Exopolysaccharide Research Articles

English

Application of untreated wastewater for vegetable production in peri-urban areas enters into the food chain leading to compromised human health. The present study was planned to evaluate the potential of cadmium (Cd) tolerant bacterial strains in combination with foliar application of Jasmonic acid (JA) under Cd stress. The Cd tolerant bacterial strains were isolated from wastewater and characterized for the production of exopolysaccharides (EPS), siderophore, and indole acdetic acid (IAA) under in vitro studies. The four most efficient strains SS5, SS7, SS8, and SS10 were selected based on growth-promoting traits and further evaluated with different levels of JA (20 μmol L-1 and 40 μmol L-1) in jar trial. Cauliflower (hyperaccumulator) was used as a test crop with Cd levels (0 and 150 mg kg-1). Our results depicted that the use of consortium (SS7+SS8) along with a foliar application of JA (40 μmol L-1) significantly improved shoot dry weight (15.5%), root dry weight (28.4%), shoot length (23.7%), root length (37%), superoxide dismutase (29.8%), peroxidase dismutase (29.7%), catalase (31.7%) and POX (29.2%). However, 29 and 26% reduction in Cd concentration in shoots and roots was observed, respectively. It was concluded that the Klebsiella strains SS7 and SS8 with foliar application of JA is a potential biofertilizer and a phyto-stabilizer for metal-contaminated soils and recommended to reduce the Cd toxicity among crop plants.

Glycosaminoglycan-mimetic infernan grafted with poly(N-isopropylacrylamide): Toward a thermosensitive polysaccharide

Glycosaminoglycans (GAGs) are essential constituents of the cell surface and extracellular matrix, where they are involved in several cellular processes through their interactions with various proteins. For successful tissue regeneration, developing an appropriate matrix supporting biological activities of cells in a similar manner than GAGs remains still challenging. In this context, this study aims to design a thermosensitive polysaccharide that could further be used as hydrogel for tissue engineering applications. For this purpose, infernan, a marine bacterial exopolysaccharide (EPS) endowed with GAG-mimetic properties was grafted with a thermosensitive polymer, poly(N-isopropylacrylamide) (pNIPAM). Eight grafted polysaccharides were obtained by varying EPS/pNIPAM molar ratio and the molecular weight of pNIPAM. Their physicochemical characteristics and their thermosensitive properties were determined using a multi-technique, experimental approach. In parallel, molecular dynamics and Monte Carlo simulations were applied at two different scales to elucidate, respectively, the molecular conformation of grafted infernan chain and their ability to form an infinite network undergoing a sol-gel transition near the percolation, a necessary condition in hydrogel formation. It comes out from this study that thermosensitive infernan was successfully developed and its potential use in tissue regeneration as a hydrogel scaffold will further be assessed.

Anti-Quorum Sensing and Anti-Biofilm Activity of Ginger (Zingiber officinale) Rhizomes against Multidrug-Resistant Clinical Isolates of Pseudomonas aeruginosa.

The aim of this study was to determination of Anti-Quorum Sensing (AQS) and anti-biofilm potential of the methanol extract of ginger (Zingiber officinale) rhizomes against multidrug-resistant clinical isolates of Pseudomonas aeruginosa (P. aeruginosa). The AQS activity of ginger was determined against Chromobacterium violaceum (C. violaceum) ATCC 12472 (CV12472), a biosensor strain, in qualitative manner using the agar well diffusion method. The violacein pigment inhibition was assessed to confirm AQS activity of ginger. The AQS potential of sub-minimum Inhibitory Concentrations (sub-MICs) of the ginger extract was determined by targeting different QS regulated virulence factors, including swarming motility (using swarm diameter measurement method), pyocyanin pigment (using chloroform extraction method), Exopolysaccharide (EPS) (using phenol-sulphuric acid method), and biofilm formation (using microtiter plate assay), against clinical isolates (CIs 2, 3, and 4) and standard reference strain of P. aeruginosa (PA01). The AQS activity of methanol extract of ginger was confirmed against C. violaceum (CV12472) as inhibition of violacein pigment formation without effecting the growth of CIs and PA01 of P. aeruginosa. The ginger extract exhibited concentration-dependent inhibition of virulence factors and biofilm formation. The maximum reduction was found in swarming motility, pyocyanin, EPS and biofilm formation against PA01 (51.38%), CI3 (57.91%), PA01 (63.29%) and CI2 (64.37%), respectively at 1/2 MIC of ginger extract. The results of present study revealed the effective AQS and anti-biofilm potential of Zingiber officinale rhizome methanol extract at a reduced dose (sub-MICs). The extract may be explored as an agent of antimicrobial compounds having AQS and anti-biofilm activity for controlling microbial infection and also for reducing the chances of emergence of resistance in P. aeruginosa.

