Nano-sized biopolymer levan: Its antimicrobial, anti-biofilm and anti-cancer effects

Vat-Based 3D-Bioprinted Scaffolds from Photocurable Bacterial Levan for Osteogenesis and Immunomodulation

Emerging techniques of additive manufacturing, such as vat-based three-dimensional (3D) bioprinting, offer novel routes to prepare personalized scaffolds of complex geometries. However, there is a need to develop bioinks suitable for clinical translation. This study explored the potential of bacterial-sourced methacrylate levan (LeMA) as a bioink for the digital light processing (DLP) 3D bioprinting of bone tissue scaffolds. LeMA was successfully synthesized, characterized, and used to fabricate 3D-bioprinted scaffolds with excellent printability and physicochemical properties. In vitro studies demonstrated superior cytocompatibility of 15% w/v LeMA gels compared to 20% gels. 15% LeMA gels supported osteogenic differentiation , as evidenced by alkaline phosphatase activity and mineral deposition by MC3T3 pre-osteoblasts. Importantly, the LeMA hydrogels positively modulated the macrophage phenotype, promoting the expression of the anti-inflammatory marker CD206. These findings suggest that 3D-printed LeMA scaffolds can create a favorable microenvironment for bone regeneration, highlighting their potential for tissue repair and regeneration applications.

Poly(lactide)-Based Materials Modified with Biomolecules: A Review

Poly(lactic acid) (PLA) is characterized by unique features, e.g., it is environmentally friendly, biocompatible, has good thermomechanical properties, and is readily available and biodegradable. Due to the increasing pollution of the environment, PLA is a promising alternative that can potentially replace petroleum-derived polymers. Different biodegradable polymers have numerous biomedical applications and are used as packaging materials. Because the pure form of PLA is delicate, brittle, and is characterized by a slow degradation rate and a low thermal resistance and crystallization rate, these disadvantages limit the range of applications of this polymer. However, the properties of PLA can be improved by chemical or physical modification, e.g., with biomolecules. The subject of this review is the modification of PLA properties with three classes of biomolecules: polysaccharides, proteins, and nucleic acids. A quite extensive description of the most promising strategies leading to improvement of the bioactivity of PLA, through modification with these biomolecules, is presented in this review. Thus, this article deals mainly with a presentation of the major developments and research results concerning PLA-based materials modified with different biomolecules (described in the world literature during the last decades), with a focus on such methods as blending, copolymerization, or composites fabrication. The biomedical and unique biological applications of PLA-based materials, especially modified with polysaccharides and proteins, are reviewed, taking into account the growing interest and great practical potential of these new biodegradable biomaterials.

Expanding the horizons of levan: from microbial biosynthesis to applications and advanced detection methods

Levan, a β-(2,6)-linked fructose polymer, exhibits diverse properties that impart versatility, rendering it a highly sought-after biopolymer with various industrial applications. Levan can be produced by various microorganisms using sucrose, food industry byproducts and agricultural wastes. Microbial levan represents the most potent cost-effective process for commercial-scale levan production. This study reviews the optimization of levan production by understanding its biosynthesis, physicochemical properties and the fermentation process. In addition, genetic and protein engineering for its increased production and emerging methods for its detection are introduced and discussed. All of these comprehensive studies could serve as powerful tools to optimize levan production and broaden its applications across various industries.

Effect of levan polysaccharide on chronological aging in the yeast Saccharomyces cerevisiae

