Peroxidase-Sensitive Tyramine Carboxymethyl Xylan Hydrogels for Enzyme Encapsulation
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Derivatives of xylans were synthesized from corncob xylan by carboxymethylation, oxidization with different molar ratios of periodate (5, 10 15 and 20 mol%) and by reductive amination with tyramine. Modifications of tyramine carboxymethyl xylans (Tyr-CMX) were confirmed by FTIR, UV and NMR spectra. Concentration of ionizable groups increased from 1.5 mmol/g for carboxymethyl xylan (CMX) to 5.4 mmol/g for Tyr-CMX oxidized with 20 mol% of periodate. All Tyr-CMXs were able to form hydrogels the cross-linking reaction with horseradish peroxidase and peroxide. Tyr-CMXs were tested for amyloglucosidase (AG) encapsulation within hydrogel microbeads obtained in a reaction of emulsion polymerization with peroxidase. Average diameter of Tyr-CMX hydrogel microbeads was 52±25 µm and after encapsulation optimization with respect to the extent of CMX modification with tyramine, the concentration of Tyr-CMX, and the amount of added AG, microbeads with AG specific activity of 2 U/mL and 20% yield of i...mmobilization were obtained. The optimum pH of the immobilized AG was not changed compared to the soluble one, while half-life at 60 °C was increased around 10 times. The Michaelis-Menten constant for the immobilized enzyme, 1.03 mM, was significantly lower than that for the soluble one, 1.54 mM. After 5 cycles of repetitive use in batch reactor, the immobilized AG retained 68% of initial activity.
Keywords:xylan / hydrogel / tyramine / polymerization / emulsion / peroxide
Source:Macromolecular Research, 2019, 27, 8, 764-771