 mol/dm3.
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