Physico-chemical properties and antibacterial activity of modified egg white—lysozyme

Strategies for enhancing the antibacterial efficacy of lysozyme and the resulting outcome

Lysozyme is a biological macromolecule with potent bactericidal activity, providing a foundation for its use as a natural preservative. It was extensively applicated in the food and pharmaceutical industries, where its active properties are harnessed effectively and sustainably. However, the effect of natural lysozyme on individual gram-positive bacteria and most gram-negative bacteria is not ideal. At present, some antibacterial profiles of extended lysozyme have been developed. With the recent advancements in biotechnology, there has been a notable increase in the potential of methods and techniques for modifying protein enzymes. This paper mainly introduces the basic structural properties of natural hen egg white lysozyme, its bactericidal properties, and mode of action, and focuses on the comparison of different methods and strategies for lysozyme modification at present, including differential isomerization of lysozyme, surface hydrophobicity modification, chemical modification and combination, and influence on lysozyme properties. These findings emphasize that the key to augmenting lysozyme's efficacy lies in manipulating charge, ion characteristics, and modifying active amino acid groups to optimize interactions with bacterial cell walls and membranes, facilitating bacterial autolysis. By applying these principles, it can lay a solid foundation for developing more effective and versatile protein-based lysozyme antibacterial agents.

2D foam film coating of antimicrobial lysozyme amyloid fibrils onto cellulose nanopapers

Amyloid fibrils made from inexpensive hen egg white lysozyme (HEWL) are bio-based, bio-degradable and bio-compatible colloids with broad-spectrum antimicrobial activity, making them an attractive alternative to existing small-molecule antibiotics. Their surface activity leads to the formation of 2D foam films within a loop, similar to soap films when blowing bubbles. The stability of the foam was optimized by screening concentration and pH, which also revealed that the HEWL amyloid foams were actually stabilized by unconverted peptides unable to undergo amyloid self-assembly rather than the fibrils themselves. The 2D foam film was successfully deposited on different substrates to produce a homogenous coating layer with a thickness of roughly 30 nm. This was thick enough to shield the negative charge of dry cellulose nanopaper substrates, leading to a positively charged HEWL amyloid coating. The coating exhibited a broad-spectrum antimicrobial effect based on the interactions with the negatively charged cell walls and membranes of clinically relevant pathogens (Staphylococcus aureus, Escherichia coli and Candida albicans). The coating method presented here offers an alternative to existing techniques, such as dip and spray coating, in particular when optimized for continuous production. Based on the facile preparation and broad spectrum antimicrobial performance, we anticipate that these biohybrid materials could potentially be used in the biomedical sector as wound dressings.

Lysozyme Modification Using Proteolytic Enzymes

The lysozyme in the chicken egg white consists of various bioactive amino acids. However, these compounds are inactive when they are in the sequence of parent proteins. They become active only when isolated from these proteins. The aim of this study was to modify lysozyme with proteolytic enzymes under specific conditions of the reaction environment so as to obtain active biopeptides. The physicochemical properties of the resulting preparations were also assessed. Our study showed that the modification of lysozyme with hydrolytic enzymes (pepsin and trypsin) under strictly specified conditions resulted in obtaining biopeptide preparations with new and valuable properties, as compared with native lysozyme. After the enzymatic modification of lysozyme, two structural fractions were distinguished in the composition of the resulting preparations-the monomeric fraction and the peptide fraction. The modified lysozyme exhibited high surface hydrophobicity and high total antibacterial activity despite the decrease in the hydrolytic activity. Modification of lysozyme with hydrolytic enzymes, especially pepsin, resulted in preparations with very good antioxidative properties.

Applications of Lysozyme, an Innate Immune Defense Factor, as an Alternative Antibiotic

Lysozyme is a ~14 kDa protein present in many mucosal secretions (tears, saliva, and mucus) and tissues of animals and plants, and plays an important role in the innate immunity, providing protection against bacteria, viruses, and fungi. Three main different types of lysozymes are known: the c-type (chicken or conventional type), the g-type (goose type), and the i-type (invertebrate type). It has long been the subject of several applications due to its antimicrobial properties. The problem of antibiotic resistance has stimulated the search for new molecules or new applications of known compounds. The use of lysozyme as an alternative antibiotic is the subject of this review, which covers the results published over the past two decades. This review is focused on the applications of lysozyme in medicine, (the treatment of infectious diseases, wound healing, and anti-biofilm), veterinary, feed, food preservation, and crop protection. It is available from a wide range of sources, in addition to the well-known chicken egg white, and its synergism with other compounds, endowed with antimicrobial activity, are also summarized. An overview of the modified lysozyme applications is provided in the form of tables.

