A Method for Rapid Screening, Expression, and Purification of Antimicrobial Peptides

Fusion Partner Facilitates Expression of Cell-Penetrating Peptide L2 in Pichia pastoris

BACKGROUND

L2 is formed by combining the pheromone of Streptococcus agalactiae (S. agalactiae) and a cell-penetrating peptide (CPP) with cell-penetrating selectivity. L2 has more significant penetration and better specificity for killing S. agalactiae. However, the production of AMPs by chemical synthesis is always a challenge because of the production cost.

METHODS

This study was devoted to the heterologous expression of the cell-penetrating peptide L2 in Pichia pastoris using SUMO and a short acidic fusion tag as fusion partners, and the high-density expression of SUMO-L2 was achieved in a 5 L fermenter.

RESULTS

The results showed that SUMO-L2 expression in the 5 L fermenter reached 629 mg/L. The antibacterial activity of recombinant L2 was examined; the minimum inhibitory concentration (MICs) and minimum bactericidal concentration (MBCs) of purified L2 were 4-8 μg/mL and 8-16 μg/mL against S. agalactiae after 84 h of lysis with 50% formic acid.

CONCLUSIONS

The findings suggest that SUMO is a suitable fusion tag to express cell-penetrating peptide L2.

Cleaving the way for heterologous peptide production: An overview of cleavage strategies

One of the main bottlenecks for recombinant peptide production is choosing the proper cleavage method to remove fusion protein tags from target peptides. While these tags are crucial for inhibiting the activity of the target peptide during heterologous expression, incorporating a cleavage site is essential for their later removal, ensuring the pure sequencing of the peptide. This review evaluates different cleavage methods, including protease-mediated, self-cleavable protein, and chemical-mediated sites, regarding their advantages and limitations. For instance, intein, Npro EDDIE, enterokinase, factor Xa, SUMO, and CNBr are options for residue-free cleavage. Although protease-mediated cleavage is widely used, it can be expensive, due to its own cost added to the whole process. As an alternative, self-cleavable sites eliminate the requirement for proteinases. Another crucial step in defining the proper cleavage method is cost consideration, which relates to the purpose of peptide production. Here, we explore a range of cleavage approaches, meeting the needs of both cost-constrained applications and a more flexible budget. Overall, selecting the most suitable cleavage method should be based on careful consideration of toxicity, cost, accuracy, and specific application requirements to ensure a state-of-the-art approach.

Antimicrobial Peptides: Mechanism, Expressions, and Optimization Strategies

Antimicrobial peptides (AMPs) are favoured because of their broad-spectrum antimicrobial properties and because they do not easily develop microbial resistance. However, the low yield and difficult extraction processes of AMPs have become bottlenecks in large-scale industrial applications and scientific research. Microbial recombinant production may be the most economical and effective method of obtaining AMPs in large quantities. In this paper, we review the mechanism, summarize the current status of microbial recombinant production, and focus on strategies to improve the yield and activity of AMPs, in order to provide a reference for their large-scale production.

Putative Role of Anti-microbial Peptide Recovered from Lactiplantibacillus spp. in Biocontrol Activity

Antimicrobial peptides (AMPs) stand as a promising alternative to conventional pesticides, leveraging a multifaceted approach to combat plant pathogens. This study focuses on identifying and characterizing the AMP produced by Lactiplantibacillus argentoratensis strain IT, demonstrating potent antibacterial activity against various harmful microorganisms. Evaluation of AMPs' antibacterial activity was conducted through an agar well diffusion assay, a reliable method for assessing secondary metabolite antimicrobial efficacy. The study unveils the antimicrobial potential of the purified extract obtained from Lactiplantibacillus argentoratensis IT, isolated from goat milk. Notably, the AMP exhibited robust antibacterial activity against phytopathogens affecting solanaceous crops, including the Gram-negative Ralstonia solanacearum. Expression conditions and purification methods were optimized to identify the peptide's mass and sequence, utilizing LC-MS and SDS-PAGE. This paper underscores the application potential of Lactiplantibacillus spp. IT as a biocontrol agent for managing bacterial infectious diseases in plants. Results indicate optimal AMP production at 37 °C, with a culture broth pH of 5 during fermentation. The obtained peptide sequence corresponded to peaks at 842.5 and 2866.4 m/z ratio, with a molecular weight of approximately 5 kDa according to tricine SDS-PAGE analysis. In conclusion, this study lays the foundation for utilizing Lactiplantibacillus spp. IT derived AMPs in plant biocontrol strategies, showcasing their efficacy against bacterial phytopathogens. These findings contribute valuable insights for advancing sustainable agricultural practices.

