Lipase immobilisation: an equilibrium study of lipases immobilised on hydrophobic and hydrophilic/hydrophobic supports

摘要

This work investigates the enzyme-support equilibrium behaviour in immobilised lipase biocatalysts. Equilibrium data determines the maximum enzyme up-take by unit weight of support. Four lipases were immobilised on two polymeric supports, respectively. They were Lipase PS from Pseudomonas, Lipolase 100L from Humicola, SP 871 from Rhizomucor miehel and QL from Alcaligenes. The supports were Accurel EP 100 (a polypropylene material) and 45SAA (a polypropylene/silica composite). Experimentally, equilibrium was expressed in terms of lipase loading (LU/g support) versus residual lipase concentration (LU/dm~3). Activity, efficiency and operational stability of the immobilised lipases were assayed by solvent-free esterification of oleic acid and octanol. Equilibrium data were modelled by the Langmuir, Freundlich and Redlich-Peterson formulae. It was found that Lipolase 100L/Accurel, PS/45SAA and SP871/45SAA systems conformed to the Langmuir behaviour, while Lipase PS/Accurel and SP871/Accurel systems followed the Freundlich behaviour and Lipolase 100L/45SAA, QL/45SAA and QL/Accurel EP100 resembled Redlich-Peterson behaviour, Whereas immobilisation of Accurel EP100 resulted in classical equilibrium isotherms with all four lipases, studied, excep for SP871. Quantiatively, for 1g lipase, Accurel and 45SAA had a maximum capacity of 140 and 260 kLU for PS, 112 and 550 kLU for Lipolase 100L, 320 and 880kLU for SP871 and 18 and 29 kLU for QL, respectively.