Lysozyme immobilization on the calcium alginate film under sonication: Development of an antimicrobial film

Effect of lysozyme combined with hydrothermal pretreatment on excess sludge and anaerobic digestion

Anaerobic digestion (AD) is widely employed for sludge stabilization and waste reduction. However, the slow hydrolysis process hinders methane production and leads to prolonged sludge issues. In this study, an efficient and eco-friendly lysozyme pre-treatment method was utilized to address these challenges. By optimizing lysozyme dosage, hydrolysis and cell lysis were maximized. Furthermore, lysozyme combined with hydrothermal pretreatment enhanced overall efficiency. Results indicate that: (1) When lysozyme dosage reached 90 mg/g TS after 240 min of pretreatment, SCOD, soluble polysaccharides, and protein content reached their maxima at 855.00, 44.09, and 204.86 mg/L, respectively. This represented an increase of 85.87%, 365.58%, and 259.21% compared to the untreated sludge. Three-dimensional fluorescence spectroscopy revealed the highest fluorescence intensity in the IV region (soluble microbial product), promoting microbial metabolic activity. (2) Lysozyme combined with hydrothermal pretreatment significantly increased SCOD, soluble proteins, and polysaccharide release from sludge, reducing SCOD release time. Orthogonal experiments identified Group 3 as the most effective for SCOD and soluble polysaccharide release, while Group 9 released the most soluble proteins. The significance order of factors influencing SCOD, soluble proteins, and polysaccharide release is hydrothermal temperature > hydrothermal time > enzymatic digestion time.(3) The lysozyme-assisted hydrothermal pretreatment group exhibited the fastest release and the highest SCOD concentration of 8,135.00 mg/L during anaerobic digestion. Maximum SCOD consumption and cumulative gas production increased by 95.89% and 130.58%, respectively, compared to the control group, allowing gas production to conclude 3 days earlier.

Characteristics of hen egg white lysozyme, strategies to break through antibacterial limitation, and its application in food preservation: A review

Hen egg white lysozyme (HEWL) is used as a food additive in China due to its outstanding antibacterial properties. It is listed as GRAS grade (generally recognized as safe) by the United States Food and Drug Administration (FDA, US) and has been extensively researched and used in food preservation. And the industrial production of HEWL already been realized. Given the complex food system that can affect the antibacterial activity of HEWL, and the limitations of HEWL itself on Gram-negative bacteria. Based on the structure and main biological characteristics of HEWL, this paper focuses on reviewing methods to enhance the stability and antibacterial properties of HEWL. Immobilization tactics such as chemically driven self-assembly, embedding and adsorption address the restriction of poor HEWL antibacterial activity effected by external factors. Both intermolecular and intramolecular modification strategies break the bactericidal deficiencies of HEWL itself. It also comprehensively analyzes the current application status and future prospects of HEWL in the food preservation. There was limited research on the biological methods in modifying HEWL. If the HEWL is genetically engineered, it can broaden its antimicrobial spectrum, improve its other biological activities, so as to further expand its application in the food industry. At present, research on HEWL mainly focused on its antibacterial properties, whereas its application in anti-inflammatory and antioxidant effects also presented great potential.

Alginate-based materials for enzyme encapsulation

Enzymes are widely used in industry due to their high efficiency and selectivity. However, their low stability during certain industrial processes can result in a significant loss of catalytic activity. Encapsulation is a promising technique that can stabilize enzymes by protecting them from environmental stresses such as extreme temperature and pH, mechanical force, organic solvents, and proteases. Alginate and alginate-based materials have emerged as effective carriers for enzyme encapsulation due to their biocompatibility, biodegradability, and ability to form gel beads through ionic gelation. This review presents various alginate-based encapsulation systems for enzyme stabilization and explores their applications in different industries. We discuss the preparation methods of alginate encapsulated enzymes and analyze the release mechanisms of enzymes from alginate materials. Additionally, we summarize the characterization techniques used for enzyme-alginate composites. This review provides insights into the use of alginate encapsulation as a means of stabilizing enzymes and highlights the potential benefits for various industrial applications.

