The ever-increasing global energy demand, juxtaposed with critical concerns about greenhouse gas emissions, emphatically underscores the urgency to pivot toward sustainable and eco-friendly energy alternatives. Tapping into microbial metabolism for clean energy generation stands out as a particularly promising avenue in this endeavor. Given this backdrop, we delved deeply into the metabolic engineering potential of Saccharomyces cerevisiae, thereby aiming for the bioconversion of formate and acetate—both CO₂ derivatives—into free fatty acids (FFAs) as precursors for biofuel production. Our study not only elucidated the metabolic pathways within S. cerevisiae that are tailored for efficient formate and acetate utilization but also shone a light on the meticulous optimization strategies that amplify FFA synthesis. The engineered strains, under refined conditions, exhibited up to an 8-fold increase in an FFA titer, thus reaching a production level of 6.6 g/L, which showcases the potential of microbial metabolism in clean energy generation. Our findings offer a promising step toward harnessing microbial metabolism for sustainable energy production, thereby bridging the gap between waste carbon utilization and greener fuel alternatives.

β-Farnesene is an advanced molecule with promising applications in agriculture, the cosmetics industry, pharmaceuticals, and bioenergy. To supplement the shortcomings of rational design in the development of high-producing β-farnesene strains, a Metabolic Pathway Design-Fermentation Test-Metabolomic Analysis-Target Mining experimental cycle was designed. In this study, by over-adding 20 different amino acids/nucleobases to induce fluctuations in the production of β-farnesene, the changes in intracellular metabolites in the β-farnesene titer-increased group were analyzed using non-targeted metabolomics. Differential metabolites that were detected in each experimental group were selected, and their metabolic pathways were located. Based on these differential metabolites, targeted strain gene editing and culture medium optimization were performed. The overexpression of the coenzyme A synthesis-related gene pantothenate kinase (PanK) and the addition of four mixed water-soluble vitamins in the culture medium increased the β-farnesene titer in the shake flask to 1054.8 mg/L, a 48.5% increase from the initial strain. In the subsequent fed-batch fermentation, the β-farnesene titer further reached 24.6 g/L. This work demonstrates the tremendous application value of metabolomics analysis for the development of industrial recombinant strains and the optimization of fermentation conditions.

Longifolene is a sesquiterpene commonly found in the heavy turpentine oil of pine plants, with various applications ranging from pest control and fragrance production to synthetic biofuels. While S. cerevisiae cell factories can effectively accumulate longifolene, further optimization and refinement of the metabolic modifications are still needed to improve the yield and conversion efficiency of longifolene production. In this study, we first explored enzyme fusion technology to enhance the efficiency of longifolene synthase catalysis, and improved acetyl-CoA availability by adjusting the pyruvate bypass pathway and introducing the synthetic chimeric citrate lyase pathway. The introduction of the formate dehydrogenase module was also used to supplement reducing power. By combining these strategies, the yield of longifolene reached 78.637 mg/L in shake flasks and 2063.7 mg/L in a 5 L bioreactor through fed-batch cultivation. This is the highest reported yield of longifolene to date. This study has important fundamental significance for the construction of biosynthetic factories for longifolene and other terpenes.

Methylparaben (MP) is an important member of the paraben family of aromatic compounds, which is under great demand in the industrial market as an antibacterial agent, preservative, and feed additive, and also has potential application value in the preparation of bio-based polyetherester materials. However, the current chemical production method of MP has various problems, such as serious environmental pollution, its dependence on petrochemical resources, and the generation of different types of waste. It is of great significance to develop an environmentally friendly MP synthesis method via synthetic biology. In this work, Saccharomyces cerevisiae was used as the host to construct the biosynthetic pathway of MP and various metabolic engineering strategies were applied to break the bottlenecks in the synthesis process, including the regulation of the rate-limiting steps in the endogenous shikimate pathway, the enhancement of central carbon flux via knocking out competitive pathways and promoting precursors synthesis, and the improvement of the exogenous enzyme expression using promoter engineering. The final engineered S. cerevisiae could produce 68.59 mg/L MP in shake flasks, which was the highest titer of MP synthesized by S. cerevisiae so far. It was indicated that the strategies applied in our work were effective in promoting the synthesis of MP, which not only laid an important foundation for the industrial production of MP, but also provided a platform for the synthesis of other aromatic compounds.