Biosynthesis of 1,3-Propanediol via a New Pathway from Glucose in Escherichia coli

D-CAPS: an efficient CRISPR-Cas9-based phage defense system for E. coli

Escherichia coli is widely used in industrial chemical synthesis but faces significant challenges due to bacteriophage contamination, which reduces product quality and yield. Therefore, developing an efficient antiphage system is essential. In this study, we develop a CRISPR-Cas9-based antiphage system (CAPS) targeting essential genes of the T7 phage (gene 5 and gene 19) with single gRNAs transformed into MG1655 strains expressing Cas9. While CAPS provides limited resistance, with plating efficiencies ranging from 10 -5 to 10 -1, further optimization is needed. To enhance efficacy, we design a double-site-targeting CRISPR-Cas9-based antiphage system (D-CAPS). D-CAPS demonstrates complete resistance, with no plaques observed even at a high multiplicity of infection (MOI of 2), and growth curve analysis reveals that antiphage E. coli strains grow normally, similar to the wild-type strain, even at a high multiplicity of infection. Furthermore, D-CAPS is effective against BL21(DE3) strains, showing strong resistance and demonstrating its versatility across different E . coli strains. Protein expression analysis via green fluorescent protein confirms that E. coli carrying D-CAPS could maintain normal protein expression levels even in the presence of phages, comparable to wild-type strains. Overall, D-CAPS offers a robust and versatile approach to enhancing E. coli resistance to phages, providing a practical solution for protecting industrial E. coli strains and improving fermentation processes.

Quantitative Characterization of Gene Regulatory Circuits Associated With Fungal Secondary Metabolism to Discover Novel Natural Products

Microbial genetic circuits are vital for regulating gene expression and synthesizing bioactive compounds. However, assessing their strength and timing, especially in multicellular fungi, remains challenging. Here, an advanced microfluidic platform is combined with a mathematical model enabling precise characterization of fungal gene regulatory circuits (GRCs) at the single-cell level. Utilizing this platform, the expression intensity and timing of 30 transcription factor-promoter combinations derived from two representative fungal GRCs, using the model fungus Aspergillus nidulans are determined. As a proof of concept, the selected GRC combination is utilized to successfully refactor the biosynthetic pathways of bioactive molecules, precisely control their production, and activate the expression of the silenced biosynthetic gene clusters (BGCs). This study provides insights into microbial gene regulation and highlights the potential of platform in fungal synthetic biology applications and the discovery of novel natural products.

Advances in biosynthesis and downstream processing of diols

Diols are important platform chemicals with a wide range of applications in the fields of chemical and pharmaceutical industries, food, feed and cosmetics. In particular, 1,3-propanediol (PDO), 1,4-butanediol (1,4-BDO) and 1,3-butanediol (1,3-BDO) are appealing monomers for producing industrially important polymers and plastics. Therefore, the commercialization of bio-based diols is highly important for supporting the growth of biomanufacturing for the fiber industry. This review focuses primarily on the microbial production of PDO, 1,4-BDO and 1,3-BDO with respect to different microbial strains and biological routes. In addition, metabolic platforms which are designed to produce various diols using generic bioconversion strategies are reviewed for the first time. Finally, we also summarize and discuss recent developments in the downstream processing of PDO according to their advantages and drawbacks, which is taken as an example to present the prospects and challenges for industrial separation and purification of diols from microbial fermentation broth.

ASIA: An automated stress-inducible adaptor for enhanced stress protein expression in engineered Escherichia coli

Orthogonal T7 RNA polymerase (T7RNAP) and T7 promoter is a potent technique for protein expression in broad cells, but the energy requirements associated with this method impede the growth, leading to cell lysis when dealing with toxic and stress proteins. A Lemo21(DE3) strain denoted as L21 offers a solution by fine-tuning T7RNAP levels under rhamnose to induce T7 lysozyme (LysY) and enhance the protein production, but it requires optimization of inducer concentration, cultural temperature, and condition, even the types of carbon sources. Herein, we construct an automated stress-inducible adaptor (ASIA) employing different stress-inducible promoters from Escherichia coli. The ASIA system is designed to automatically regulate LysY expression in response to stress signals, thereby suppressing T7RNAP and amplifying the overexpression of stress protein cutinase ICCM. This approach fine-tunes T7RNAP levels and outperforms L21 in various temperatures and carbon source conditions. The ASIAhtp strain maintains ICCM yield at 91.6 mg/g-DCW even in the limiting carbon source at 1 g/L, which is 12-fold higher in protein productivity compared to using L21. ASIA as a versatile and robust tool for enhancing overexpression of stress proteins in E. coli is expected to address more difficult proteins in the future.