Antimicrobial Properties and Application of Polysaccharides and Their Derivatives

Isolation, structural, biological activity and application of Gleditsia species seeds galactomannans

Gleditsia fruits have been known as a valuable traditional Chinese herb for tens of centuries. Previous studies showed that the galactomannans are considered as one of the major bioactive components in Gleditsia fruits seeds (GSGs). Here, we systematically review the major studies of GSGs in recent years to promote their better understanding. The extraction methods of GSGs mainly include hot water extraction, microwave-assisted extraction, ultrasonic extraction, acid extraction, and alkali extraction. The analysis revealed that GGSs exhibited in the form of semi-flexible coils, and its molecular weight ranged from 0.018 × 103 to 2.778 × 103 KDa. GSGs are composed of various monosaccharide constituents such as mannose, galactose, glucose, and arabinose. In terms of pharmacological effects, GSGs exhibit excellent activity in antioxidation, hypoglycemic, hypolipidemic, anti-inflammation. Moreover, GSGs have excellent bioavailability, biocompatibility, and biodegradability, which make them used in food additives, food packaging, pharmaceutical field, industry and agriculture. Of cause, the shortcomings of the current research and the potential development and future research are also highlighted. We believe our work provides comprehensive knowledge and underpinnings for further research and development of GSGs.

Polysaccharides from shell waste of shellfish and their applications in the cosmeceutical industry: A review

Shell waste from shellfish processing contains valuable natural polysaccharides, including sulfated polysaccharides, acidic polysaccharides, glycosaminoglycans, chitin and their derivatives. These shellfish waste-derived polysaccharides have numerous functional and biological properties that can be applied in various industries, including the cosmeceutical industry. In keeping with global sustainability and green industry trends, the cosmeceuticals industry is transitioning from petrochemical-based ingredients to natural substitutes. In this context, shell waste-derived polysaccharides and their derivatives can play a major role as natural substitutes for petroleum-based components in various cosmeceutical skincare, hair care, oral care and body care products. This review focuses on the presence of polysaccharides and their derivatives in shell waste and discusses their various cosmeceutical applications in skin care, hair care, sun care, oral care and body care products. This indicates that shell waste utilization will help create a circular economy in which extracted polysaccharides are used to produce green cosmeceutical products.

Hyperbranched Poly-L-Lysine-Based Water-Insoluble Complexes as Antibacterial Agents with Efficient Antibacterial Activity And Cytocompatibility

Despite the advances in technology, bacterial infection associated with biomedical devices is still one of the most challenging issues in clinical practice. Incorporation of antimicrobial agents is regarded as an efficient way to combat medical device associated infectious. However, most of antimicrobial agents have high toxicity to host cells. Thus, fabrication of novel antimicrobial agents that simultaneously fulfill the requirements of antibacterial activity as well as biocompatibility is urgently needed. Herein, a series of water-insoluble antibacterial complexes based on hyperbranched poly-L-lysine (HBPL) and four different surfactants through non-covalent interactions are developed. Such kinds of surfactants have great effects on the antibacterial property of poly(ɛ-caprolactone) (PCL) films that incorporate with the HBPL-based complexes. The results reveal that the PCL films that doped with HBPL/phosphate ester surfactant complexes showed the highest bacterial killing efficiency. Moreover, the cytocompatibility of the composite films is also investigated. Hemolysis experiments indicate that all the films  had low hemolytic activities. Considering the excellent antimicrobial and cytocompatibility properties, this work believes that the optimized complexes have great potential to be used as antimicrobial agents in biomedical field.

