Sustainable CO2 valorization using Komagataella phaffii formate dehydrogenase immobilized on mesoporous silica

This work evaluates the potential of formate dehydrogenase from the methylotrophic yeast Komagataella phaffii (KpFDH) for the valorization of CO2 reduction into formate. The catalytic performance of the soluble form was benchmarked against the model enzyme of Candida boidinii (CbFDH). Both enzymes exhibited very similar optimal pH and temperature profiles. Structural bioinformatics revealed a root-mean-square deviation (RMSD) of 0.334 Å, confirming the high conservation of catalytic residues between both yeast-derived enzymes. KpFDH was immobilized on amino-functionalized mesoporous silica (MSU-F-NH2). Successful protein immobilization was confirmed by Fourier-Transform Infrared (FT-IR) Spectroscopy, photoluminescence analysis, and catalytic activity measurements, achieving complete protein loading (4 mg g−1) with 76% retained activity. During batch CO2 reduction without cofactor regeneration, both configurations (using immobilized and free enzyme) yielded 2.4 mM of formate within 7 h. Both setups achieved a competitive volumetric space-time yield (STY) of 0.357 mM h−1 (0.343 mM h−1 for the free form). Owing to the exceptionally low enzyme dosages deployed (0.3 U), the platforms demonstrated outstanding active-site efficiencies: the free enzyme achieved a turnover number (TON) of 42,283 and a turnover frequency (TOF) of 6040.4 h−1, while the immobilized KpFDH_MSU-F system maintained a high TON (5497) and TOF (785.3 h−1). Notably, the immobilized system enabled four consecutive reuse cycles retaining 71% residual activity. These findings position KpFDH as a viable candidate for sustainable process design, leveraging the natural methanol utilization pathway of K. phaffii to bypass costly downstream purification steps