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Utilization of one-carbon chemicals such as CO 2 , formate, and methanol by microorganisms can enable the sustainable production of fuels and chemicals. However, the low conversion efficiency of these chemicals by microorganisms is a major challenge. To address this, we designed a one-carbon strategy that can utilize CO 2 and its derivative formate. Here, a platform yeast strain with improved formate utilization and NAD(P)H production was constructed and evaluated for its ability to produce free fatty acids (FFAs). Based on 13C-marked analysis, the one-carbon assimilation efficiency of the platform strain reached 11.24%. Through continuous optimization, under conditions of glucose feeding the formate utilization rate of the final strain reached 0.48 g/L/h, with the final titer of FFAs reached 10.1 g/L, which represented improvements of 21.8 times and 33.7 times, respectively. As such, the produced FFAs can be easily transformed into biodiesel by combining them with downstream technologies in future research. [Display omitted] [ABSTRACT FROM AUTHOR]

• A photo-enzyme nanosystem for CO 2 reduction was constructed. • In-CdS was prepared to improve its photocatalytic performance. • NADH regeneration yield of 10 %In-CdS@ZIF-8 is 94.10 %. • FDH was immobilized to produce 267.18 μM HCOOH. • 85.98% of the residual activity was retained after reusing 8 times. Replacement of fossil fuel by renewable resources is a central resource and energy efficiency strategy, where CO 2 is the key molecule to proceed effectively in this direction. Here, we synthesized In-doped CdS and constructed a new photo-enzyme nanosystem 10 %In-CdS@ZIF-8&FDH, which can catalyze CO 2 to formic acid (HCOOH) via formate dehydrogenase immobilized on ZIF-8 while photocatalytic regenerating NADH via indium-doped CdS. Indium doping greatly enhances the photocatalytic performance of CdS. The NADH regeneration rate reaches 94.10 %. The nanosystem can produce 267.18 μM HCOOH, which is 4.27 times that of the free enzyme system. And 85.98 % of the residual activity can be retained after reusing 8 times. This study will inspire more research efforts for light-driven enzymatic nanosystems in CO 2 fixation and lay the foundation for realizing renewable energy-driven CO 2 conversion to produce chemical products. [ABSTRACT FROM AUTHOR]

• Created a precise and controllable enzyme cross-linking method. • Expanded the application of microbial transglutaminase in multi-enzyme assembly. • Constructed a double enzyme system for efficient conversion of CO 2 to formic acid. • This cross-linking method hardly affects enzyme activity. • Improved thermal stability of cross-linked enzyme. Inspired by the cascades performed in vivo , the assembly of multiple enzymes in vitro has strongly moved into the focus of researchers in the field of biocatalysis. In this study, a new, mild and accurate enzyme cross-linking method is revealed. Microbial transglutaminase (MTG) acts as a "cross-linking medium" by identifying the amide group of the glutamine and the primary amine group of lysine in the artificial peptide tags specifically to form an iso-peptide bond. Here, carbonic anhydrase (CA) and formate dehydrogenase (FDH) with different peptide tags that can be recognized by MTG were linked together to obtain different proportions of cross-linked enzymes for efficient conversion of greenhouse gas carbon dioxide to formic acid. After cross-linking, we obtained "one-to-one" and "one-to-more" cross-linked enzyme aggregates. There is a minor residual loss of the two enzymes, the remaining enzyme activity of CA is more than 93%, and the remaining enzyme activity of FDH is more than 84%. In particular, the overall catalytic efficiency of the cross-linked enzyme is increased by 5.8 times compared with free enzymes and the thermal stability of FDH at different temperatures is improved. The applied strategy demonstrates the potential application of MTG in multi-enzyme assembly and synthetic biology. [ABSTRACT FROM AUTHOR]

• Highly selective production of formic acid from CO 2 is achieved. • The simultaneous encapsulation of two enzymes in ZIF-8 improved reaction efficiency. • ZIF-8 provided a large amount of loaded protein with little damage to enzyme. • Efficient in situ regeneration of NADH was achieved by visible-light irradiation. • The designed nanosystem exhibited excellent operational stability and recyclability. Natural photosynthesis plays an important role in maintaining environmental carbon balance. Taking inspiration from this, we developed a light-driven, enzymatic nanosystem for the highly selective production of formic acid from CO 2. The system combines photocatalytic graphitic carbon nitride (g-C 3 N 4) with two natural enzyme catalysts, carbonic anhydrase (CA) and formate dehydrogenase (FateDH), encapsulated in ZIF-8, a porous metal-organic framework (MOF). Efficient in situ regeneration of reduced nicotinamide adenine dinucleotide (NADH) is realized through visible-light irradiation of g-C 3 N 4 with a suitable redox potential (−0.3 V (NHE)). The introduction of ZIF-8 ensures a large amount of loaded protein with little damage to enzyme activity, and its encapsulation of CA and FateDH shortens the distance between the enzymes. This is conducive to increasing the diffusion of substances during the CO 2 -to-formic acid cascade reaction, thus improving the reaction efficiency. This work is expected to provide new insight into the design and development of highly selective, artificial photosynthesis systems to efficiently convert CO 2 into fuels, chemicals, and other materials. [ABSTRACT FROM AUTHOR]