Structural characteristics and biological activity of lactic acid bacteria exopolysaccharides separated by ethanol/(NH4)2SO4 ATPS

Improved exopolysaccharide production by Lactiplantibacillus plantarum Z-1 under hydrogen peroxide stress and its physicochemical properties

In this study, a strain with good exopolysaccharide (EPS)-producing ability was isolated from the fermented Benincasa hispida and identified as Lactiplantibacillus plantarum Z-1. Its EPS production was further improved by H2O2 stress under optimized culture conditions, increasing from 180 ± 0.45 mg/L to 409.52 ± 2.16 mg/L. Purification of EPS with DEAE-52 and subsequent Sephadex G-100 column chromatography provided three fractions, namely, EPS-0, EPS-1 and EPS-3, respectively. The molecular weight of EPS, EPS-0, EPS-1 and EPS-3 were 85.4, 25.7, 131.88 and 93.2 kDa, respectively. EPS, EPS-1 and EPS-3 were mainly composed of glucose, rhamnose, arabinose and galactose with molar ratios of 1:0.544:0.211:0.281, 1:1.279:0.807:0.704, and 1:1.459:0.759:0.75, respectively, along with small proportions of fucose, mannose and xylose. EPS-0 was composed of glucose, arabinose, galactose and xylose, with molar ratios of 1:0.618:0.206:0.275. The structural analysis indicated that EPS-3 was mainly consisted of (1,2,4)-β-Rhap, (1,2,3)-β-Araf, (1,4)-β-Galp, T-α-Glcp units. The three purified fractions showed typical characteristics of non-Newtonian fluids and good viscoelasticity. Congo red test revealed that irregular triple-helical conformation existed in EPS and EPS-3. These physicochemical properties of EPSs make them a potential candidate for the use as a health-beneficial food additive in the food processing industry.

Advances in microbial exopolysaccharides as α-amylase inhibitors: Effects, structure-activity relationships, and anti-diabetic effects in vivo

The rapid digestion of starch, as the main source of energy in the human diet, causes an acute increase in blood sugar levels that will affect blood glucose homeostasis. The inhibition of α-amylase activity is an effective way of reducing starch digestibility, thereby controlling postprandial glycemia. As a class of carbohydrate polymers, microbial exopolysaccharides (EPSs) have garnered widespread attention for their inhibitory effects on α-amylase, but there is a lack of comprehensive review in this area. This paper aimed to review the inhibitory activity of microbial EPSs on α-amylase and their interaction mechanisms, and the effect of microbial EPSs on lowering blood glucose levels and regulating glycolipid metabolism in vivo were also discussed. Numerous studies have reported that EPSs with α-amylase inhibition activity are primarily produced by lactic acid bacteria. Microbial EPSs with an appropriate range of molecular weight, high proportion of glucose or mannose or arabinose residues, and high uronic acid content might be acceptable to inhibit α-amylase activity. Additionally, microbial EPSs exhibited potential anti-diabetic effects in mice, reducing blood glucose levels, and regulating glycolipid metabolism and gut microbiota. The information covered in this review may enhance the development and application of EPSs in functional food and pharmaceutical research.

Structural characteristics of Lacticaseibacillus rhamnosus ACS5 exopolysaccharide in association with its antioxidant and antidiabetic activity in vitro

A novel structure of exopolysaccharide from the Lactic Acid Bacteria (LAB) Lacticaseibacillus rhamnosus ACS5, isolated from home-made Turkish cheese, is described. After lyophilization, the L-EPS-ACS5 was characterized in production and functional activities in vitro, including antioxidant and antidiabetic activities. The physicochemical characterizations of the L-EPS-ACS5 were determined through molecular weight, UV, FTIR, SEM, TGA, HPLC, NMR, methylation, and GC-MS analysis. Strong antioxidant activities of L-EPS-ACS5 were confirmed from the results obtained in the hydroxyl radical, DPPH, ABTS, FRAP, superoxide anion radical, total antioxidant activity, and DNA damage protective effect, and also the L-EPS-ACS5 exhibited high antidiabetic activity (60 %). This study isolated L-EPS-ACS5 from a home-made cheese L. rhamnosus strain, demonstrating its novel and enhanced functionalities compared to existing strains. This opens exciting avenues for its development in the fields of biomedicine and pharmaceuticals.

Structural analysis and biological activity of cell wall polysaccharides and enzyme-extracted polysaccharides from pomelo (Citrus maxima (Burm.) Merr.)