Heterotypic stress-induced adaptive evolution enhances freeze-drying tolerance and storage stability of Leuconostoc mesenteroides WiKim33

Lactic acid bacteria (LAB) are currently being investigated for their potential use as probiotics and starter cultures. Researchers have developed powdering processes for the commercialization of LAB. Previous studies have focused on identifying innovative cryoprotective agents and freeze-drying (FD) techniques to enhance the stability of LAB. In this study, adaptive laboratory evolution (ALE) was employed to develop a strain with high FD tolerance and enhanced storage stability. Leuconostoc mesenteroids WiKim33 was subjected to heterotypic shock (heat and osmosis shock) to induce the desired phenotype and genotype. An FD-tolerant enhanced Leu. mesenteroides WiKim33 strain (ALE50) was obtained, which harbored a modified fatty acid composition and cell envelope characteristics. Specifically, ALE50 showed a lower unsaturated fatty acid (UFA)/saturated fatty acid (SFA) ratio and a higher cyclic fatty acid (CFA) composition. Moreover, the exopolysaccharide (EPS) thickness increased significantly by 331% compared to that of the wild type (WT). FD tolerance, which was evaluated using viability testing after FD, was enhanced by 33.4%. Overall, we demonstrated the feasibility of ALE to achieve desirable characteristics and provided insights into the mechanisms underlying increased FD tolerance.

Determination and Kinetic Characterization of a New Potential Inhibitor for AmsI Protein Tyrosine Phosphatase from the Apple Pathogen Erwinia amylovora

Erwinia amylovora is a Gram-negative bacterium, responsible for the fire blight disease in Rosaceae plants. Its virulence is correlated with the production of an exopolysaccharide (EPS) called amylovoran, which protects the bacterium from the surrounding environment and helps its diffusion inside the host. Amylovoran biosynthesis relies on the expression of twelve genes clustered in the ams operon. One of these genes, amsI, encodes for a Low Molecular Weight Protein Tyrosine Phosphatase (LMW-PTP) called EaAmsI, which plays a key role in the regulation of the EPS production pathway. For this reason, EaAmsI was chosen in this work as a target for the development of new antibacterial agents against E. amylovora. To achieve this aim, a set of programs (DOCK6, OpenEye FRED) was selected to perform a virtual screening using a database of ca. 700 molecules. The six best-scoring compounds identified were tested in in vitro assays. A complete inhibition kinetic characterization carried out on the most promising molecule (n-Heptyl β-D-glucopyranoside, N7G) showed an inhibition constant of 7.8 ± 0.6 µM. This study represents an initial step towards the development of new EaAmsI inhibitors able to act as antibacterial agents against E. amylovora infections.

