Identification of antibacterial peptides generated from enzymatic hydrolysis of cottonseed proteins

Enhancing the stability and therapeutic potential of the antimicrobial peptide Feleucin-K3 against Multidrug-Resistant a. Baumannii through rational utilization of a D-amino acid substitution strategy

Antimicrobial peptides (AMPs), which have a low probability of developing resistance, are considered the most promising antimicrobial agents for combating antibiotic resistance. Feleucin-K3 is an amphiphilic cationic AMP that exhibits broad-spectrum antimicrobial activity. In our previous research, the first phenylalanine residue was identified as the critical position affecting its biological activity. Here, a series of Feleucin-K3 analogs containing hydrophobic D-amino acids were developed, leveraging the low sensitivity of proteases to unnatural amino acids and the regulatory effect of hydrophobicity on antimicrobial activity. Among them, K-1dF, which replaced the phenylalanine of Feleucin-K3 with its enantiomer (D-phenylalanine), exhibited potent antimicrobial activity with a therapeutic index of 46.97 and MICs between 4 to 8 μg/ml against both sensitive and multidrug-resistant Acinetobacter baumannii. The introduction of D-phenylalanine increased the salt tolerance and serum stability of Feleucin-K3. Moreover, K-1dF displayed a rapid bactericidal effect, a low propensity to develop resistance, and a synergistic effect when combined with antibiotics. More importantly, it exhibited considerable or superior efficacy to imipenem against pneumonia and skin abscess infection. In brief, the K-1dF obtained by simple and effective modification strategy has emerged as a promising candidate antimicrobial agent for tackling multidrug-resistant Acinetobacter baumannii infections.

Cottonseed meal protein hydrolysate influences growth performance, carcass characteristics, serum biochemical indices, and intestinal morphology in yellow-feather broilers

This study investigated the effects of cottonseed meal protein hydrolysate (CPH) on the growth performance, carcass characteristics, serum biochemical indices, intestinal morphology, and enzyme activities of yellow-feather broilers. We randomly divided 240 chicks into four groups, each with six replicates: a basal diet with 0% (CON), 1% (LCPH), 3% (MCPH), or 5% (HCPH) CPH. The trail spanned 63 days and included three phases: Days 1-21, 22-42, and 43-63. Increased average daily gain (ADG) and decreased ratio of feed to gain (F/G) with LCPH were observed in 21-day-old broilers (P < 0.05). MCPH led to higher ADG and average daily feed intake (ADFI) in 42-day-old broilers (P < 0.05). Additionally, CPH supplementation resulted in increased dressing percentage, percentage of half-eviscerated yield, percentage of eviscerated yield, breast muscle rate, and leg muscle rate were observed (P < 0.05) with diet. The serum levels of total protein (TP), high-density lipoprotein cholesterol (HDL-C), calcium (Ca), and phosphorus (P) were enhanced, and blood urea nitrogen (BUN) and triglyceride (TG) levels decreased with diet and CPH (P < 0.05). CPH increased the length of the jejunum and ileum and the weight of the duodenum, jejunum, and ileum in 21-day-old broilers (P < 0.05). Alterations in the duodenal villus structure in broilers occurred on Days 21 and 42, and the CPH groups performed better; however, a similar change occurred in the jejunum on Days 42 and 63 (P < 0.05). MCPH and HCPH enhanced trypsin activity in the duodenum of 21-day-old and 63-day-old broilers (p < 0.05). Chymotrypsin activity increased (P > 0.05) in the duodenum of 63-day-old broilers fed MCPH. Lipase activity increased (P < 0.05) in the jejuna of 21-day-old broilers treated with HCPH. CPH increased trypsin activity in the ilea of 21-day-old broilers (P < 0.05). These results showed that CPH influenced the growth performance, carcass characteristics, serum biochemical indices, and intestinal morphology of yellow-feather broilers, which are related to growth stage. The recommended CPH level in broilers is 1% before 21 days of age and 3% after 21 days of age.