Levan is a fructose-based biopolymer with diverse applications in the medicinal, pharmaceutical, and food industries. However, despite its extensive biological and pharmacological actions, including antioxidant, anti-inflammatory, and antidiabetic properties, research on its anti-aging potential is limited. This study explored levan's impact on the chronological lifespan (CLS) of yeast Saccharomyces cerevisiae for the first time. The results show that levan treatment significantly extended the CLS of wild-type (WT) yeast by preventing the accumulation of oxidative stress markers (reactive oxygen species, malondialdehyde, and protein carbonyl content) and ameliorating apoptotic features such as reduced mitochondrial membrane potential, loss of plasma membrane integrity, and externalization of phosphatidylserine. By day 40 of the CLS, a significant increase in yeast viability of 6.8 % (p < 0.01), 11.9 % (p < 0.01), and 20.8 % (p < 0.01) was observed at 0.25, 0.5, and 1 mg/mL of levan concentrations, respectively, compared to control (0 %). This study's results indicate that levan treatment substantially modulates the expression of genes involved in the TORC1/Sch9 pathway. Moreover, levan treatment significantly extended the CLS of yeast antioxidant-deficient mutant sod2Δ and antiapoptotic gene-deficient mutant pep4Δ. Levan also extended the CLS of signaling pathway gene-deficient mutants such as pkh2Δ, rim15Δ, atg1, and ras2Δ, while not affecting the CLS of tor1Δ and sch9Δ.

Sustainable production of heavy metal-binding levan by a subarctic permafrost thaw lake Pseudomonas strain 2ASCA

Pseudomonas strain 2ASCA isolated in subarctic Québec, Canada, produced a cell membrane bound levan-type exopolymer (yield 1.17 g/L), after incubation in growth media containing 6 % sucrose (w/v) at temperature of 15 °C for 96 h. The objective of this study was to optimize levan production by varying the growth parameters. Moreover, the polymer's chemical characterization has been studied with the aim of increasing knowledge and leading to future applications in many fields, including heavy metal remediation. Higher levan yields (7.37 g/L) were reached by setting up microbial fermentation conditions based on the re-use of the molasses obtained from sugar beet processing. Spectroscopy analyses confirmed the levan-type nature of the exopolymer released by strain 2ASCA, consisting of a β-(2,6)-linked fructose repeating unit. Gel permeation chromatography revealed that the polymer has a molecular weight of 13 MDa. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) showed that the levan sequestered with a strong affinity Cr(III), which has never been previously reported, highlighting an interesting biosorption potential. In addition, SEM analysis revealed the formation of nanoparticles in acidified water solution.

Antimicrobial activities of Agave fructans against multi-resistant and biofilm-producing Staphylococcus aureus isolated from bovine mastitis

Bovine mastitis is an emerging disease that causes large economic losses. Staphylococcus aureus its main etiological agent, is multi-resistant to antimicrobials and produces biofilm. The objective of this study was to investigate the effect of Agave fructans (AF), a type of prebiotic, on multi-resistant and biofilm-forming isolates of S. aureus. Ten isolates of S. aureus from bovine subclinical mastitis previously characterized as highly resistant to antimicrobials and biofilm formers were used in this study. The growth kinetics of S. aureus in the presence of AF was evaluated by the Baranyi and Roberts microbial growth model using the DMFit program. The antibacterial activity of AF against S. aureus was studied by the well-diffusion method and the effect on biofilm formation by the crystal violet method. All assays were performed in triplicate for each isolate and an ANOVA with Tukey's post hoc was performed considering p < 0.05 as significant. The AF showed a decrease in maximum growth rate (µmax) and OD max levels (Ymax) in all isolates with all concentrations. Also, zones of inhibition were observed due to the effect of all AF concentrations in all isolates in a dose-dependent manner. Interestingly, S. aureus biofilm formation was inhibited by all AF concentrations assessed in this study. More investigations are required to elucidate the mechanisms of action of AF on S. aureus as well as in vivo studies to evaluate its therapeutic efficacy for bovine mastitis.

