Recombinant expression, purification and antimicrobial activity of a novel antimicrobial peptide PaDef in Pichia pastoris

Revolutionizing agroindustry: Towards the industrial application of antimicrobial peptides against pathogens and pests

Antibiotics are essential chemicals for medicine and agritech. However, all antibiotics are small molecules that pathogens evolve antimicrobial resistance (AMR). Alternatively, antimicrobial peptides (AMPs) offer potential to overcome or evade AMR. AMPs provide broad-spectrum activity, favourable biosafety profiles, and a rapid and efficient mechanism of action with low resistance incidence. These properties have driven innovative applications, positioning AMPs as promising contributors to advancements in various industrial sectors. This review evaluates the multifaceted nature of AMPs and their biotechnological applications in underexplored sectors. In the food industry, the application of AMPs helps to suppress the growth of microorganisms, thereby decreasing foodborne illnesses, minimizing food waste, and prolonging the shelf life of products. In animal husbandry and aquaculture, incorporating AMPs into the diet reduces the load of pathogenic microorganisms and enhances growth performance and survival rates. In agriculture, AMPs provide an alternative to decrease the use of chemical pesticides and antibiotics. We also review current methods for obtaining AMPs, including chemical synthesis, recombinant DNA technology, cell-free protein synthesis, and molecular farming, are also reviewed. Finally, we look to the peptide market to assess its status, progress, and transition from the discovery stage to benefits for society and high-quality products. Overall, our review exemplifies the other side of the coin of AMPs and how these molecules provide similar benefits to conventional antibiotics and pesticides in the agritech sector.

Unlocking the power of antimicrobial peptides: advances in production, optimization, and therapeutics

Antimicrobial peptides (AMPs) are critical effectors of innate immunity, presenting a compelling alternative to conventional antibiotics amidst escalating antimicrobial resistance. Their broad-spectrum efficacy and inherent low resistance development are countered by production challenges, including limited yields and proteolytic degradation, which restrict their clinical translation. While chemical synthesis offers precise structural control, it is often prohibitively expensive and complex for large-scale production. Heterologous expression systems provide a scalable, cost-effective platform, but necessitate optimization. This review comprehensively examines established and emerging AMP production strategies, encompassing fusion protein technologies, molecular engineering approaches, rational peptide design, and post-translational modifications, with an emphasis on maximizing yield, bioactivity, stability, and safety. Furthermore, we underscore the transformative role of artificial intelligence, particularly machine learning algorithms, in accelerating AMP discovery and optimization, thereby propelling their expanded therapeutic application and contributing to the global fight against drug-resistant infections.

Antimicrobial Peptides: The Production of Novel Peptide-Based Therapeutics in Plant Systems

The increased prevalence of antibiotic resistance is alarming and has a significant impact on the economies of emerging and underdeveloped nations. The redundancy of antibiotic discovery platforms (ADPs) and injudicious use of conventional antibiotics has severely impacted millions, across the globe. Potent antimicrobials from biological sources have been extensively explored as a ray of hope to counter the growing menace of antibiotic resistance in the population. Antimicrobial peptides (AMPs) are gaining momentum as powerful antimicrobial therapies to combat drug-resistant bacterial strains. The tremendous therapeutic potential of natural and synthesized AMPs as novel and potent antimicrobials is highlighted by their unique mode of action, as exemplified by multiple research initiatives. Recent advances and developments in antimicrobial discovery and research have increased our understanding of the structure, characteristics, and function of AMPs; nevertheless, knowledge gaps still need to be addressed before these therapeutic options can be fully exploited. This thematic article provides a comprehensive insight into the potential of AMPs as potent arsenals to counter drug-resistant pathogens, a historical overview and recent advances, and their efficient production in plants, defining novel upcoming trends in drug discovery and research. The advances in synthetic biology and plant-based expression systems for AMP production have defined new paradigms in the efficient production of potent antimicrobials in plant systems, a prospective approach to countering drug-resistant pathogens.