Sono-activation of food enzymes: From principles to practice

Over the last decade, sono-activation of enzymes as an emerging research area has received considerable attention from food researchers. This kind of relatively new application of ultrasound has demonstrated promising potential in facilitating the modern food industry by broadening the application of various food enzymes, improving relevant industrial unit operation and productivity, as well as increasing the yield of target products. This review aims to provide insight into the fundamental principles and possible industrialization strategies of the sono-activation of food enzymes to facilitate its commercialization. This review first provides an overview of ultrasound application in the activation of food protease, carbohydrase, and lipase. Then, the recent development on ultrasound activation of food enzymes is discussed on aspects including mechanisms, influencing factors, modification effects, and its applications in real food systems for free and immobilized enzymes. Despite the far fewer studies on sono-activation of immobilized enzymes compared with those on free enzymes, we endeavored to summarize the relevant aspects in three stages: ultrasound pretreatment of free enzyme/carrier, assistance in immobilization process, and modification of the already immobilized enzyme. Lastly, challenges for the scalability of ultrasound in these target areas are discussed and future research prospects are proposed.

Development of multifarious carrier materials and impact conditions of immobilised microbial technology for environmental remediation: A review

Microbial technology is the most sustainable and eco-friendly method of environmental remediation. Immobilised microorganisms were introduced to further advance microbial technology. In immobilisation technology, carrier materials distribute a large number of microorganisms evenly on their surface or inside and protect them from external interference to better treat the targets, thus effectively improving their bioavailability. Although many carrier materials have been developed, there have been relatively few comprehensive reviews. Therefore, this paper summarises the types of carrier materials explored in the last ten years from the perspective of structure, microbial activity, and cost. Among these, carbon materials and biofilms, as environmentally friendly functional materials, have been widely applied for immobilisation because of their abundant sources and favorable growth conditions for microorganisms. The novel covalent organic framework (COF) could also be a new immobilisation material, due to its easy preparation and high performance. Different immobilisation methods were used to determine the relationship between carriers and microorganisms. Co-immobilisation is particularly important because it can compensate for the deficiencies of a single immobilisation method. This paper emphasises that impact conditions also affect the immobilisation effect and function. In addition to temperature and pH, the media conditions during the preparation and reaction of materials also play a role. Additionally, this study mainly reviews the applications and mechanisms of immobilised microorganisms in environmental remediation. Future development of immobilisation technology should focus on the discovery of novel and environmentally friendly carrier materials, as well as the establishment of optimal immobilisation conditions for microorganisms. This review intends to provide references for the development of immobilisation technology in environmental applications and to further the improve understanding of immobilisation technology.

Enhanced Antibacterial Performance of Chitosan/Corn Starch Films Containing TiO2/Graphene for Food Packaging

Chitosan (CTS)/corn starch (CSH)/nano-TiO₂/graphene (Gr) antibacterial active packaging films were prepared by ultrasonic-assisted electrospray deposition and solution-casting methods, and the effects of the TiO₂:Gr mass ratio and ultrasonication power on their morphology and mechanical, optical, thermal, barrier, and antibacterial properties were investigated. The film fabricated at a TiO₂:Gr ratio of 6:4 and an ultrasonication power of 160 W exhibited a uniform distribution of the nanofillers in the CTS/CSH matrix and significantly enhanced the mechanical, barrier, and water-resistance properties. Furthermore, this film demonstrated superior ultraviolet and visible light-shielding characteristics as compared with those of the non-filled CTS/CSH film, while its Escherichia coli and Staphylococcus aureus inhibition efficiencies were equal to 96.67 ± 0.09% and 99.85 ± 0.13%, respectively. Therefore, the film can effectively prevent food spoilage, indicating its potential for food-packaging applications.

Antioxidant and Antimicrobial Properties of Mung Bean Phyto-Film Combined with Longkong Pericarp Extract and Sonication

