Novel Synthesis Strategy for Biocatalyst: Fast Purification and Immobilization of His- and ELP-Tagged Enzyme from Fermentation Broth

Inspired by natural biomineralization process, inorganic phosphates system has been selected as a candidate for the encapsulation of enzyme; however, during the long-term fabrication process, the loss of enzyme activity is unavoidable, and the biomimetic mineralization mechanism is still poorly understood. Meanwhile, the purification process plays a key role in the preparation of immobilized enzyme with high enzyme loading and activity, while the rapid, low-cost, and eco-friendly purification of biocatalyst from crude fermentation broth remains a critical challenge in biochemical engineering. Here, a binary tag composed of elastin-like polypeptide (ELP) and His-tag was presented for the first time to be fused with β-glucosidase (Glu) to construct a recombinant Glu-linker-ELP-His (GLEH) with the aim of developing a fast synthesis strategy combining purification and immobilization processes for a biocatalyst with better stability and recyclability. The purification fold and activity recovery of GLEH reached 18.1 and 95.2%, respectively, once a single inverse transition cycling was conducted at 25 °C for 10 min. Then, efficient biomineralization of hybrid enzyme-Cu3(PO4)2 nanoflowers was realized in 15 min by the action of His-tag and ultrasonic-assisted reaction method. The activity recovery and relative activity reached the maximum at 90.3 and 111.0%, respectively. We demonstrate that the crystal growth process of a hybrid nanoflower involves obvious nucleation, self-assembly, and the Ostwald ripening process, and the enzyme GLEH acts as a "binder" to assemble Cu3(PO4)2 nanoflakes. The immobilized GLEH nanoflowers show outstanding operation stability and recyclability, and their catalytic efficiency is close to that of free Glu.