Polymeric biocatalytic membranes with immobilized thermostable phosphotriesterase

Abstract

In this work the catalytic performance of a mutant (named SsoPox W263F) of the thermophilic Phosphotriesterase-like lactonase (PLL) isolated from Sulfolobus solfataricus (SsoPox) was reported both on free and immobilized membrane systems using as substrate the pesticide paraoxon. The single mutant SsoPox W263F was immobilized on/into hydrophilic (Non standard grade Polyethersulphone, NGS-PES) and hydrophobic (Polyvinylidenefluoride, PVDF) membranes. Biocatalytic membrane systems able to work in liquid and vapour phase were developed aimed at decontamination of water and air, respectively. The work aimed at membranes characterization in terms of vapour and water permeability, free and immobilized enzyme catalytic and specific activity. Enzyme stability was also monitored for more than 5 months in order to evaluate the stability of developed systems.Results demonstrated that although free SsoPox W263F showed a higher performance up to 30 days it completely loses its activity after two months. On the contrary biocatalytic membranes showed an initial loss of activity in the first days (residual specific activity of about 54%when immobilized on/into NSG-PES and 5% when immobilized on/into PVDF) but any change in stability during more than 5 months. In the case of PVDF, the residual specific activity can be enhanced tuning the amount of immobilized SsoPox W263F, in fact it was demonstrated that there is a trade-off between amount of immobilized enzyme and catalytic performance.