The effect of an exopolysaccharide probiotic molecule from Bacillus subtilis on breast cancer cells

IntroductionMany well-known risk factors for breast cancer are associated with dysbiosis (an aberrant microbiome). However, how bacterial products modulate cancer are poorly understood. In this study, we investigated the effect of an exopolysaccharide (EPS) produced by the commensal bacterium Bacillus subtilis on breast cancer phenotypes. Although B. subtilis is commonly included in probiotic preparations and its EPS protects against inflammatory diseases, it was virtually unknown whether B. subtilis-derived EPS affects cancer.MethodsThis work investigated effects of EPS on phenotypes of breast cancer cells as a cancer model. The phenotypes included proliferation, mammosphere formation, cell migration, and tumor growth in two immune compromised mouse models. RNA sequencing was performed on RNA from four breast cancer cells treated with PBS or EPS. IKKβ or STAT1 signaling was assessed using pharmacologic or RNAi-mediated knock down approaches. ResultsShort-term treatment with EPS inhibited proliferation of certain breast cancer cells (T47D, MDA-MB-468, HCC1428, MDA-MB-453) while having little effect on others (MCF-7, MDA-MB-231, BT549, ZR-75-30). EPS induced G1/G0 cell cycle arrest of T47D cells while increasing apoptosis of MDA-MB-468 cells. EPS also enhanced aggressive phenotypes in T47D cells including cell migration and cancer stem cell survival. Long-term treatment with EPS (months) led to resistance in vitro and promoted tumor growth in immunocompromised mice. RNA-sequence analysis showed that EPS increased expression of pro-inflammatory pathways including STAT1 and NF-κB. IKKβ and/or STAT1 signaling was necessary for EPS to modulate phenotypes of EPS sensitive breast cancer cells. DiscussionThese results demonstrate a multifaceted role for an EPS molecule secreted by the probiotic bacterium B. subtilis on breast cancer cell phenotypes. These results warrant future studies in immune competent mice and different cancer models to fully understand potential benefits and/or side effects of long-term use of probiotics.

Sugar Substitute Stevia Inhibits Biofilm Formation, Exopolysaccharide Production, and Downregulates the Expression of Streptococcal Genes Involved in Exopolysaccharide Synthesis.

Acid production by sucrose fermentation disturbs the balance in dental plaque by lowering the oral pH. As a consequence of the profound effect of sucrose on caries initiation and progression, many studies have been directed towards finding non-cariogenic artificial sweeteners that can be used as a substitute to sucrose. Existing literature shows that dietary sucrose upregulates the expression of biofilm associated genes involved in exopolysaccharide (EPS) production. In this study, we aimed to investigate the effect of the sugar substitute stevia on biofilm formation, EPS secretion, and streptococcal genes encoding glucan-binding proteins (Gbps) and glucosyltransferases (Gtfs), which are essential for the synthesis of EPS. Streptococcus mutans and Streptococcus gordonii were grown as biofilm cultures with or without stevia and sucrose. Biomass was quantified for biofilm and EPS production by crystal violet staining and the phenol-sulfuric acid method, respectively. Expression of gtfB and gbpB genes was studied by RT-PCR. The quantities of biofilm were significantly lower when grown in the presence of stevia compared to sucrose in both species (p < 0.05). The proportion of EPS in the biofilm pellet decreased with increasing concentrations of stevia in both species but remained nearly unchanged with sucrose with respect to the control. In both streptococcal species, exposure of stevia decreased the expression of gtfB and gbpB genes compared to sucrose (p < 0.05). In comparison to the untreated control, the expression was decreased in the presence of stevia in both species, while it increased 2.5- to 4-fold in S. mutans and 1.5- to 2.5-fold in S. gordonii in the presence of sucrose. The ability of stevia to inhibit biofilm formation, reduce EPS production, and downregulate the expression of gtfB and gbpB genes in S. mutans and S. gordonii may have potential therapeutic applications in controlling dental plaques and caries.

Fabrication and characterisation of human gut microbiome derived exopolysaccharide mediated silver nanoparticles – An in-vitro and in-vivo approach of Bio-Pm-AgNPs targeting Vibrio cholerae

