Genome Engineering Platform for Highly Efficient and Low-Toxicity Multiplex Editing in Clostridium Species

Background

The field of microbial biofuel production, particularly butanol fermentation, has garnered significant attention due to the urgent need for sustainable and renewable energy sources. Butanol is considered a superior biofuel compared to ethanol because of its higher energy content, lower volatility, and compatibility with existing fuel infrastructure. Traditionally, butanol is produced via the acetone-butanol-ethanol (ABE) fermentation pathway using Clostridium species. However, the economic feasibility of this process is hampered by low product yields, the accumulation of unwanted byproducts, and the metabolic limitations of wild-type strains. As global energy demands rise and environmental concerns intensify, there is a pressing need for advanced genetic engineering tools that can optimize microbial metabolism for higher butanol yields and reduced byproduct formation.

Despite advances in genome editing technologies, current approaches to engineering Clostridium species remain fraught with challenges. Conventional methods, such as chemical mutagenesis or homologous recombination, are inefficient and labor-intensive, offering limited precision and scalability. The adoption of heterologous CRISPR-Cas9 or Cpf1 systems has been explored to improve gene editing efficiency, but these systems often introduce significant toxicity to Clostridium cells, drastically reducing transformation efficiency and cell viability. Furthermore, the anaerobic and spore-forming nature of Clostridia complicates both genetic manipulation and strain recovery. These limitations have stymied efforts to achieve high-yield, industrial-scale butanol production, highlighting the critical need for safer, more efficient, and species-compatible genome engineering platforms.

Technology

This engineered bacterial strain allows enhanced butanol production. The platform facilitates the replacement of the butyrate production gene (cat1) with an alcohol dehydrogenase gene (adhE1 or adhE2), redirecting the metabolic pathway toward butanol synthesis. Engineered strains using this approach have demonstrated record butanol yields of 26.2 g/L in batch fermentation, with minimal byproduct formation and no acetone, simplifying downstream processing. The gene-editing technology used to engineer this strain is adaptable, supporting markerless genome edits and precise control over CRISPR activity through inducible promoters, and is compatible with both single and multiplex gene modifications. It enables the rapid development of industrial strains with superior butanol yields, positioning the technology as a leading solution for renewable biofuel production.

Benefits

• Significantly enhances bacterial-based butanol production yield to a record 26.2 g/L with minimal byproducts, improving economic viability
• Reduces formation of unwanted byproducts such as acetone, simplifying downstream processing
• Offers a scalable and environmentally friendly alternative to traditional chemical synthesis of butanol
• Provides a versatile platform potentially adaptable to other Clostridium species and industrial bioproducts

Applications

• High-yield renewable butanol production
• Low-toxicity industrial strain engineering
• Markerless gene deletions for bioprocessing

Additional info

Engineering of clostridium for enhanced butanol production has been performed, replacing the *cat1* gene with *adhE* genes, resulting in a bacterial strain that can yield up to 26.2 g/L butanol per batch fermentation with minimal byproducts. Higher yields are possible with further optimization. Issued US patents cover the strain and engineering tools.