Expression of Human β-defensin 2 (hBD-2) in Pichia Pastoris and Investigation of Its Binding Efficiency with ACE-2

COVID-19 is a disease that have affected the entire world, and it continues to spread with new variants. A patient's innate immune system plays a critical role in the mild and severe transition of COVID-19. Antimicrobial peptides (AMPs), which are important components of the innate immune system, are potential molecules to fight pathogenic bacteria, fungi, and viruses. Human β-defensin 2 (hBD-2), a 41-amino-acid antimicrobial peptide, is one of the defensins inducibly expressed in the skin, lungs, and trachea in humans. In this study, it was aimed to investigate the interaction of hBD-2 produced recombinantly in Pichia pastoris with the human angiotensin-converting enzyme 2 (ACE-2) under in vitro conditions. First, hBD-2 was cloned in P. pastoris X-33 via the pPICZαA vector, a yeast expression platform, and its expression was confirmed by SDS-PAGE, western blotting, and qRT-PCR. Then, the interaction between recombinant hBD-2 and ACE-2 proteins was revealed by a pull-down assay. In light of these preliminary experiments, we suggest that the recombinantly produced hBD-2 may be protective against SARS-CoV-2 and be used as a supplement in treatment. However, current findings need to be supported by cell culture studies, toxicity analyses, and in vivo experiments.

Comparing the Ability of Secretory Signal Peptides for Heterologous Expression of Anti-Lipopolysaccharide Factor 3 in Chlamydomonas reinhardtii

Anti-lipopolysaccharide factor 3 (ALFPm3) possesses a wide antimicrobial spectrum and high antibacterial and viral activities for broad application prospects in the aquaculture industry. However, the application of ALFPm3 is limited by its low production in nature, as well as its low activity when expressed in Escherichia coli and yeast. Although it has been proven that its secretory expression can be used to produce antimicrobial peptides with strong antimicrobial activity, there is no study on the high-efficiency secretory expression of ALFPm3 in Chlamydomonas reinhardtii. In this study, signal peptides ARS1 and CAH1 were fused with ALFPm3 and inserted into the pESVH vector to construct pH-aALF and pH-cALF plasmids, respectively, that were transformed to C. reinhardtii JUV using the glass bead method. Subsequently, through antibiotic screening, DNA-PCR, and RT-PCR, transformants expressing ALFPm3 were confirmed and named T-JaA and T-JcA, respectively. The peptide ALFPm3 could be detected in algal cells and culture medium by immunoblot, meaning that ALFPm3 was successfully expressed in C. reinhardtii and secreted into the extracellular environment. Moreover, ALFPm3 extracts from the culture media of T-JaA and T-JcA showed significant inhibitory effects on the growth of V. harveyi, V. alginolyticus, V. anguillarum, and V. parahaemolyticus within 24 h. Interestingly, the inhibitory rate of c-ALFPm3 from T-JcA against four Vibrio was 2.77 to 6.23 times greater than that of a-ALFPm3 from T-JaA, indicating that the CAH1 signal peptide was more helpful in enhancing the secreted expression of the ALFPm3 peptide. Our results provided a new strategy for the secretory production of ALFPm3 with high antibacterial activity in C. reinhardtii, which could improve the application potentiality of ALFPm3 in the aquaculture industry.

Secretory Expression and Application of Antilipopolysaccharide Factor 3 in Chlamydomonas reinhardtii

