Carbon-negative bio-production of short-chain carboxylic acids (SCCAs) from syngas via the sequential two-stage bioprocess by Moorella thermoacetica and metabolically engineered Escherichia coli

Economic and sustainable revolution to facilitate one-carbon biomanufacturing

One-carbon (C1) biomanufacturing serves as a substitute for fossil-based feedstocks, aiming to de-fossilize chemical production and foster a circular carbon economy by recycling waste greenhouse gases. Here, we review the key economic and technical barriers associated with the commercialization of C1 biomanufacturing through case studies. Additionally, a viable roadmap to enhance cost competitiveness is unveiled, underscoring its potential to facilitate carbon neutrality as scalable and sustainable alternatives to traditional chemical production.

High-Yield Biosynthesis of 3-Hydroxypropionic Acid from Acetate in Metabolically Engineered Escherichia coli

The third-generation biorefineries aimed at "carbon-negative" production of fuels and chemicals utilizing one-carbon molecules and renewable energy sources were raised to tackle the pressing climate change and food scarcity issues. Acetate derived from syngas fermentation, a viable nonfood carbon source, has recently been elevated in bulk chemicals biosynthesis. In this study, we successfully engineered Escherichia coli to produce 3-hydroxypropionic acid (3-HP) from acetate via the malonyl-CoA pathway. Initially, the constitutive promoter of the 3-HP biosynthetic pathway for efficient 3-HP production was screened in acetate-based medium. Then, efforts were focused on reducing the competition for malonyl-CoA by inhibiting the fatty acids (FAs) synthesis pathway. Furthermore, we enhanced the supply of NADPH and acetyl-CoA through cofactor engineering. The engineered strain ZWR18(M*DA) accumulated 5.53 g/L 3-HP, corresponding to a yield of 0.732 g/g, and achieved 97.60% of the theoretical yield. In whole-cell catalysis, ZWR18(M*DA) produced 23.89 g/L 3-HP with a yield of 0.734 g/g, reaching 97.87% of the theoretical yield. Utilizing syngas-derived acetate for whole-cell catalysis allowed ZWR18(M*DA) to accumulate 18.87 g/L 3-HP with a yield of 0.58 g/g. These results indicate that acetate from syngas can serve as a cost-effective and environmentally friendly alternative to traditional carbon sources, offering a sustainable biorefinery pathway for industrial biomanufacturing.

Improved biosynthesis of C4 derivatives by engineered thiolase

Ethylene glycol (EG), a major product of the enzymatic degradation of polyethylene terephthalate (PET), provides a promising feedstock for sustainable biomanufacturing. Herein, we developed a novel metabolic pathway using Escherichia coli(E. coli) as a host for the biosynthesis of four-carbon compounds such as 1,4-butanediol (1,4-BDO), 1,2,4-butanetriol (1,2,4-BTO), and succinate, from two-carbon substrates such as glycolate and EG. This represents an efficient strategy of using C2 precursors for these high-value chemicals. Through directed evolution of the β-ketoacyl thiolase B of Cupriavidus necator (CnBktB), one of the rate-limiting enzymes in the pathway, via an established growth-coupled screening platform, we identified the L89S mutant, which exhibits significantly enhanced catalytic efficiency in assimilating glycolyl-CoA and acetyl-CoA. Using glycolate and glucose as substrates, the route achieves production titers of >200 mg/L for 1,4-BDO, 266 mg/L for 1,2,4-BTO, and 9.22 g/L for succinate. Furthermore, integrating an upstream module for EG conversion to glycolate allows direct utilization of PET-derived EG, yielding 11.4 g/L succinate with 93 % conversion efficiency from EG. This work bridges the fields of synthetic biology and plastic waste recycling, demonstrating a sustainable and scalable route for converting PET-derived EG into valuable four-carbon compounds. The novel biosynthetic pathways developed in this study offer a foundation for advancing circular bioeconomy strategies and reducing the environmental impact of plastic waste.