The development of efficient, non-natural C1 assimilation pathways is a key challenge in non-natural CO₂ fixation, as native carbon fixation routes are complex and poorly suited for in vitro deployment. Biocatalysis presents a sustainable route for CO₂ valorisation, enabled by enzyme engineering strategies that enhance catalytic efficiency and stability under industrial conditions[1], [2]. Here, we target the implementation of the formolase pathway, a short and energetically favourable route enabling biocatalytic conversion of CO₂-derived formate into carbohydrates via an enzymatic cascade. The work focuses on development and integration of two rate-limiting enzymatic steps. First, we aim to establish biocatalytic reduction of formate to formaldehyde by repurposing a carboxylic acid reductase (CAR) into a formic acid reductase (FAR). This is accomplished by screening a library of carboxylic acid reductases (CAR) with activity towards ammonium formate, applying both fluorescence and HPLC-based screening methods. [3] Extensive enzyme screening unveiled four CARs with moderate to high activity for formate. Our best FAR hits are being characterized further using protein crystallography and cryo-electron microscopy (cryo-EM) to understand substrate preferences and enable guided FAR engineering for improved total turnover and formaldehyde stability. Our efforts now concentrate on building a one-pot cascade by implementing the biocatalytic formose-type reaction using benzaldehyde lyase (BLS). variants. [4], [5] Active site remodelling of a thermostable BLS resulted in formolase (FLS) variants exhibiting altered substrate specificity from benzaldehyde to formaldehyde. The enzyme activity is verified using enzyme-coupled assays of the DHA product. Through integrated computational design and ML-guided mutagenesis we aim to improve C1–C1 bond formation rates. Ultimately, the optimized cascade establishes a foundation to build a scalable, biocatalytic platform for CO₂ upgrading, contributing to carbon circular economy.