Structure characterization of exopolysaccharides from Lactobacillus casei LC2W from skim milk

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.

New progress in the identifying regulatory factors of exopolysaccharide synthesis in lactic acid bacteria

The exopolysaccharides (EPSs) of lactic acid bacteria (LAB) have presented various bioactivities and beneficial characteristics, rendering their vast commercial value and attracting a broad interest of researchers. The diversity of EPS structures contributes to the changes of EPS functions. However, the low yield of EPS of LAB has severely limited these biopolymers' comprehensive studies and applications in different areas, such as functional food, health and medicine fields. The clarification of biosynthesis mechanism of EPS will accelerate the synthesis and reconstruction of EPS. In recent years, with the development of new genetic manipulation techniques, there has been significant progress in the EPS biosynthesis mechanisms in LAB. In this review, the structure of LAB-derived EPSs, the EPS biosynthesis basic pathways in LAB, the EPS biosynthetic gene cluster, and the regulation mechanism of EPS biosynthesis will be summarized. It will focus on the latest progress in EPS biosynthesis regulation of LAB and provide prospects for future related developments.

Direct Utilization and Conversion of raw Starch to Exopolysaccharides by a newly isolated Amylolytic Streptococcus sp

A newly isolated culture is identified as Streptococcus lutetiensis with significant starch saccharifying activity. Along with considerable amylolytic property (~ 2.71U/mL), the culture exhibited significant production of exopolysaccharide (EPS) in starch medium. Interestingly, the glycosyl transferase activity which is essential in the biosynthesis of polysaccharide is also detected in the culture and after screening and process optimization, a maximum EPS titre of 19.92 ± 0.5g/L was obtained from cassava starch. The crude EPS, after purification and characterization (monosaccharide analysis, FT-IR, TGA, GPC, NMR, and SEM) was found to be of dextran nature with a Mw of 1275.36kDa. Dextran type exopolysaccharide are synthesized by dextransucrase enzyme by the transfer of glucosyl residues from sucrose to dextran polymer. Iinterestingly, the glycosyl transferase enzyme activity which is essential in the biosynthesis of EPS is also detected in the culture. The particle size (447.8 dnm) and the zeta potential (-33.4) analysis of the purified EPS showed that the EPS produced is a stable molecule and has a random coil confirmation when exposed to alkaline condition with shear thinning property. One step conversion of sustainable low-cost starchy raw materials without adding external enzymes for hydrolysis, improved the economic viability of EPS production.

Structure of a unique fucose-containing exopolysaccharide from Sayram ketteki yoghurt and its anti-MRSA biofilm effect

In this work, we reported an in situ exopolysaccharide (in situ-EPS1) containing rare fucose produced by Lactobacillus helveticus MB2-1 in Sayram ketteki yoghurt, which made it unique. Its fine structure was characterized by GPC, HPLC, FT-IR, GC-MS,¹HNMR and ¹³CNMR together with two-dimensional (2D) NMR spectra. The results revealed that in situ-EPS1 was a new heteropolysaccharide with molecular weight of 1.06 × 10⁵ Da, and was composed of mannose, rhamnose, glucose, galactose and fucose with the following repeating units. Furthermore, the in situ-EPS1 exhibited significant antibiofilm effect against Methicillin-resistant Staphylococcus aureus (MRSA). Notably, the in situ-EPS1 did not interfere with the planktonic growth of MRSA strain, whereas inhibited its cell metabolic activity and the transcription of genes related to biofilm formation. This unique antibiofilm but non-antibacterial mechanism supposedly prevented the development of bacterial drug resistance, which may open a new door to fight against these drug-resistant microorganisms.

Rapid isolation of exopolysaccharide-producing Streptococcus thermophilus based on molecular marker screening

BACKGROUND

As a natural food additive, exopolysaccharide (EPS) produced by Streptococcus thermophilus can improve product viscosity and texture. The protein EpsA is a putative pathway-specific transcriptional regulator for EPS biosynthesis in S. thermophilus.

RESULTS

According to comparative analysis of EPS biosynthetic gene clusters, a conserved region of epsA (609 bp) was employed to design primer pair epsA-F/R as a molecular marker for the isolation of EPS-producing (EPS⁺ ) S. thermophilus. Two EPS⁺ S. thermophiles strains, AR333 and S-3, were band-positive, whereas Lactococcus lactis NZ9000 (non-EPS-producing, EPS^- ), Lactobacillus casei LC2W (EPS⁺ ) and L. plantarum AR113 (EPS⁺ ) were negative by polymerase chain reaction (PCR) amplicon bands using the epsA probe. This indicated good specificity of the epsA probe to EPS⁺ S. thermophilus. Moreover, based on PCR screening with the epsA probe, 23 positive strains were isolated and identified as S. thermophilus from our microbial library and natural fermented milk with 141.3-309.2 mg L^-1 of EPS production, demonstrating the validity of our molecular marker screening method.

