Multi-walled carbon nanotubes (MWCNT)-tannase composite was investigated as an immobilized biocatalyst on the basis of its facile preparation, low cost, and excellent aqueous dispersibility. Cross-linked tannase enzymes, obtained in the presence of glutaraldehyde, were composited with MWCNT via physical adsorption. Multiple techniques were applied to investigate, and corroborate the successful adsorption of cross-linked tannase onto the MWCNT structure. Green tea infusion extract post-treatment using the composite preparation showed elevated radical scavenging activities relative to the control. Green tea infusion extract exhibited a markedly reduced EC50 value on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals following its treatment with the enzyme composite, which represents 20%-34% enhancement in its free radical scavenging capacity. Stoichiometry and number of reduced DPPH were determined and compared. The antioxidative potential of a widely consumed, health-beneficial green tea is elevated by the treatment with MWCNT-tannase composite. PRACTICAL APPLICATIONS: Cross-linked tannase enzymes were composited with pristine multi-walled carbon nanotubes via simple physical adsorption. The composite presents key advantages such as low specific volume compared to other well-known immobilization media, inert, facile enzyme composition, and ease of recovery for repeated use. The work demonstrated carbon nanotube prosthetic utility in the biotransformation of food-based health commodity sought after for its nutritional benefits. The approach is of both industrial- and agricultural importance, and is a promising and viable strategy to obtain a natural, functional food supplement for the multi-billion dollar well-being and health-related industries.
Keywords: antioxidants; composite; green tea; immobilization; multi-walled carbon nanotubes; tannase.
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