Novel combined Cre-Cas system for improved chromosome editing in Bacillus subtilis

Enhanced lignocellulose degradation in Bacillus subtilis RLI2019 through CRISPR/Cas9-mediated chromosomal integration of ternary cellulase genes

Bacillus subtilis (B. subtilis) is a crucial industrial microorganism for lignocellulose biomass degradation. However, wild-type strains from natural environments have inherent deficiencies in the composition of cellulase genes, so constructing recombinant strains through genome engineering is a generalizable strategy to overcome these shortcomings. Herein, eglS, cel48S, and bglS were integrated into the aprE, epr, and amyE loci of the B. subtilis RLI2019 chromosome, respectively, through CRISPR/Cas9-mediated genome editing, deriving the engineered strain B. subtilis AEA3. The activities of endoglucanase, exoglucanase, β-glucosidase, xylanase, and total cellulase in B. subtilis AEA3 were enhanced by 3.1-fold, 6.6-fold, 3.0-fold, 1.2-fold, and 1.8-fold, respectively, reaching 26.31 U/mL, 9.77 U/mL, 3.91 U/mL, 19.63 U/mL, and 2.42 U/mL. Notably, the engineered strain improved the saccharification efficiency of crop straws, effectively disrupting fiber structure, and significantly reducing the content of neutral and acid detergent fibers, lignocellulose and hemicellulose. In summary, this study provides a general strategy for enhancing the cellulose degradation capabilities of B. subtilis through comprehensive and systematic multi-module genetic engineering, broadening its potential application in lignocellulose biomass conversion.

Advancements in gene editing technologies for probiotic-enabled disease therapy

Probiotics typically refer to microorganisms that have been identified for their health benefits, and they are added to foods or supplements to promote the health of the host. A growing number of probiotic strains have been identified lately and developed into valuable regulatory pharmaceuticals for nutritional and medical applications. Gene editing technologies play a crucial role in addressing the need for safe and therapeutic probiotics in disease treatment. These technologies offer valuable assistance in comprehending the underlying mechanisms of probiotic bioactivity and in the development of advanced probiotics. This review aims to offer a comprehensive overview of gene editing technologies applied in the engineering of both traditional and next-generation probiotics. It further explores the potential for on-demand production of customized products derived from enhanced probiotics, with a particular emphasis on the future of gene editing in the development of live biotherapeutics.

Integration of Multiple Phage Attachment Sites System to Create the Chromosomal T7 System for Protein Production in Escherichia coli Nissle 1917

Escherichia coli Nissle 1917 (EcN) is a probiotic used to treat gastrointestinal diseases. The probiotic and endotoxin-free characteristics of EcN support its potential to be developed into a microbial expression system. With this aim, in this study, the powerful T7 expression system was constructed in the cryptic plasmid-free EcN (EcNP) to generate the T7 expression host ENL6P. The concept of multiple copies of gene expression cassettes regulated by the chromosomal T7 promoter was promoted due to plasmid instability issues with protein production in ENL6P. The integration of multiple phage attachment sites (IMPACT) system, which combined Cre-lox72, CRIM, and lambda red recombinase systems, was designed to simplify the manipulation and achieve the multiple φ80 bacterial attachment sites (attB) in ENL6P to generate the new strain ENL6PP4 with four φ80 attB sites. The strain can simultaneously integrate four copies of gene expression cassettes in the chromosome to produce recombinant proteins. The IMPACT systems incorporated several tools in gene editing to rapidly achieve more robust and stable microbial strains for research and various industrial applications.