Anti-lipopolysaccharide factor is a class of antimicrobial peptides with lipopolysaccharide-binding structural domains, which has a broad antimicrobial spectrum, high antimicrobial activities, and broad application prospects in terms of the aquaculture industry. However, the low yield of natural antimicrobial peptides and their poor expression activity in bacteria and yeast have hindered their exploration and utilization. Therefore, in this study, the extracellular expression system of Chlamydomonas reinhardtii, by fusing the target gene with the signal peptide, was used to express anti-lipopolysaccharide factor 3 (ALFPm3) from Penaeus monodon in order to obtain highly active ALFPm3. Transgenic C. reinhardtii T-JiA2, T-JiA3, T-JiA5, and T-JiA6, were verified using DNA-PCR, RT-PCR, and immunoblot. Additionally, the IBP1-ALFPm3 fusion protein could be detected not only within the cells but also in the culture supernatant. Moreover, the extracellular secretion containing ALFPm3 was collected from algal cultures, and then its bacterial inhibitory activity was analyzed. The results showed that the extracts from T-JiA3 had an inhibition rate of 97% against four common aquaculture pathogenic bacteria, including Vibrio harveyi, Vibrio anguillarum, Vibrio alginolyticus, and Vibrio parahaemolyticus. The highest inhibition rate of 116.18% was observed in the test against V. anguillarum. Finally, the minimum inhibition concentration (MIC) of the extracts from T-JiA3 to V. harveyi, V. anguillarum, V. alginolyticus, and V. parahaemolyticus were 0.11 μg/μL, 0.088 μg/μL, 0.11 μg/μL, and 0.011 μg/μL, respectively. This study supports the foundation of the expression of highly active anti-lipopolysaccharide factors using the extracellular expression system in C. reinhardtii, providing new ideas for the expression of highly active antimicrobial peptides.

The future of recombinant host defense peptides

The antimicrobial resistance crisis calls for the discovery and production of new antimicrobials. Host defense peptides (HDPs) are small proteins with potent antibacterial and immunomodulatory activities that are attractive for translational applications, with several already under clinical trials. Traditionally, antimicrobial peptides have been produced by chemical synthesis, which is expensive and requires the use of toxic reagents, hindering the large-scale development of HDPs. Alternatively, HDPs can be produced recombinantly to overcome these limitations. Their antimicrobial nature, however, can make them toxic to the hosts of recombinant production. In this review we explore the different strategies that are used to fine-tune their activities, bioengineer them, and optimize the recombinant production of HDPs in various cell factories.

Current advances of Pichia pastoris as cell factories for production of recombinant proteins

Pichia pastoris (syn. Komagataella spp.) has attracted extensive attention as an efficient platform for recombinant protein (RP) production. For obtaining a higher protein titer, many researchers have put lots of effort into different areas and made some progress. Here, we summarized the most recent advances of the last 5 years to get a better understanding of its future direction of development. The appearance of innovative genetic tools and methodologies like the CRISPR/Cas9 gene-editing system eases the manipulation of gene expression systems and greatly improves the efficiency of exploring gene functions. The integration of novel pathways in microorganisms has raised more ideas of metabolic engineering for enhancing RP production. In addition, some new opportunities for the manufacture of proteins have been created by the application of novel mathematical models coupled with high-throughput screening to have a better overview of bottlenecks in the biosynthetic process.

Strategies for improving antimicrobial peptide production

Antimicrobial peptides (AMPs) found in a wide range of animal, insect, and plant species are host defense peptides forming an integral part of their innate immunity. Although the exact mode of action of some AMPs is yet to be deciphered, many exhibit membrane lytic activity or interact with intracellular targets. The ever-growing threat of antibiotic resistance has brought attention to research on AMPs to enhance their clinical use as a therapeutic alternative. AMPs have several advantages over antibiotics such as broad range of antimicrobial activities including anti-fungal, anti-viral and anti-bacterial, and have not reported to contribute to resistance development. Despite the numerous studies to develop efficient production methods for AMPs, limitations including low yield, degradation, and loss of activity persists in many recombinant approaches. In this review, we outline available approaches for AMP production and various expression systems used to achieve higher yield and quality. In addition, recent advances in recombinant strategies, suitable fusion protein partners, and other molecular engineering strategies for improved AMP production are surveyed.