Utilising bacteria to produce silver nanoparticles was highly favoured due to its ability to minimise costs and mitigate any potential negative environmental impact. Exopolysaccharides (EPS) extracted from the human gut microbe have demonstrated remarkable efficacy in combating various bacterial infections. Exopolysaccharide (EPS), a naturally occurring biomolecule found in the human gut isolate Proteus mirabilis DMTMMR-11, was characterised using analytical techniques such as Fourier transform infrared spectroscopy (FTIR), 1H-nuclear magnetic resonance, 13C-nuclear magnetic resonance (NMR), and chemical composition analysis, which confirms the presence of carbohydrates (81.03 ± 0.23), proteins (4.22 ± 1.2), uronic acid (12.1 ± 0.12), and nucleic acid content (2.44 ± 0.15) in exopolysaccharide. The one factor at a time (OFAT) and response surface methodology (RSM) – central composite design (CCD) approaches were used to optimise the production of Bio-Pm-AgNPs, leading to an increase in yield of up to 1.86 g/l. The Bio-Pm-AgNPs were then subjected to Fourier transform infrared spectroscopy (FTIR) which determines the functional groups, X-ray diffractometer confers that Bio-Pm-AgNPs are crystalline in nature, field emission-scanning electron microscopy (FE-SEM) reveals the morphology of Bio-Pm-AgNPs, energy dispersive X-ray spectroscopy (EDX) confirms the presence of elements like Ag, C and O, high-resolution transmission electron microscopy (HR-TEM) determines that the Bio-Pm-AgNPs are sphere-shaped at 75 nm. Dynamic light scattering (DLS) and zeta potential analysis were also carried out to reveal the physiological nature of Bio-Pm-AgNPs. Bio-Pm-AgNPs have a promising effect on the inhibitory mechanism of Vibrio cholerae cells at a MIC concentration of 20 μg/ml which significantly affects cellular respiration and energy metabolism through glycolysis and TCA cycles by deteriorating the enzyme responsible for ATP and NADH utilisation. The action of Bio-Pm-AgNPs reduces the purity and concentration of nucleic acids, which leads to higher DNA damage. In-vivo analysis reveals that the treatment of Bio-Pm-AgNPs decreased the colonisation of V. cholerae and improved the survival rates in C. elegans.

Polyhydroxyalkanoates and exopolysaccharides: An alternative for valuation of the co-production of microbial biopolymers.

Polyhydroxyalkanoates (PHAs) and exopolysaccharides (EPSs) belong to a class of abundant biopolymers produced by various fermenting microorganisms. These biocompounds have high value-added potential and can be produced concurrently. Co-production of PHAs and EPSs is a strategy employed by researchers to reduce costs associated with large-scale production. EPSs and PHAs are non-toxic, biocompatible, and biodegradable, making them suitable for various industrial sectors, including packaging and the medical and pharmaceutical industries. These biopolymers can be derived from agro-industrial residues, thus contributing to the bioeconomy by producing high-value-added products. This review investigates approaches for simultaneously synthesizing PHAs and EPSs using different carbon sources and microorganisms.

Effects of Sub-Minimum Inhibitory Concentrations of Bacteriocin BM173 on Listeria Monocytogenes Biofilm Formation.

Listeria monocytogenes is a significant foodborne pathogen that can form biofilms on various food processing surfaces, thereby enhancing resistance to disinfectants and exacerbating harm to human health. Previous studies have indicated that bacteriocin BM173 exhibits antibacterial and antibiofilm activities. In the current study, our aim was to assess the inhibitory mode of action of sub-inhibitory concentrations (SICs, 1/32 × MIC and 1/16 × MIC) of BM173 on the biofilm formation L. monocytogenes. Crystal violet staining assay revealed that SICs of BM173 significantly inhibit L. monocytogenes biofilm formation. Furthermore, the results of swimming motility assay, plate count, ruthenium red staining, and scanning electron microscopy (SEM) revealed that SICs of BM173 could effectively reduce the movement, cell adhesion, and exopolysaccharide (EPS) production of L. monocytogenes, thereby inhibiting biofilm formation. Real-time quantitative PCR analyses further demonstrated that SICs of BM173 down-regulated the expression of biofilm-associated genes, including those encoding adhesion, virulence factors, and quorum sensing. Additionally, SICs of BM173 effectively reduced the biofilm formation of L. monocytogenes on the surfaces of three food-grade materials (glass, stainless steel, and silicone) at 4 and 25 °C. These outcomes suggest that BM173 holds great potential for development as a promising food preservative for application in the food industry.