Quorum Sensing in Gram-Negative Bacteria: Strategies to Overcome Antibiotic Resistance in Ocular Infections

Truly miraculous medications and antibiotics have helped save untold millions of lives. Antibiotic resistance, however, is a significant issue related to health that jeopardizes the effectiveness of antibiotics and could harm everyone's health. Bacteria, not humans or animals, become antibiotic-resistant. Bacteria use quorum-sensing communication routes to manage an assortment of physiological exercises. Quorum sensing is significant for appropriate biofilm development. Antibiotic resistance occurs when bacteria establish a biofilm on a surface, shielding them from the effects of infection-fighting drugs. Acylated homoserine lactones are used as autoinducers by gram-negative microscopic organisms to impart. However, antibiotic resistance among ocular pathogens is increasing worldwide. Bacteria are a significant contributor to ocular infections around the world. Gram-negative microscopic organisms are dangerous to ophthalmic tissues. This review highlights the use of elective drug targets and treatments, for example, combinational treatment, to vanquish antibiotic-resistant bacteria. Also, it briefly portrays anti-biotic resistance brought about by gram-negative bacteria and approaches to overcome resistance with the help of quorum sensing inhibitors and nanotechnology as a promising medication conveyance approach to give insurance of anti-microbials and improve pathways for the administration of inhibitors of quorum sensing with a blend of anti-microbials to explicit target destinations and penetration through biofilms for treatment of ocular infections. It centres on the methodologies to sidestep the confinements of ocular anti-biotic delivery with new visual innovation.

Control the carcinogenic bacteria with new polysaccharides from agricultural wastes

Agriculture activities industries produce a huge amount of waste every year. Agricultural wastes are a great source of natural polysaccharides characterized by accessibility, biocompatibility, and ease of modification. Finding new safe antibacterial agents has become one of the top priorities of health organizations worldwide. This priority emerged from the antibiotic resistance pathogenic bacteria hazard. Carcinogenic bacteria are one of the most dangerous antibiotic-resistant pathogenic bacteria. This study tries to investigate the antibacterial activity of polysaccharides from some agricultural wastes against carcinogenic bacteria related to gastrointestinal cancers. We determined the antibacterial activity (in terms of minimum inhibitory concentration (MIC)) and the biofilm reduction capacity. We studied the mechanism of the antibacterial activity by determining the effect of the MIC of the extracted polysaccharides on the plasma membrane permeability and the bacterial DNA content. All extracted polysaccharides showed effective antibacterial activity with low MICs ranging from 2 to 20 μg/mL. The barely straw polysaccharides showed the highest MIC (19.844 μg/mL) against Bacteroides fragilis, while the grape bagasse showed the lowest MIC (2.489 μg/mL) against Helicobacter pylori. The extracted polysaccharide showed high antibiofilm activity. Their capacity to reduce the formation of the pathogenic biofilm ranged from 75 to 95%. Regarding the antibacterial mechanism, the extracted polysaccharides showed destructive action on the DNA and the plasma membrane permeability. The bacterial DNA change percent after the treatment with the different polysaccharides ranged from 29% to -58%. The plasma membrane permeability increased by a high percentage, ranging from 92% to 123%. Agricultural waste polysaccharides are a promising antibacterial agent against antibiotic-resistant carcinogenic bacteria.

Natural polysaccharides protect against diet-induced obesity by improving lipid metabolism and regulating the immune system

Unhealthy dietary patterns-induced obesity and obesity-related complications pose a great threat to human health all over the world. Accumulating evidence suggests that the pathophysiology of obesity and obesity-associated metabolic disorders is closely associated with dysregulation of lipid and energy metabolism, and metabolic inflammation. In this review, three potential anti-obesity mechanisms of natural polysaccharides are introduced. Firstly, natural polysaccharides protect against diet-induced obesity directly by improving lipid and cholesterol metabolism. Since the immunity also affects lipid and energy metabolism, natural polysaccharides improve lipid and energy metabolism by regulating host immunity. Moreover, diet-induced mitochondrial dysfunction, prolonged endoplasmic reticulum stress, defective autophagy and microbial dysbiosis can disrupt lipid and/or energy metabolism in a direct and/or inflammation-induced manner. Therefore, natural polysaccharides also improve lipid and energy metabolism and suppress inflammation by alleviating mitochondrial dysfunction and endoplasmic reticulum stress, promoting autophagy and regulating gut microbiota composition. Specifically, this review comprehensively summarizes underlying anti-obesity mechanisms of natural polysaccharides and provides a theoretical basis for the development of functional foods. For the first time, this review elucidates anti-obesity mechanisms of natural polysaccharides from the perspectives of their hypolipidemic, energy-regulating and immune-regulating mechanisms.