Characterization of Recombinant Antimicrobial Peptide BMGlv2 Heterologously Expressed in Trichoderma reesei

Antimicrobial peptides (AMPs) serve as alternative candidates for antibiotics and have attracted the attention of a wide range of industries for various purposes, including the prevention and treatment of piglet diarrhea in the swine industry. Escherichia coli, Salmonella, and Clostridium perfringens are the most common pathogens causing piglet diarrhea. In this study, the antimicrobial peptide gloverin2 (BMGlv2), derived from Bombyx mandarina, was explored to determine the efficient prevention effect on bacterial piglet diarrhea. BMGlv2 was heterologously expressed in Trichoderma reesei Tu6, and its antimicrobial properties against the three bacteria were characterized. The results showed that the minimum inhibitory concentrations of the peptide against E. coli ATCC 25922, S. derby ATCC 13076, and C. perfringens CVCC 2032 were 43.75, 43.75, and 21.86 μg/mL, respectively. The antimicrobial activity of BMGlv2 was not severely affected by high temperature, salt ions, and digestive enzymes. It had low hemolytic activity against rabbit red blood cells, indicating its safety for use as a feed additive. Furthermore, the measurements of the leakage of bacterial cell contents and scanning electron microscopy of C. perfringens CVCC 2032 indicated that BMGlv2 exerted antimicrobial activity by destroying the cell membrane. Overall, this study showed the heterologous expression of the antimicrobial peptide BMGlv2 in T. reesei and verified its antimicrobial properties against three common pathogenic bacteria associated with piglet diarrhea, which can provide a reference for the applications of AMPs as an alternative product in industrial agriculture.

The Transcriptomic Mechanism of a Novel Autolysis Induced by a Recombinant Antibacterial Peptide from Chicken Expressed in Pichia pastoris

Autolysis is a common physiological process in eukaryotic cells that is often prevented or applied, especially in yeast expression systems. In this study, an antimicrobial peptide from chicken (AMP) was recombinantly expressed in the Pichia pastoris expression system, which induced a series of cellular autolysis phenotypes after methanol treatment, such as the aggregated, lysed, irregular, and enlarged cell morphology, while the cells expressing a recombinant aflatoxin-detoxifizyme (ADTZ) were not autolyzed. A comparative transcriptomic analysis showed that the transcriptomic profiles of cells derived from the autolysis and non-autolysis groups were well discriminated, suggesting that the mechanisms of autolysis were at the transcriptional level. A further differential expression gene (DEG) analysis showed that the DEGs from the two groups were involved mainly in autophagy, the MAPK signaling pathway, transcriptional factors, the central carbon metabolism, anti-stress functions, and so on. In the autolysis group, the cell activity was significantly reduced with the MAPK signaling pathway, the central carbon metabolism was down-regulated, and components of the cytoplasm-to-vacuole targeting (CVT) and mitophagy pathways were up-regulated, suggesting that the autophagy involved in the trafficking of intracellular molecules in the vacuole and mitochondrion contributed to autolysis, which was regulated by transcriptional factors and signal pathways at the transcriptional level. This study provides a theoretical basis for genetic modifications to prevent or utilize cell autolysis in the recombinant protein expression system.

Antimicrobial property of Pichia pastoris-derived natto peptide against foodborne bacteria and its preservative potential to maintain pork quality during refrigerated storage

Pork spoilage caused by foodborne bacteria contamination always leads to substantial economic loss in the meat industry. The toxicity and drug resistance of chemical preservatives have raised public concerns about their safety and stability. In this study, natto peptide from Pichia pastoris was prepared using DNA recombinant technology. It showed an excellent antibacterial effect against Gram-positive and -negative bacteria, with minimum inhibitory concentrations (MICs) ranging from 6 to 30 μg/ml. Of note, natto peptide exhibited low cytotoxicity and hemolytic activity. The application of natto peptide on pork during refrigerated storage dramatically decreased the growth of Staphylococcus spp., Escherichia spp., and Pseudomonas spp. The bactericidal properties remained in force when natto peptide was used in pork models contaminated with artificial bacteria. Moreover, the application of natto peptide (90 μg/ml) inhibited the increase in pH variation and drip loss, decreased the generation of total volatile basic nitrogen (TVB-N) and thiobarbituric acid reactive substances (TBARS), and maintained a high sensory quality score during pork storage. These results implied that P. pastoris-derived natto peptide could extend the storage time of pork, and it has the potential to be a promising antiseptic biopreservative to replace chemical preservatives.