Mung bean (Vigna radiata) flour serves as an excellent biopolymer and a potential material for producing antioxidant and antimicrobial phyto-films. In addition to mung bean flour, this study also combined the longkong (Aglaia dookkoo Griff.) pericarp extract (LPE, 1.5%) and ultrasonication process (0 (C1), 2 (T1), 4 (T2), 6 (T3), 8 (T4), and 10 (T5) min, sonicated at 25 kHz, 100% amplitude) in film emulsion production to improve the antioxidant and antimicrobial efficiency in the phyto-films. This study showed that sonication increased the phyto-films’ color into more lightness and yellowness, and the intensity of the color changes was in accordance with the increased sonication time. Alternatively, the thickness, water vapor permeability, and solubility of the films were adversely affected by extended sonication. In addition, elongation at break and tensile strength increased while the Young modulus decreased in the phyto-films with the extended sonication. Furthermore, the droplet size and polydispersity index of the phyto-films decreased with extended sonication. Conversely, the zeta potential of the film tended to increase with the treatments. Furthermore, phytochemicals such as total phenolic content and total flavonoid contents, and the radical scavenging ability of phyto-films against the DPPH radical, ABTS radical, superoxide radical, hydroxyl radical, and ferrous chelating activity, were significantly higher, and they were steadily increased in the films with the extended sonication time. Furthermore, the phyto-films showed a significant control against Gram (-) pathogens, followed by Gram (+) pathogens. A higher inhibitory effect was noted against L. monocytogens, followed by S. aureus and B. subtilis. Similarly, the phyto-films also significantly inhibited the Gram (-) pathogens, and significant control was noted against C. jejuni, followed by E. coli and P. aeruginosa. Regardless of the mung bean flour, this study found that longkong pericarp extract and the sonication process could also effectively be used in the film emulsions to enhance the efficiency of the antioxidant and antimicrobial properties of phyto-films.

Effect of Cold Plasma Treatment on the Packaging Properties of Biopolymer-Based Films: A Review

Biopolymers, like polysaccharides and proteins, are sustainable and green materials with excellent film-forming potential. Bio-based films have gained a lot of attention and are believed to be an alternative to plastics in next-generation food packaging. Compared to conventional plastics, biopolymers inherently have certain limitations like hydrophilicity, poor thermo-mechanical, and barrier properties. Therefore, the modification of biopolymers or their films provide an opportunity to develop packaging materials with desired characteristics. Among different modification approaches, the application of cold plasma has been a very efficient technology to enhance the functionality and interfacial characteristics of biopolymers. Cold plasma is biocompatible, shows uniformity in treatment, and is suitable for heat-sensitive components. This review provides information on different plasma generating equipment used for the modification of films and critically analyses the impact of cold plasma on packaging properties of films prepared from protein, polysaccharides, and their combinations. Most studies to date have shown that plasma treatment effectively enhances surface characteristics, mechanical, and thermal properties, while its impact on the improvement of barrier properties is limited. Plasma treatment increases surface roughness that enables surface adhesion, ink printability, and reduces the contact angle. Plasma-treated films loaded with antimicrobial compounds demonstrate strong antimicrobial efficacy, mainly due to the increase in their diffusion rate and the non-thermal nature of cold plasma that protects the functionality of bioactive compounds. This review also elaborates on the existing challenges and future needs. Overall, it can be concluded that the application of cold plasma is an effective strategy to modify the inherent limitations of biopolymer-based packaging materials for food packaging applications.

Ultrasonication effects on physicochemical properties of biopolymer-based films: A comprehensive review

Biopolymeric films manufactured from materials such as starch, cellulose, protein, chitosan, gelatin, and polyvinyl alcohol are widely applied due to their complete biodegradability. While biopolymer-based films exhibit good gas barriers and optical properties when used in packaging, poor moisture resistance and mechanical properties limit their further application. Ultrasonication is a promising, effective technology for resolving these shortcomings, with its high efficiency, environmentally friendly nature, and safety. This review briefly introduces basic ultrasonication principles and their main effects on mechanical properties, transparency, color, microstructure, water vapor permeability, and oxygen resistance. We also describe the thermal performance of biopolymeric films. While ultrasonication has many positive effects on the physicochemical properties of biopolymeric films, many factors influence their behavior during film preparation, including power density, amplitude, treatment time, frequency, and the inherent properties of the source materials. This review focuses on biopolymers as film-forming materials and comprehensively discusses the promotional effects of ultrasonication on their physicochemical properties.

