Hierarchical Enzyme Reactors for Out-of-equilibrium CO2 capture and fixation

Carbon capture, utilization and storage (CCUS) technologies are considered crucial for reaching carbon neutrality.

Biocatalysis could offer sustainable alternatives to utilize emitted CO2 as building block for green industrial processes.

However, CO2 low solubility in aqueous media and high stability result in low substrate availability for the enzymes and in thermodynamic limitations.

In this project we propose to address two challenging CO2 biotransformations: i) the reduction to methanol; ii) the carboxylation of methional to 4-methylthio-2-oxobutanoate (MOTB), that can be further aminated to give the L-methionine amino acid. However, only high CO2 concentration can lead to high product yield and overcoming thermodynamic limitations.

The purpose of the HEROCO2 project is to overcome these limitations through the design of hierarchical porous heterogeneous biocatalysts.

The final material will be obtained by the assembly of microporous nanostructured sorbents, deputed to generate reservoirs of CO2 surrounding a macroporous material acting as carrier for the enzyme cascades.

CO2 controlled desorption from the micropores is expected to keep high local CO2 concentrations within the macropores where the enzymes are immobilised, allowing out-of-equilibrium reactions under atmospheric pressure conditions.

The selected cascades will be immobilized together with the corresponding cofactors, resulting in self-sufficient biocatalysts.

Deep eutectic solvents (DESs) will be selected as green solvents since they combine high CO2 solubility with the preservation of enzyme activity.

The two biocatalytic pathways will be finally tested in continuous flow reactors.This project could inaugurate new sustainable technological routes for carbon capture and utilization, addressing significant environmental challenges and advancing the field of biocatalysis towards carbon-negative processes by introducing innovative approaches never explored before.