Under the strategic goal of carbon neutrality, enhancing the carbon atom utilization efficiency of microbial cell factories has emerged as a core scientific challenge and imperative technical demand for advanced green biomanufacturing. Conventional fermentation processes possess mature industrial applicability, yet they are constrained by inevitable carbon losses via oxidative decarboxylation in central carbon metabolism. Such inherent limitation hinders fundamental improvement in substrate carbon conversion efficiency and restricts the green and high-quality advancement of the biomanufacturing industry. Multi-carbon source co-fermentation enables the rational integration of carbohydrate substrates with C1 feedstocks (formic acid, methanol, and syngas) and C2 feedstocks (acetic acid), constructing a mixotrophic metabolic system featured with carbon skeleton complementation, energy supply synergy, and intracellular redox balance. This strategy offers an innovative technological paradigm to break the theoretical carbon yield bottleneck of conventional bioprocesses. This paper systematically reviews the advances in multi-carbon source co-fermentation driven by synthetic biology. We emphatically elaborate on metabolic pathway reconstruction and regulatory mechanisms of typical co-fermentation systems consisting of organic substrates, C1/C2 compounds, and industrial waste gas. The state-of-the-art applications in synthetic fuels, bio-based materials, and high-value natural product biosynthesis are summarized. Furthermore, this paper discusses the industrial potential of this technology in integrating carbon capture and utilization and high-value biomanufacturing, aiming to provide a theoretical basis and strategic references for the innovation of efficient biomanufacturing towards carbon neutrality.

Against the backdrop of global climate change and resource scarcity, biological carbon fixation technologies driven by clean energy have emerged and attracted widespread attention. Hydrogen (H₂), as a renewable and clean energy carrier with abundant sources and easy production, can serve as both the energy and the electron donor for microbial carbon fixation. This review summarizes the metabolic foundations of hydrogen-driven carbon-fixing chassis cells represented by hydrogen-oxidizing bacteria (HOB), and highlights recent advances in several representative strains. Furthermore, engineering strategies for HOB are discussed, including the development of enabling technologies, the reconstruction and reinforcement of metabolic pathways, and microbe-material coupling approaches. Additionally, this paper analyzes the current challenges facing HOB and proposes the future perspectives. Despite existing technical bottlenecks, with the advancement of metabolic engineering and systems biology, HOB are expected to play an important role in carbon recycling and sustainable biomanufacturing.

As efficient and sustainable proteins, single-cell proteins (SCPs) demonstrate significant potential in alleviating the constraints of traditional agricultural resources and reducing the carbon footprint of food manufacturing. Low-carbon C1/C2 feedstocks, such as carbon dioxide, methanol, and acetate, offer distinct advantages, including broad availability, low costs, and minimal carbon footprints. However, the assimilation of these feedstocks and the accumulation of proteins are still limited by key bottlenecks such as poor host cell adaptability, imbalanced metabolic flux distribution, and inefficient energy supply. In recent years, remarkable progress has been achieved in the discovery, evaluation, and rational engineering of host strains for the efficient bioconversion of C1/C2 feedstocks. The application of synthetic biology, metabolic engineering, and laboratory adaptive evolution has enabled the continuous improvements of the strain tolerance to C1/C2 feedstocks, assimilation efficiency, and intracellular protein accumulation capacity. On the basis of these advancements, various SCP production processes utilizing C1/C2 feedstocks are gradually advancing toward pilot-scale and industrial applications. This review systematically summarizes the strategies for constructing chassis cells that efficiently utilize C1/C2 feedstocks, key metabolic engineering technologies driving efficient SCP production, and the current technological and industrial status of SCP production from different C1/C2 feedstocks. Furthermore, it discusses challenges related to energy efficiency, nutritional quality, safety, and downstream scale-up, aiming to provide a theoretical foundation and technical reference for the sustainable development and industrial application of SCPs produced from C1/C2 feedstocks.

With the proposal of carbon neutrality goals, microbial conversion of CO₂ into high-value chemicals, fuels, and biomaterials has emerged as an important strategy for clean energy and green manufacturing. Although single-strain carbon fixation systems have ideal controllability, they still face limitations, including heavy metabolic burden, limited carbon fixation flux, insufficient energy and reducing power supply, low yield, and challenges in industrial-scale application. In contrast, synthetic microbial consortia enable rational metabolic division of labor among functionally distinct microorganisms, thereby alleviating metabolic burden, enhancing carbon fixation efficiency, and expanding product diversity. These advantages further improve product value and promote the industrial application of CO₂ fixation. This review summarizes recent advances in the application of synthetic microbial consortia for CO₂ conversion, including photosynthesis-driven systems, hydrogen-driven systems, and potentially safer chemoautotrophic systems classified according to carbon fixation modules. In addition, this paper discusses the design principles for constructing carbon cycling systems based on synthetic microbial consortia, together with current challenges and future perspectives, providing theoretical and practical guidance for the development of efficient and stable artificial carbon cycling systems.

Methane, the second most abundant greenhouse gas after carbon dioxide, represents a critical target in climate change mitigation efforts. Owing to their unique ability to utilize methane, methanotrophs have received substantial attention in greenhouse gas mitigation and low-carbon biomanufacturing, making the understanding of their metabolic pathways and ecological functions a vibrant research area worldwide. In recent years, the rapid development of high-throughput omics technologies and the integration of multi-omics analysis have accelerated a paradigm shift in methanotroph research, enabling the deep evolution from the identification of single gene functions to the elucidation of systemic metabolic processes. This review systematically summarizes the progress in the application of genomics, transcriptomics, proteomics, and metabolomics in methanotroph research, highlighting the decisive roles of omics technologies in elucidating carbon assimilation flux distribution in aerobic methanotrophs, uncovering novel metabolic pathways of anaerobic methane oxidation, and deciphering cross-domain interactions and electron transfer mechanisms within microbial consortia. To address current bottlenecks in the industrial application of methanotrophs, including poorly understood environmental adaptation mechanisms, imbalanced metabolic flux in chassis cells, and limited gas-liquid mass transfer efficiency, this review proposes a shift from descriptive omics toward function-driven and precision-intervention research. By integrating single-cell multi-omics and artificial intelligence-enhanced modeling, future studies may construct efficient artificial methanotrophic cell factories and synthetic microbial communities, thereby providing innovative biological solutions for achieving the global carbon neutrality goal.

