Construction of a biomimetic core-shell PDA@Lac bioreactor from intracellular laccase as a nano-confined biocatalyst for decolorization

• Published in: Chemosphere (Oxford) 2023-07, Vol.330, p.138654-138654, Article 138654
• Main Authors: Bo, Hongqing, Zhang, Ziyan, Chen, Zhonglin, Qiao, Wenrui, Jing, Siyi, Dou, Tongtong, Tian, Tian, Zhang, Ming, Qiao, Weichuan
• Format: Article
• Language: English
• Subjects: Biomimetics; Bioreactors; Coloring Agents; Confined environments; Enzymes, Immobilized - chemistry; Immobilization of laccase; Laccase - chemistry; Polydopamine; Polymers - chemistry
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2023.138654

Enzymes immobilized on the surface of the carriers are difficult to maintain their conformation and high activity due to the influence of the external harsh environments. A biomimetic core-shell PDA@Lac bioreactor was constructed by depositing polydopamine (PDA) on the surface of the recombinant Escherichia coli with CotA laccase gene, and releasing intracellular laccase into the PDA shell using ultrasound to break the cell wall of the bacteria. The bioreactor provided a nano-confined environment for the laccase and accelerated the mass and electron transfer in the volume-confined space, with a 2.77-fold increase in Km compared with the free laccase. Since there was no barrier of the cell wall, the crystal violet dye can enter the bioreactor to participate in the enzymatic reaction. As a result, PDA@Lac achieved excellent decolorization performance even without ABTS as an electron mediator. Moreover, the cytoplasmic solution retained in the PDA shell promoted the enzyme's tolerance to pH, temperature and harsh environments. In addition to PDA encapsulation, carbonyl and –NH2 groups of PDA were bound covalently with –NH2 and –COOH on the laccase in the PDA@Lac, resulting in an extremely high laccase loading of 817.59 mg/g. Also, the relative activity of the bioreactor maintained approximately 75% after 10 cycles of reuse. In addition, the protection of the PDA shell increased the resistance of laccase to UV irradiation. This work provides a novel method of laccase immobilization for application in wastewater treatment. [Display omitted] •A novel immobilization method of intracellular laccase was developed.•Biomimetic core-shell PDA@Lac provided a nanoconfinement for efficient catalysis.•The enzyme loading of PDA@lac was 817.59 mg/g.•The laccase in PDA@lac had good tolerance to UV irradiation.•PDA@lac had a good decolorization ability on crystal violet with no ABTS as mediator.