Anti-Salmonella Activity of a Novel Peptide, KGGDLGLFEPTL, Derived from Egg Yolk Hydrolysate

The present study aimed to characterize the mode of action of a novel antimicrobial peptide isolated from egg yolk hydrolysate. The EYHp6, KGGDLGLFEPTL, exhibited inhibition against Salmonella enterica serovar Typhimurium TISTR 292 and S. enterica serovar Enteritidis DMST 15679 with a MIC value of 2 mM. In contrast, S. enterica serovar Newport ATCC 6962 and other strains of Typhimurium and Enteritidis were inhibited at 4 mM. EYHp6 increased the cell membrane permeability of S. Typhimurium TISTR 292, leading to DNA leakage. Membrane integrity determined by propidium iodide and SYTO9 staining visualized by confocal microscopy demonstrated that EYHp6 at 1 × MIC induced disruption of cell membranes. Electron microscopy revealed that treatment of S. Typhimurium with EYHp6 led to damage to the cell membrane, causing the leakage of intracellular contents. Synchrotron-based Fourier-transform infrared spectroscopy indicated that EYHp6 killed S. Typhimurium by targeting fatty acids and nucleic acids in the cell membrane. The peptide did not show hemolytic activity up to 4 mM. These findings suggest that EYHp6 could be a promising antibacterial agent for controlling the growth of S. enterica.

Nutritional composition, health benefits and bio-active compounds of chickpea (Cicer arietinum L.)

Chickpea (Cicer arietinum L.), an annual plant of the family Fabaceae is mainly grown in semiarid and temperate regions. Among pulses, cultivated worldwide chickpeas are considered an inexpensive and rich source of protein. Chickpea is a good source of protein and carbohydrate, fiber, and important source of essential minerals and vitamins. The quality of protein is better among other pulses. Consumption of chickpeas is related to beneficial health outcomes. Dietary peptides from the protein of chickpeas gaining more attention. Peptides can be obtained through acid, alkali, and enzymatic hydrolysis. Among all these, enzymatic hydrolysis is considered safe. Various enzymes are used for the production of peptides, i.e., flavorzyme, chymotrypsin, pepsin, alcalase, papain, and trypsin either alone or in combinations. Chickpea hydrolysate and peptides have various bioactivity including angiotensin 1-converting enzyme inhibition, digestive diseases, hypocholesterolemic, CVD, antioxidant activity, type 2 diabetes, anti-inflammatory, antimicrobial, and anticarcinogenic activity. This review summarizes the nutritional composition and bioactivity of hydrolysate and peptides obtained from chickpea protein. The literature shows that chickpea peptides and hydrolysate have various functional activities. But due to the limited research and technology, the sequences of peptides are unknown, due to which it is difficult to conduct the mechanism studies that how these peptides interact. Therefore, emphasis must be given to the optimization of the production of chickpea bioactive peptides, in vivo studies of chickpea bioactivity, and conducting human study trials to check the bioactivity of these peptides and hydrolysate.

Recent Progress in the Characterization, Synthesis, Delivery Procedures, Treatment Strategies, and Precision of Antimicrobial Peptides

Infectious diseases are constantly evolving to bypass antibiotics or create resistance against them. There is a piercing alarm for the need to improve the design of new effective antimicrobial agents such as antimicrobial peptides which are less prone to resistance and possess high sensitivity. This would guard public health in combating and overcoming stubborn pathogens and mitigate incurable diseases; however, the emergence of antimicrobial peptides' shortcomings ranging from untimely degradation by enzymes to difficulty in the design against specific targets is a major bottleneck in achieving these objectives. This review is aimed at highlighting the recent progress in antimicrobial peptide development in the area of nanotechnology-based delivery, selectivity indices, synthesis and characterization, their doping and coating, and the shortfall of these approaches. This review will raise awareness of antimicrobial peptides as prospective therapeutic agents in the medical and pharmaceutical industries, such as the sensitive treatment of diseases and their utilization. The knowledge from this development would guide the future design of these novel peptides and allow the development of highly specific, sensitive, and accurate antimicrobial peptides to initiate treatment regimens in patients to enable them to have accommodating lifestyles.

Effects of Replacing Fish Meal with Enzymatic Cottonseed Protein on the Growth Performance, Immunity, Antioxidation, and Intestinal Health of Chinese Soft-Shelled Turtle (Pelodiscus sinensis)

