Gas fermentation is a promising approach to reduce carbon emissions of production processes by using microorganisms to convert industrial gas streams into valuable carbon-based products. Here, isopropanol production by engineered Cupriavidus necator from CO2-rich gas streams is presented. Four different engineered strains were tested first on synthetic gas mixture, and one was selected, namely Re2133/pEG7d, for further evaluation on two different industrial CO2-rich gas streams. Up to 1.6 g L-1 of isopropanol was obtained in autotrophic gas flasks with this strain. Then, raw biogas from landfill containing 45% methane was successfully used as a CO2 source for isopropanol production with this strain Re2133/pEG7d producing up to 2.35 ± 0.25 g L-1, and methane enrichment was demonstrated. Finally, flue gases from a municipal incinerator were used as a source of CO2 and O2 for the autotrophic cultivation of the strain Re2133/pEG7d, obtaining a final isopropanol concentration of 2.5 ± 0.3 g L-1. This work highlighted the robustness of C. necator to potential industrial gas stream impurities and its versatility in using diverse gaseous feedstocks, promising future developments at larger scale.

The performance of enzyme electrodes depends critically on the interactions between the enzyme and the electrode surface. In this study, L-lactate oxidase with an N-terminal His-tag (His-LOx) was immobilized on planar gold electrode modified with self-assembled monolayers (SAMs) engineered to provide distinct surface characteristics: hydrophilic, hydrophobic, or Ni²⁺-chelating for His-tag affinity binding. Electrochemical measurements revealed that the hydrophilic 1-thioglycerol (TG) SAM supported the highest initial activity (10.5 µA/cm²), whereas the hydrophobic 1-octanethiolled to a substantially lowered activity. Ni²⁺-complexed nitrilotriacetic acid (Ni-NTA) SAM markedly enhanced the operational stability of His-LOx, retaining over 65% of activity after 20 h compared to less than 20% for TG. A mixed SAM combining TG and Ni-NTA enabled the simultaneous achievement of high activity and improved stability, demonstrating a synergistic effect of hydrophilic and affinity-based interactions. These results provide mechanistic insight into how SAM surface properties and enzyme-surface interactions govern both activity and stability of LOx, offering practical design principles for the development of robust and sensitive LOx electrodes for biosensing applications.