Effects of EPS-producing Leuconostoc mesenteroides XR1 on texture, rheological properties, microstructure and volatile flavor of fermented milk

Leuconostoc mesenteroides XR1, a high-quality exopolysaccharides (EPS) producing strain, was isolated from wild Kefir grains. The effect of strain XR1 as a compound starter on yoghurt fermentation and storage was studied. The EPS content, viable counts, titratable acidity, pH, water holding capacity (WHC), texture, rheological properties, microstructure, volatile flavor compounds and sensory evaluation of yoghurts were determined. The EPS content of the yoghurt with XR1 was shown to be 1.64, 2.14, 1.37, and 1.29 times higher than those of the control group at days 1, 7, 14, and 21 of storage, respectively. The WHC, cohesiveness, gumminess, apparent viscosity and gel strength of the yoghurt containing XR1 were higher than those of the control group (P < 0.05). It is worth noting that supplementation with XR1 improved the acidification of the yoghurt. Scanning electron microscope (SEM) observation confirmed that the microstructure of the yoghurt containing XR1 had stronger compactness. Volatile substance analysis showed that after 7 days of storage, yoghurt supplemented with XR1 had an increased aroma of ketones and alkanes. In terms of texture, flavor and taste, Y-XR1 group obtained higher sensory scores (P < 0.05). These results collectively indicated that XR1 improved the quality of the yoghurt by increasing EPS production, thus reducing the use of chemical thickeners or stabilizers.

Elaboration of Nanostructured Levan-Based Colloid System as a Biological Alternative with Antimicrobial Activity for Applications in the Management of Pathogenic Microorganisms.

Considering the documented health benefits of bacterial exopolysaccharides (EPSs), specifically of bacterial levan (BL), including its intrinsic antimicrobial activity against certain pathogenic species, the current study concentrated on the development of active pharmaceutical ingredients (APIs) in the form of colloid systems (CoSs) containing silver nanoparticles (AgNPs) employing in-house biosynthesized BL as a reducing and capping agent. The established protocol of fermentation conditions implicating two species of lactic acid bacteria (LAB), i.e., Streptococcus salivarius K12 and Leuconostoc mesenteroides DSM 20343, ensured a yield of up to 25.7 and 13.7 g L-1 of BL within 72 h, respectively. An analytical approach accomplished by Fourier-transform infrared (FT-IR) spectroscopy allowed for the verification of structural features attributed to biosynthesized BL. Furthermore, scanning electron microscopy (SEM) revealed the crystalline morphology of biosynthesized BL with a smooth and glossy surface and highly porous structure. Molecular weight (Mw) estimated by multi-detector size-exclusion chromatography (SEC) indicated that BL biosynthesized using S. salivarius K12 has an impressively high Mw, corresponding to 15.435 × 104 kilodaltons (kDa). In turn, BL isolated from L. mesenteroides DSM 20343 was found to have an Mw of only 26.6 kDa. Polydispersity index estimation (PD = Mw/Mn) of produced BL displayed a monodispersed molecule isolated from S. salivarius K12, corresponding to 1.08, while this was 2.17 for L. mesenteroides DSM 20343 isolate. The presence of fructose as the main backbone and, to a lesser extent, glucose and galactose as side chain molecules in EPS hydrolysates was supported by HPLC-RID detection. In producing CoS-BL@AgNPs within green biosynthesis, the presence of nanostructured objects with a size distribution from 12.67 ± 5.56 nm to 46.97 ± 20.23 was confirmed by SEM and energy-dispersive X-ray spectroscopy (EDX). The prominent inhibitory potency of elaborated CoS-BL@AgNPs against both reference test cultures, i.e., Pseudomonas aeruginosa, Escherichia coli, Enterobacter aerogenes, and Staphylococcus aureus and those of clinical origin with multi-drug resistance (MDR), was confirmed by disc and well diffusion tests and supported by the values of the minimum inhibitory and bactericidal concentrations. CoS-BL@AgNPs can be treated as APIs suitable for designing new antimicrobial agents and modifying therapies in controlling MDR pathogens.

