Candida rugosa lipase immobilization on hydrophilic charged gold nanoparticles as promising biocatalysts: Activity and stability investigations.

In this work, a simple and versatile methodology to obtain two different bioconjugated systems has been developed by the immobilization of Candida rugosa lipase (CRL) on hydrophilic gold nanoparticles functionalized with 2-diethylaminoethanethiol hydrochloride (DEA) or with sodium 3-mercapto-1-propanesulfonate (3MPS), namely Au-DEA@CRL and Au-3MPS@CRL. Both spectroscopic and morphological properties of metal nanoparticles have been deeply investigated. The enzyme loading and lipolytic activity of AuNPs@CRL bioconjugates have been studied with respect to different surface functionalization and compared with the free enzyme. Some physical and chemical parameters had a strong effect on enzyme activity and stability, that were improved in the case of the Au-DEA@CRL bioconjugate, which showed a remarkable biocatalytic performance (95% of residual lipolytic activity compared with free CRL) and stability in experimental conditions concerning pH (range 5-8) and temperature (range 20-60°C), as often required for the industrial scale up of catalytic systems.