Reversed micelle solvents represent nanometer-sized aqueous droplets stabilized by surfactants inside the bulk organic solvents. The aqueous cores can host various hydrophilic solutes, including ...bioactive substances thus revealing a challenge to the biotechnology's needs of the safe media for bioseparations and bioconversions. This review discusses the structure and the properties of reversed micelle solvents in view of the parameters that can be easily operated in technology to achieve safe liquid–liquid extraction of proteins/enzymes or bioconversion of hydrophobic substrates. The paper highlights the importance of how the reversed micelle microenvironment should be arranged with respect to the preservation of the activity of the enzyme as target product or biocatalyst. The main aspects are demonstrated with own experimental results on α-amylase purification and lipase-catalyzed esterification using cationic reversed micelle solvents. The trials of performing continuous processes involving reversed micellar separation and reaction media are also reviewed and the current problems are addressed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The thermal stability of Candida rugosa (C. rugosa) lipase was investigated and compared in n-hexane, benzene, dibutyl-ether as well as bmimPF6 and omimPF6 ionic liquids and the effect of solvent ...polarity and water activity were evaluated. Deactivation of the enzyme followed a series-type kinetic model. First order deactivation rate constants and the ratios of specific activities were determined and the kinetics of deactivation were studied. Among the organic solvents, the best stability was observed in n-hexane with a half-life of 6.5 h at water activity of 0.51. In ionic liquids, however, even longer half lives were obtained, and the enzyme was stable in these solvents at 50°C. The highest half-life times were obtained in bmimPF6 (12.3 h) and omimPF6 (10.6 h). A direct correlation was found between solvent polarity and thermal stability since the higher the polarity of the solvent, the lower was the stability decrease at 50°C comparing to that at 30°C.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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.
In this work, the complex enzyme purification process by means of RME (reversed micelle extraction) was examined using the system α-amylase/CTAB/KBr. The research was focussed on the enzyme aqueous ...source composition. The influence of different inorganic salts present in the source (NaCl, NaBr, and NH
4Cl) as well as salt and protein concentrations on the purification efficiency of the system was investigated. The RME-based enzyme purification was analyzed considering the protein and activity yield changes during the two-step procedure—solubilization and stripping (recovery). The results show that relatively high purification factors could be achieved at relatively low salt concentrations in the source providing the formation of RMs with an appropriate water capacity. A part of the activity lost in the sources containing NaBr, and NH
4Cl was recovered through RM-solubilization and stripping into an aqueous solution containing a small amount of KBr. The RM-system proposed preserves the enzyme stability and biological activity for a long time.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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