Exopolysaccharide Research Articles

Biofilm exopolysaccharides alter sensory-neuron-mediated sickness during lung infection

Infections of the lung cause observable sickness thought to be secondary to inflammation. Signs of sickness are crucial to alert others via behavioral-immune responses to limit contact with contagious individuals. Gram-negative bacteria produce exopolysaccharide (EPS) that provides microbial protection; however, the impact of EPS on sickness remains uncertain. Using genome-engineered Pseudomonas aeruginosa (P.aeruginosa) strains, we compared EPS-producers versus non-producers and a virulent Escherichia coli (E.coli) lung infection model in male and female mice. EPS-negative P.aeruginosa and virulent E.coli infection caused severe sickness, behavioral alterations, inflammation, and hypothermia mediated by TLR4 detection of the exposed lipopolysaccharide (LPS) in lung TRPV1+ sensory neurons. However, inflammation did not account for sickness. Stimulation of lung nociceptors induced acute stress responses in the paraventricular hypothalamic nuclei by activating corticotropin-releasing hormone neurons responsible for sickness behavior and hypothermia. Thus, EPS-producing biofilm pathogens evade initiating a lung-brain sensory neuronal response that results in sickness.

Enhancing sunflower resilience: Zinc-solubilizing bacteria mitigate cadmium uptake and translocation

<p>Cadmium (Cd) is a highly hazardous metal known for its easy absorption and accumulation in plants, particularly in edible vegetable oils. Sunflower (Helianthus annuus L.) holds global significance as an oil crop. This study aims to assess the potential of zinc-solubilizing bacterial strains in reducing cadmium uptake by enhancing zinc availability in sunflower plants. For this investigation, we selected twelve pre-isolated zinc-solubilizing bacterial (ZSB) strains for screening against cadmium tolerance and were evaluated for their exopolysaccharides (EPS) and siderophore production capabilities. Four strains exhibiting excellent tolerance to cadmium, EPS production, and siderophore production were subsequently inoculated into sunflower plants to determine the cadmium concentration to determine EC50 at various cadmium levels (ranging from 0 to 200 mg kg-1). Following the compatibility assessment of these strains as single and consortium inoculation, sunflower seeds were cultivated in jars containing soil with two cadmium levels (0 and 125 mg kg-1), totaling 600 g of soil. Our findings demonstrated that the application of ZSB significantly enhanced sunflower growth while simultaneously reducing cadmium uptake. Particularly noteworthy was the performance of the bacterial consortium, composed of strains ZM27 and AN31, which resulted in a remarkable 96% reduction in cadmium translocation, an 86% decrease in cadmium bioaccumulation, and a 97% reduction in overall cadmium uptake compared to the control group. Moreover, the same treatment has caused increase in root length (21.6%), shoot length (18.8%), chlorophyll contents (23.5%), Zn in shoot (30.8%), root Zn contents (13.5%), seedling vigor (49.6%) and leaf area (23.1%) of sunflower under Cd stress as compared to control. The present study concludes that zinc-solubilizing bacterial strains, in consortium ZM27+AN31 were found effective in mitigating the adverse effects of cadmium uptake in sunflower plants. These results suggest that bacterial inoculation strategies hold significant promise for reducing cadmium content in sunflower crops, thereby enhancing the safety and suitability of sunflower-derived edible oils for human consumption and safeguarding human health.</p>

Enzymatic hydrolysis of soybean hulls to produce a potential carbon source for cultivation of exopolysaccharide-producing diazotrophic bacteria

Lignocellulosic biomass, such as soybean hulls, constitutes a promising alternative substrate for application in biotechnological processes, as it is abundant, inexpensive, and renewable. However, its use is limited by the inability of bacteria and yeasts to assimilate it. To solve this problem, pretreatment and enzymatic hydrolysis conditions of soybean hulls were studied to produce a substrate capable of assimilating by exopolysaccharide-producing diazotrophic bacteria. Pretreatments by microwave (power of 1.4 kW during 30 s, 60 s, or 120 s) or autoclave (1.1 atm and 121 °C during 15 min, 30 min, or 60 min) were tested to favor the enzymatic action. Celluclast 1.5L® was used as a biocatalyst. The best results for pretreatment were obtained in an autoclave (121 °C for 15 min), with an increase of 6.7 times in the concentration of reducing sugars (40.4 g/L) in relation to hydrolysis without any previous pretreatment (6.0 g/L). The best hydrolysis conditions were established as a temperature of 50 °C, pH 5.3, and enzyme/substrate ratio of 20 FPU/g, reaching 40.4 g/L of reducing sugars. The hydrolysate was composed mainly of cellobiose, followed of glucose, xylose, and arabinose. It was used for the cultivation of Mesorhizobium sp. Semia 816, producing 1.26 g/L biomass and 3.93 g/L exopolysaccharides (EPS). An increase in viscosity with a pH decrease was observed, as well as a high degradation temperature. These results proved that soybean hull hydrolysate can be assimilated by Mesorhizobium sp. Semia 816 to produce EPS with potential industrial applications.