The dietary effects of replacing fish meal with enzymatic cottonseed protein (ECP) on the growth performance, immunity, antioxidant, and intestinal health of Chinese soft-shelled turtles have not been explored. An eight-week feeding trial was conducted with a quadruplicated group of turtles (3.44 ± 0.01 g) that were randomly assigned to 16 cages (0.6 m × 0.6 m × 0.6 m) with 30 turtles that were stocked in each cage. Four dietary groups were fed with diets supplemented with 0, 2%, 4%, and 6% (ECP0 group (control group), ECP2 group, ECP4 group, ECP6 group) of enzymatic cottonseed protein replacing fishmeal. The present study illustrated that the final weight and WG in the ECP2 and ECP4 groups were significantly increased (P < 0.05) compared with the control group. The ECP2, ECP4, and ECP6 groups significantly reduced the feed coefficient (P < 0.05) and significantly increased the SGR (P < 0.05). The serum TP and ALB of the ECP4 group were significantly increased (P < 0.05). The ECP2, ECP4, and ECP6 groups significantly increased the activity of intestinal pepsin (P < 0.05), and the activity of intestinal lipase of the EPC4 group was significantly increased (P < 0.05). The intestinal villus height of the EPC4 group and EPC6 group, the villus width of the EPC2 group and EPC4 group, and the intestinal muscle thickness of the EPC4 group were significantly increased (P < 0.05). At the same time, replacing fishmeal with enzymatic cottonseed protein also affected the intestinal inflammation-related genes compared with the control group. Besides that, the expression of the IL-10 gene in the experimental group was significantly upregulated (P < 0.05). Nevertheless, the expression of TNF-α and IL-8 genes in the ECP2 group and TNF-α and IL-1β genes in the ECP4 group was significantly downregulated (P < 0.05). In summary, replacing fish meal with enzymatic cottonseed protein positively affects the growth, immunity, and intestinal health of Chinese soft-shelled turtles. The appropriate proportion of enzymatic cottonseed protein to replace fish meal in turtle feed is 4%.

Effects of molecular weight fraction on antioxidation capacity of rice protein hydrolysates

Rice protein was used as a starting material to provide rice protein hydrolysates (RPH) through enzyme-assisted extraction. RPH was further fractionated using ultrafiltration membrane (UF) and classified by molecular weight (MW; MW < 1 kDa, MW 1-10 kDa, and MW > 10 kDa). Peptides with MW < 1 kDa possessed superior antioxidant properties (p < 0.05). Therefore, UF demonstrated great efficacy in selectively separating antioxidant peptides. A Pearson correlation analysis revealed that the total phenolic concentration was correlated with oxygen radical absorbance capacity (ORAC; r = 0.999, p < 0.05). Amino acid contents had negative correlations with the scavenging activity (specifically, IC50) of 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radicals (r =  - 0.986 to - 1.000). Reducing power was related to aromatic amino acid contents (r = 0.997, p < 0.05). In this study, enzymatic hydrolysis was discovered to be an effective method of extracting and isolating natural antioxidant proteins from broken rice, thus preserving the nutritional quality of rice and making those proteins more accessible in future applications.

A critical review on immunomodulatory peptides from plant sources; action mechanisms and recent advances

Plant protein components contribute positively to human well-being as they modulate the immune status of a consumer, especially when the enzymatic method is employed in order to release their bioactive peptides. These peptides are derived from plant-based foods such as soy, wheat, barley, rye, oats, rice, corn, sorghum, and millet, the famous staple foods around the world. Since these peptides are crucial to functional food among other key industries, the present study endeavored to scout for relevant information within the past three decades, using the Web of Science, Scopus, and Google search engines. In this review, first, the core of immunomodulation and types of immunomodulatory agents will be discussed, followed by the production of plant-based immunomodulatory peptides and their immunomodulatory mechanisms in cells, animals, and humans are also studied. Finally, applications and challenges associated with plant-based immunomodulatory peptides are put forward.

Green Antimicrobials as Therapeutic Agents for Diabetic Foot Ulcers

Diabetic foot ulcers (DFU) are one of the most serious and devastating complications of diabetes and account for a significant decrease in quality of life and costly healthcare expenses worldwide. This condition affects around 15% of diabetic patients and is one of the leading causes of lower limb amputations. DFUs generally present poor clinical outcomes, mainly due to the impaired healing process and the elevated risk of microbial infections which leads to tissue damage. Nowadays, antimicrobial resistance poses a rising threat to global health, thus hampering DFU treatment and care. Faced with this reality, it is pivotal to find greener and less environmentally impactful alternatives for fighting these resistant microbes. Antimicrobial peptides are small molecules that play a crucial role in the innate immune system of the host and can be found in nature. Some of these molecules have shown broad-spectrum antimicrobial properties and wound-healing activity, making them good potential therapeutic compounds to treat DFUs. This review aims to describe antimicrobial peptides derived from green, eco-friendly processes that can be used as potential therapeutic compounds to treat DFUs, thereby granting a better quality of life to patients and their families while protecting our fundamental bio-resources.

