Beyond CO2 Storage: Enzyme-Amyloid Fibril Catalytic Hybrids for Long Cascade Reactions Converting CO2 into Fructose

Abstract

Enzyme immobilization is an efficient and cost-effective approach to recovering, stabilizing, and enhancing enzyme catalytic properties. It is a challenge, however, for coimmobilized multiple enzymes to perform consecutive reactions without being inactivated under similar conditions. Here, we present a facile enzyme immobilization platform using β-lactoglobulin amyloid fibril hydrogels. Two different hydrogels, loading either RuBisCO alone (hereby termed AFR*) or seven enzymes related to the Calvin Cycle (hereby termed AF7E hydrogel), show immobilization efficiency of over ∼95% while simultaneously exhibiting excellent activity and stability. The AFR* hydrogel enables the fixation of CO₂ into 3-phosphoglycerate (3-PGA), which is then utilized as the initial step in the Calvin Cycle cascade catalytic reactions if the AF7E hydrogel is used, mimicking the light-independent part of the more complex natural photosynthesis full process. The converted substrates of this process contain precursors (α-glycerophosphate dehydrogenase and dihydroxyacetone phosphate), which can be further converted to fructose by additional aldolase. Due to the proteinaceous nature of the amyloid substrate, the AF7E hydrogel is completely biodegradable by pepsin, as confirmed via atomic force microscopy and circular dichroism spectroscopy analysis. This original enzyme-amyloid hybrid is biocompatible, sustainable, and scalable and may serve as a general template for multienzymatic catalytic platforms.