Optimization of Culture Medium for the Production of an Exopolysaccharide (p-CY02) with Cryoprotective Activity by Pseudoalteromonas sp. RosPo-2 from the Antarctic Sea.

When cells are exposed to freezing temperatures, high concentrations of cryoprotective agents (CPA) prevent ice crystal formation, thus enhancing cell survival. However, high concentrations of CPAs can also cause cell toxicity. Exopolysaccharides (EPSs) from polar marine environments exhibit lower toxicity and display effects similar to traditional CPA. In this study, we sought to address these issues by i) selecting strains that produce EPS with novel cryoprotective activity, and ii) optimizing culture conditions for EPS production. Sixty-six bacteria producing mucous substances were isolated from the Ross Sea (Antarctic Ocean) using solid marine agar plates. Among them, Pseudoalteromonas sp. RosPo-2 was ultimately selected based on the rheological properties of the produced EPS (p-CY02). Cryoprotective activity experiments demonstrated that p-CY02 exhibited significantly cryoprotective activity at a concentration of 0.8% (w/v) on mammalian cells (HaCaT). This activity was further improved when combined with various concentrations of dimethyl sulfoxide (DMSO) compared to using DMSO alone. Moreover, the survival rate of HaCaT cells treated with 5% (v/v) DMSO and 0.8% (w/v) p-CY02 was measured at 87.9 ± 2.8% after freezing treatment. This suggests that p-CY02 may be developed as a more effective, less toxic, and novel non-permeating CPA. To enhance the production of EPS with cryoprotective activity, Response Surface Methodology (RSM) was implemented, resulting in a 1.64-fold increase in production of EPS with cryoprotective activity.

A non-immunotoxic exopolysaccharide with anticancer effect in colorectal cancer isolated from Lacticaseibacillus rhamnosus ACS5 strain

Recent studies demonstrated the potential of exopolysaccharides (EPS) produced by LAB (lactic acid bacteria), to be used in different fields. In our study, L-EPS-ACS5 from Lacticaseibacillus rhamnosus ACS5 strain isolated from Ayvalık Cunda Sepet Cheese, one of the traditional cheeses of Turkey, showed antiproliferative effect in a time-dependent manner in human colon cancer (HT-29) cell line compared to healthy control line (L929). This effect was also confirmed by colony formation analysis. Apoptotic changes were investigated at molecular level using qPCR, Western blot and it was determined that the relevant L-EPS induced apoptosis by increasing Bax, Caspase 3, and 9 expression while reducing the Bcl-2 expression. These changes were confirmed by observations done at nuclear and cellular morphology level using a fluorescence microscope (Hoescht 33258) and TEM. In addition, the immunostimulatory activity of the relevant L-EPS was evaluated in terms of proliferation, phagocytosis ability and nitric oxide (NO) production parameters in the RAW 264.7 macrophage cell line. The increase in proliferative activity was not significant, and in parallel with these results, the differences in the control and application groups as a result of 'phagocytic activity and NO production analyzes' were also not significant. However, L-EPS-ACS5 did not show immunotoxic/cytotoxic activity in macrophage cells (% viability >70). All these cellular and molecular evidences indicate that L-EPS-ACS5 may be a good alternative to synthetic anti-cancer agents with its anticancer effect and non-immunotoxic properties in colorectal cancer.

Comparative Analysis of Plant Growth-Promoting Rhizobacteria's Effects on Alfalfa Growth at the Seedling and Flowering Stages under Salt Stress.