Fabrication and characterization of new levan@CBD biocomposite sponges as potential materials in natural, non-toxic wound dressing applications

Wound healing is a complex process; therefore, new dressings are frequently required to facilitate it. In this study, porous bacterial levan-based sponges containing cannabis oil (Lev@CBDs) were prepared and fully characterized. The sponges exhibited a suitable swelling ratio, proper water vapor transmission rate, sufficient thermal stability, desired mechanical properties, and good antioxidant and anti-inflammatory properties. The obtained Lev@CBD materials were evaluated in terms of their interaction with proteins, human serum albumin and fibrinogen, of which fibrinogen revealed the highest binding effect. Moreover, the obtained biomaterials exhibited antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, as well as being non-hemolytic material as indicated by hemolysis tests. Furthermore, the sponges were non-toxic and compatible with L929 mouse fibroblasts and HDF cells. Most significantly, the levan sponge with the highest content of cannabis oil, in comparison to others, retained its non-hemolytic, anti-inflammatory, and antimicrobial properties after prolonged storage in a climate chamber at a constant temperature and relative humidity. The designed sponges have conclusively proven their beneficial physicochemical properties and, at the preliminary stage, biocompatibility as well, and therefore can be considered a promising material for wound dressings in future in vivo applications.

Similarities and differences of nano-sized levan synthesized by Bacillus haynesii at low and high temperatures: Characterization and bioactivity

Levan is a biopolymer with many different uses. Temperature is an important parameter in biopolymer synthesis. Herein, levan production was carried out from Bacillus haynesii, a thermophilic microorganism, in the temperature range of 4 °C-95 °C. The highest levan production was measured as 10.9 g/L at 37 °C. The synthesized samples were characterized by FTIR and NMR analysis. The particle size of the levan samples varied between 153 and 824.4 nm at different temperatures. In levan samples produced at high temperatures, the water absorption capacity is higher in accordance with the particle size. Irregularities were observed in the surface pores at temperatures of 60 °C and above. The highest emulsion capacity of 83.4 % was measured in the sample synthesized at 4 °C. The antioxidant activity of all levan samples synthesized at different temperatures was measured as 84 % on average. All synthesized levan samples showed antibacterial effect on pathogenic bacteria. In addition, levan synthesized at 45 °C showed the highest antimicrobial effect on E. coli ATCC 35218 with an inhibition zone of 21.3 ± 1.82 mm. Antimicrobial activity against yeast sample C. albicans, was measured only in levan samples synthesized at 80 °C, 90 °C, 95 °C temperatures. Levan synthesized from Bacillus haynesii at low and high temperatures showed differences in characterization and bioactivity.

Deep eutectic solvent assisted recovery of high molecular weight levan from an isolated Neobacillus pocheonensis BPSCM4

The present study demonstrates the usage of deep eutectic solvent to recover microbial levan from the clarified fermented broth. The classic ethanol precipitation method for levan recovery is expensive because ethanol can be utilized as a biofuel. Production of ethanol consumes more energy and is not easily recycled. As a result, the current work concentrates on using environmentally friendly solvents for levan recovery. Deep Eutectic Solvents (DES) are greener and can replace ethanol from the microbial polysaccharides precipitation. Thus the proposed approach is environment friendly, technically feasible, reliable and economically viable. The levan was produced from a microbial isolate of aged sugarcane molasses, recovered using traditional ethanol and proposed DES (Choline Chloride and Ethylene Glycol) assisted precipitation. The levan-producing strain was characterized and identified as Neobacillus pocheonensis BPSCM4. The DES-precipitated levan has a high molecular weight of levan, 1.54 × 106 KDa, compared with the ethanol-precipitated levan, 4.246 KDa. The high molecular weight of DES-precipitated levan is due to the low viscosity and hydrogen interaction of ChCl:EG with the levan present in the fermented broth. Further, the optimization enhanced the levan yield to 32.56 g/L when the sucrose concentration was 250 g/L.

