Thomas Gamse

Enzymatic catalysis in supercritical carbon dioxide: Comparison of different lipases and a novel esterase

SummaryThe resolution of racemic citronellol and menthol by enzymatically catalyzed transesterification in supercritical carbon dioxide (SC-CO2) was investigated. Different lipases and an esterase in connection with various acylating reagents were employed. While the transesterification of (±)-menthol was reasonably fast and gave high enantiomeric excess, resolution of (±)-citronellol was not feasible.

High-pressure phase equilibria of the binary systems carvone–carbon dioxide and limonene–carbon dioxide at 30, 40 and 50°C

Phase equilibrium data for the systems carvone–CO2 and limonene–CO2 were determined at 30, 40 and 50°C using an equilibrium cell with circulating gas phase. The experimental data could be successfully correlated by using the Peng–Robinson equation of state using different sets of mixing rules.

Activation and denaturation of hydrolases in dry and humid supercritical carbon dioxide (SC-CO2)

Abstract The effects of enzyme treatment with dry and humid supercritical carbon dioxide (SC-CO 2 ) were investigated using hydrolases (EC 3.1.1.1 and EC 3.1.1.3). A crude and a purified preparation of esterase EP10 from Burkholderia gladioli was incubated in SC-CO 2 for long term and repeated high pressure treatments. Concerning the crude preparation, incubation for 24 h in SC-CO 2 at 150 bar and 35°C had no effect on enzyme activity while incubation at 75°C led to a distinct loss of residual activity. After 30 pressurization and depressurization steps at 35°C and 150 bar, the crude enzyme preparation showed an activity increase. Using the purified enzyme preparation of esterase EP10 from B. gladioli , no significant effects could be observed. Fluorescence spectra indicated no conformational change before and after treatment with SC-CO 2 . Treatment of a preparation of esterase from porcine liver with wet and dry SC-CO 2 at 200 bar at different temperatures showed a significant denaturing influence of the dissolved water on residual activities of the enzyme at temperatures of more than 40°C. Lipase from Candida rugosa and esterase from porcine liver were treated at 150 and 300 bar at a constant temperature of 40°C and an incubation time of 22 h. During these treatments, different amounts of water were introduced into the SC-CO 2 . The results showed an increase of the water content in the treated enzyme preparation while the enzyme activity remained stable till the maximum amount of water soluble in this medium was injected into the SC-CO 2 .

Enzymatic catalysis in supercritical carbon dioxide: Effect of water activity*

Publisher Summary This chapter discusses the enzymatic catalysis in supercritical carbon dioxide (scCO 2 ). scCO 2 offers some advantages over organic solvents. It is not flammable, non toxic, and relatively cheap and offers the possibility of an integrated separation process. To take advantage of the stereoselectivity of enzymatic catalysis, this chapter describes the use of transesterification of menthol as model system. Esterase EP10 from Pseudomonas marginata proved to be a suitable catalyst for the production of enantiomerically pure menthyl acetate. The water content of the reaction medium is an important factor governing the reaction rate of the transesterification. Various groups have investigated the role of water content on reaction velocity. The chapter describes the use of aluminum oxide humidity sensor to measure inline, the water vapor pressure. The partitioning of water between scCO 2 and the enzyme preparation is examined and the influence of water activity on the initial reaction velocity is determined in the chapter.

Solubilities and phase equilibria for the system furfural — CH3COOH — H2O and supercritical CO2

Publisher Summary Furfural is produced by hydrolyzing the pentoses of several natural products. The recovery of furfural and acetic acid from aqueous effluents of a paper mill has successfully been achieved on an industrial scale by a process based on the extraction of furfural and acetic acid with the solvent tri-octylphosphinoxide (TOPO). This chapter discusses the recovery and purification of furfural with supercritical carbondioxide. The chapter reviews the high-pressure extraction of furfural from aqueous effluents, considering the multi-component system furfural–acetic acid and water. The solubility of furfural in supercritical CO 2 is measured at different temperatures and pressures. For the solubility measurements of furfural in compressed CO 2 , a high-pressure equilibrium cell with a total volume of 300 ml is used. The solubility of furfural in supercritical CO 2 is determined in the equilibrium cell at temperatures of 298, 313, and 333 K within a pressure range of 80 to 340 bar.