Enzyme-loaded membrane reactor to degrade a pesticide in vegetative waters

Abstract

Selective removal of pesticides from agro-food streams containing valuable biomolecules similar in size and structure to pesticides, is challenging. This work proved that a phosphotriesterase-loaded membrane was able to selectively degrade the paraoxon-ethyl pesticide in vegetative waters (VW) coming from olive mill, containing biophenols. The biofunctionalized membranes were use in a biocatalytic membrane reactor (BMR) operating in continuous. Regenerated cellulose (RC) was selected for the BMR development, because among tested membranes, it showed the lowest biophenols adsorption and the highest specific activity after biofunctionalization. Kinetic studies clarified that, even though biophenols interacted with the enzyme through a competitive inhibition mechanism, there was no reaction towards these biomolecules, which were not damaged by the decontamination process. A comparison between the enzyme-loaded membrane and the free enzyme confirmed an increase of the catalytic stability of the former, which showed a deactivation constant four-fold lower (3.5·10−2 days−1) compared to the latter (1.5·10−1 days−1). Strategies to minimize the competitive inhibition were identified using sodium dodecyl sulphate, which improved by 50% the immobilized enzyme specific activity. Overall, the work proved the BMR ability to selectively remove pesticide, promoted a thorough understood the parameters influencing the BMR and identified strategies to improve its performance.