Exopolysaccharides Synthesized by Rhizospheric Bacteria: A Review Focused on Their Roles in Protecting Plants against Stress

Plants are constantly exposed to a wide range of environmental factors that cause different kinds of stress, such as drought, salinity, heat, frost, and low nutrient availability. There are also biotic sources of stress, which include pathogens (bacteria, viruses, pests), herbivores, and plant competitors. These various types of stress affect normal plant physiology and development, and may lead to significantly lower yields. However, certain microorganisms (MOs), known as plant growth-promoting rhizobacteria (PGPR), can interact with and benefit plants in stressful environments. They do so through a series of mechanisms which contribute to minimizing the negative effects of plants’ responses to stress. This review summarizes current knowledge about those mechanisms, with a focus on the production of exopolysaccharides (EPSs). These compounds can act as osmoprotectants, promote the production of phytohormones, prevent the entry of pathogens through roots, bioremediate metals, and improve soil structure and permeability, among many other beneficial effects. This makes them suitable alternatives to guarantee food security while reducing the excessive use of chemical agricultural inputs and their harmful consequences for the environment.

RNase D Is Involved in 5S rRNA Degradation and Exopolysaccharide Production in Xanthomonas campestris pv. campestris.

Ribonucleases (RNases) play critical roles in RNA metabolism and are collectively essential for cell viability. However, most knowledge about bacterial RNases comes from the studies on Escherichia coli; very little is known about the RNases in plant pathogens. The crucifer black rot pathogen Xanthomonas campestris pv. campestris (Xcc) encodes 15 RNases, but none of them has been functionally characterized. Here, we report the physiological function of the exoribonuclease RNase D in Xcc and provide evidence demonstrating that the Xcc RNase D is involved in 5S rRNA degradation and exopolysaccharide (EPS) production. Our work shows that the growth and virulence of Xcc were not affected by deletion of RNase D but were severely attenuated by RNase D overexpression. However, deletion of RNase D in Xcc resulted in a significant reduction in EPS production. In addition, either deletion or overexpression of RNase D in Xcc did not influence the tRNAs tested, inconsistent with the finding in E. coli that the primary function of RNase D is to participate in tRNA maturation and its overexpression degrades tRNAs. More importantly, deletion, overexpression, and in vitro enzymatic analyses revealed that the Xcc RNase D degrades 5S rRNA but not 16S and 23S rRNAs that share an operon with 5S rRNA. Our results suggest that Xcc employs RNase D to realize specific modulation of the cellular 5S rRNA content after transcription and maturation whenever necessary. The finding expands our knowledge about the function of RNase D in bacteria.

Silica nanoparticles containing nano-silver and chlorhexidine respond to pH to suppress biofilm acids and modulate biofilms toward a non-cariogenic composition