Alfalfa (Medicago sativa L.), a forage legume known for its moderate salt-alkali tolerance, offers notable economic and ecological benefits and aids in soil amelioration when cultivated in saline-alkaline soils. Nonetheless, the limited stress resistance of alfalfa could curtail its productivity. This study investigated the salt tolerance and growth-promoting characteristics (in vitro) of four strains of plant growth-promoting rhizobacteria (PGPR) that were pre-selected, as well as their effects on alfalfa at different growth stages (a pot experiment). The results showed that the selected strains belonged to the genera Priestia (HL3), Bacillus (HL6 and HG12), and Paenibacillus (HG24). All four strains exhibited the ability to solubilize phosphate and produce indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. Among them, except for strain HG24, the other strains could tolerate 9% NaCl stress. Treatment with 100 mM NaCl consistently decreased the IAA production levels of the selected strains, but inconsistent changes (either enhanced or reduced) in terms of phosphate solubilization, ACC deaminase, and exopolysaccharides (EPS) production were observed among the strains. During the various growth stages of alfalfa, PGPR exhibited different growth-promoting effects: at the seedling stage, they enhanced salt tolerance through the induction of physiological changes; at the flowering stage, they promoted growth through nutrient acquisition. The current findings suggest that strains HL3, HL6, and HG12 are effective microbial inoculants for alleviating salt stress in alfalfa plants in arid and semi-arid regions. This study not only reveals the potential of indigenous salt-tolerant PGPR in enhancing the salt tolerance of alfalfa but also provides new insights into the mechanisms of action of PGPR.

Effect of biogenic exopolysaccharides in characteristics and stability of a novel Requeson-type cheese

Whey is a by-product of the dairy industry with considerable nutritional value but tends to be discarded with industrial effluents. One of the alternatives for its use is the production of whey cheeses, although they need to add extra ingredients to raise the yields, which elevates production costs. A less expensive alternative is using exopolysaccharides (EPS), carbohydrate polymers microorganisms produce. This research aimed to formulate and evaluate the stability of a Requeson-type cheese employing whey that has EPS produced biogenically by in situ fermentation with lactic acid bacteria. Two EPS-producing strains, Lactobacillus delbrueckii subsp bulgaricus NCFB 2772 and Streptococcus thermophilus SY-102, were used separately and in coculture (1:1 ratio). We found that coculture had the highest EPS production (1.49 mg/mL of whey) compared to the monocultures. This influenced the yield of the processed Requeson-type cheese (5.56%), which was higher than the produced with unfermented whey (3.77%). Similarly, the physicochemical and sensory parameters of the developed product showed differences. Furthermore, none of the Requeson-type cheeses made with fermented whey showed microbial growth after 21 days of storage (4 °C). Therefore, EPS is a potential strategy for producing Requeson-type whey cheeses with a high yield and stability.

Characterization of exopolysaccharide EPSSE from marine Pseudoalteromonas shioyasakiensis and its biological activity potential

Microbial marine exopolysaccharides (EPS) are one of the essential and functional commercial-grade products and have several biotechnological applications. In this study, marine Pseudoalteromonas shioyasakiensis SE strain isolated from Alexandria, Egypt, was identified and characterized biochemically and molecularly. A novel exopolysaccharide (EPSSE) was extracted and isolated. The molecular weight (Mw) of EPSSE, as determined by structural characterization, is a glycosidic heteropolysaccharide with 8 kDa and has no uronic acid. Additionally, the results showed that EPSSE was a basic EPS composed of sucrose, glucose, and fructose with the ratio of ≈ 5:18:1 respectively. The maximum antioxidant activity was 12.43% at 2000 µg/mL. The anti-inflammatory activity of EPSSE indicated that it has significant inhibitory activity toward cyclooxygenase (COX-1) and (COX-2) activities with IC50 values of 19.24 ± 1.14 µg/mL and 4.12 ± 0.21) µg/mL, respectively. Furthermore, EPSSE exhibited considerable inhibitory activity toward the proliferation of WI-38, MCF-7 cells, HepG-2 cells and A-549 cell lines with IC50 values of 756.2 ± 36.8 µg/mL, 480.2 ± 21, 244.1 ± 9.3 µg/mL and 398.3 ± 20.9, respectively. This study revealed that EPS produced by the marine P. shioyasakiensis SE strain could be considered an important source of pharmacologically active compounds that would be useful for the healthcare system.

Comparison of Milk Kefirs Obtained from Cow's, Ewe's and Goat's Milk: Antioxidant Role of Microbial-Derived Exopolysaccharides.