Pomelo peel is a valuable source of pectin, but research on its cell wall polysaccharides is limited. This study compared the cell wall polysaccharides of pomelo peel, enzyme-extracted polysaccharides of pomelo peel, and enzyme-extracted polysaccharides of whole pomelo fruit. Cell wall polysaccharides, including water-soluble pectin (WSP), chelator-soluble pectin (CSP), sodium carbonate-soluble pectin (NSP), 1 mol/L KOH soluble hemicellulose (KSH-1), and 4 mol/L KOH soluble hemicellulose (KSH-2), were obtained by sequence-extraction method. Total polysaccharides from whole pomelo fruit (TP) and peel-polysaccharides from pomelo pericarps (PP) were obtained using enzyme-extraction method. The structural, thermal, rheological, antioxidant properties, and wound healing effect in vitro were described for each polysaccharide. WSP had a uniform molecular weight distribution and high uronic acid (UA) content, suitable for commercial pectin. NSP had the highest Rhamnose (Rha)/UA ratio and a rich side chain with highest viscosity and water retention. PP displayed the highest DPPH radical scavenging activity and reducing capacity at 0.1 to 2.0 mg/mL concentration range, with an IC50 of 1.05 mg/mL for DPPH free radicals. NSP also demonstrated the highest hydroxyl radical scavenging activity and promoted Human dermal keratinocyte proliferation and migration at 10 μg/mL, suggesting potential applications in daily chemical and pharmaceutical industries.

Purification, characterization, and hypoglycemic activity of exopolysaccharides from Lactiplantibacillus plantarum MY04

As natural polymers, Lactiplantibacillus plantarum exopolysaccharides (EPS) possess a wide range of bioactivities but suffer from low yields and unclear relationships between functional activity and structure. To this end, the chemical structure and bioactive properties of EPS from Lactiplantibacillus plantarum MY04 were investigated. As a result, three polysaccharide fractions (EPS-1, EPS-2, EPS-3) were separated and purified, of which EPS-2 had better antioxidant activity and α-glucosidase inhibitory ability. More importantly, EPS-2 can significantly enhance insulin sensitivity in HepG2 cells by upregulating enzyme activities in the glycolytic pathway and mitigating oxidative stress-induced damage. In addition, the structural characterization of EPS-2 was also comprehensively elucidated. It was found that EPS-2 was mainly composed of mannose with a molecular weight of 2.3 × 106 Da, and its main chain structure is →3)-Manp-(1 → 2)-Manp-(1 → 2,6)-Manp-(1 → 2,6)-Manp-(1→, providing a theoretical basis for understanding the relationship between structure and function of polysaccharides.

Comparative study on physicochemical properties and hypoglycemic activities of intracellular and extracellular polysaccharides from submerged fermentation of Morchella esculenta

The structural characteristic, physicochemical properties and structure-hypoglycemic activity relationship of intracellular (IPS) and extracellular (EPS) from submerged fermentation of Morchella esculenta were systematically compared and assessed. Both IPS and EPS were neutral, with a triple-helical conformation, and composed of galactose, glucose and mannose monosaccharides in different molar ratios. The molecular weight and particle size of IPS were higher than those of EPS. FTIR and SEM showed that the main functional group absorption peak intensity, glycosidic bond type and surface morphology of the two polysaccharides differed. Analysis of rheological and thermal properties revealed that the viscosity of IPS was higher than that of EPS, while thermal stability of EPS was greater than that of IPS. Hypoglycemic activity analysis in vitro showed that both IPS and EPS were non-competitive inhibitors of α-amylase and α-glucosidase. EPS showed strong digestive enzyme inhibitory activity due to its higher sulphate content and molar ratio of galactose, lower Mw and particle size. Meanwhile, with its higher Mw and apparent viscosity, IPS showed stronger glucose adsorption capacity and glucose diffusion retardation. These results indicate that IPS and EPS differed considerably in structure and physicochemical properties, which ultimately led to differences in hypoglycemic activity. These results not only suggested that IPS and EPS has the potential to be functional foods or hypoglycemic drugs, but also provided a new target for the prevention and treatment of diabetes with natural polysaccharides.

Exopolysaccharides of lactic acid bacteria as protective agents against bacterial and viral plant pathogens

In this study, 25 exopolysaccharides produced by lactic acid bacteria (LAB) were screened for their effect on plant pathogens. The molecular masses of EPS were found to be 3,8-5,0 × 104 Da. The GC-MS analysis revealed that EPSs were majorly composed of glucose (85.85-97.98 %). The FT-IR spectra of EPSs were in agreement with the typical absorption peaks of polysaccharides. EPSs showed a hydroxyl radical scavenging ability. The scavenging rate of EPS ranged from 20 to 50 % at a concentration of 5.0 mg/mL. Significant growth delay of phytopathogenic bacteria was observed after 3-6 h of cultivation. Optical density values of indicator cultures growing in the medium with EPS (1 mg/mL) were lower compared to the control by 24-100 % for Pseudomonas fluorescens, 9-46 % for P. syringae, 47-79 % for Pectobacterium carotovorum, 14-90 % for Clavibacter michiganensis, 9-100 % for Xantomonas campestris, and 45-100 % for X. vesicatorium. EPS retained their inhibitory effect on the growth of X. campestris, X. vesicatorium and C. michiganensis strains after 24-48 h of cultivation, but stimulating effect on the growth of some strains also was observed. LAB EPS showed antibiofilm activity against P. carotovorum, P. syringae, and P. fluorescent, decreasing their biofilm formation by 16-50 %, 14-39 %, and 29-59 %, respectively. Also, stimulation of biofilm formation by X. campestris (by 8-29 %), X. vesicatorium (by 3-32 %) and C. michiganensis (by 31-41 %) strains was observed. EPSs showed antiviral activity against tobacco mosaic virus (TMV). At a concentration of 100 μg/mL, they decreased the infective ability of TMV by 61-92 %. This is the first study demonstrating that LAB EPS exhibited in vitro antibacterial and antibiofilm activity against phytopathogenic bacteria and anti-viral activity against TMV. Thus, LAB EPSs could have great potential for plant protection strategies.

