Protein inorganic hybrid nanoflowers of a microbial carbonic anhydrase as efficient tool for the conversion of CO₂ into value added product

Abstract

BACKGROUND: Carbonic anhydrase (CA) is one of the most widely distributed enzymes among plants, animals, and microorganisms, and it has an enormous ability to capture carbon dioxide (CO 2 ). However, the real-time application of CA is still a challenge due to its low operational stability, its difficulty in recovery from the reaction medium, and its poor durability.RESULTS: The synthesis of insoluble protein inorganic hybrid structures at nanoscale was proven as quite useful to catalyze enzymatic biotransformation. Here, CA nanoflowers (CANF) were synthesized with the self-assembly of metal phosphate and CA. The synthesis of CANF was performed using 0.2 mg mL −1 protein and 2.0 mM CuSO 4 at 4 °C under mild shaking conditions. The CANF exhibited optimum activity at pH 7.5 and a temperature of 40°C. The synthesized CANF were used for CO 2 conversion under optimized conditions and their kinetic parameters were studied using p-NPA hydrolysis. The V max and K m of CANF were 185.18 ∼mol min −1 mL −1 and 4.72 mM, compared with those of free CA, 166.66 ∼mol min −1 mL −1 and 5.12 mM, respectively. The stability of CANF has improved remarkably. The CANF made of metal ions and protein showed higher stability and enzyme activity than free enzymes. Furthermore, the CANF showed good reusability due to their mechanical properties and monodispersity. The production of CaCO 3 by CANF was 1.71-fold higher than that by free CA. CONCLUSION:The newly formed CANF showed flower-like morphology with good catalytic activity. This study demonstrated that CANF technology has a bright future in the conversion of CO 2 into CaCO 3 .