Recombinant expression and coexpression of oyster defensin and proline-rich peptide in Komagataella phaffii

Proline-rich peptide (CgPrp) and defensin (CgDef), oyster (Crassostrea gigas)-originated antimicrobial peptides (AMPs), were produced by the recombinant technique in Komagataella phaffii GS115 cells. For this purpose, the nucleotide sequences encoding the CgPrp and CgDef peptides were synthesized by the recursive PCR technique, and ligated in pPICZaA expression vector. Additionally, the expression cassettes of pPICZαA-CgDef and pPICZαA-CgPrp were combined using in vitro multimer ligation strategy to construct the coexpression vector pPICZaA-CgPrp-CgDef. The expression and coexpression vectors transformed into K. phaffii GS115 cells by electroporation. At the end of the 0.5% methanol-induced expression stage for 96 h, the recombinant peptides were purified from the culture medium. The concentrations of purified peptides were changed between 1.05 and 1.21 mg/L. The recombinant peptides successfully inhibited the growth of tested Gram-positive bacterial strains belonging to Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Listeria monocytogenes, and Bacillus cereus. The minimum inhibitory concentrations (MIC) of recombinant CgPrp, CgDef, and CgPrp-CgDef peptides against tested bacteria were in the range of 12.50-25.00, 18.75-75.00, and 5.80-11.60 pg/μl, respectively. The results of the study proved that the recombinant CgPrp, CgDef, and CgPrp-CgDef peptides expressed in K. phaffii might have good potential for the inhibition of common Gram-positive pathogenic bacteria, including drug-resistant MRSA.

Synthetic promoters from blueberry red ringspot virus (BRRV)

MAIN CONCLUSION

We analyzed the synthetic full-length transcript promoter of Blueberry red ringspot virus (BRRV) and developed two chimeric promoters (MBR3 and FBR3). Transcriptional activities of these chimeric promoters were found equivalent to that of the CaMV35S2 promoter. Chimeric promoters driven plant-derived PaDef protein showed high antimicrobial activities against several pathogens. Blueberry red ringspot virus (BRRV) is a pararetrovirus under the genus, Soymovirus belongs to the Caulimoviridae family. We have made a synthetic version of the BRRV-Flt promoter and analyzed its activity in detail. A 372 bp promoter fragment BR3 (- 212 to + 160) showed the strongest transcriptional activity compared with other fragments in both transient and transgenic assays; its activity was found near equivalent to that of the CaMV35S promoter. We constructed two chimeric promoters; MBR3 and FBR3 by fusing the UASs (Upstream activation sequences) of Mirabilis mosaic virus (MUAS; - 297 to - 38; 335 bp) and Figwort mosaic virus (FUAS; - 249 to - 54; 303 bp) respectively to the core promoter domain of BR3 (BR3; - 212 to + 160; 372 bp). The activities of MBR3 and FBR3 promoters were found equivalent to that of the activity of the CaMV35S2 promoter and approximately 4.0 (four) times stronger than that of the CaMV35S promoter. Histochemical and fluorometric GUS assays confirmed the above observation. The transcriptional efficacies of these recombinant promoters were tested by evaluating the antibacterial and antifungal activities of recombinant plant-derived antimicrobial peptide Persea americana var. drymifolia defensin (PaDef) driven under these promoters. Bioassays showed promising antifungal activities of the plant made PaDef against Alternaria alternata and antibacterial property against Gram-positive (S. aureus and R. fascians) and Gram-negative bacteria (E. coli and P. aeruginosa). Based upon the above results, MBR3 and FBR3 could be useful promoters for plant genetic engineering and can become useful substitutes for the widely used CaMV35S2 promoter in plant biology.