Different types of milk are used in the production of milk kefir, but little information is available on the release of potentially antioxidant exopolysaccharides (EPS). The aim of this study was to investigate whether the microbial dynamics and EPS release are dependent on the milk substrate. In our study, the inoculated microbial consortium was driven differently by each type of milk (cow, ewe, and goat). This was evident in the sugar consumption, organic acid production, free amino release, and EPS production. The amount and the composition of the secreted EPS varied depending on the milk type, with implications for the structure and functional properties of the EPS. The low EPS yield in ewe's milk was associated with a higher lactic acid production and thus with the use of carbon sources oriented towards energy production. Depending on the milk used as substrate, the EPS showed different monosaccharide and FT-IR profiles, microstructures, and surface morphologies. These differences affected the antiradical properties and reducing power of the EPS. In particular, EPS extracted from cow's milk had a higher antioxidant activity than other milk types, and the antioxidant activity was concentration dependent.

Enhanced production of mycelium biomass and exopolysaccharides of Pleurotus ostreatus by integrating response surface methodology and artificial neural network

This study aimed to enhance the production of mycelium biomass and exopolysaccharides (EPS) of Pleurotus ostreatus in submerged fermentation. Response Surface Methodology (RSM)sought to optimize culture conditions, whereas Artificial Neural Network (ANN)aimed to predict the mycelium biomass and EPS. After optimization of RSM model conditions, the maximum biomass (36.45 g/L) and EPS (6.72 g/L) were obtained at the optimum temperature of 22.9 °C, pH 5.6, and agitation of 138.9 rpm. Further, the Genetic Algorithm (GA) was employed to optimize the cultivation conditions in order to maximize the mycelium biomass and EPS production. The ANN model with an optimized network structure gave the coefficient of determination (R2) value of 0.99 and the least mean squared error of 1.9 for the validation set. In the end, a graphical user interface was developed to predict mycelium biomass and EPS production.

Microbial exopolysaccharide composites with inorganic materials and their biomedical applications: A review

Microbial exopolysaccharides (EPS) are high molecular weight carbohydrate-based materials produced and secreted in response to external environmental stress to protect microbial cells. These molecules also contain non-carbohydrate moieties including acetate, pyruvate, phosphate, and succinate along with sugar molecules. EPS has been incorporated into industrial operations as a gelling, emulsifying, and stabilizing agent to increase viscosity. Besides, these molecules have also shown high biocompatibility, immunomodulatory, antitumor, anti-microbial, and anti-viral activity which suggest their possible applications in healthcare. However, these molecules are facing some commercial shortcomings due to low stability, bioactivity, and poor mechanical and tensile strength in comparison to the required standard. Hence use of composites of EPS with other polymers and moieties has been suggested for higher performance. Especially in the context of inorganic moieties like silver, gold nanomaterials, clay, salts, and minerals will add bioactivity and functional sites for the attachment of drug molecules and other compounds. The current review summarizes the higher physical and chemical characteristics of EPS composites with inorganic materials and their immense potential in the biomedical sector.

Evaluate the Structural and Physicochemical Properties of Exopolysaccharides Produced by Bacillus halotolerans Isolated from Locally Sourced Vegetables.

In this study, a Bacillus halotolerans (B. halotolerans) strain DT1 capable of producing exopolysaccharides (EPS) was isolated from dried cabbages of Tianjin, a local fermented vegetable product. Three distinct polysaccharide fractions were isolated from the fermentation broth of DT1, namely, DT1-0, DT1-2, and DT1-5. The structural composition and properties of these fractions were investigated. The predominant EPS, DT1-0, was identified as a novel heteropolysaccharide composed of fructose and glucose with branched structures. The repeating unit was determined to be [4)-α-D-Glcp-(1→6)-α-D-Glcp-(1→6)-β-D-Fruf-(2→6)-β-D-Fruf-(2→6-)-β-D-Fruf-(2→], with fructose and glucose connected by β-(2→1) and α-(1→4) glycosidic linkages between the third fructose and the first glucose, respectively. The molecular weight (Mw) was estimated to be 4.253 × 103 Da. DT1-0 presented a smooth and porous surface structure as observed through SEM and exhibited a water-holding capacity of 504 ± 5.3%, maximum thermal stability at 245 °C, and an oil-holding capacity of 387 ± 1.9% for coconut oil. DT1-2 was identified as a fructooligosaccharide. DT1-5 was characterized as a polysaccharide composed of glucose and fructose. In conclusion, these findings provide substantial support for the further application of B. subtilis strain DT1 and its EPS fractions, DT1-0, DT1-2, and DT1-5, as potential alternatives for functional food additives or ingredients.

