Surfactant-coated lipase

Enzyme activity for the polymerization of lactones was improved by the immobilization on Celite [93]. Immobilized lipase PF adsorbed on a Celite showed much higher catalytic activity than that before the immobilization. The catalytic activity was further enhanced by the addition of a sugar or poly(ethylene glycol) in the immobilization. Surfactant-coated lipase efficiently polymerized the ring-opening polymerization of lactones in organic solvents [94]. 

In case of lipases, one of the simplest methods to combine an enzyme with an organic solvent is to coat the lipase with a lipid or surfactant layer before lyophilisation. It is estimated that about 150 surfactant molecules are sufficient for encapsulating one lipase molecule. Following this route the surfactant coated lipase forms reverse micelles with a minimum of water concentration. The modified lipases are soluble in most organic solvents, and the reaction rates are increased compared to the suspended hpases due to the interfacial activation [59,60]. 

Immobilized lipase showing high catalytic activity toward the macrolide polymerization was demonstrated.169 The immobilization of lipase PF on Celite greatly improved the rate of the DDL polymerization. Catalytic activity was further enhanced by the addition of a sugar or polyethylene glycol) (PEG) during immobilization. A surfactant-coated enzyme was used... 

Goto, M., Kamiya, N., Miyata, M., and Nakashio, R, Enzymatic esterification by surfactant-coated lipase in organic media, Biotechnol. Prog., 10, 263-268, 1994. 

Goto, M. Noda, S. Kamiya, N. Nakashio, F. Enzymatic resolution of racemic ibuprofen by surfactant-coated lipases in organic media. Biotechnol. Lett, 1996, 18, 839-844. 

FIG. 6 Comparison of catalytic activities for di- and trilaurin syntheses of (A) the surfactant-coated hpase B, (B) PEG-grafted lipase B, (C) Lipase B in W/O emulsion, and (D) dispersion of lipase B powder, in benzene solution at 40°C. (From Ref. 48.)... 

When PEG-grafted lipase B was employed, the esterification proceeded at a fair rate [Vq = 6.0 mM min (mg of protein)" ]. However, the conversion reached a plateau at 70% after 40-80 h. The further addition of molecular sieves could not improve the conversion. This indicates that the PEG lipase can keep the produced water near the amphiphilic PEG-grafted chains so that the water molecules may not be removed by the addition of molecular sieves. The water solubilized near the lipase surface inhibits the ester synthesis in organic solvents. In contrast, the hydrophobic surfactant-coated lipase cannot solubilize the produced water, and the glyceride synthesis can proceed completely when molecular sieves Ifom the solution remove the produced water. 

Therefore, it was proved that the surfactant-coated lipase could catalyze effectively and completely the glyceride synthesis in dry organic solvents, as compared with other enzyme systems, such as water-in-oil emulsion, enzyme dispersion, and PEG-grafted enzyme. 

In some instances, water may not be necessary at all for the solubilization of the enzyme in a hydrocarbon solvent. A striking example has been provided by Okahata and coworkers [78] who solubilized lipase in benzene or n-hexane by coating the enzyme with the nonionic surfactant (24) or 2Ci6Br. The lipid-coated lipase showed activity for the synthesis of di- and triglycerides from monoglycerides and aliphatic acids. 

About 150 lipid molecules were present per 1 of enzyme. It was used to esterify 1-phenylethanol with lauric acid in isooctane, giving 95% conversion in 2 h. A lipid-coated lipase has also been used to esterify lauric acid with glycerol in sc carbon dioxide with 90% conversion.98 Catalase with less than 5% of its surface amino groups modified by the nonionic surfactant 9.7 had a higher activity in 1,1,1-trichloroethane than when the enzyme was conjugated with polyethylene glycol.99... 

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