Exopolysaccharides Producing Bacteria: A Review

Bacterial exopolysaccharides (EPS) are essential natural biopolymers used in different areas including biomedicine, food, cosmetic, petroleum, and pharmaceuticals and also in environmental remediation. The interest in them is primarily due to their unique structure and properties such as biocompatibility, biodegradability, higher purity, hydrophilic nature, anti-inflammatory, antioxidant, anti-cancer, antibacterial, and immune-modulating and prebiotic activities. The present review summarizes the current research progress on bacterial EPSs including their properties, biological functions, and promising applications in the various fields of science, industry, medicine, and technology, as well as characteristics and the isolation sources of EPSs-producing bacterial strains. This review provides an overview of the latest advances in the study of such important industrial exopolysaccharides as xanthan, bacterial cellulose, and levan. Finally, current study limitations and future directions are discussed.

Synthesis of Cationic Quaternized Nanolevan Derivative for Small Molecule and Nucleic Acid Delivery

Levan is a biopolymer composed of fructose chains covalently linked by β−2,6 glycosidic linkages. This polymer self−assembles into a nanoparticle of uniform size, making it useful for a wide range of applications. Also, levan exhibits various biological activities such as antioxidants, anti-inflammatory, and anti-tumor, that make this polymer very attractive for biomedical application. In this study, levan synthesized from Erwinia tasmaniensis was chemically modified by glycidyl trimethylammonium chloride (GTMAC) to produce cationized nanolevan (QA-levan). The structure of the obtained GTMAC−modified levan was determined by FT-IR, 1H-NMR and elemental (CHN) analyzer. The size of the nanoparticle was calculated using the dynamic light scattering method (DLS). The formation of DNA/QA-levan polyplex was then investigated by gel electrophoresis. The modified levan was able to increase the solubility of quercetin and curcumin by 11-folds and 205-folds, respectively, compared to free compounds. Cytotoxicity of levan and QA−levan was also investigated in HEK293 cells. This finding suggests that GTMAC−modified levan should have a potential application for drug and nucleic acid delivery.

A new approach to nanocomposite carbohydrate polymer films: Levan and chia seed mucilage

Plastic pollution is increasing day by day and the search for new, environmentally friendly products continues. Herein, for the first time, different degrees of mucilage were obtained from chia seeds and the film-forming behavior of levan biopolymer with these mucilages was investigated. Glycerol and sorbitol were used as plasticizers in the film design. Films prepared with sorbitol were characterized physically, mechanically and morphologically. The antioxidant and antimicrobial effects of the films were examined. The films formed as nanocomposites of levan and chia seed mucilages obtained at different temperatures (25 °C, 55 °C and 80 °C) exhibited structurally and mechanically different properties. It was observed that the films obtained with chia mucilages and levan preserved their antibacterial properties but lost their antifungal properties. In addition, quorum sensing property of the mucilage obtained at 55 °C during the investigation of the antibacterial property was reported for the first time with this study. The levan-based chia seed mucilages films obtained have the potential to be used in industrial and medical fields, and the nature-friendly nature of these films is very important for our green world.

Production and bioactivities of nanoparticulated and ultrasonic-degraded levan generated by Erwinia tasmaniensis levansucrase in human osteosarcoma cells

Levan is a bioactive polysaccharide that can be synthesized by various microorganisms. In this study, the physicochemical properties and bioactivity of levan synthesized by recombinant levansucrase from Erwinia tasmaniensis were investigated. The synthesis conditions, including the enzyme concentration, substrate concentration, and temperature, were optimized. The obtained levan generally appeared as a cloudy suspension. However, it could transform into a hydrogel at concentrations exceeding 10 % (w/v). Then, ultrasonication was utilized to reduce the molecular weight and increase the bioavailability of levan. Dynamic light scattering (DLS) and gel permeation chromatography (GPC) indicated that the size of levan was significantly decreased by ultrasonication, whereas Fourier transform infrared spectroscopy, ¹H-nuclear magnetic resonance, and X-ray powder diffraction revealed that the chemical structure of levan was not changed. Finally, the bioactivities of both levan forms were examined using human osteosarcoma (Saos-2) cells. The result clearly illustrated that sonicated levan had higher antiproliferative activity in Saos-2 cells than original levan. Sonicated levan also activated Toll-like receptor expression at the mRNA level. These findings suggested the important beneficial applications of sonicated levan for the development of cancer therapies.