Molecular docking and antibacterial activity of Sargassum fusiforme extracts against major coral pathogens

The present study evaluates the antibacterial properties of alkaloids and the crude extracts (ethanol, n-hexane and ethyl acetate) from seaweed Sargassum fusiforme against coral pathogens (Photobacterium galatheae, Vibrio harveyi, Bordetella trematum, and Ochrobactrum pseudogrignonese) isolated from coral Porites lutea. To our knowledge, this is the first in vitro assay for such extracts on Porites lutea coral pathogens. Bacterial pathogens have been identified using 16S RNA and BankIt into gene bank and given the accession numbers (OR401000; OR401001; OR401336, and OR400998 respectively). GC-Mass profiling conducted for n-hexane compounds confirmed the presence of thirty-eight molecules, twelve of which have been previously reported for their bioactivity. The results revealed that alkaloids and n-hexane extract demonstrated eminent antibacterial activity compared to the other extracts against the tested coral pathogenic bacteria. Molecular docking was conducted to evaluate the twelve previously mentioned bioactive molecules to get a full understanding of the interaction of those bioactive molecules on vital bacterial proteins (Hemolysin protein (PDB ID: 1XEZ) and Cytoplasmic proteins (PDB ID: 3TZC)). Docked twelve molecules against hemolysin protein (PDB ID: 1XEZ) came exactly in line with the docked result of the same molecules with cytoplasmic proteins (PDB ID: 3TZC), proving the bioactivity of 6-O-Palmitoyl-L-ascorbic acid, 3TMS derivative; Glycerol monostearate, 2TMS derivative and Eicosanoic acid complexes in antibacterial activity action and score higher than reference ligand. Those three compounds will be investigated separately in future in vitro assay soon. Our conclusions align with the study's antibacterial in vitro assay results. The present study reports the novelty of different extracts of S. fusiforme as an antibacterial agent against coral pathogenic bacteria that trigger diseases in Porites lutea.

Ultrasound-assisted extraction and analysis of maidenhairtree polysaccharides

The maidenhairtree polysaccharides (MTPs) have important application prospects. So, the extraction, purification, structure, derivatization and biological activities of polysaccharides from leaves, fruits, and testae of maidenhairtree were disscussed. Polysaccharides were extracted by collaborative extraction methods such as ultrasound-assisted extraction and microwave-assisted extraction. The ultrasound-assisted extraction had higher content and higher efficiency. The structural characteristics and structure-activity relationship of maidenhairtree polysaccharides were studied in order to provide theoretical basis and technical support for the further development and utilization of maidenhairtree polysaccharides.

A natural polyphenol-functionalized chitosan/gelatin sponge for accelerating hemostasis and infected wound healing

Natural polymers have been particularly appealing for constructing hemostatic materials/devices, but it is still desirable to develop new natural polymer-based biomaterials with balanced hemostatic and wound-healing performance. In this work, a natural polyphenol-functionalized chitosan/gelatin sponge (PCGS) was prepared by the lyophilization of a chitosan/gelatin mixture solution (under a self-foaming condition to prepare the CGS) and subsequent chemical cross-linking with procyanidin (PC). Compared with the original CGS, PCGS exhibited an enhanced liquid-absorption ability, reduced surface charges, and similar/low hemolysis rate. Benefiting from such a liquid-absorption ability (∼4000% for whole blood and normal saline) and moderate surface charges, PCGS exhibited high in vitro hemostatic property and promising hemostatic performance in an in vivo femoral-artery-injury model. In addition, PCGS possessed higher antioxidant property and slightly decreased antibacterial ability than CGS, owing to the incorporation of PC. The feasibility of PCGS for treating infected wounds was further confirmed in an in vivo infected-tooth-extraction model, as the typical complication of intractable tooth-extraction bleeding. The present work demonstrated a facile approach for developing multifunctional hemostatic materials through the flexible management of natural polymers and polyphenols.

