Core Viewpoint - The article discusses the advancements in the production of 1,3-propanediol (1,3-PDO) using engineered strains of Klebsiella pneumoniae, highlighting significant improvements in yield and efficiency through metabolic engineering and strain evolution [2][20][23]. Summary by Sections 1. Production Methodology - 1,3-PDO is a high-value fine chemical used in cosmetics, pharmaceuticals, and plastics, traditionally produced through chemical synthesis, which involves toxic substances and high pressure. Microbial fermentation has emerged as a more economical and environmentally friendly production method [2]. - The research team led by Professor Liu Liming achieved a production yield of 138.6 g/L of 1,3-PDO using the engineered strain FMME-51, with a conversion rate of 0.52 g/g, without the need for additional VB12 [2][20]. 2. Strain Optimization - Initial strain FMME-01 produced 67.2 g/L of 1,3-PDO but generated multiple by-products that reduced yield. Subsequent modifications led to strain FMME-14, which showed improved production performance [6]. - Further optimization of the cell membrane composition in strain FMME-38 resulted in a 62.5% increase in tolerance to high 1,3-PDO concentrations and a 41.2% reduction in cell death [9][10]. 3. Enhancements in Co-Factor Synthesis - The production process relies on VB12 and NADH. The integration of genes responsible for VB12 synthesis into the genome of strain FMME-48 resulted in a VB12 concentration of 50.8 μg/L and a 1,3-PDO yield of 118.3 g/L [14]. - The dynamic regulation of NADH levels was achieved through the construction of a biosensor-based system, enhancing the NADH/NAD⁺ ratio by 31.3% in strain FMME-51, leading to a 12.3% increase in 1,3-PDO yield [18][14]. 4. Process Optimization - The optimization of glycerol feeding rates and pH levels significantly improved the production performance of strain FMME-51, achieving a 1,3-PDO yield of 135.9 g/L at a pH of 6.8 [19]. - The final optimized strain FMME-51 demonstrated a production capacity of 122.7 g/L of 1,3-PDO using low-cost crude glycerol as a substrate, showcasing its industrial potential [20][23]. 5. Industrial Implications - The research indicates a significant advancement in the bioproduction of 1,3-PDO, achieving unprecedented yields and efficiencies while eliminating the need for expensive co-factors, thus reducing production costs [20][23]. - The ability of engineered strain FMME-51 to efficiently utilize crude glycerol highlights its potential for large-scale industrial applications in the production of high-value chemicals [23].

Core Viewpoint - O-acetyl-L-homoserine (OAH) is a significant platform compound for producing L-methionine and other valuable chemicals, with recent advancements in sustainable production methods using E. coli, achieving a record yield of 94.1 g/L through innovative metabolic engineering strategies [1][16]. Group 1: Research Content and Key Technical Breakthroughs - The team enhanced OAH production by integrating a dual-module approach with L-homoserine and MetX, increasing initial yield from 5.29 g/L to 8.30 g/L, a 56.9% improvement [3]. - A dynamic regulation strategy for acetyl-CoA was developed, leading to an OAH yield of 11.59 g/L by optimizing multiple pathways and reducing competition [4]. - The use of sRNA for identifying rate-limiting steps in OAH synthesis revealed four critical areas for optimization, including precursor carbon flux distribution and amino supply [7]. - A multi-node fine-tuning approach led to a series of yield improvements, with the final strain OAH33 achieving 19.40 g/L by addressing nutrient deficiencies and optimizing metabolic pathways [12]. Group 2: Production Optimization Techniques - The innovative two-stage pH control in a 5 L bioreactor allowed for the efficient synthesis of OAH, achieving a yield of 94.1 g/L within 68.7 hours, enhancing production by 15.5%-37.3% compared to single pH control [16]. - The research demonstrated that the combination of ATP turnover enhancement and metabolic pathway optimization significantly improved OAH production, with the final strain OAH37 achieving a yield of 20.08 g/L, a 137% increase from the initial strain [14]. Group 3: Future Research and Development - The findings from this research are set to be published in "Metabolic Engineering" in July 2025, indicating ongoing advancements in the field of synthetic biology and metabolic engineering [17].