Magnetic macromolecular cross linked enzyme aggregates (CLEAs) of glucoamylase

• Novel method of preparation of magnetic macromolecular CLEAs of glucoamylase was developed.
• Glucoamylase was cross linked by dialdehydic pectin in presence of FMNs.
• Maximum activity and enhanced thermal stability was obtained after cross linking by pectin.
• Porous morphology of magnetic macromolecular CLEAs improved accessibility to macro-substrates.
• Biocompatibility of pectin made preparation methodology eco-friendly and worker safer.

This work illustrates the preparation of magnetic macromolecular glucoamylase CLEAs using dialdehydic pectin, as a cross linker instead of traditional glutaraldehyde. The effect of precipitators type and amount, cross linker concentration, cross linking time and amount of amino functionalized magnetic nanoparticles (AFMNs) on glucoamylase activity was studied. Glucoamylase magnetic macromolecular CLEAs prepared by precipitation in presence of AFMNs by ammonium sulfate were subsequently cross linked by dialdehydic pectin. After cross-linked by pectin, 95.4% activity recovery was achieved in magnetic macromolecular CLEAs, whereas in case of glutaraldehyde cross linker, 85.3% activity recovery was achieved. Magnetic macromolecular CLEAs showed 2.91 and 1.27 folds higher thermal stability as compared to free and magnetic glutaraldehyde CLEAs. In kinetics study, magnetic macromolecular CLEAs retained same Km values, whereas magnetic glutaraldehyde CLEAs showed higher Km value than free enzyme. The porous structure of magnetic macromolecular CLEAs was not only enhanced mass transfer toward macromolecular substrates, but also showed compression resistance for 5 consecutive cycles which was checked in terms of effectiveness factor. At the end, in reusability study; magnetic macromolecular CLEAs were retained 84% activity after 10th cycle without leaching of enzyme which is 22% higher than traditional magnetic CLEAs.