Polymerization of Glucans by Enzymatically Active Membranes

Abstract

Conventional enzyme membrane reactors are not appropriate for a continuous synthesis of macromolecules and simultaneous product release. By immobilizing the enzyme in sufficiently large pores of a membrane an ensemble of miniaturized bioreactors is created. Product molecules are continuously removed from the enzyme by the flow of the reaction mixture across the membrane. Additionally, by varying the flow rate, it ought to be possible to influence the substrate as well as the enzyme-product residence times and thereby the product macromolecule's size. In this paper we present the first results of experiments involving enzymatic 1,4-alpha-glucan synthesis, using sucrose as substrate, maltooligosaccharides (DP 3-6) as primers, and membrane-immobilized amylosucrase. Epoxy groups for a covalent enzyme immobilization were generated on polypropylene microfiltration membranes by heterogeneous photoinitiated graft polymerization of glycidyl methacrylate. The influence of primer concentration and flow rate through the enzyme-membrane on amylosucrase activity, molecule growth, and coupling efficiency for glucose (% of coupled glucose versus free glucose) were investigated. The enzymatically mediated chain elongation of maltooligosaccharides by the successive addition of glucose units was achieved for the first time in a transmembrane process utilizing amylosucrase membranes.

Molecular Basis of the Amylose-like Polymer Formation Catalyzed by Neisseria polysaccharea Amylosucrase

“…This perfectly corroborates the results of Becker et al (29), who reported that glucosylation of maltotriose by AS is minor when the enzyme is in the presence of sucrose and MOS acceptors ranging from G3 to G6. In addition, these data are also in accordance with the size selectivity previously demonstrated in the case of the disproportionation of maltooligosaccharides.…”

Photoreactive Functionalization of Poly(ethylene terephthalate) Track‐Etched Pore Surfaces with “Smart” Polymer Systems

“…The resulting even intraporous functionalization of the track-etched membranes had also previously been obtained for amino-functional graft copolymer layers which then had been used for covalent enzyme immobilization; the obtained enzyme binding capacities and activities could be explained by an even coverage of the pore surface. [26,27] There is a clear correlation between the gravimetrically determined degree of functionalization and the carboxylic group amounts on the membranes, determined by reversible ionic dye binding (see Figure 7; cf. Table 2 and 3).…”

“…[8,9,16,26,27] Effects of functionalization were detected by gravimetry (DG) and using the reversible dye binding to carboxylic groups.…”

“…[14,15,17,19,25] Also, the resulting porous composite membranes may directly find interesting applications, for examples as enzyme-membrane reactor. [26,27] Furthermore, the knowledge about suited functionalization methods could be applied to the functionalization of other objects made from the same base polymer, for example components for ''labs-on-a-chip''.…”

Synergist Immobilization Method for Photo‐Grafting: Factors Affecting Surface Selectivity

“…[4] Track-etched membranes have been used for various surface functionalizations by 'grafting-from' or 'grafting-to' methods. [1,[5][6][7][8] In addition, the resulting porous composite membranes may directly find interesting applications, for examples, as an enzyme-membrane reactor [9,10] and a 'smart', i.e., stimuliresponsive porous membrane. [11,12] Therefore, as an example for extending the application of the novel method, the surface functionalization of track-etched PET with pores of %350 nm diameter by 'grafting-from' using the synergist immobilization method and the respective characterizations form the second part of this paper.…”