|
Laccase belongs to a group of polyphenol oxidases containing copper atoms inthe catalytic centre, which can oxidize polyphenols, methoxy-substuted phenols,aromatic diamines and a range of compounds. Laccase has been widely used in manyfields, such as food industry, synthetic chemistry, and paper industry. Recently, itspotential application on bioremediation also rosed public attention. As a result, it is ofgreat importance to optimaze the enzymatic reaction efficiency of laccase.Usually, laccase’s catalytic reactions are always carried on in water solutions,which limits boths activity of itself and the solution of hydropholic substrates. Tosolve this problem, a novel system, the reversed micellar system (RMS) has beenreported. A reversed micelle is a surfactant-stabilized aqueous microdropletsuspended in an organic solvent with a narometer surfactant water pool which canhost proteins like enzymes, and that makes it possible for RMS to be used asmicroreactors for enzymes. Because of its particular structure properties, RMS canprovide a location for both hydrophilic enzymes and hydrophobic substrates. Besides,its water pool, which mimics the status of intracellular water, can protect the enzymefrom the adverse effects of organic solvent at the same time, thus many kinds ofenzymes show a superactivity in RMS. Traditional RMS is always contrasted withchemical surfactants, whose toxicity will bring adverse influence to both enzymes andthe environment. Using bio-surfactants instead of chemical surfactants to constructRMS as microreactors for enzymes provides an approach for those problems at thesame time.In this paper, the catalytic performance of laccase in a novel RMS, whichadopted rhamnolipid(RL, an anionic biosurfactant) as surfactant with isooctane andhexanol as solvent and cosurfactant, have been studied. The effect of severalsignificant factors on the catalytic performance of laccase, including theconcentration of RL, water content(W0), pH value and salt concentration, have beeninvestigated and analyzed respectively. The study showed that the optimum catalyticactivity and stability laccase could be reached when the RL concentration was13mmol/L, W0was42, pH was5.0and the KCl concentration was10mmol/L. Acomparison of the catalytic performance of laccase in AOT-based reverse micellarsystem(AOT-RMS) and RL-based reverse micellar system(RL-RMS) was made for acomparative purpose. It was found that both of laccase’s catalytic activity and stability in RL-RMS were much higher than those in AOT-RMS, which meant,compared with traditional synthetic surfactants, bio-surfactants were much moresuitable in contructing enzyme-reversed micellar systems.
|