Significantly improved antifouling capability of silicone rubber surfaces by covalently bonded acrylated agarose towards biomedical applications

Bacteria have the extraordinary ability to adhere to biomaterial surfaces and form multicellular structures known as biofilms, which have a detrimental impact on the performance of medical devices. Herein, an investigation highlighted the effective inhibition of bacteria adhesion and overgrowth on silicone rubber surface by grafting polysaccharide, agarose (AG), to construct hydrophilic and negatively charged surfaces. Because of the strong hydration capacity of agarose, the water contact angle of the modified silicone rubber surfaces was significantly reduced from 107.6 ± 2.7° to 19.3 ± 2.6°, which successfully limited bacterial adherence. Most importantly, the durability and stability of coating were observed after 10 days of simulated dynamic microenvironment in vivo, exhibiting a long service life. This modification method did not compromise biocompatibility of silicone rubber, opening a door to new applications for silicone rubber in the field of biomedical materials.

Hyaluronic acid association with bacterial, fungal and viral infections: Can hyaluronic acid be used as an antimicrobial polymer for biomedical and pharmaceutical applications?

The relationships between hyaluronic acid (HA) and pathological microorganisms incite new understandings on microbial infection, tissue penetration, disease progression and lastly, potential treatments. These understandings are important for the advancement of next generation antimicrobial therapeutical strategies for the control of healthcare-associated infections. Herein, this review will focus on the interplay between HA, bacteria, fungi, and viruses. This review will also comprehensively detail and discuss the antimicrobial activity displayed by various HA molecular weights for a variety of biomedical and pharmaceutical applications, including microbiology, pharmaceutics, and tissue engineering.

Modification and Functionalization of Polymers for Targeting to Bone Cancer and Bone Regeneration

Bone is one of the most complex, inaccessible body structures, responsible for calcium storage and haematopoiesis. The second highest cause of death across the world is cancer. Amongst all the types of cancers, bone cancer treatment modalities are limited due to the structural complexity and inaccessibility of bones. The worldwide incidence of bone diseases and bone defects due to cancer, infection, trauma, age-related bone degeneration is increasing. Currently different conventional therapies are available for bone cancer such as chemotherapy, surgery and radiotherapy, but they have several disadvantages associated with them. Nanomedicine is being extensively researched as viable therapeutics to mitigate drug resistance in cancer therapy and promote bone regeneration. Several natural polymers such as chitosan, dextran, alginate, hyaluronic acid, and synthetic polymers like polyglycolic acid, poly(lactic-co-glycolic acid), polycaprolactone are investigated for their application in nanomedicine for bone cancer treatment and bone regeneration. Nanocarriers have shown promising results in preclinical experimental studies. However, they still face a major drawback of inadequate targetability. The paper summarizes the status of research and the progress made so far in modifications and functionalization of natural polymers for improving their site specificity and targeting for effective treatment of bone cancer and enhancing bone regeneration.

Progress in the application of sustained-release drug microspheres in tissue engineering

Sustained-release drug-loaded microspheres provide a long-acting sustained release, with targeted and other effects. There are many types of sustained-release drug microspheres and various preparation methods, and they are easy to operate. For these reasons, they have attracted widespread interest and are widely used in tissue engineering and other fields. In this paper, we provide a systematic review of the application of sustained-release drug microspheres in tissue engineering. First, we introduce this new type of drug delivery system (sustained-release drug carriers), describe the types of sustained-release drug microspheres, and summarize the characteristics of different microspheres. Second, we summarize the preparation methods of sustained-release drug microspheres and summarize the materials required for preparing microspheres. Third, various applications of sustained-release drug microspheres in tissue engineering are summarized. Finally, we summarize the shortcomings and discuss future prospects in the development of sustained-release drug microspheres. The purpose of this paper was to provide a further systematic understanding of the application of sustained-release drug microspheres in tissue engineering for the personnel engaged in related fields and to provide inspiration and new ideas for studies in related fields.

