| Summary: | Functional properties of each enzyme strictly depend on immobilization protocol used for linking enzyme and carrier. Different strategies were applied to prepare the immobilized derivatives of <i>Rhizomucor miehei</i> lipase (RML) and chemically aminated RML (NH<sub>2</sub>-RML). Both RML and NH<sub>2</sub>-RML forms were covalently immobilized on glyoxyl sepharose (Gx-RML and Gx-NH<sub>2</sub>-RML), glyoxyl sepharose dithiothreitol (Gx-DTT-RML and Gx-DTT-NH<sub>2</sub>-RML), activated sepharose with cyanogen bromide (CNBr-RML and CNBr-NH<sub>2</sub>-RML) and heterofunctional epoxy support partially modified with iminodiacetic acid (epoxy-IDA-RML and epoxy-IDA-NH<sub>2</sub>-RML). Immobilization varied from 11% up to 88% yields producing specific activities ranging from 0.5 up to 1.9 UI/mg. Great improvement in thermal stability for Gx-DTT-NH<sub>2</sub>-RML and epoxy-IDA-NH<sub>2</sub>-RML derivatives was obtained by retaining 49% and 37% of their initial activities at 70 °C, respectively. The regioselectivity of each derivative was also examined in hydrolysis of fish oil at three different conditions. All the derivatives were selective between cis-5,8,11,14,17-eicosapentaenoic acid (EPA) and cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) in favor of EPA. The highest selectivity (32.9 folds) was observed for epoxy-IDA-NH<sub>2</sub>-RML derivative in the hydrolysis reaction performed at pH 5 and 4 °C. Recyclability study showed good capability of the immobilized biocatalysts to be used repeatedly, retaining 50−91% of their initial activities after five cycles of the reaction.
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