Detergentless microemulsions as media for enzymatic reactions: Catalytic properties of laccase in the ternary system hexane-2-propanol-water

Abstract

The catalytic activity and stability of laccase in the detergentless ternary system hexane - 2-propanol - water were studied. In the microemulsion region of the phase diagram the enzyme exhibited the highest catalytic activity and stability, which were comparable to those in aqueous solution. The character of the microenvironment inside microemulsion droplets was studied using nitrate anion as spectral probe and its polarity was found to correspond to that of 75% v/v aqueous 2-propanol. In principle, laccase can be recovered many times from the microemulsion without loss of catalytic activity.

Reversed micelles of polymeric surfactants in nonpolar organic solvents

“…Nevertheless, the stability of laccase entrapped into CEPEIreversed micelles is comparable to that reported for other nonaqueous microemulsion systems [20]. The thermostability of laccase was studied in the temperature range 20 -45 "C. Results are plotted in Fig.…”

Oxidation Catalysis by Enzymes in Microemulsions

“…The first report in the literature appears 10 years after the first studied surfactant-free microemulsion by Smith et al [120], when Khmelnitsky et al [121] investigated the use of trypsin in ternary systems composed of hexane, isopropanol, and water. Since then, a wide range of enzymes has been successfully solubilized in that type of microemulsion, such as different types of hydrolases with emphasis on lipases [122] and oxidoreductases such as laccases [123] and peroxidases [124].…”

“…Khmelnitsky et al [123] studied the activity patterns for laccase and cholesterol oxidase in isopropanol/n-hexane/water system. In the first case lacasse revealed higher activity in the monophasic region of the ternary phase diagram that corresponds to water-in-oil microemulsions, in contrast to cholesterol oxidase and polyphenoloxidase [126], which in the same region presented the lowest activity.…”

“…Since then, a wide range of enzymes has been successfully solubilized in that type of microemulsion, such as different types of hydrolases with emphasis on lipases [122] and oxidoreductases such as laccases [123] and peroxidases [124]. These surfactantless systems have been mainly composed of non-polar solvents (as the "oil phase") with hexane [16,[121][122][123][125][126][127] and toluene [126,128,129] being the most frequently used.…”

“…In the first case lacasse revealed higher activity in the monophasic region of the ternary phase diagram that corresponds to water-in-oil microemulsions, in These surfactantless systems have been mainly composed of non-polar solvents (as the "oil phase") with hexane [16,[121][122][123][125][126][127] and toluene [126,128,129] being the most frequently used. Tziala et al demonstrated for the first time the use of cyclic terpenes as natural organic solvents, such as α-pinene and D-limonene [130].…”