Synergistic regulation of hydrogen sulfide and nitric oxide on biochemical components, exopolysaccharides, and nitrogen metabolism in nickel stressed rice field cyanobacteria.

The present study examined the regulatory mechanism of hydrogen sulfide (H2S) and nitric oxide (NO) in nickel (Ni) stressed cyanobacteria viz., Nostoc muscorum and Anabaena sp. by analyzing growth, photosynthetic pigments, biochemical components (protein and carbohydrate), exopolysaccharides (EPS), inorganic nitrogen content, and activity of enzymes comprised in nitrogen metabolism and Ni accumulation. The 1µM Ni substantially diminished growth by 18% and 22% in N. muscorum and Anabaena sp. respectively, along with declining the pigment contents (Chl a/Car ratio and phycobiliproteins), and biochemical components. It also exerted negative impacts on inorganic uptake of nitrate and nitrite contents; nitrate reductase and nitrite reductase; and ammonium assimilating enzymes (glutamine synthetase, glutamate synthase, and glutamate dehydrogenase exhibited a reverse trend) activities. Nonetheless, the adverse impact of Ni can be mitigated through the exogenous supplementation of NaHS [sodium hydrosulfide (8µM); H2S donor] and SNP [sodium nitroprusside (10µM); NO donor] which showed substantial improvement on growth, pigments, nitrogen metabolism, and EPS layer and noticeably occurred as a consequence of a substantial reduction in Ni accumulation content which minimized the toxicity effects. The accumulation of Ni on both the cyanobacterial cell surface (EPS layer) are confirmed by the SEM-EDX analysis. Further, the addition of NO scavenger (PTIO; 20µM) and inhibitor of NO (L-NAME; 100µM); and H2S scavenger (HT; 20µM) and H2S inhibitor (PAG; 50µM) reversed the positive responses of H2S and NO and damages were more prominent under Ni stress thereby, suggesting the downstream signaling of H2S on NO-mediated alleviation. Thus, this study concludes the crosstalk mechanism of H2S and NO in the mitigation of Ni-induced toxicity in rice field cyanobacteria.

Revisiting microbial exopolysaccharides: a biocompatible and sustainable polymeric material for multifaceted biomedical applications.

Microbial exopolysaccharides (EPS) have gained significant attention as versatile biomolecules with multifarious applications across various sectors. This review explores the valorisation of EPS and its potential impact on diverse sectors, including food, pharmaceuticals, cosmetics, and biotechnology. EPS, secreted by microorganisms, possess unique physicochemical properties, such as high molecular weight, water solubility, and biocompatibility, making them attractive for numerous functional roles. Additionally, EPS exhibit significant bioactivity, contributing to their potential use in pharmaceuticals for drug delivery and tissue engineering applications. Moreover, the eco-friendly and sustainable nature of microbial EPS production aligns with the growing demand for environmentally conscious processes. However, challenges still exist in large-scale production, purification, and regulatory approval for commercial use. Advances in bioprocessing and microbial engineering offer promising solutions to overcome these hurdles. Stringent investigations have concluded EPS as novel sources for sustainable applications that are likely to emerge and develop, further reinforcing the significance of these biopolymers in addressing contemporary societal needs and driving innovation in various industrial sectors. Overall, the microbial EPS represents a thriving field with immense potential for meeting diverse industrial demands and advancing sustainable technologies.

Molecular Dynamics of Outer Membrane-Embedded Polysaccharide Secretion Porins Reveals Closed Resting-State Surface Gates Targetable by Virtual Fragment Screening for Drug Hotspot Identification.