Effects of Enzymatic Cottonseed Protein Concentrate as a Feed Protein Source on the Growth, Plasma Parameters, Liver Antioxidant Capacity and Immune Status of Largemouth Bass (Micropterus salmoides)

This study appraised the impact of enzymatic cottonseed protein concentrate (ECP) as a fish meal (FM) substitute on the growth and health of largemouth bass (Micropterus salmoides) (initial weight 14.99 ± 0.03 g). Five diets with equal nitrogen, fat, and energy were designed to replace 0%, 7.78%, 15.56%, 23.33%, and 31.11% FM by adding 0%, 3.6%, 7.2%, 10.8%, and 14.4% ECP, named ECP0, ECP3.6, ECP7.2, ECP10.8, and ECP14.4, respectively. We fed 300 fish with five experimental diets for 60 days. The results revealed that weight gain rate (WGR) and specific growth rate (SGR) did not notably reduce until the addition of ECP exceeded 7.2%. The proximate composition of fish was not affected by the amount of ECP added in diets. Plasma total protein (TP), albumin (ALB), and high-density lipoprotein (HDL) concentrations increased with the increase of ECP dosage, while the triglyceride (TG) and low-density lipoprotein (LDL) concentrations and alkaline phosphatase (ALP) activity showed an opposite trend. For hepatic antioxidant capacity, the hepatic total superoxide dismutase (T-SOD) and catalase (CAT) activities, glutathione (GSH) content, and the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), superoxide dismutase (SOD), and CAT were increased by ECP, while the hepatic malondialdehyde (MDA) content and the expression of kelch-like-ECH-associated protein 1 (Keap1) were decreased. With regard to inflammation, the expression of nuclear factor-kappa B (NF-κB), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) were inhibited by ECP. In summary, the amount of ECP added to diet can reach 7.2% to replace 15.56% FM without hampering the growth of largemouth bass, and ECP can improve the antioxidant and immune capacity.

Antibacterial Peptide NP-6 Affects Staphylococcus aureus by Multiple Modes of Action

Our previous study extracted and identified an antibacterial peptide that was named NP-6. Herein, we investigated the physicochemical properties of NP-6, and elucidated the mechanisms underlying its antimicrobial activity against Staphylococcus aureus. The results showed that the hemolysis activity of NP-6 was 2.39 ± 0.13%, lower than Nisin A (3.91 ± 0.43%) at the same concentration (512 µg/mL). Negligible cytotoxicity towards RAW264.7 cells was found when the concentration of NP-6 was lower than 512 µg/mL. In addition, it could keep most of its activity in fetal bovine serum. Moreover, transmission electron microscopy, confocal laser scanning microscopy, and flow cytometry results showed that NP-6 can destroy the integrity of the bacterial cell membrane and increase the membrane permeability. Meanwhile, NP-6 had binding activity with bacterial DNA and RNA in vitro and strongly inhibited the intracellular β-galactosidase activity of S. aureus. Our findings suggest that NP-6 could be a promising candidate against S. aureus.

Harsh Sensitivity and Mechanism Exploration of an Antibacterial Peptide Extracted from Walnut Oil Residue Derived from Agro-Industrial Waste

Walnut (Juglans regia L.) cake meal constitutes a significant amount of solid byproduct from the production of walnut oil, comprising more than 40% protein. However, it is usually not well utilized. Therefore, an antibacterial peptide was obtained by hydrolyzing walnut oil residue protein with pepsin based on the diameter parameters of the antibacterial zone in this research. The purified antibacterial peptide WRPH-II-6 was obtained by two-part purification (ultrafiltration and reversed-phase liquid chromatography) and possessed higher antibacterial activity against Escherichia coli (MIC = 1.33 mg/mL), Staphylococcus aureus (MIC = 0.33 mg/mL), and Bacillus subtilis (MIC = 0.66 mg/mL). The amino acid sequence of WRPH-II-6 was identified as TGSAVPSPRASATATMEMAAAMGLMPGSPSSVSAVMSPF, where the presence of a large proportion of hydrophobic amino acid residues, such as alanine, proline, and methionine, explained the marked antibacterial activity of WRPH-II-6. The harsh sensitivity experiment demonstrated that WRPH-II-6 retains the stability of antibacterial activity when exposed to broad-spectrum pH values, variable temperatures, and long-lasting UV irradiation. The antibacterial mechanism of the WRPH-II-6 peptide against S. aureus and B. subtilis involves nonmembrane disruption: the contact of anions and cations causes the folding and collapse of the bacterial cell membrane to achieve the inhibitory effect. The antibacterial mechanism against E. coli is membrane disruption, which markedly disrupts the bacterial cell membrane to achieve the bactericidal effect. Significantly, the walnut residual protein hydrolysate is a potent preservative and antibacterial agent.