ObjectivesDental caries is caused by acids from biofilms. pH-sensitive nanoparticle carriers could achieve improved targeted effectiveness. The objectives of this study were to develop novel mesoporous silica nanoparticles carrying nanosilver and chlorhexidine (nMS-nAg-Chx), and investigate the inhibition of biofilms as well as the modulation of biofilm to suppress acidogenic and promote benign species for the first time. MethodsnMS-nAg was synthesized via a modified sol-gel method. Carboxylate group functionalized nMS-nAg (COOH-nMS-nAg) was prepared and Chx was added via electrostatic interaction. Minimal inhibitory concentration (MIC), inhibition zone, and growth curves were evaluated. Streptococcus mutans (S. mutans), Streptococcus gordonii (S. gordonii), and Streptococcus sanguinis (S. sanguinis) formed multispecies biofilms. Metabolic activity, biofilm lactic acid, exopolysaccharides (EPS), and TaqMan real-time polymerase chain reaction (RT-PCR) were tested. Biofilm structures and biomass were observed by scanning electron microscopy (SEM) and live/dead bacteria staining. ResultsnMS-nAg-Chx possessed pH-responsive properties, where Chx release increased at lower pH. nMS-nAg-Chx showed good biocompatibility. nMS-nAg-Chx exhibited a strong antibacterial function, reducing biofilm metabolic activity and lactic acid as compared to control (p < 0.05, n = 6). Moreso, biofilm biomass was dramatically suppressed in nMS-nAg-Chx groups. In control group, there was an increasing trend of S. mutans proportion in the multispecies biofilm, with S. mutans reaching 89.1% at 72 h. In sharp contrast, in nMS-nAg-Chx group of 25 μg/mL, the ratio of S. mutans dropped to 43.7% and the proportion of S. gordonii and S. sanguinis increased from 19.8% and 10.9 to 69.8% and 56.3%, correspondingly. ConclusionpH-sensitive nMS-nAg-Chx had potent antibacterial effects and modulated biofilm toward a non-cariogenic tendency, decreasing the cariogenic species nearly halved and increasing the benign species approximately twofold. nMS-nAg-Chx is promising for applications in mouth rinse and endodontic irrigants, and as fillers in resins to prevent caries.

Marine versus Non-Marine Bacterial Exopolysaccharides and Their Skincare Applications.

Bacteria are well-known to synthesize high molecular weight polysaccharides excreted in extracellular domain, which constitute their protective microenvironment. Several bacterial exopolysaccharides (EPS) are commercially available for skincare applications in cosmetic products due to their unique structural features, conferring valuable biological and/or textural properties. This review aims to give an overview of bacterial EPS, an important group of macromolecules used in cosmetics as actives and functional ingredients. For this purpose, the main chemical characteristics of EPS are firstly described, followed by the basics of the development of cosmetic ingredients. Then, a focus on EPS production, including upstream and downstream processes, is provided. The diversity of EPS used in the cosmetic industry, and more specifically of marine-derived EPS is highlighted. Marine bacteria isolated from extreme environments are known to produce EPS. However, their production processes are highly challenging due to high or low temperatures; yield must be improved to reach economically viable ingredients. The biological properties of marine-derived EPS are then reviewed, resulting in the highlight of the challenges in this field.

Enzymolysis and photothermal-mediated synergistic antimicrobial nanoplatform with programmed EPS degradation and biofilm penetration capabilities for eradication of biofilm wound infections

It is an effective method of eradicating biofilm infection and promoting wound healing by exopolysaccharides (EPS) degradation and penetration of antimicrobial agents into biofilms. In this study, a synergistic antimicrobial nanoplatform (Pec@PLL-MoS2) based on programmed enzymolysis and photothermal therapy was developed. Pectinase (Pec) was modified onto the surface of molybdenum disulfide nanosheets (MoS2 NSs) by ε-poly-L-lysine (PLL) linkage via electrostatic adsorption. With the 808-nm laser irradiation, the activity of Pec was regulated by the photothermal effect produced by the MoS2 NSs. Pec efficiently degraded the EPS and destroyed the structural integrity of the biofilms, thus promoting the penetration of Pec@PLL-MoS2 into the biofilms. With the penetration of Pec@PLL-MoS2, the local hyperthermia produced by the photothermy of the MoS2 NSs further killed the bacteria inside the biofilms, eventually eradicating biofilm infections. In vitro experiments indicated that 81.1 % of Staphylococcus aureus (S. aureus) biofilms and 89.9 % of Escherichia coli (E. coli) biofilms were eradicated within 5 min. The survival rates of the bacteria in the biofilms of S. aureus and E. coli were reduced to 5.1 % and 0.1 %, respectively. In vivo, biofilm infections in wounds were completely eradicated by Pec@PLL-MoS2 under irradiation, thereby reducing inflammation and promoting wound healing. This study demonstrated that Pec@PLL-MoS2 based on programmed enzymolysis and photothermia is a new synergistic treatment strategy for biofilm infections.