Recent advances in iterative neural network analyses (e.g., AlphaFold2 and RoseTTA fold) have been revolutionary for protein 3D structure prediction, especially for difficult-to-manipulate α-helical/β-barrel integral membrane proteins. These model structures are calculated based on the coevolution of amino acids within the protein of interest and similarities to existing protein structures; the local effects of the membrane on folding and stability of the calculated model structures are not considered. We recently reported the discovery, 3D modeling, and characterization of 18-β-stranded outer-membrane (OM) WzpX, WzpS, and WzpB β-barrel secretion porins for the exopolysaccharide (EPS), major spore coat polysaccharide (MASC), and biosurfactant polysaccharide (BPS) pathways (respectively) in the Gram-negative social predatory bacterium Myxococcus xanthus DZ2. However, information was not obtained regarding the dynamic behavior of surface-gating WzpX/S/B loop domains or on potential treatments to inactivate these porins. Herein, we developed a molecular dynamics (MD) protocol to study the core stability and loop dynamism of neural network-based integral membrane protein structure models embedded in an asymmetric OM bilayer, using the M. xanthus WzpX, WzpS, and WzpB proteins as test candidates. This was accomplished through integration of the CHARMM-graphical user interface (GUI) and Molecular Operating Environment (MOE) workflows to allow for a rapid simulation system setup and facilitate data analysis. In addition to serving as a method of model structure validation, our molecular dynamics simulations revealed a minimal movement of extracellular WzpX/S/B loops in the absence of an external stimulus as well as druggable cavities between the loops. Virtual screening of a commercial fragment library against these cavities revealed putative fragment-binding hotspots on the cell-surface face of each β-barrel, along with key interacting residues, and identified promising hits for the design of potential binders capable of plugging the β-barrels and inhibiting polysaccharide secretion.

Utilisation of Lacticaseibacillus casei ATCC 393‐derived exopolysaccharide for camel milk yoghurt production and its potential anticancer and hepatoprotective properties

Camel milk yoghurts were created using probiotic lactic acid bacteria (LAB) with exopolysaccharide (EPS) production capabilities. Lacticaseibacillus casei ATCC 393, identified as the most efficient EPS producer, was incorporated into conventional yoghurt culture. We compared the effects of adding L. casei ATCC 393 with EPS powder (SLLP) against lactulose. Evaluations included LAB, yeast, mould, cytotoxicity and IC50 values in the samples. The results demonstrated increased bacterial counts, LAB viability, viscosity, antiproliferative effects and a lower IC50 in SLLP, indicating the potential application of EPS‐producing L. casei ATCC 393 and its derived EPS in the development of functional foods.

Smart multifaceted potential microbial inoculant isolated from rhizospheric soils of Bergenia ciliata and possible role in developing green biosynthesized nanoparticles

Nanotechnology employs miniscule yet potential nanoparticles and has immense applications in various fields of scientific research. This has revolutionized technological advancements in multiple spheres and recently touched the field of plant biology and sustainable agriculture. Beneficial rhizobacteria isolated from plants may prove efficacious as they are able to impart plant growth. From the medicinal plant Bergenia ciliata, one isolate BC-I-15 was characterized in this study and displayed growth promoting traits. 16s rDNA sequencing and molecular characterization confirmed the isolate as Pseudomonas sp. (NCBI accession number- OQ891764) which showed similarity with other Pseudomonads in phylogenetic tree. The isolate exhibited oxidative stress tolerance assay, nitrogen fixing ability, IAA, calcite and phosphate solubilization etc. But such microbial bioinoculants suffers from few limitations and can be enriched when their nanoparticle counterparts are developed for efficient function. The citation network analysis showed good and encouraging relationships between terms like ‘Nanoparticles, Microbes, Sustainable agriculture’. So, when such beneficial microbes in bulk form, or biofilm and exopolysaccharides (EPS) secreting, secondary metabolites etc. parts thereof are used as starting material for nanoparticle formation, then such nanoparticles possess intrinsic and enriched capacity to impart stress tolerance to plants and impart qualities in sustainable agriculture. The results of the present study, further aids in the efficient utilization of the selected beneficial BC-I-15 rhizobacteria and their future exploration in developing biogenic nanoparticles for active agents in sustainable agriculture.

Rhizobial oxidized 3-hydroxylbutanoyl glycan-based gelatin hydrogels with enhanced physiochemical properties for pH-responsive drug delivery