Inhibitory Effect of Bacillus licheniformis Strains Isolated from Canine Oral Cavity

Bacillus licheniformis is used in a broad spectrum of areas, including some probiotic preparations for human and veterinary health. Moreover, B. licheniformis strains are known producers of various bioactive substances with antimicrobial and antibiofilm effects. In searching for new potentially beneficial bacteria for oral health, the inhibitory effect of B. licheniformis strains isolated from canine dental biofilm against pathogenic oral bacteria was evaluated. The antimicrobial effect of neutralized cell-free supernatants (nCFS) was assessed in vitro on polystyrene microtiter plates. Furthermore, molecular and morphological analyses were executed to evaluate the production of bioactive substances. To determine the nature of antimicrobial substance present in nCFS of B. licheniformis A-1-5B-AP, nCFS was exposed to the activity of various enzymes. The nCFS of B. licheniformis A-1-5B-AP significantly (p < 0.0001) reduced the growth of Porphyromonas gulae 3/H, Prevotella intermedia 1/P and Streptococcus mutans ATCC 35668. On the other hand, B. licheniformis A-2-11B-AP only significantly (p < 0.0001) inhibited the growth of P. intermedia 1/P and S. mutans ATCC 35668. However, enzyme-treated nCFS of B. licheniformis A-1-5B-AP did not lose its antimicrobial effect and significantly (p < 0.0001) inhibited the growth of Micrococcus luteus DSM 1790. Further studies are needed for the identification of antimicrobial substances.

Bio_Fabricated Levan Polymer from Bacillus subtilis MZ292983.1 with Antibacterial, Antibiofilm, and Burn Healing Properties

The biopolymer levan has sparked a lot of interest in commercial production and various industrial applications. In this study, a bacterial isolate with promising levan-producing ability was isolated from a soil sample obtained from Princess Nourah bint Abdulrahman University in Saudi Arabia. The isolate has been identified and submitted to GenBank as Bacillus subtilis MZ292983.1. The bacterial levan polymer was extracted using ethyl alcohol (75%) and CaCl2 (1%) and then characterized using several approaches, such as Fourier transform infrared spectrometry and nuclear magnetic resonance. The IR spectrum of the levan polymer showed characteristic peaks confirming characteristics of polysaccharides, including a broad stretching peak of OH around 3417 cm−1 and aliphatic CH stretching was observed as two peaks at 2943, and 2885 cm−1. In addition, the FTIR spectrum featured an absorption at 2121 cm−1, indicating the fingerprint of the β-glycosidic bond. Based on 1H and 13C NMR spectroscopy analysis, six unexchanged proton signals related to fructose as a forming monomer of levan were observed. Evaluation of levan’s antibacterial effect against two pathogenic bacteria, S. aureus (ATCC 33592) and E. coli (ATCC 25922), showed inhibition zones of 1 cm and 0.8 cm in diameter, respectively, with MICs of more than 256 μg mL−1 for both strains. Moreover, the antibiofilm property of the levan polymer was assessed and the results showed that the inhibition rate was positively proportional to the levan concentration, as the inhibition percentages were 50%, 29.4%, 29.4%, 26.5%, and 14.7% at concentrations of 2, 1, 0.5, 0.25, and 0.125 mg mL−1, respectively. Levan showed a significant role in burn healing properties since it accelerated the process of healing burn-induced areas in rats when compared with those either treated with normal saline or treated with the cream base only.