Pseudomonas Exopolysaccharides: A Game Changer for Attaining Environmental Sustainability

Exopolysaccharides (EPS) are the polymeric substance obtained from diverse species of the genera Pseudomonas for a variety of purposes. Recently, large focus have been given on isolation and characterization of EPS from diverse microorganisms employing various strategies, but very less attention have been given on the theme of harnessing EPS from the master microbe Pseudomonas and exploiting its multifaceted roles. Hence, the main essence of this review article is to emphasize protocols opted for EPS production, extraction and optimization, detailing its architecture, composition, mechanisms and genetic regulation. In the process it will also discuss various approaches used nowadays for novel usage of EPS bioformulations derived from Pseudomonas for plant growth promotion, stress amelioration, bioremediation and disease management in an eco-friendly and sustainable manner.

Exopolysaccharide-Treated Dendritic Cells Effectively Ameliorate Acute Graft-versus-Host Disease

Graft-versus-host disease (GVHD) is a primary and often lethal complication of allogenic hematopoietic stem cell transplantation (HSCT). Prophylactic regimens for GVHD are given as standard pretransplantation therapy; however, up to 50% of these patients develop acute GVHD (aGVHD) and require additional immunosuppressive intervention. Using a mouse GVHD model, we previously showed that injecting mice with exopolysaccharide (EPS) from Bacillus subtilis prior to GVHD induction significantly increased 80-day survival after transplantation of complete allogeneic major histocompatibility complex-mismatched cells. To ask whether EPS might also inhibit GVHD in humans, we used humanized NSG-HLA-A2 mice and induced GVHD by i.v. injection of A2neg human peripheral blood mononuclear cells (PBMCs). Because we could not inject human donors with EPS, we transferred EPS-pretreated dendritic cells (DCs) to inhibit aGVHD. We derived these DCs from CD34+ human cord blood cells, treated them with EPS, and then injected them together with PBMCs into the NSG-HLA-A2 mice. We found that all mice that received untreated DCs were dead by day 35, whereas 25% of mice receiving EPS-treated DCs (EPS-DCs) survived. This DC cell therapy could be readily translatable to humans, because we can generate large numbers of human EPS-DCs and use them as an "off the shelf" treatment for patients undergoing HSCT.

Glycoside hydrolase family 32 enzymes from Bombella spp. catalyze the formation of high-molecular weight fructans from sucrose

Abstract Aims Acetic acid bacteria of the genus Bombella have not been reported to produce exopolysaccharides (EPS). In this study, the formation of fructans by B. apis TMW 2.1884 and B. mellum TMW 2.1889 was investigated. Methods and Results Out of eight strains from four different Bombella species, only B. apis TMW 2.1884 and B. mellum TMW 2.1889 showed EPS formation with 50 g l−1 sucrose as substrate. Both EPS were identified as high-molecular weight (HMW) polymers (106–107 Da) by asymmetric flow field-flow fractionation coupled to multi angle laser light scattering and UV detecors (AF4-MALLS/UV) and high performance size exclusion chromatography coupled to MALLS and refractive index detectors (HPSEC-MALLS/RI) analyses. Monosaccharide analysis via trifluoroacetic acid hydrolysis showed that both EPS are fructans. Determination of glycosidic linkages by methylation analysis revealed mainly 2,6-linked fructofuranose (Fruf) units with additional 2,1-linked Fruf units (10%) and 2,1,6-Fruf branched units (7%). No glycoside hydrolase (GH) 68 family genes that are typically associated with the formation of HMW fructans in bacteria could be identified in the genomes. Through heterologous expression in Escherichia coli Top10, an enzyme of the GH32 family could be assigned to the catalysis of fructan formation. The identified fructosyltransferases could be clearly differentiated phylogenetically and structurally from other previously described bacterial fructosyltransferases. Conclusions The formation of HMW fructans by individual strains of the genus Bombella is catalyzed by enzymes of the GH32 family. Analysis of the fructans revealed an atypical structure consisting of 2,6-linked Fruf units as well as 2,1-linked Fruf units and 2,1,6-Fruf units.