BIOCATALYSIS IN FLUOROUS SYSTEMS AND SUPERCRITICAL CARBON DIOXIDE

摘要

The activities of solubilised and immobilised enzymes were investigated in fluorous biphasic system (FBS) and supercritical carbon dioxide (scCO_2) batch reactors. The kinetic resolution (KR) and dynamic kinetic resolution (DKR) of racemic 1-phenylethanol with an acyl donor were catalysed by Pseudomonas cepacia lipase (PCL), either as the suspended native protein (native PCL) or immobilised on ceramic particles (commercial lipase Amano PS CI) in scCO_2. These results were compared to similar experiments carried out in hexane. The immobilised lipase PS CI shows excellent activities (48-49%) and enantioselectivities (98-99%) to the desired (R)-phenylethyl acetate after 2.5 hours reaction at 40°C in scCO_2. Its activity appeared to be increased compared to the reaction carried out in hexane under comparable conditions. Unlike native PCL, the immobilised lipase PS CI was then successfully reused to catalyse the KR with no loss of activity or selectivity observed over four cycles. Transesterification of N-acetyl-L-phenyl alanine ethyl ester (APEE) with 1-butanol or 2-butanol was catalysed by protease α-chymotrypsine (CMT) in hexane-perfluoromethylcyclohexane (PFMC) or scCO_2 at 40 °C for two hours. Hydrophobic ion pairing (HIP) was used to extract the protein into PFMC using the fluorinated surfactant KDP 4606 and under comparable conditions, the activity of the solubilised protease CMT-KDP in PFMC (6-10 %) was shown to be significantly higher than that of the suspended protease (1-3%) in both hexane-PFMC and scCO_2. CMT-KDP was then successfully reused over four cycles with no loss of activity. The particle size of the solubilised CMT-KDP in PFMC was estimated using dynamic light scattering (DLS) to 25 nm which suggested the formation of an active protein aggregate (of about 100 molecules).