Fabrication and characterization of an alginate-based film incorporated with cinnamaldehyde for fruit preservation

Sodium alginate (SA) is widely used in the food, biomedical, and chemical industries due to its biocompatibility, biodegradability, and excellent film-forming properties. This article introduces a simple method for preparing uniform alginate-based packaging materials with exceptional properties for fruit preservation. The alginate was uniformly crosslinked by gradually releasing calcium ions triggered by the sustained hydrolysis of gluconolactone (GDL). A cinnamaldehyde (CA) emulsion, stabilized by xanthan without the use of traditional surfactants, was tightly incorporated into the alginate film to enhance its antimicrobial, antioxidant, and UV shielding properties. The alginate-based film effectively blocked ultraviolet rays in the range of 400-200 nm, while allowing for a visible light transmittance of up to 70 %. Additionally, it showed an increased water contact angle and decreased water vapor permeability. The alginate-based film was also employed in the preparation of coated paper through the commonly used coating process in the papermaking industry. The alginate-based material displayed excellent antioxidant properties and antimicrobial activity against Escherichia coli, Staphylococcus aureus and Botrytis cinerea, successfully extending the shelf life of strawberries to 7 days at room temperature. This low-cost and facile method has the potential to drive advancements in the food and biomedical fields by tightly incorporating active oil onto a wide range of biomacromolecule substrates.

Fractionation of Extracellular Polymeric Substances by Aqueous Three-Phase Partitioning Systems

Extracellular polymeric substances (EPS) are natural polymers secreted by microorganisms and represent a key chemical for the development of a range of circular economy applications. The production of EPS comes with notable challenges such as downstream processing. In this work, a three-phase partitioning (TPP) system was investigated as a fractionation technique for the separation of polysaccharides and proteins, both present in the EPS culture broth. The effect of the type of phase-forming compounds (alcohol, polymer, or ionic liquid, in combination with salt) and its concentration were evaluated and compared to the results previously obtained with model systems. The recyclability of phase-forming compounds used to form the fractionation platform was assessed by ultrafiltration. The best fractionation of EPS was achieved using a TPP system composed of 23 wt % ethanol and 25% K3C6H5O7 as 82% EPS-PS partitioned to the salt-rich/bottom phase, and 76% EPS-PN was recovered as an interfacial precipitate, which could be readily resolubilized in water. This represented an increase of 1.24 and 2.83-fold in the purity of EPS-PS and EPS-PN, respectively, in relation to the initial feed concentration. Finally, high recovery yields of phase-forming compounds (>99%) and fractionated EPS (>80%) were obtained using ultrafiltration/diafiltration (UF/DF) as the regeneration technique. The substantial fractionation yields, selectivity, and recyclability of the phase-forming compounds confirm the potential of TPP systems in combination with UF/DF as the separation method for real biopolymer mixtures. Key contributions of this study include the demonstration of the applicability of a readily scalable and cost-effective separation technique for the fractionation of EPS from real EPS-containing broths, while also the limitations of prescreening with model systems became clear through the observed deviating trends between model system studies and real broth studies.

One-step high efficiency separation of prolyl endopeptidase from Aspergillus niger and its application

Prolyl endopeptidase from Aspergillus niger (An-PEP) is an enzyme that recognizes C-terminal peptide bonds of amino acid chains and cleaves them by hydrolysis. An aqueous two-phase system (ATPS) was used to separate An-PEP from fermentation broth. Through single factor experiments, the ATPS containing 16 % (w/w) PEG2000 and 15 % (w/w) (NH4)2SO4 at pH 6.0 obtained the recovery of 79.74 ± 0.16 % and the purification coefficient of 7.64 ± 0.08. It was then used to produce soy protein isolate peptide (SPIP) by hydrolysis of soy protein isolate (SPI), and SPIP-Ferrous chelate (SPIP-Fe) was prepared with SPIP and Fe2+. The chelation conditions were optimized by RSM, as the chelation time was 30 min, chelation temperature was 25 °C, SPIP mass to VC mass was two to one and pH was 6.0. The obtained chelation rate was 82.56 ± 2.30 %. The change in the structures and functional features of SPIP before and after chelation were investigated. The FTIR and UV-Vis results indicated that the chelation of Fe2+ and SPIP depended mainly on the formation of amide bonds. The fluorescence, SEM and amino acid composition analysis results indicated that Fe2+ could induce and stabilize the surface conformation and change the amino acid distribution on the surfaces of SPIP. The chelation of SPIP and Fe2+ resulted in the enhancement of radical scavenging activities and ACE inhibitory activities. This work provided a new perspective for the further development of peptide-Fe chelates for iron supplement.

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.