Structural Characterization of an Alcohol-Soluble Polysaccharide from Bletilla striata and Antitumor Activities in Vivo and in Vitro

In general, Bletilla striata polysaccharides were mostly water-soluble. However, the structural property, immunomodulatory effects and antitumor activities of alcohol-soluble Bletilla striata polysaccharide were rarely reported. In this study, an alcohol-soluble Bletilla striata polysaccharide was firstly extracted, investigated the structural property and evaluated the antitumor activity in vivo and in vitro. Results showed that BSAP was a low molecular weight polysaccharide (2.29×10⁴  Da) and consisted of glucose, xylose and mannose (molar ratio: 2.39 : 1.00 : 0.21). Animal experiments results suggested that BSAP could effectively inhibit the expansion of H22 solid tumors, protect thymus and spleen, improve macrophages, lymphocytes and NK cells activities and enhance lymphocyte subsets proportion, presenting a better immunological enhancement effect in vivo. Additionally, the results of cell experiments showed that BSAP had obvious antitumor effect in vitro, including inhibiting the proliferation of H22 cells and inducing the apoptosis of tumor cells. These results would provide theoretical basis and new ideas for the further development and utilization of BSAP in the biomedical field.

Enzyme-triggered smart antimicrobial drug release systems against bacterial infections

The rapid emergence and spread of drug-resistant bacteria, as one of the most pressing public health threats, are declining our arsenal of available antimicrobial drugs. Advanced antimicrobial drug delivery systems that can achieve precise and controlled release of antimicrobial agents in the microenvironment of bacterial infections will retard the development of antimicrobial resistance. A variety of extracellular enzymes are secreted by bacteria to destroy physical integrity of tissue during their invasion of host body, which can be utilized as stimuli to trigger "on-demand" release of antimicrobials. In the past decade, such bacterial enzyme responsive drug release systems have been intensively studied but few review has been released. Herein, we systematically summarize the recent progress of smart antimicrobial drug delivery systems triggered by bacteria secreted enzymes such as lipase, hyaluronidase, protease and antibiotic degrading enzymes. The perspectives and existing key issues of this field will also be discussed to fuel the innovative research and translational application in the future.

Precise Assembly of Proteins and Carbohydrates for Next-Generation Biomaterials

The complexity and diversity of biomacromolecules make them a unique class of building blocks for generating precise assemblies. They are particularly available to a new generation of biomaterials integrated with living systems due to their intrinsic properties such as accurate recognition, self-organization, and adaptability. Therefore, many excellent approaches have been developed, leading to a variety of quite practical outcomes. Here, we review recent advances in the fabrication and application of artificially precise assemblies by employing proteins and carbohydrates as building blocks, followed by our perspectives on some of new challenges, goals, and opportunities for the future research directions in this field.

New Materials Based on Molecular Interaction between Hyaluronic Acid and Bovine Albumin

In this work, the interactions between hyaluronic acid and bovine serum albumin were investigated. The film-forming properties of the mixture were proven, and the mechanical and surface properties of the films were measured. The results showed the interactions between hyaluronic acid and albumin, mainly by hydrogen bonds. Molecular docking was used for the visualization of the interactions. The films obtained from the mixture of hyaluronic acid possessed different properties to films obtained from the single component. The addition of bovine serum albumin to hyaluronic acid led to a decrease in the mechanical properties, and to an increase in the surface roughness of the film. The new materials that have been obtained by blending can form a new group of materials for biomedicine and cosmetology.

