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<p>Laccases are multicopper oxidases that offer environmentally friendly routes for polymer synthesis and modification under mild aqueous conditions; however, their application in alkaline systems and in the development of functional material remains limited. In this study, a recombinant bacterial laccase (rBCLac) from Antarctic <i>Bacillus</i> sp. PAMC28748 was employed as a green biocatalyst for the oxidative polymerization of catechol and its simultaneous attachment onto chitosan in fully aqueous media, without the use of organic solvents or harsh reagents. The enzymatic oxidation generated reactive o-quinone intermediates, which subsequently underwent non-enzymatic coupling to form catechol-functionalized chitosan. The modified biopolymer exhibited enhanced swelling behavior, controlled methylene blue release, and increased iron-chelation capacity. Optimal polymerization was achieved at pH 8–9 and 20&#xa0;°C. Kinetic analysis and molecular dynamics simulations confirmed that the enzyme maintained sufficient catalytic activity and structural stability under alkaline aqueous conditions. The enzymatically generated poly(catechol) was further utilized for surface functionalization of Fe₃O₄ nanoparticles, yielding well-dispersed composites with enhanced surface functionality. FTIR analysis revealed broadening of the O-H band and the formation of C-O-C bonds, confirming catechol polymerization, while Fe-O vibrations verified preservation of the Fe₃O₄ core after modification. These materials exhibited rapid adsorption behavior and pronounced selectivity toward congo red over methylene blue, which can be attributed to synergistic π–π interactions, hydrogen bonding, and electrostatic interactions. The poly(catechol)-Fe<sub>3</sub>O<sub>4</sub> composite showed a high adsorption capacity for Congo red (q<sub>m</sub> = 384.62 mg g<sup>− 1</sup>), whereas adsorption of methylene blue remined limited. Reusability studies demonstrated partial retention of adsorption performance over multiple cycles. Overall, this work presents a sustainable, enzyme-mediated strategy for polysaccharide modification and functional polymer development under environmentally relevant aqueous conditions, with potential applications in selective dye remediation.</p>

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CotA Laccase-Catalyzed Catechol Oxidation for Functional Chitosan and Iron oxide Nanoparticles in Aqueous Systems

  • 期刊论文

  • 发表日期：

    2026年6月16日

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  • Jayram Karmacharya,
  • Prasansah Shrestha,
  • Tae-Jin Oh

摘要

Laccases are multicopper oxidases that offer environmentally friendly routes for polymer synthesis and modification under mild aqueous conditions; however, their application in alkaline systems and in the development of functional material remains limited. In this study, a recombinant bacterial laccase (rBCLac) from Antarctic Bacillus sp. PAMC28748 was employed as a green biocatalyst for the oxidative polymerization of catechol and its simultaneous attachment onto chitosan in fully aqueous media, without the use of organic solvents or harsh reagents. The enzymatic oxidation generated reactive o-quinone intermediates, which subsequently underwent non-enzymatic coupling to form catechol-functionalized chitosan. The modified biopolymer exhibited enhanced swelling behavior, controlled methylene blue release, and increased iron-chelation capacity. Optimal polymerization was achieved at pH 8–9 and 20 °C. Kinetic analysis and molecular dynamics simulations confirmed that the enzyme maintained sufficient catalytic activity and structural stability under alkaline aqueous conditions. The enzymatically generated poly(catechol) was further utilized for surface functionalization of Fe₃O₄ nanoparticles, yielding well-dispersed composites with enhanced surface functionality. FTIR analysis revealed broadening of the O-H band and the formation of C-O-C bonds, confirming catechol polymerization, while Fe-O vibrations verified preservation of the Fe₃O₄ core after modification. These materials exhibited rapid adsorption behavior and pronounced selectivity toward congo red over methylene blue, which can be attributed to synergistic π–π interactions, hydrogen bonding, and electrostatic interactions. The poly(catechol)-Fe3O4 composite showed a high adsorption capacity for Congo red (qm = 384.62 mg g− 1), whereas adsorption of methylene blue remined limited. Reusability studies demonstrated partial retention of adsorption performance over multiple cycles. Overall, this work presents a sustainable, enzyme-mediated strategy for polysaccharide modification and functional polymer development under environmentally relevant aqueous conditions, with potential applications in selective dye remediation.