Metabolic engineering of Pichia pastoris for malic acid production from methanol

The application of rational design in reallocating metabolic flux to accumulate desired chemicals is always restricted by the native regulatory network. In this study, recombinant Pichia pastoris was constructed for malic acid production from sole methanol through rational redistribution of metabolic flux. Different malic acid accumulation modules were systematically evaluated and optimized in P. pastoris. The recombinant PP-CM301 could produce 8.55 g/L malic acid from glucose, which showed a 3.45-fold increase compared to the parent strain. To improve the efficiency of site-directed gene knockout, NHEJ-related protein Ku70 was destroyed, whereas leading to the silencing of heterogenous genes. Hence, genes related to by-product generation were deleted via a specially designed FRT/FLP system, which successfully reduced succinic acid and ethanol production. Furthermore, a key node in the methanol assimilation pathway, glucose-6-phosphate isomerase was knocked out to liberate metabolic fluxes trapped in the XuMP cycle, which finally enabled 2.79 g/L malic acid accumulation from sole methanol feeding with nitrogen source optimization. These results will provide guidance and reference for the metabolic engineering of P. pastoris to produce value-added chemicals from methanol.

Strategies for recombinant production of antimicrobial peptides with pharmacological potential

INTRODUCTION

The need to develop new drugs for the control of pathogenic microorganisms has redoubled efforts to prospect for antimicrobial peptides (AMPs) from natural sources and to characterize its structure and function. These molecules present a broad spectrum of action against different microorganisms and frequently present promiscuous action, with anticancer and immunomodulatory activities. Furthermore, AMPs can be used as biopharmaceuticals in the treatment of hospital-acquired infections and other serious diseases with relevant social and economic impacts.Areas covered: The low yield and the therefore difficult extraction and purification process in AMPs are problems that limit their industrial application and scientific research. Thus, optimized heterologous expression systems were developed to significantly boost AMP yields, allow high efficiency in purification and structural optimization for the increase of therapeutic activity.Expert opinion: This review provides an update on recent developments in the recombinant production of ribosomal and non-ribosomal synthesis of AMPs and on strategies to increase the expression of genes encoding AMPs at the transcriptional and translational levels and regulation of the post-translational modifications. Moreover, there are detailed reports of AMPs that have already reached marketable status or are in the pipeline under advanced stages of preclinical testing.

A new high-yielding antimicrobial peptide NZX and its antibacterial activity against Staphylococcus hyicus in vitro/vivo

Staphylococcus hyicus, considered as a leading pathogen of exudative epidermitis, is a serious threat to humans and animals. The emergency of bacterial resistance to antibiotics, especially in human and animal health fields, leads to an urgent need of exploration of new antimicrobial agents. In this study, NZX, a plectasin-derived peptide, was firstly expressed in Pichia pastoris X-33 and was purified by cation exchange chromatography, followed by detection of its antibacterial activity in vitro and in vivo. The results showed that the total secreted protein concentration in fermentation supernatant was up to 2820 mg/L (29 °C) after 120-h induction in a 5-L fermentor. The yield of NZX reached up to 965 mg/L with a purity of 92.6%. The recombinant expressed NZX had a strong antimicrobial activity, high stability, and low toxicity. The minimal inhibitory concentrations (MICs) of NZX and ceftriaxone (CRO) against Gram-positive bacteria were 0.46 to 0.91 μM and 6.04 to 12.09 μM, respectively. The time-killing curves showed that S. hyicus NCTC10350 was killed completely by 2× and 4 × MIC of NZX within 24 h. NZX also exhibited the intracellular activity against S. hyicus in Hacat cells. After treatment with NZX (10 mg/kg) and CRO (60 mg/kg), the survival rates of mice were 100% and 83.3%, respectively. NZX inhibited the bacterial translocation, downregulated pro-inflammatory cytokines (TNF-α/IL-1β/IL-6), upregulated the anti-inflammatory cytokine (IL-10), and ameliorated multiple-organ injuries (the liver, spleen, lung, and kidney). This study provides evidence that the expressed NZX has the potential to become a powerful candidate as novel antimicrobial agents against S. hyicus infections.