Extracellular production of Ulp1403-621 in leaky E. coli and its application in antimicrobial peptide production

Small ubiquitin-like modifier (SUMO) tag is widely used to promote soluble expression of exogenous proteins, which can then be cleaved by ubiquitin-like protease 1 (Ulp1) to obtain interested protein. But the application of Ulp1 in large-scale recombinant protein production is limited by complicated purification procedures and high cost. In this study, we describe an efficient and simple method of extracellular production of Ulp1_403-621 using a leaky Escherichia coli BL21(DE3), engineered by deleting the peptidoglycan-associated outer membrane lipoprotein (pal) gene. Ulp1_403-621 was successfully leaked into extracellular supernatant by the BL21(DE3)-Δpal strain after IPTG induction. The addition of 1% glycine increased the extracellular production of Ulp1_403-621 approximately four fold. Moreover, extracellular Ulp1_403-621 without purification had high activities for cleaving SUMO fusion proteins, and antimicrobial peptide pBD2 obtained after cleavage can inhibit the growth of Staphylococcus aureus. The specific activity of extracellular Ulp1_403-621 containing 1 mM EDTA and 8 mM DTT reached 2.0 × 10⁶ U/L. Another commonly used protease, human rhinovirus 3C protease, was also successfully secreted by leaky E. coli strains. In conclusion, extracellular production of tool enzymes is an attractive way for producing large-scale active recombinant proteins at a lower cost for pharmaceutical, industrial, and biotechnological applications. KEY POINTS: • First report of extracellular production of Ulp1_403-621 in leaky Escherichia coli BL21(DE3) strain. • One percent glycine addition into cultivation medium increased the extracellular production of Ulp1_403-621 approximately four fold. • The specific activity of extracellular Ulp1_403-621 produced in this study reached 2.0 × 10⁶ U/L.

Two Foreign Antimicrobial Peptides Expressed in the Chloroplast of Porphyridium purpureum Possessed Antibacterial Properties

To solve the problem of antibiotic abuse in aquaculture and to utilize the application potential of antimicrobial peptides (AMPs), a chloroplast transformation system of Porphyridium purpureum was successfully constructed for effectively expressing two exogenous AMPs. The endogenous fragments of 16S rDNA/trnA-23S rDNA were used as flanking fragments for the homologous recombination in the chloroplast genome. Two AMPs encoded by the transformation vector were controlled by the native promoter psbB in a polycistron. The plasmids were transferred into P. purpureum via particle bombardment and the transformation vectors were screened using phosphinothricin (bar), a dominant selection marker under the control of the psbA promoter. Subsequently, in the positive transformed colonies, the exogenous fragments were found to be inserted in the flanking fragments directionally as expected and two foreign AMPs were successfully obtained. Finally, two exogenous peptides with antibacterial properties were obtained from the transformed strain. The two AMPs expressed by the transformed strain were shown to have similar inhibitory effects to antibiotics by inhibition tests. This suggested that AMPs can be introduced into aquaculture using baited microalgae, providing new ideas and ways to solve a series of aquaculture diseases caused by bacteria.

In situ synthesis of TiO2/NC on cotton fibers with antibacterial properties and recyclable photocatalytic degradation of dyes

A cotton fabric/titanium dioxide-nanocellulose (TiO2-Cot.) flexible and recyclable composite material with highly photocatalytic degradation of dyes and antibacterial properties was synthesized. During the preparation process, nano-TiO2 particles were synthesized through an in situ strategy and grown on cotton fiber, and were wrapped with cellulose nanocrystals (NC). The prepared TiO2-Cot. was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The SEM and EDS results showed that nano-TiO2 particles were evenly distributed on the fiber surface. The prepared TiO2@Cot. has excellent photocatalytic efficiency of 95.68% for MB and 92.77% for AR under weak ultraviolet irradiation over 6 h. At the same time, it has excellent antibacterial activity against S. aureus and E. coli. The stability and reusability of the materials were also investigated.