Tailorable antibacterial and cytotoxic chitosan derivatives by introducing quaternary ammonium salt and sulfobetaine

Chitosan (CS) derivatives with improved water solubility, antibacterial activity and adequate biocompatibility are attracting increasingly interest in medical application. Herein, we have successfully synthesized isocyanate terminated quaternary ammonium salt (IQAS) and sulfopropylbetaine (ISB) to be readily covalently bounded to CS skeleton by selective reaction with amino and hydroxyl groups. And their molecular structures and crystallinity were confirmed by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and X-ray diffraction. The effect of the substitution degree, carbon chain length, content ratio of IQAS/ISB on their water solubility, antibacterial activity and cytotoxicity were systematically investigated, which shows that those properties of the CS derivatives can be tailored by adjusting the grafted antibacterial agents and their additive amount. The structure-property relationship of these CS derivatives may provide a solid guidance on the development of CS derivatives for more efficient practical applications.

Application of innovative packaging technologies to manage fungi and mycotoxin contamination in agricultural products: Current status, challenges, and perspectives

The consumer demand for safe, "healthy," and premium foods, preferably with an extended shelf-life; demand for easy packaging; and choice for more sustainable food packaging have contributed to the development of novel packaging technologies. The application of adequate packaging materials has recently become a major post-harvest challenge concerning the control of fungi and mycotoxin. This review will describe the current antifungal packaging technology involved to prevent the contamination of fungi and mycotoxin, along with the characteristics and mechanism of action in food products. Antifungal packaging has incredible potential in the food packaging sector. The most suitable approach for the safe storage of agricultural produce for farmers is the hermetic packaging technology, which maintains quality while providing a good barrier against fungi and mycotoxin. Furthermore, active antifungal packaging is a viable method for incorporating antifungal agents against pathogenic fungi. Essential oils and organic acid have received more scientific attention due to their increased efficacy against mold growth. Polypeptides, chitosan, and natamycin incorporated in active packaging significantly reduced fungi. Even though nanotechnological advancements in antifungal packaging are promising, safety and regulation issues remain significant concerns.

Antimicrobial Peptides and Macromolecules for Combating Microbial Infections: From Agents to Interfaces

Bacterial resistance caused by the overuse of antibiotics and the shelter of biofilms has evolved into a global health crisis, which drives researchers to continuously explore antimicrobial molecules and strategies to fight against drug-resistant bacteria and biofilm-associated infections. Cationic antimicrobial peptides (AMPs) are considered to be a category of potential alternative for antibiotics owing to their excellent bactericidal potency and lesser likelihood of inducing drug resistance through their distinctive antimicrobial mechanisms. In this review, the hitherto reported plentiful action modes of AMPs are systematically classified into 15 types and three categories (membrane destructive, nondestructive membrane disturbance, and intracellular targeting mechanisms). Besides natural AMPs, cationic polypeptides, synthetic polymers, and biopolymers enable to achieve tunable antimicrobial properties by optimizing their structures. Subsequently, the applications of these cationic antimicrobial agents at the biointerface as contact-active surface coatings and multifunctional wound dressings are also emphasized here. At last, we provide our perspectives on the development of clinically significant cationic antimicrobials and related challenges in the translation of these materials.

Non-Leaching, Rapid Bactericidal and Biocompatible Polyester Fabrics Finished with Benzophenone Terminated N-halamine

Pathogenic bacteria can proliferate rapidly on porous fabrics to form bacterial plaques/biofilms, resulting in potential sources of cross-transmissions of diseases and increasing cross-infection in public environments. Many works on antibacterial modification of cotton fabrics have been reported, while very few works were reported to endow poly(ethylene terephthalate) (PET) fabrics with non-leaching antibacterial function without compromising their innate physicochemical properties though PET is the most widely used fabric. Therefore, it is urgent to impart the PET fabrics with non-leaching antibacterial activity. Herein, a novel N-halamine compound, 1-chloro-3-benzophenone-5,5-dimethylhydantoin (Cl-BPDMH), was developed to be covalently bonded onto PET fabrics, rendering non-leaching antibacterial activity while negligible cytotoxicity based on contact-killing principle. Bacterial was easily adhered to Cl-BPDMH finished PET fabrics, and then it was inactivated quickly within 10 s. Furthermore, the breaking strength, breaking elongation, tearing strength, water vapor permeability, air permeability and whiteness of Cl-BPDMH finished PET fabrics were improved obviously compared to raw PET fabrics. Hence, this work developed a facile approach to fabricate multifunctional synthetic textiles to render outstanding and rapid bactericidal activity without compromising their physicochemical properties and biocompatibility.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s42765-021-00100-z.