Characterization of a Novel Antimicrobial Peptide Isolated from Moringa oleifera Seed Protein Hydrolysates and Its Membrane Damaging Effects on Staphylococcus aureus

The present study sought to identify and characterize a novel antimicrobial peptide, named MOp2 from Moringa oleifera seed protein hydrolysates, and elucidate its potential antimicrobial effects on Staphylococcus aureus. MOp2, with the amino acid sequence of His-Val-Leu-Asp-Thr-Pro-Leu-Leu (HVLDTPLL), was characterized as a hydrophobic anionic AMP of the β-sheet structure. MOp2 exhibited negligible hemolytic activity at 2.0× MIC, suggesting its inhibitory effect on the growth of S. aureus (MIC: 2.204 mM). It maintained more than 90% of antimicrobial activity under 5% salt and about 78% of antimicrobial activity at a high temperature of 115 °C for 30 min. Protease, especially acid protease, reduced its antimicrobial activity to different extents. Moreover, MOp2 caused irreversible membrane damage to S. aureus cells by increasing the membrane permeability, resulting in the release of intracellular nucleotide pools. Additionally, molecular docking revealed that MOp2 could inhibit S. aureus growth by interacting with dihydrofolate reductase and DNA gyrase through hydrogen bonding and hydrophobic interactions. Overall, MOp2 could be a potential novel antimicrobial agent against S. aureus in food processing.

Plant Bioactive Peptides: Current Status and Prospects Towards Use on Human Health

Large numbers of bioactive peptides with potential applications in protecting against human diseases have been identified from plant sources. In this review, we summarized recent progress in the research of plant-derived bioactive peptides, encompassing their production, biological effects, and mechanisms. This review focuses on antioxidant, antimicrobial, antidiabetic, and anticancer peptides, giving special attention to evidence derived from cellular and animal models. Studies investigating peptides with known sequences and well-characterized peptidic fractions or protein hydrolysates will be discussed. The use of molecular docking tools to elucidate inter-molecular interactions between bioactive peptides and target proteins is highlighted. In conclusion, the accumulating evidence from in silico, in vitro and in vivo studies to date supports the envisioned applications of plant peptides as natural antioxidants as well as health-promoting agents. Notwithstanding, much work is still required before the envisioned applications of plant peptides can be realized. To this end, future researches for addressing current gaps were proposed.

Preparation and identification of antioxidant peptides from cottonseed proteins

The objective of this study was to investigate the antioxidant properties of cottonseed peptides. Results indicated that cottonseed peptides prepared by enzymatic hydrolysis and microbial fermentation both showed antioxidant properties. The cottonseed protein enzymatic hydrolysate with molecular weight less than 3 kDa exhibited excellent DPPH, ABTS and hydroxyl radical scavenging activity and ferrous ion chelating activity with EC₅₀ values of 0.49 ± 0.02, 2.05 ± 0.02, 2.21 ± 0.12, and 0.99 ± 0.03 mg/mL, respectively. Amino acid composition analysis revealed that cottonseed protein hydrolysates are rich in acidic/basic and aromatic amino acids. In addition, among the 19 identified cottonseed protein-derived peptides, YSNQNGRF had the lowest CDOCKER energy and formed hydrogen bonds with Tyr334, Arg380, Arg415, Ser508, and Ser602, and van der Waals interactions with Asn382, Tyr525, Gln530, and Ser555, which all located in the binding site of Keap1-Nrf2 interaction. These findings suggested that the antioxidant peptides from cottonseed protein had the potential as functional ingredients in foods.

Use of Alcalase in the production of bioactive peptides: A review

This review aims to cover the uses of the commercially available protease Alcalase in the production of biologically active peptides since 2010. Immobilization of Alcalase has also been reviewed, as immobilization of the enzyme may improve the final reaction design enabling the use of more drastic conditions and the reuse of the biocatalyst. That way, this review presents the production, via Alcalase hydrolysis of different proteins, of peptides with antioxidant, angiotensin I-converting enzyme inhibitory, metal binding, antidiabetic, anti-inflammatory and antimicrobial activities (among other bioactivities) and peptides that improve the functional, sensory and nutritional properties of foods. Alcalase has proved to be among the most efficient proteases for this goal, using different protein sources, being especially interesting the use of the protein residues from food industry as feedstock, as this also solves nature pollution problems. Very interestingly, the bioactivities of the protein hydrolysates further improved when Alcalase is used in a combined way with other proteases both in a sequential way or in a simultaneous hydrolysis (something that could be related to the concept of combi-enzymes), as the combination of proteases with different selectivities and specificities enable the production of a larger amount of peptides and of a smaller size.