Antimicrobial Peptides: Recent Insights on Biotechnological Interventions and Future Perspectives

With the unprecedented rise of drug-resistant pathogens, particularly antibiotic-resistant bacteria, and no new antibiotics in the pipeline over the last three decades, the issue of antimicrobial resistance has emerged as a critical public health threat. Antimicrobial Peptides (AMP) have garnered interest as a viable solution to this grave issue and are being explored for their potential antimicrobial applications. Given their low bioavailability in nature, tailoring new AMPs or strategizing approaches for increasing the yield of AMPs, therefore, becomes pertinent. The present review focuses on biotechnological interventions directed towards enhanced AMP synthesis and revisits existing genetic engineering and synthetic biology strategies for production of AMPs. This review further underscores the importance and potential applications of advanced gene editing technologies for the synthesis of novel AMPs in future.

Heterologous expression of Thrombocidin-1 in Pichia pastoris: Evaluation of its antibacterial and antioxidant activity

The antimicrobial peptide Thrombocidin-1 (TC-1) isolated from human blood that derived from NAP-2 by deleting of two amino acids from C-terminal region. In this study, a C-terminal 6 _ His tagged recombinant TC-1 was expressed as a secreted peptide in Pichia pastoris, for the first time. The recombinant P. pastoris was inoculated in to BMMY culture medium, incubation with 5 μl/ml absolute methanol for 72 h at 30 °C. The TC-1 peptide was concentrated with nickel affinity chromatography and electrophoresis on 16% acrylamide gels. The molecular weight of recombinant TC-1 is approximately 8 kDa and under these conditions, the concentration of TC-1 considered 190 μg/ml that determined by the Bradford method. The antimicrobial activity test (Minimum Inhibitory Concentration and Minimum Bactericidal Concentration) was done against: Listeria monocytogenes, Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, Enterococcus faecalis and Pseudomonas aeruginosa. The growth of these pathogenic bacteria was limited when we used peptide at a concentration of as low as 19.56 μg/ml. Based on DPPH radical scavenging (DPPH-RS) activity and reducing power assays, this peptide showed relatively good antioxidant potential in comparison with standard antioxidant used in this study (BHT). Due to the existence of TC-1 in blood, which makes it safe for human consumption, and the good results of its antimicrobial and antioxidant activity, it can be introduced as a good alternative and a novel effective peptide to food industry for bio-preservation.

Efficient production of a recombinant Venerupis philippinarum defensin (VpDef) in Pichia pastoris and characterization of its antibacterial activity and stability

VpDef is a novel defensin isolated from the clam Venerupis philippinarum. Previously it was expressed in Escherichia coli; however, the E. coli-derived recombinant VpDef did not show effective antimicrobial activity against Staphyloccocus aureus or the Gram-negative bacteria tested. As such, the goal of this study was to design, express, and purify a recombinant VpDef (rVpDef) in Pichia pastoris and to determine its antibacterial potency and stability. A 6.9 KDa rVpDef was successfully expressed as a secreted peptide in P. pastoris, and the amount of rVpDef accumulation was shown to reach as high as approximate 60 μg per 1 ml of culture medium only after an initial optimization was performed. The purified rVpDef demonstrated a broad antibacterial spectrum and was active against six typical common bacteria, both Gram-positive and Gram-negative. A minimal inhibition concentration of as low as 50 μg/ml was observed for rVpDef against the growth of E. coli O157 (ATCC 35150). Moreover, rVpDef was tolerant to temperature shock and proteinase digestion and maintained a high stability over a relatively broad pH range. In addition, rVpDef had a low hemolytic activity against rabbit erythrocytes. Taken together, this study demonstrated that rVpDef could be produced in a large-scale manner in P. pastoris and has a good antibacterial activity and suitable stability. This is the first report on heterologous expression of a biologically active VpDef in P. pastoris, supporting its use for both research and application purposes.