Encapsulation of Natural Bioactive Compounds by Electrospinning-Applications in Food Storage and Safety

Packaging is used to protect foods from environmental influences and microbial contamination to maintain the quality and safety of commercial food products, to avoid their spoilage and to extend their shelf life. In this respect, bioactive packaging is developing to additionally provides antibacterial and antioxidant activity with the same goals i.e., extending the shelf life while ensuring safety of the food products. New solutions are designed using natural antimicrobial and antioxidant agents such as essential oils, some polysaccharides, natural inorganic nanoparticles (nanoclays, oxides, metals as silver) incorporated/encapsulated into appropriate carriers in order to be used in food packaging. Electrospinning/electrospraying are receiving attention as encapsulation methods due to their cost-effectiveness, versatility and scalability. The electrospun nanofibers and electro-sprayed nanoparticles can preserve the functionality and protect the encapsulated bioactive compounds (BC). In this review are summarized recent results regarding applications of nanostructured suitable materials containing essential oils for food safety.

Low Molar Mass Dextran: One-Step Synthesis With Dextransucrase by Site-Directed Mutagenesis and its Potential of Iron-Loading

Iron dextran is a common anti-anemia drug, and it requires low molar mass dextran as substrate. In this work, we selected 11 amino acid residues in domain A/B of DSR-MΔ2 within a 5-angstrom distance from sucrose for site-directed mutagenesis by molecular docking. Mutation of Q634 did not affect the enzyme catalytic activity, but showed an obvious impact on the ratio of low molecular weight dextran (L-dextran, 3,000–5,000 Da) and relatively higher molecular weight dextran (H-dextran, around 10,000 Da). L-dextran was the main product synthesized by DSR-MΔ2 Q634A, and its average molecular weight was 3,951 Da with a polydispersity index <1.3. The structural characterization of this homopolysaccharide revealed that it was a dextran, with 86.0% α(1→6) and 14.0% α(1→4) glycosidic linkages. Moreover, L-dextran was oxidized with NaOH and chelated with ferric trichloride, and an OL-dextran-iron complex was synthesized with a high iron-loading potential of 33.5% (w/w). Altogether, mutation of amino acids near the sucrose binding site of dextransucrase can affect the chain elongation process, making it possible to modulate dextran size.

Polysaccharide-Based Nanocomposites for Food Packaging Applications

The article presents a review of the literature on the use of polysaccharide bionanocomposites in the context of their potential use as food packaging materials. Composites of this type consist of at least two phases, of which the outer phase is a polysaccharide, and the inner phase (dispersed phase) is an enhancing agent with a particle size of 1-100 nm in at least one dimension. The literature review was carried out using data from the Web of Science database using VosViewer, free software for scientometric analysis. Source analysis concluded that polysaccharides such as chitosan, cellulose, and starch are widely used in food packaging applications, as are reinforcing agents such as silver nanoparticles and cellulose nanostructures (e.g., cellulose nanocrystals and nanocellulose). The addition of reinforcing agents improves the thermal and mechanical stability of the polysaccharide films and nanocomposites. Here we highlighted the nanocomposites containing silver nanoparticles, which exhibited antimicrobial properties. Finally, it can be concluded that polysaccharide-based nanocomposites have sufficient properties to be tested as food packaging materials in a wide spectrum of applications.