Unconventional effects of long-term storage of microwave-modified chicken egg white lysozyme preparations

Thermal modification is an effective method that induces significant expansion of the antimicrobial properties and other valuable properties of chicken egg white lysozyme. In our latest research, a new innovative method of enzyme modification was developed, in which microwave radiation was used as an energy source to process liquid lysozyme concentrate (LLC). After modification, high-quality preparations were obtained. However, long-term storage in a concentrated form initiated various processes that caused darkening over time and could also lead to other significant changes to their structure and, consequently, to their functional properties. This necessitated multidirectional research to explain this phenomenon. This paper presents the results of research aimed at assessing the physicochemical changes in the properties of microwave-modified lysozyme in the form of a liquid concentrate after long-term storage under refrigeration conditions. The assessment also considered the conditions under the acidity of the modifying medium and the duration of the microwave modification. The analysis showed that the values of the basic parameters determining the quality and usefulness of the modified enzyme significantly improved during long-term storage of the preparations. The greatest changes were observed in the preparations modified for the longest time and in the most acidic environment (process time 260 s, pH 2.0), the number of oligomers under these conditions increased by 18% after 12 months of holding, and the surface hydrophobicity increased by as much as 31%. In addition, microbiological tests showed that the preparations of microwave-modified lysozyme had an effect on gram-positive bacteria as well as on gram-negative, and this effect was significantly enhanced after 12 months. The results confirm that LLC modification with microwave radiation is a highly efficient method to prepare high-quality and high utility potential lysozyme. Notably, an interesting and important phenomenon was the observation of the unconventional behaviour of the preparations during their long-term storage, which increased their utility potential significantly.

The Effect of Modified Lysozyme Treatment on the Microflora, Physicochemical and Sensory Characteristics of Pork Packaged in Preservative Gas Atmospheres

The aim of the study was to investigate the effect of modified lysozyme on the microflora, physicochemical and sensory characteristics of pork loin packaged in modified atmospheres and stored at 4 ± 1 °C. Different gas compositions (M1 65:25:10 O2:CO2:N2; M2 50:40:10 O2:CO2:N2; M3 80:20 O2:CO2) were used. The microbiological parameters (APC, Enterobacteriaceae, Pseudomonas spp., lactic acid bacteria), physicochemical indexes (pH, colour) as well as a sensory attribute, i.e., aroma were analysed. Meat samples were tested after five, 12, 19, 23, and 28 days of storage. Changes in the qualities of pork were determined throughout the storage. The proportions of polymeric forms, hydrolytic activity and hydrophobicity were determined in the lysozyme preparation. Modified lysozyme exhibited higher hydrophobicity and lower hydrolytic activity than lysozyme monomer. The colour parameters L* and a* were not considerably affected by the addition of modified lysozyme. The sample with the modified lysozyme was given the highest score for aroma. In comparison with the monomer, the modified lysozyme exhibited greater antibacterial effect, especially against Pseudomonas and Enterobacteriaceae. Microbial growth rates in the sample with modified lysozyme, packaged in an atmosphere with the highest content of CO2 (total plate count 4.59 log CFU/cm2; moulds and yeasts 2.17 log CFU/cm2) were lower than those observed in the sample without lysozyme packed under M1 and M3 (20−25% CO2). The use of an atmosphere with gas composition and modified lysozyme considerably extended the shelf life of pork. The combination of the atmosphere with the highest content of carbon dioxide (50% O2, 40% CO2, 10% N2) and modified lysozyme resulted in the best effect. This strategy extended the shelf-life by more than 20%, as compared with the control sample without lysozyme, packaged in an atmosphere of 50:40:10 O2:CO2:N2.

Isolation of a broad spectrum antimicrobial producing thermophilic Bacillus and characterization of its antimicrobial protein

The hot spring water of Atri in India was believed to have disease curing property. An antibacterial producing organism was isolated and identified as Bacillus paralicheniformis by morphology, microscopy, and 16S-rRNA. Its secretion inhibited bacteria, yeast, and fungus in well-diffusion-method. The secreted antimicrobial was a 16.74 kDa protein homologous of chicken-lysozyme-C. The novel lysozyme's activities were recorded under different parameters. It was active from pH 5-9 and endured up to 60 °C for 120 min. Complete cell wall lysis of S. flexneri and P. aeruginosa was observed under a microscope at 4500× with a minimum inhibitory concentration of 7.8 µg/ml, while others required a higher dose, i.e., 13 µg/ml, and 20 µg/ml for E.coli and S. typhimurium, respectively. The discovered lysozyme has the extraordinary potential to lyse Gram-positive bacteria, yeast, fungus, and more efficiently lyse chick-lysozyme-C resistant lipopolysaccharide rich Gram-negative bacteria's outer cell wall.