Application of Levan-Rich Digestate Extract in the Production of Safe-to-Use and Functional Natural Body Wash Cosmetics

The study focused on the evaluation of the possibility of using a levan-rich digestate extract in the production of safe and functional body wash cosmetics. Model shower gels were designed and formulated on the basis of raw materials of natural origin. Prepared prototypes contained various extract concentrations (16.7; 33; 50%). A gel without extract was used as a reference. The samples were evaluated for their safety in use and functionality. The results showed that the use of high-concentration levan-rich digestate extract in a shower gel resulted in a significant reduction in the negative impact on the skin. For example, the zein value decreased by over 50% in relation to the preparation without the extract. An over 40% reduction in the emulsifying capacity of hydrophobic substances was also demonstrated, which reduces skin dryness after the washing process. However, the presence of the extract did not significantly affect the parameters related to functionality. Overall, it was indicated that levan-rich digestate extract can be successfully used as a valuable ingredient in natural cleansing cosmetics.

Development of Antibiofilm Therapeutics Strategies to Overcome Antimicrobial Drug Resistance

A biofilm is a community of stable microorganisms encapsulated in an extracellular matrix produced by themselves. Many types of microorganisms that are found on living hosts or in the environment can form biofilms. These include pathogenic bacteria that can serve as a reservoir for persistent infections, and are culpable for leading to a broad spectrum of chronic illnesses and emergence of antibiotic resistance making them difficult to be treated. The absence of biofilm-targeting antibiotics in the drug discovery pipeline indicates an unmet opportunity for designing new biofilm inhibitors as antimicrobial agents using various strategies and targeting distinct stages of biofilm formation. The strategies available to control biofilm formation include targeting the enzymes and proteins specific to the microorganism and those involved in the adhesion pathways leading to formation of resistant biofilms. This review primarily focuses on the recent strategies and advances responsible for identifying a myriad of antibiofilm agents and their mechanism of biofilm inhibition, including extracellular polymeric substance synthesis inhibitors, adhesion inhibitors, quorum sensing inhibitors, efflux pump inhibitors, and cyclic diguanylate inhibitors. Furthermore, we present the structure–activity relationships (SAR) of these agents, including recently discovered biofilm inhibitors, nature-derived bioactive scaffolds, synthetic small molecules, antimicrobial peptides, bioactive compounds isolated from fungi, non-proteinogenic amino acids and antibiotics. We hope to fuel interest and focus research efforts on the development of agents targeting the uniquely complex, physical and chemical heterogeneous biofilms through a multipronged approach and combinatorial therapeutics for a more effective control and management of biofilms across diseases.

Bioactive Levan-Type Exopolysaccharide Produced by Pantoea agglomerans ZMR7: Characterization and Optimization for Enhanced Production

Levan is an industrially important, functional biopolymer with considerable applications in the food and pharmaceutical fields owing to its safety and biocompatibility. Here, levan-type exopolysaccharide produced by Pantoea agglomerans ZMR7 was purified by cold ethanol precipitation and characterized using TLC, FTIR, ¹H, and ¹³C NMR spectroscopy. The maximum production of levan (28.4 g/l) was achieved when sucrose and ammonium chloride were used as carbon and nitrogen sources, respectively, at 35°C and an initial pH of 8.0. Some biomedical applications of levan like antitumor, antiparasitic, and antioxidant activities were investigated in vitro. The results revealed the ability of levan at different concentrations to decrease the viability of rhabdomyosarcoma and breast cancer cells compared with untreated cancer cells. Levan appeared also to have high antiparasitic activity against the promastigote of Leishmania tropica. Furthermore, levan had strong DPPH radical scavenging (antioxidant) activity. These findings suggest that levan produced by P. agglomerans ZMR7 can serve as a natural biopolymer candidate for the pharmaceutical and medical fields.

Biomedical Applications of Bacterial Exopolysaccharides: A Review

Bacterial exopolysaccharides (EPSs) are an essential group of compounds secreted by bacteria. These versatile EPSs are utilized individually or in combination with different materials for a broad range of biomedical field functions. The various applications can be explained by the vast number of derivatives with useful properties that can be controlled. This review offers insight on the current research trend of nine commonly used EPSs, their biosynthesis pathways, their characteristics, and the biomedical applications of these relevant bioproducts.