Further stabilization of lipase from Pseudomonas fluorescens immobilized on octyl coated nanoparticles via chemical modification with bifunctional agents.

The lipase from Pseudomonas fluorescens (PFL) was adsorbed on superparamagnetic NiZnFe2O4 octyl-nanoparticles via interfacial activation, producing the biocatalyst OCTYL-NANO-PFL. In order to further improve the stability of the immobilized lipase, the immobilized enzyme biocatalyst was chemically modified with different concentrations of diverse bifunctional molecules (glutaraldehyde (GA), divinylsulfone (DVS) or p-benzoquinone (BQ)). The concentrations of bifunctional agents were varied (0.5, 1, 2.5 and 5% (v/v for GA and DVS and w/v for BQ)). The results showed a greatly improved stability after chemical modification with all bifunctional molecules, mainly with 5% (v/v) GA or 1% (v/v) DVS. The biocatalysts OCTYL-NANO-PFL-GA 5% and -DVS 1% were about 60 folds more stable at pH 7 than the unmodified preparation and, at pH 5, >200 folds for 5% GA modified enzyme. The most stable BQ treated biocatalysts, OCTYL-NANO-PFL-BQ 0.5%, was about 8.3 more stable than OCTYL-NANO-PFL at pH 7, while was 20 fold more stable at pH 9.