Changes in selected physicochemical properties of lysozyme modified with a new method using microwave field and oxidation

Lysozyme is a type of enzymatic protein found in a wide range of organisms. Among the many applications of lysozyme, the antibacterial activity features caused by the hydrolysis of 1–4 glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine of gram-positive bacteria are beneficial in the food industry, medicine, trade, and pharmacology. Studies have indicated that specific modifications of lysozyme cause oligomerization of the enzyme, and the resulting dimer, which also undergoes changes in physicochemical properties, shows greater total antibacterial activity. Among these modifications, thermo-chemical methods are one of the most important groups. In this study, the microwave method of the enzyme heating with the associated process of enzyme oxidation was used as a novel thermo-chemical method to induce lysozyme oligomerization. The research shows that using this new method can produce enzymatic preparations composed of approximately 58.9% oligomers, including 33.5% dimer and 25.4% trimer under a hydrogen peroxide concentration of 4% and pH of 8. The maximum percentage of lysozyme dimer of 39.4% was obtained at pH 6.0 with the addition of 2% oxidant. In addition, as a result of the modification process, the hydrolytic activity and surface hydrophobicity of the enzyme were changed.

The antimicrobial spectrum of lysozyme broadened by reductive modification

In order to broaden the antimicrobial action spectrum of lysozyme against Gram-negative bacteria, different partially reduced lysozyme derivatives were obtained by reducing the R-S-S-R bonds of lysozyme using the reducing agent Na2SO3. The circular dichroism behavior analysis showed that the tertiary structure of the partially reduced lysozyme molecules became more flexible, leading to an obvious increase in the surface hydrophobicity and the tryptophan fluorescence intensity. Zeta potential analysis indicated that the introduction of SO32- led to a decrease in the surface charges of the reduced lysozyme molecules. Compared with the native lysozyme, the reduced lysozymes not only showed a 1 log increase in the antimicrobial activity against Escherichia coli ATCC 25922 and Salmonella enteritidis ATCC 13076 (P <0.05), but also maintained nearly the same antimicrobial activity against Staphylococcus aureus ATCC 29213 (P >0.05). Overall, the reductive modification with the food-friendly, compatible, and safe reducing agent Na2SO3 has broadened the antimicrobial action spectrum of the modified lysozymes against Gram-negative bacteria, with the enhancement extent depending on the reduction degree and the type of bacterial strains. The integrated results suggest that the Na2SO3-reduced lysozyme can be used as a novel safe potential bactericidal additive for food-processing industry.

Inhibition of Human Immunodeficiency Type 1 Virus (HIV-1) Life Cycle by Different Egg White Lysozymes

Lysozyme is a relatively small enzyme with different biological activities, which is found in tears, saliva, egg white, and human milk. In the study, the anti-HIV-1 activity of lysozymes purified from quail, Meleagris, and hen egg white has been determined. For this end, a time-of-drug-addition assay was performed to identify the target of anti-HIV-1 agents and for determination of probable anti HIV-1 mechanism of the studied lysozyme, the binding affinity of the lysozymes to the human CD4 receptor was studied by molecular docking method. To define structural differences between studied lysozymes, structural motifs of them were predicted by MEME tool. Quail, hen, and Meleagris lysozymes showed potent anti-HIV-1 activity with EC₅₀ of 7.5, 10, and 55 nM, respectively. The time-of-drug-addition study demonstrated that the inhibitory effect of all purified lysozymes is before HIV-1 infection. The frequency and intensity of CD4 expression in PBMCs decreased in the presence of all mentioned lysozymes. Also, the expression level of C-C chemokine receptor type 5 (CCR5) and chemokine receptor type 4 (CXCR4) on CD4+ T cells was not changed in cells treated with these lysozymes. The results of in silico study confirmed that the binding energy of quail lysozyme with CD4 was more than that of other studied lysozymes. The results revealed that these lysozymes restrict HIV-1 attachment to host cell CD4.

An Environmentally Benign Antimicrobial Coating Based on a Protein Supramolecular Assembly

The use of antimicrobial materials, for example, silver nanoparticles, has been a cause for concern because they often exert an adverse effect on environmental and safety during their preparation and use. In this study, we report a class of green antimicrobial coating based on a supramolecular assembly of a protein extracted from daily food, without the addition of any other hazardous agents. It is found that a self-assembled nanofilm by mere hen egg white lysozyme has durable in vitro and in vivo broad-spectrum antimicrobial efficacy against Gram-positive/negative and fungi. Such enhanced antimicrobial capability over native lysozyme is attributed to a synergistic combination of positive charge and hydrophobic amino acid residues enriched on polymeric aggregates in the lysozyme nanofilm. Accompanied with high antimicrobial activity, this protein-based PTL material simultaneously exhibits the integration of multiple functions including antifouling, antibiofilm, blood compatibility, and low cytotoxicity due to the existence of surface hydration effect. Moreover, the bioinspired adhesion mediated by the amyloid structure contained in the nanofilm induces robust transfer and self-adhesion of the material onto virtually arbitrary substrates by a simple one-step aqueous coating or solvent-free printing in 1 min, thereby allowing an ultrafast route into practical implications for surface-functionalized commodity and biomedical devices. Our results demonstrate that the application of pure proteinaceous substance may afford a cost-effective green biomaterial that has high antimicrobial activity and low environmental impact.