An Overview on the Rheology, Mechanical Properties, Durability, 3D Printing, and Microstructural Performance of Nanomaterials in Cementitious Composites

The most active research area is nanotechnology in cementitious composites, which has a wide range of applications and has achieved popularity over the last three decades. Nanoparticles (NPs) have emerged as possible materials to be used in the field of civil engineering. Previous research has concentrated on evaluating the effect of different NPs in cementitious materials to alter material characteristics. In order to provide a broad understanding of how nanomaterials (NMs) can be used, this paper critically evaluates previous research on the influence of rheology, mechanical properties, durability, 3D printing, and microstructural performance on cementitious materials. The flow properties of fresh cementitious composites can be measured using rheology and slump. Mechanical properties such as compressive, flexural, and split tensile strength reveal hardened properties. The necessary tests for determining a NM’s durability in concrete are shrinkage, pore structure and porosity, and permeability. The advent of modern 3D printing technologies is suitable for structural printing, such as contour crafting and binder jetting. Three-dimensional (3D) printing has opened up new avenues for the building and construction industry to become more digital. Regardless of the material science, a range of problems must be tackled, including developing smart cementitious composites suitable for 3D structural printing. According to the scanning electron microscopy results, the addition of NMs to cementitious materials results in a denser and improved microstructure with more hydration products. This paper provides valuable information and details about the rheology, mechanical properties, durability, 3D printing, and microstructural performance of cementitious materials with NMs and encourages further research.

Recent Developments in Smart Food Packaging Focused on Biobased and Biodegradable Polymers

Food packaging has a crucial function in the modern food industry. New food packaging technologies seek to meet consumers and industrial's demands. Changes related to food production, sale practices and consumers' lifestyles, along with environmental awareness and the advance in new areas of knowledge (such as nanotechnology or biotechnology), act as driving forces to develop smart packages that can extend food shelf-life, keeping and supervising their innocuousness and quality and also taking care of the environment. This review describes the main concepts and types of active and intelligent food packaging, focusing on recent progress and new trends using biodegradable and biobased polymers. Numerous studies show the great possibilities of these materials. Future research needs to focus on some important aspects such as possibilities to scale-up, costs, regulatory aspects, and consumers' acceptance, to make these systems commercially viable.

Fortification of edible films with bioactive agents: a review of their formation, properties, and application in food preservation

Biodegradable films constructed from food ingredients are being developed for food coating and packaging applications to create more sustainable and environmentally friendly alternatives to plastics and other synthetic film-forming materials. In particular, there is a focus on the creation of active packaging materials from natural ingredients, especially plant-based ones. The film matrix is typically constructed from film-forming food components, such as proteins, polysaccharides and lipids. These matrices can be fortified with active ingredients, such as antioxidants and antimicrobials, so as to enhance their functional properties. Edible active films must be carefully designed to have the required optical, mechanical, barrier, and preservative properties needed for commercial applications. This review focuses on the fabrication, properties, and functional performance of edible films constructed from natural active ingredients. It provides an overview of the type of active ingredients that can be used, how they interact with the film matrix, how they migrate through the films, and how they are released. It also discusses the potential application of these active films for food preservation. Finally, future trends are highlighted and areas where further research are required are discussed.

Oral Administration of Fucosylated Chondroitin Sulfate Oligomers in Gastro-Resistant Microcapsules Exhibits a Safe Antithrombotic Activity

Fucosylated chondroitin sulfate (FCS) polysaccharide isolated from sea cucumber has potent anticoagulant activity. Based on its resistance to the enzymes present in vertebrates, it may serve as an anticoagulant and shows antithrombotic effects when delivered through gastro-resistant (GR) tablets. However, due to the multiple plasma targets of FCS polysaccharide in the coagulation pathway, bleeding can occur after its oral administration. In the current study, we used FCS oligomers, in particular a mixture of oligosaccharides having 6 to 18 saccharide units, as the active ingredient in GR microcapsules for oral anticoagulation. In a Caco-2 model, the FCS oligomers showed higher absorption than native FCS polysaccharides. Oral administration of FCS oligomer-GR microcapsules provided a dose-dependent, prolonged anticoagulant effect with a selective inhibition of the intrinsic coagulation pathway when compared with subcutaneous administration of FCS oligomers or oral administration of unformulated FCS oligomers or native FCS-GR microspheres. Continued oral administration of FCS oligomer-GR microcapsules did not result in the accumulation of oligosaccharides in the plasma. Venous thrombosis animal models demonstrated that FCS oligomers delivered via GR microcapsules produced a potent antithrombotic effect dependent on their anticoagulant properties in the plasma, while oral administration of unformulated FCS oligomers at the same dose exhibited a weaker antithrombotic effect than the formulated version. Oral administration of FCS oligomer-GR microcapsules resulted in no bleeding, while oral administration of native FCS-GR microcapsules resulted in bleeding (p < 0.05). Our present results suggest that a FCS oligomer-GR microcapsule formulation represents an effective and safe oral anticoagulant for potential clinical applications.

