An enzymatic membrane reactor for oligodextran production: Effects of enzyme immobilization strategies on dextranase activity

Ziran Su,Jianquan Luo,Sigyn Björk Sigurdardóttir,Thomas Manferrari,Katarzyna Jankowska,Manuel Pinelo

doi:10.1016/j.carbpol.2021.118430

Abstract

An enzymatic membrane reactor (EMR) with immobilized dextranase provides an excellent opportunity for tailoring the molecular weight (Mw) of oligodextran to significantly improve product quality. However, a highly efficient EMR for oligodextran production is still lacking and the effect of enzyme immobilization strategy on dextranase hydrolysis behavior has not been studied yet. In this work, a functional layer of polydopamine (PDA) or nanoparticles made of tannic acid (TA) and hydrolysable 3-amino-propyltriethoxysilane (APTES) was first coated on commercial membranes. Then cross-linked dextranase or non-cross-linked dextranase was loaded onto the modified membranes using incubation mode or fouling-induced mode. The fouling-induced mode was a promising enzyme immobilization strategy on the membrane surface due to its higher enzyme loading and activity. Moreover, unlike the non-cross-linked dextranase that exhibited a normal endo-hydrolysis pattern, we surprisingly found that the cross-linked dextranase loaded on the PDA modified surface exerted an exo-hydrolysis pattern, possibly due to mass transfer limitations. Such alteration of hydrolysis pattern has rarely been reported before. Based on the hydrolysis behavior of the immobilized dextranase in different EMRs, we propose potential applications for the oligodextran products. This study presents a unique perspective on the relation between the enzyme immobilization process and the immobilized enzyme hydrolysis behavior, and thus opens up a variety of possibilities for the design of a high-performance EMR.

Highlights

The enzymatic membrane reactor (EMR) is nowadays regarded as a green platform that enables the integration of bioconversion and membrane separation (Giorno et al, 2014; Giorno & Drioli, 2000)
Effect of enzyme immobilization mode on enzyme loading Firstly, the effects of PDA coating parameters on enzyme loading were investigated (Table S1), and it was found that neither increased PDA concentration nor coating time significantly improved enzyme loading in incubation mode
The Gel permeation chromatography (GPC) chromatograms in our study show that dextranase immobilized by incubation mode tended to produce end-products during the reaction and that the bulk of the large dextran molecules remained unattacked at the beginning

Summary

Introduction

The enzymatic membrane reactor (EMR) is nowadays regarded as a green platform that enables the integration of bioconversion and membrane separation (Giorno et al, 2014; Giorno & Drioli, 2000). The EMR approach, in which the enzymes function as efficient biocatalysts in concert with a membrane separator for simultaneous product purifi cation, has been increasingly reported for its various applications in both upstream and downstream processes (Jochems et al, 2011; Luo et al, 2020). To obtain maximum amount of the target oligodextran products, the enzymatic hydrolysis should occur near the membrane surface for immediate removal of the target oligodextran from the reaction system and to avoid over-degradation. By this approach, products with narrow Mw distribution could be obtained. Enzyme immobilization on the membrane offers a promising opportunity for better control of the overall process near the membrane surface

Methods

Results

Conclusion