As an important branch of carbon capture, utilization, and storage (CCUS) technology, microbial carbon capture and utilization technology has become a vital bridge linking carbon neutrality and the sustainable bioeconomy. This paper systematically reviews the research progress in four technical pathways for converting CO₂ into starch, protein, microalgae biomass, and ethanol, and conducts carbon footprint and techno-economic analysis with ethanol as a typical case. The results indicate that the carbon reduction potential of microbial carbon capture and utilization technology depends on the supply mode of energy and value positioning of products. The in-depth integration of synthetic biology and electrocatalysis is reshaping the economic boundaries of carbon utilization. This study can provide references for technical pathway selection, research and development investment decision-making, and policy formulation.

Against the dual constraints of shrinking carbon budgets and geopolitical rivalry for resource supplies, traditional manufacturing is confronted with various bottlenecks and needs to transform into a sustainable development mode imperatively. Microbial gas fermentation adopts feedstocks including industrial off-gas, gasification syngas, and natural gas to produce diversified products such as green biofuels, fine chemicals, and microbial proteins. With the advantages of high carbon utilization efficiency, mild reaction conditions, and environmental friendliness, it plays a vital role in carbon resource recycling and emission reduction of greenhouse gases. This paper systematically reviews the research and industrial progress in microbial gas fermentation. First, the performance and limitations of three generations of biomass feedstocks are analyzed and compared, and the technical advantages of microbial gas fermentation are illustrated. Secondly, the core metabolic pathways, growth preferences, and product synthesis characteristics of different gas-fermenting microorganisms are summarized. For commercial application, this study comprehensively sorts out the technical characteristics and limiting factors of industrial gas fermentation processes including feed gas pretreatment, gas-liquid mass transfer, multistage continuous fermentation, and in-situ product recovery, as well as their impacts on the fermentation process. Meanwhile, this work reviews global and domestic industrial cases, and elaborates on the characteristics of core microbial strains, typical technical routes, and product structures of various enterprises. In addition, in view of the technical shortcomings and further development needs of industrial gas fermentation, feasible strategies are proposed, mainly including strain performance improvement, fermentation equipment upgrading, intelligent process control, and improvement of economic benefits. This review aims to provide pivotal insights into the scaled-up and industrial application of microbial gas fermentation technology.

Achieving carbon peaking and carbon neutrality is a major strategic priority for China. Third-generation biomanufacturing, which uses one-carbon (C1) compounds such as methanol, carbon dioxide, and formic acid as feedstocks for bioconversion, has attracted increasing research interest. Among these C1 feedstocks, methanol is considered a promising substrate for biomanufacturing because of its ease of storage and transportation, high degree of reduction, and potential for large-scale production via CO₂ hydrogenation. This review systematically compares natural and synthetic methanol assimilation pathways and elucidates their advantages. It further summarizes methanol metabolism in natural methylotrophic microorganisms and pathway design strategies for constructing synthetic methylotrophs, while also discussing the major challenges associated with methanol utilization. On this basis, this paper reviews recent progress in the methanol-based biosynthesis of various high-value chemicals and discusses the bottlenecks and corresponding engineering strategies for methanol bioconversion. This review provides a theoretical foundation for methanol-driven green biomanufacturing.

[Objective] To address the low yield and conversion rate in the biosynthesis of glycolic acid, we developed a whole-cell catalytic system with ethylene glycol as the substrate to obtain a strain with a high yield of glycolic acid and an efficient biosynthesis process. [Methods] With ethylene glycol as the substrate, wild-type strains were screened for their glycolic acid synthetic performance. The catalytic conditions of the optimal strain were systematically optimized to enhance the whole-cell catalytic efficiency in the production of glycolic acid. Ultraviolet mutagenesis combined with a glycolic acid biosensor-based high-throughput screening was employed to isolate high-yield strains, which were further validated in a 5-L fermenter. [Results] Pichia kudriavzevii GX-01 was successfully screened out, which could grow on glucose and produce glycolic acid from ethylene glycol via whole-cell catalysis. The whole-cell catalytic conditions were optimized by single-factor experiments as a catalytic temperature of 30 ℃, supplementation with 0.50 g MgCO₃ to adjust the system pH after 6 h of reaction, a loading volume of 50 mL in a 250-mL flask, an initial glucose concentration of 25 g/L, and an initial ethylene glycol concentration of 20 g/L. Under these conditions, the glycolic acid titer in shake flasks reached 19.30 g/L after 96 h of catalysis, and the strain showed favorable tolerance to glycolic acid. A positive mutant strain P. kudriavzevii GSUV-7 was obtained through UV mutagenesis and high-throughput screening, whose glycolic acid productivity was 2.90-fold higher than that of the original strain. In a 5-L fermenter, P. kudriavzevii GSUV-7 produced 117.60 g/L of glycolic acid after 106 h of catalysis, with a 100% conversion rate. [Conclusion] This study successfully obtains a mutant strain P. kudriavzevii GSUV-7 with a high yield of glycolic acid, providing strain resources and new insights for the research on biosynthesis of glycolic acid.