Rhizobial exopolysaccharide (EPS) is an acidic polysaccharide involved in nitrogen fixation-related signal transduction in the rhizosphere, serving as a structural support for biofilms, and protecting against various external environmental stresses. Rhizobial EPS as a hydrogel biomaterial was used for a pH-responsive drug delivery system combing with gelatins. Pure gelatin (GA) hydrogels have limited practical applications due to their poor mechanical strength and poor thermal stability. We developed new GA hydrogels using oxidized 3-hydroxylbutanoyl glycan (OHbG) as a polymer cross-linking agent to overcome these limitations. OHbG was synthesized from sodium periodate oxidation of 3-hydroxylbutanoyl glycan directly isolated from Rhizobium leguminosarum bv. viciae VF39. The newly fabricated OHbG/GA hydrogels exhibited 21-fold higher compressive stress and 4.7-fold higher storage modulus (G') than GA at the same strain. This result suggested that OHbG provided mechanical improvement. In addition, these OHbG/GA hydrogels showed effective pH-controlled drug release for 5-fluorouracil, self-healable, and self-antioxidant capacity by uronic acids of OHbG. Cell viability tests using HEK-293 cells in vitro also showed that the OHbG/GA hydrogels were non-toxic. This suggests that the new OHbG/GA hydrogels can be used as a potentially novel biomaterial for drug delivery based on its self-healing ability, antioxidant capacity, and pH-responsive drug delivery.

Structures, physical properties and antibacterial activity of silver nanoparticles of Lactiplantibacillus plantarum exopolysaccharide

Lactic acid bacteria (LAB) exopolysaccharide (EPS) has good water absorption, high viscosity, good stability, so it was widely used in probiotics fields. In this study, EPS-producing LAB strain Lactiplantibacillus plantarum HDL-03 was isolated and identified. Moreover, the HDL-03 EPS was used as a stabilizer and mixed with AgNO3 to synthesize a novel nanoparticle AgNPs whose structure and properties were explored. The monosaccharide composition and molecular weight indicated that HDL-03 EPS was a heteropolysaccharide composed of mannose and glucose. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy analysis and methylation results jointly proved it was a heteropolysaccharide containing 1,3-Manp and 1,6-Glcp. The X-Ray diffraction (XRD) results showed that this EPS has an amorphous structure, while the synthesized AgNPs have crystalline properties. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicated EPS had a smooth and dense sheet structure, while the surface of AgNPs became rougher and large holes appeared after synthesis. Zeta particle size analysis suggested that the particle size of AgNPs increased by 36.63 nm compared to HDL-03 EPS. FT-IR analysis exhibited that the position of the characteristic peaks of AgNPs changed. The OH moving from a wavelength of 3388.49 cm−1 to a wavelength of 3316.79 cm−1 and telescopic vibration peak changed from 1356.07 cm−1 to 1344.22 cm−1. A plate inhibition test revealed the effect of different concentrations of EPS and AgNO3 synthesized AgNPs on the diameter of inhibition circle produced by the indicator bacteria Escherichia coli and Staphylococcus aureus. Furthermore, AgNPs were applied to the indicator bacteria, which the minimum inhibitory concentration (MIC), time-inhibitory curve, and changes in extracellular conductivity, nucleic acids, proteins, ATP, and lactate dehydrogenase (LDH) levels were determined. The AgNPs inhibited the growth of E. coli and S. aureus and exhibited outstanding antimicrobial properties. With the increase of treatment time, the degree of cell membrane damage increased, the permeability enhanced, and the intracellular substances leaked. These results indicate that HDL-03 EPS has good potential for applications in the production of food packaging, antimicrobials, catheters, textiles and coatings.

Levan Production by Suhomyces kilbournensis Using Sugarcane Molasses as a Carbon Source in Submerged Fermentation.

The valorization of byproducts from the sugarcane industry represents a potential alternative method with a low energy cost for the production of metabolites that are of commercial and industrial interest. The production of exopolysaccharides (EPSs) was carried out using the yeast Suhomyces kilbournensis isolated from agro-industrial sugarcane, and the products and byproducts of this agro-industrial sugarcane were used as carbon sources for their recovery. The effect of pH, temperature, and carbon and nitrogen sources and their concentration in EPS production by submerged fermentation (SmF) was studied in 170 mL glass containers of uniform geometry at 30 °C with an initial pH of 6.5. The resulting EPSs were characterized with Fourier-transform infrared spectroscopy (FT-IR). The results showed that the highest EPS production yields were 4.26 and 44.33 g/L after 6 h of fermentation using sucrose and molasses as carbon sources, respectively. Finally, an FT-IR analysis of the EPSs produced by S. kilbournensis corresponded to levan, corroborating its origin. It is important to mention that this is the first work that reports the production of levan using this yeast. This is relevant because, currently, most studies are focused on the use of recombinant and genetically modified microorganisms; in this scenario, Suhomyces kilbournensis is a native yeast isolated from the sugar production process, giving it a great advantage in the incorporation of carbon sources into their metabolic processes in order to produce levan sucrose, which uses fructose to polymerize levan.