Modified lysozymes as novel broad spectrum natural antimicrobial agents in foods

In recent years much attention and interest have been directed toward application of natural antimicrobial agents in foods. Some naturally occurring proteins such as lactoperoxidase, lactoferrin, and lysozyme have received considerable attention and are being considered as potential antimicrobial agents in foods. Lysozyme kills bacteria by hydrolyzing the peptidoglycan layer of the cell wall of certain bacterial species, hence its application as a natural antimicrobial agent has been suggested. However, limitations in the action of lysozyme against only Gram-positive bacteria have prompted scientists to extend the antimicrobial effects of lysozyme by several types of chemical modifications. During the last 2 decades extensive research has been directed toward modification of lysozyme in order to improve its antimicrobial properties. This review will report on the latest information available on lysozyme modifications and examine the applicability of the modified lysozymes in controlling growth of Gram-positive and Gram-negative bacteria in foods. The results of modifications of lysozyme using its conjugation with different small molecule, polysaccharides, as well as modifications using proteolytic enzymes will be reviewed. These types of modifications have not only increased the functional properties of lysozyme (such as solubility and heat stability) but also extended the antimicrobial activity of lysozyme. Many examples will be given to show that modification can decrease the count of Gram-negative bacteria in bacterial culture and in foods by as much as 5 log CFU/mL and in some cases essentially eliminated Escherichia coli. In conclusion this review demonstrates that modified lysozymes are excellent natural food preservatives, which can be used in food industry.

PRACTICAL APPLICATION

The subject described in this review article can lead to the development of methods to produce new broad-spectrum natural antimicrobial agents, based on modification of chicken egg white lysozyme, which might potentially replace the currently used synthetic food preservatives.

Thermal, mechanical, and moisture absorption properties of egg white protein bioplastics with natural rubber and glycerol

Petroleum-based plastics have many drawbacks: the large amount of energy required to produce the plastic, the waste generated as a result of plastic production, and the accumulation of waste due to slow degradation rate. It is because of these negative attributes of conventional plastic use that attention is being focused on environmentally friendly plastics from alternative sources. Albumin protein provides one possible source of raw material, with inherent antimicrobial properties that may make it suitable for medical applications. We conducted this study to investigate the various bioplastic properties of the albumin with the use of three plasticizers - water, glycerol, and natural rubber latex. Based on results, 75:25 albumin-water, 75:25 albumin-glycerol, and 80:20 albumin-natural rubber were the best blending ratios for each plasticizer for a subsequent time study to determine water stability, with the 80:20 albumin-natural rubber blend ratio having possessed the best thermal, tensile, and viscoelastic properties overall.

Effect of modified lysozyme on the microflora and sensory attributes of ground pork

The effects of lysozyme monomer and thermochemically modified lysozyme on the microflora and sensory attributes of heated and unheated ground pork were investigated in this study. The dimer and trimer fractions of the modified lysozyme were 36.1 and 33.5%, respectively. The modified lysozyme exhibited higher hydrophobicity (40,600 U/mg of protein) and lower enzymatic activity (1,020 U/mg of protein) than the hydrophobicity (890 U/mg of protein) and activity (17,950 U/mg of protein) of the lysozyme monomer. Portions of ground pork (150 g) without lysozyme or supplemented with 5 mg/g lysozyme or modified lysozyme and either not heated or heated at 60°C for 10 min were stored at 4 ± 1°C and sampled at various times between 1 and 144 h. Meat color was not affected by either additive. After storage for 72 h, the mean odor score for meat supplemented with modified lysozyme and heated decreased from 5.0 at 1 h to 4.1, while the scores for all the other preparations were ≤3.2. After 144 h, the counts of Pseudomonas and Enterobacteriaceae in meat that was supplemented with modified lysozyme and not heated were, respectively, 1.1 and 0.9 log less than in the controls, and the numbers in such meat that was heated were, respectively, 1.2 and 2.4 log less than the numbers in the controls. The counts in meat supplemented with lysozyme and the controls were comparable. Heat treatment increased the bacteriostatic effect of modified lysozyme on gram-negative bacteria.