Effects of Ultrasonication Time on the Properties of Polyvinyl Alcohol/Sodium Carboxymethyl Cellulose/Nano-ZnO/Multilayer Graphene Nanoplatelet Composite Films

Ultrasonication-assisted solution casting was used to prepare polyvinyl alcohol (PVA)/sodium carboxymethyl cellulose (CMC)/nano-ZnO/multilayer graphene nanoplatelet (xGnP) composite films; the performances (mechanical properties, water vapor permeability (WVP), biodegradability and antibacterial activity) of these films were investigated as a function of the ZnO NPs:xGnP mass ratio and ultrasonication time. Intermolecular interactions among ZnO NPs, xGnP and the PVA/CMC matrix were shown to improve WVP, while X-ray diffraction and scanning electron microscopy analyses revealed that the internal reticular structure of ultrasound-treated PVA/CMC/ZnO NPs/xGnP composite films was in a fluffier state than that of the untreated composite films and the PVA/CMC film. The incorporation of ZnO NPs and xGnP into the composite film reduced its tensile strength and elongation at break, and increased antibacterial activity and biodegradability. In addition, we carried out the experiment of strawberry preservation and measured weight loss ratio, firmness, content of total soluble solids and titration acid. Finally, the composite film of 7:3 had the best preservation effect on strawberries. Thus, the obtained results paved the way to develop novel biodegradable composite films with antimicrobial activity for a wide range of applications.

Long-Term Antibacterial Effect of Electrospun Polyvinyl Alcohol/Polyacrylate Sodium Nanofiber Containing Nisin-Loaded Nanoparticles

Response Surface Methodology (RSM) was used to assess the optimal conditions for a Water/Oil/Water (W/O/W) emulsion for encapsulated nisin (EN). Nano-encapsulated nisin had high encapsulation efficiencies (EE) (86.66 ± 1.59%), small particle size (320 ± 20 nm), and low polydispersity index (0.27). Biodegradable polyvinyl alcohol (PVA) and polyacrylate sodium (PAAS) were blended with EN and prepared by electrospinning. Scanning electron microscopy (SEM) revealed PVA/PAAS/EN nanofibers with good morphology, and that their EN activity and mechanical properties were enhanced. When the ultrasonication time was 15 min and 15% EN was added, the nanofibers had optimal mechanical, light transmittance, and barrier properties. Besides, the release behavior of nisin from the nanofibers fit the Korsemeyer–Peppas (KP) model, a maximum nisin release rate of 85.28 ± 2.38% was achieved over 16 days. At 4 °C, the growth of Escherichia coli and Staphylococcus aureus was inhibited for 16 days in nanofibers under different ultrasonic times. The application of the fiber in food packaging can effectively inhibit the activity of food microorganisms and prolong the shelf life of strawberries, displaying a great potential application for food preservation.

Dual-Functional, Superhydrophobic Coatings with Bacterial Anticontact and Antimicrobial Characteristics

Bacterial pathogens are responsible for millions of cases of illnesses and deaths each year throughout the world. The development of novel surfaces and coatings that effectively inhibit and prevent bacterial attachment, proliferation, and growth is one of the crucial steps for tackling this global challenge. Herein, we report a dual-functional coating for aluminum surfaces that relies on the controlled immobilization of lysozyme enzyme (muramidase) into interstitial spaces of presintered, nanostructured thin film based on ∼200 nm silica nanoparticles and the sequential chemisorption of an organofluorosilane to the available interfacial areas. The mean diameter of the resultant lysozyme microdomains was 3.1 ± 2.5 μm with an average spacing of 8.01 ± 6.8 μm, leading to a surface coverage of 15.32%. The coating had an overall root-mean-square (rms) roughness of 539 ± 137 nm and roughness factor of 1.50 ± 0.1, and demonstrated static, advancing, and receding water contact angles of 159.0 ± 1.0°, 155.4 ± 0.6°, and 154.4 ± 0.6°, respectively. Compared to the planar aluminum, the coated surfaces produced a 6.5 ± 0.1 (>99.99997%) and 4.0 ± 0.1 (>99.99%) log-cycle reductions in bacterial surfaces colonization against Gram-negative Salmonella Typhimurium LT2 and Gram-positive Listeria innocua, respectively. We anticipate that the implementation of such a coating strategy on healthcare environments and surfaces and food-contact surfaces can significantly reduce or eliminate potential risks associated with various contamination and cross-contamination scenarios.

