Base editor-mediated large-scale screening of functional mutations in bacteria for industrial phenotypes.

Base editing, the targeted introduction of point mutations into cellular DNA, holds promise for improving genome-scale functional genome screening to single-nucleotide resolution. Current efforts in prokaryotes, however, remain confined to loss-of-function screens using the premature stop codons-mediated gene inactivation library, which falls far short of fully releasing the potential of base editors. Here, we developed a base editor-mediated functional single nucleotide variant screening pipeline in Escherichia coli.

CRISPRi-microfluidics screening enables genome-scale target identification for high-titer protein production and secretion.

Genome-scale target identification promises to guide microbial cell factory engineering for higher-titer production of biomolecules such as recombinant proteins (r-protein), but challenges remain due to the need not only for comprehensive genotypic perturbation but also in conjunction with high-throughput phenotypic screening strategies. Here, we developed a CRISPRi-microfluidics screening platform to systematically identify crucial gene targets that can be engineered to enhance r-protein secretion in Corynebacterium glutamicum. We created a CRISPR interference (CRISPRi) library containing 46,549 single-guide RNAs, where we aimed to unbiasedly target all genes for repression.

A versatile toolbox for CRISPR-based genome engineering in Pichia pastoris.

Pichia pastoris has gained much attention as a popular microbial cell factory for the production of recombinant proteins and high-value chemicals from laboratory to industrial scale. However, the lack of convenient and efficient genome engineering tools has impeded further applications of Pichia pastoris towards metabolic engineering and synthetic biology. Here, we report a CRISPR-based toolbox for gene editing and transcriptional regulation in P.

New Method for Genome-Scale Functional Genomic Study in Bacteria with Superior Performance: CRISPR Interference Screen.

High-throughput genetic screens based on CRISPR/Cas9 technology are powerful tools to genome-wide identify gene function and genotype-phenotype association. Here, we describe a detailed protocol for conducting and evaluating pooled CRISPR screens interfering with gene expression in Escherichia coli. We provide step-by-step instructions for guide RNA library design and construction, genome-scale screening and next-generation sequencing data processing.

[Functional discovery and production technology for natural bioactive peptides].

Bioactive peptides play important roles in promoting human health, such as lowering blood pressure, blood sugar and blood lipid, anti-obesity, and anti-cancer. Thus, exploring functional bioactive peptides and developing efficient production technologies are of crucial importance. Herein, we review the development of function discovery and production technology for natural bioactive peptides.

Overexpression of the regulatory subunit of protein kinase A increases heterologous protein expression in Pichia pastoris.

Objective: Translational regulation plays an important role in protein synthesis. Our goal was to screen translation-related factors to improve heterologous protein expression in Pichia pastoris.

Results: Twenty-eight translation-related factors were overexpressed in P.

Enhancing the substrate tolerance of DszC by a combination of alanine scanning and site-directed saturation mutagenesis.

The biodesulfurization 4S pathway can specifically desulfurize an aromatic S heterocyclic compound (which is difficult to desulfurize by hydrodesulfurization) and maintain the integrity of its combustion value. The four Dsz enzymes in the pathway convert the model compound dibenzothiophene (DBT) into the sulfur-free compound 2-hydroxybiphenyl (HBP). DszC is the first enzyme in the 4S pathway and is subject to feedback inhibition and substrate inhibition.

A kinetic model to optimize and direct the dose ratio of Dsz enzymes in the 4S desulfurization pathway in vitro and in vivo.

Objective: To enhance the biodesulfurization rate using a kinetic model that directs the ratio of Dsz enzymes.

Results: This study established a kinetic model that predicted the optimal ratio of Dsz enzymes in the 4S biodesulfurization system to be A:B:C = 1:2:4 and 1:4:2. When BCAD+1A+4B+2C, the conversion rate of dibenzothiophene (DBT) to 2-hydroxybiphenyl (HBP) was close to 100% in vitro.

Improved Efficiency of the Desulfurization of Oil Sulfur Compounds in Escherichia coli Using a Combination of Desensitization Engineering and DszC Overexpression.

The 4S pathway of biodesulfurization, which can specifically desulfurize aromatic S-heterocyclic compounds without destroying their combustion value, is a low-cost and environmentally friendly technology that is complementary to hydrodesulfurization. The four Dsz enzymes convert the model compound dibenzothiophene (DBT) into the sulfur-free compound 2-hydroxybiphenyl (HBP). Of these four enzymes, DszC, the first enzyme in the 4S pathway, is the most severely affected by the feedback inhibition caused by HBP.

Enhancing co-translational folding of heterologous protein by deleting non-essential ribosomal proteins in .

Background: Translational regulation played an important role in the correct folding of heterologous proteins to form bioactive conformations during biogenesis. Translational pausing coordinates protein translation and co-translational folding. Decelerating translation elongation speed has been shown to improve the soluble protein yield when expressing heterologous proteins in industrial expression hosts.

Recycling of a selectable marker with a self-excisable plasmid in Pichia pastoris.

Pichia pastoris is a widely used heterologous protein production workhorse. However, with its multiple genetic modifications to solve bottlenecks for heterologous protein productivity, P. pastoris lacks selectable markers.

Combined strategies for improving expression of Citrobacter amalonaticus phytase in Pichia pastoris.

Background: Phytase is used as an animal feed additive that degrades phytic acid and reduces feeding costs and pollution caused by fecal excretion of phosphorus. Some phytases have been expressed in Pichia pastoris, among which the phytase from Citrobacter amalonaticus CGMCC 1696 had high specific activity (3548 U/mg). Improvement of the phytase expression level will contribute to facilitate its industrial applications.