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The liposome containing cellulase from Trichoderma viride was prepared under the condition that an appreciable amount of cellulase was incorporated in lipid membranes. The liposomal cellulase and free enzyme were examined in their hydrolytic activities to insoluble cellulose powder CC31 in the acetate buffer solution (pH 4.8) of 15 w/w% [Bmim][Cl] (1-butyl-3-methylimidazolium chloride). The mean diameter and size distribution of cellulase-containing liposome were practically unchanged under the above condition. The free cellulase was deactivated more rapidly than the liposomal cellulase in catalyzing the hydrolysis of 2.0 g/l CC31 at 45°C in the presence of [Bmim][Cl] for 48 h. The activities of liposomal and free cellulase to cellobiose as soluble substrate were less susceptible to [Bmim][Cl] than their cellulolytic activities to CC31, meaning that β-glucosidase is relatively stable among the three enzyme components of cellulase. The rate of glucose production could be appreciably improved by the pretreatment of CC31 with [Bmim][Cl] alone at 120°C for 30 min followed by the liposomal cellulase-catalyzed hydrolysis of the substrate at 45°C at the [Bmim][Cl] concentration of 15 w/w%., (© 2013 American Institute of Chemical Engineers.)

Formate dehydrogenase from Candida boidinii (CbFDH) is potentially applicable in reduction of CO(2) through oxidation of cofactor NADH into NAD(+). For this, the CbFDH activity needs to be maintained under practical reaction conditions, such as CO(2) gas-liquid flow. In this work, CbFDH and cofactor were encapsulated in liposomes and the liposomal enzymes were characterized in an external loop airlift bubble column. The airlift was operated at 45 degrees C with N(2) or CO(2) as gas phase at the superficial gas velocity U(G) of 2.0 or 3.0 cm/s. The activities of liposomal CbFDH/cofactor systems were highly stable in the airlift regardless of the type of gas phase because liposome membranes prevented interactions of the encapsulated enzyme and cofactor molecules with the gas-liquid interface of bubbles. On the other hand, free CbFDH was deactivated in the airlift especially at high U(G) with CO(2) bubbles. The liposomal CbFDH/NADH could catalyze reduction of CO(2) in the airlift giving the fractional oxidation of the liposomal NADH of 23% at the reaction time of 360 min. The cofactor was kept inside liposomes during the reaction operation with less than 10% of leakage. All of the results obtained demonstrate that the liposomal CbFDH/NADH functions as a stable catalyst for reduction of CO(2) in the airlift., ((c) 2010 American Institute of Chemical Engineers)

The possibility of the translocation of the enzyme across the phospholipid bilayer membrane was investigated by using the liposomes prepared by 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in which beta-galactosidase (beta-gal) was entrapped. Exposing the POPC liposomes entrapping beta-gal inside to heat treatment (40-50 degrees C, 1-60 min) was found to induce its translocation across the liposome membrane. The translocated activity of beta-gal from inner to outer aqueous phase of liposomes indicated the maximal value when the liposomes entrapping beta-gal were heated at 45 degrees C for 30 min. The gel permeation profiles of the liposomes before and after heat treatment (45 degrees C, 30 min) also supported the translocation of beta-gal across the liposome membrane. The membrane fluidity of liposomes was found to be increased with increasing temperature, so that the hydrophobicity of liposome membrane was also increased. The local hydrophobicity of beta-gal was maximized at the temperature of 40-50 degrees C. The mechanisms of beta-gal translocation have been suggested to be triggered by the enhancement of hydrophobic interaction between the liposome surface and beta-gal molecules. Finally, a minimal scheme of possible mechanism on the heat-induced translocation of beta-gal has been presented on the basis of the hydrophobic interaction between the liposome and the proteins. The experimental data on the heat-induced translocation of beta-gal were well corresponding to those from model calculation.