Alginate-based composite materials for wound dressing application:A mini review

Alginate biopolymer has been used in the design and development of several wound dressing materials in order to improve the efficiency of wound healing. Mainly, alginate improves the hydrophilic nature of wound dressing materials in order to create the required moist wound environment, remove wound exudate and increase the speed of skin recovery of the wound. In addition, alginate can easily cross-link with other organic and inorganic materials and they can promote wound healing in clinical applications. This review article addresses the importance of alginates and the roles of derivative polymeric materials in wound dressing biomaterials. Additionally, studies on recent alginate-based wound dressing materials are discussed.

An easy and rapid separation method for five major proteins from egg white: Successive extraction and MALDI-TOF-MS identification

Five major proteins from egg white were separated using a successive extraction/precipitation protocol. The yield and purity of the separated proteins were measured. The separated proteins were confirmed by MALDI-TOF-MS, and their structures were characterized by CD spectrum. Lysozyme was first separated using FPC 3500 resin and then ovomucin from the lysozyme-free egg white. Ammonium sulfate and citric acid were added to the resulting lysozyme- and ovomucin-free egg white solution to precipitate ovotransferrin. Ovomucoid and ovalbumin were separated from the resulting supernatant using ethanol. The separated proteins were further purified and the optimal conditions for the further purifications were suggested. The purity and yield of lysozyme, ovotransferrin, ovalbumin, and ovomucoid were higher than 90% and 77%, while those of ovomucin were about 72% and 75%, respectively. This study separated five major proteins in egg white successively using resin adsorption, pH adjustment, salt/ethanol precipitation, and ultrafiltration.

Effects of ultrasonication duration and graphene oxide and nano-zinc oxide contents on the properties of polyvinyl alcohol nanocomposites

Nanofibrous composite membranes consisting of polyvinyl alcohol (PVA), graphene oxide (GO), and zinc oxide nanoparticles (ZnO NPs) were prepared by and ultrasonic processing, and electrospinning. The performance of the membranes containing different GO-to-ZnO NP mass ratios was comprehensively investigated in terms of density, mechanical properties, water vapor permeability, optical property, biodegradability and antimicrobial properties. The results showed that an appropriate sonication time (30 min) improved the membrane performance; the composite nanofibrous membrane with a GO-to-ZnO NP mass ratio of 3:7 and 30 min sonication exhibited the best performance with a water vapor permeability of (0.62 ± 0.01) × 10^-2 g·h^-1 m^-2 pa^-1, and strain and stress values of 307.84 ± 2.96% and 12.82 ± 0.56 MPa, respectively. Particularly, the UV barrier property of the composite nanofibrous membrane was enhanced. Furthermore, the membrane exhibited strong antibacterial activity against foodborne pathogenic and spoilage bacteria. Thu, it can thus be used as an active food packaging material to ensure the safety of food products and to extend their shelf-life.

Preparation and Characterization of Ultrasound Treated Polyvinyl Alcohol/Chitosan/DMC Antimicrobial Films

In this research, chitosan (CS) and poly (vinyl alcohol) (PVA) were adopted as a material, methacryloyloxyethyl trimethyl ammonium chloride (DMC) was added in various concentrations and was treated ultrasonically for the formation of films with the use of the polymer blending method. The influences exerted by the ultrasonication period on PVA/CS/DMC antimicrobial active materials underwent material characteristic tests. The consequences revealed that at the break of the compound films, ultrasonication raised the elongation and tensile strength on the whole. Ultrasonication further or also enhanced the light transmittance performance and composite films’ barrier property. Furthermore, the compound film with a DMC concentration of 2% had good antibacterial properties, the film’s inhibition rates against Staphylococcus aureus and Escherichia coli after ultrasonication were 79.23% ± 1.92% and 72.31% ± 1.35%, respectively.