Core Viewpoint - Lignocellulosic biomass, a renewable organic resource, can be efficiently converted into fermentable sugars using engineered strains of Clostridium thermocellum through consolidated bioprocessing (CBP) and consolidated bioconversion (CBS) strategies, which significantly reduce costs and enhance economic feasibility [2][3]. Group 1: Engineering Strains Development - The research team at Qingdao Energy Institute introduced an exogenous β-glucosidase (CaBglA) into Clostridium thermocellum to address feedback inhibition from cellobiose, resulting in the development of a third-generation CBS strain that significantly improved cellulose saccharification performance [3]. - The fourth-generation CBS strain, GB2, was constructed by integrating the CaBglA gene into the genome, achieving a cellulose-glucose conversion rate of up to 94% without relying on antibiotics, demonstrating stable and efficient cellulose degradation capabilities [4]. - Further enhancements were made by introducing a bifunctional xylanase/xylosidase (CcXyl0074) from Clostridium clariflavum into GB2, which improved the hemicellulose degradation ability of Clostridium thermocellum [4]. Group 2: Performance and Cost Efficiency - The engineered strain expressing CcXyl0074 was able to convert 84% of xylan into xylose within three days while maintaining high cellulose conversion efficiency, indicating a significant enhancement in hemicellulose degradation [4]. - The integration of both CcXyl0074 and CaBGL into the genome resulted in the GBX1 strain, which exhibited a 1.5 times higher maximum saccharification rate compared to GB2, showcasing synergistic degradation of cellulose and hemicellulose components [4]. - Optimization of the saccharification medium formulation led to an 87.3% reduction in cultivation costs, further improving the technical and economic viability of the CBS process [4]. Group 3: Research Contributions and Recognition - The research findings were published in the journal Bioresource Technology, with significant contributions from doctoral and master's students, as well as researchers from the Japan International Research Center for Agricultural Sciences [6]. - A patent application has been filed for the engineered strain expressing bifunctional enzymes, indicating the potential for commercialization and industrial application of the developed technology [6].

Core Viewpoint - The article discusses the advancements in third-generation biorefining technology that utilizes one-carbon (C1) resources, such as CO2, to produce biofuels and chemicals, contributing to carbon capture and utilization, and supporting carbon neutrality goals [1][3][9]. Summary by Sections 1. Development of Biorefining Technology - The oil crisis in the 1970s spurred research and industrialization of biofuels, leading to the introduction of biorefining concepts in the 1980s [7]. - The first-generation biorefining technology, using food crops, faced challenges related to resource efficiency and competition with food production [8]. - The second-generation technology, based on lignocellulosic biomass, has potential but is hindered by high costs and technical barriers [8]. 2. Third-Generation Biorefining Technology - Third-generation biorefining aims to convert CO2 and renewable energy sources into fuels and chemicals, overcoming limitations of previous technologies [9]. - This technology has shown significant progress, with over 10 carbon fixation pathways validated, and some CO2 fixation technologies have reached commercialization [4][9]. - Examples include projects that convert industrial emissions into bioethanol, significantly reducing CO2 emissions [4]. 3. Carbon Fixation Pathways - More than 10 carbon fixation pathways have been identified, including natural pathways like the Calvin cycle and engineered pathways [11][36]. - The article details various pathways, such as the Wood-Ljungdahl pathway and reductive TCA cycle, highlighting their unique characteristics and potential for industrial application [16][33]. 4. Engineering of Carbon Fixation - Key factors influencing carbon fixation efficiency include energy sources, substrate types, and enzyme characteristics [36]. - Engineering efforts focus on optimizing microbial strains for better CO2 utilization and product yield, with examples of successful modifications in various microorganisms [38]. 5. Commercialization and Future Prospects - The commercialization of third-generation biorefining technologies is underway, with successful projects demonstrating the feasibility of using CO2 as a raw material [4][9]. - Future developments are expected to enhance the efficiency and cost-effectiveness of these technologies, contributing to sustainable bio-manufacturing [9][36].