Tailored Covalent Organic Frameworks Enable the Encapsulation of Living Cells to Produce Rare Ginsenoside.
TL;DR
A scalable whole-cell immobilization platform through in situ assembly of recombinant Escherichia coli expressing Sulfolobus solfataricus β-glycosidase with three covalent organic frameworks that enabled the immobilization of various prokaryotic and eukaryotic microbes, demonstrating favorable universality.
Abstract
Whole-cell catalysis holds great potential in the production of rare ginsenoside compound K (CK), but it is limited by poor mass transfer and inadequate stability in practice. Herein, we report a scalable whole-cell immobilization platform through in situ assembly of recombinant Escherichia coli expressing Sulfolobus solfataricus β-glycosidase with three covalent organic frameworks (COFs: TpPa, TpBD, and TpTAP) in phosphate-buffered saline. As demonstrated with TpBD, 18.6 grams of TpBD COF could be synthesized in one pot at room-temperature. The COF shell uniformly encapsulated the cell surface, yielding a robust biocatalyst with high catalytic efficiency, enhanced stability, and excellent recyclability. Specifically, E. coli@TpBD-2 showed 1.98-fold higher catalytic efficiency than free E. coli, while the COF shell significantly improved the E. coli's tolerance to industrially relevant harsh conditions. Notably, the scale-up synthesis in continuous-flow reactors using abundant ginsenoside Rb1 as substrate afforded a space-time yield of 0.67 g·L-1·d-1 for CK at 70°C, with 75.25% initial conversion rate retained after 10 h of continuous operation. Additionally, this platform enabled the immobilization of various prokaryotic and eukaryotic microbes, demonstrating favorable universality. This work establishes a versatile platform for engineering stable whole-cell biocatalysts, which is beneficial for facilitating the industrialization of biocatalysis.