CONCLUSION

The designed molecular marker of epsA can rapidly screen EPS⁺ S. thermophilus, which has potential application in the dairy and other food industries. © 2021 Society of Chemical Industry.

Structure characterization of a pyruvated exopolysaccharide from Lactobacillus plantarum AR307

A pyruvated exopolysaccharide designated as LPE-1 was isolated and purified from the fermentation broth of Lactobacillus plantarum AR307 and characterized for its chemical structure. The results indicated that LPE-1 contained galactopyranose (Galp) and glucopyranose (Glcp) at a molar ratio of 2: 1. The weight-averaged molecular weight (M_w) of LPE-1 was 605 kDa, with a polydispersity index (PDI) of 1.57, intrinsic viscosity ([ƞ]) of 3.28 dL/g, Mark-Houwink-Sakurada exponent α of 0.65 and gyration of radius (R_g) of 36.10 nm. The results of GC-MS and NMR revealed that pyruvate (Pyr) was found to form cyclic ketals at O-4 and O-6 position of terminal galactopyranose (T-Galp). The backbone of LPE-1 was identified to be consisted of 1,4-β-D-Glcp (23.19%), 1,4-α-D-Glcp (11.38%) and 1,4,6-β-D-Galp (12.05%), branched by 1,6-β-D-Galp (38.88%) at O-6 position of 1,4,6-β-D-Galp residue and terminated by T-β-D-Galp (5.60%) or T-β-D-(4,6-Pyr)-Galp (8.90%). A possible structural unit was proposed for LPE-1 as follows: where Galp* is either T-β-D-(4,6-Pyr)-Galp or T-β-D-Galp. The presence of pyruvate group in LPE-1 would play an important role in improving the viscosity and plasticity of dairy products.

Structural characterization, functional and biological activities of an exopolysaccharide produced by probiotic Bacillus licheniformis AG-06 from Indian polyherbal fermented traditional medicine

An exopolysaccharide (EPS) was purified from the probiotic bacterium Bacillus licheniformis AG-06 isolated from the polyherbal fermented traditional medicine (Ashwagandharishta) of Indian Ayurveda. High-performance liquid chromatography (HPLC) based compositional analysis exhibits the heteropolymeric nature of the EPS consisting of galactose, rhamnose, xylose, mannose, and glucose, as the monomeric units. Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopic analyses confirm the presence of typical carbohydrate polymer functional groups and structural units, respectively. The purified EPS demonstrates the web-like fibrous and porous nature in scanning electron microscopic and atomic force microscopic studies. The purified EPS had shown 71.83% and 67.79% of flocculation and emulsification activities, respectively. Antioxidant activity was evaluated against 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), nitric oxide, and superoxide free radicals and the scavenging actions were increased in a dose-dependent manner. Moreover, the purified EPS exhibits a significant cytotoxic activity against the human lung carcinoma cells (A549), which strongly suggests the anticancer potential of the EPS derived from B. licheniformis AG-06.

Structural characterization of Lanzhou lily (Lilium davidii var. unicolor) polysaccharides and determination of their associated antioxidant activity

BACKGROUD

The Lanzhou lily (Lilium davidii var. unicolor) is the only Lilium species that is used for both culinary and medicinal purposes in China. Its bulbs contain various bioactive substances, such as polysaccharides, saponins and colchicine. Lanzhou lily polysaccharides are known to have anti-immunity, anti-tumor and anti-oxidation functions.

RESULTS

The present study used a Box-Behnken design to optimize the ultrasound-assisted extraction of Lanzhou lily polysaccharides. Compared to other enzymes, trypsin significantly increased the polysaccharide yields, whereas the protein content of polysaccharides extracted with trypsin was the lowest. Monosaccharide mainly includes glucose (> 50%) and mannose (> 10%). 1,1-Diphenyl-2-picrylhydrazyl radical scavenging activity, chelating activity, total antioxidant capacity and hydroxyl radical scavenging activity of Lanzhou lily polysaccharides extracted with trypsin were stronger than those extracted without enzymes (control). Structural characteristics of Lanzhou lily polysaccharides extracted with trypsin and extracted without enzymes were characterized by scanning electron microscopy and nuclear magnetic resonance spectroscopy. When water extracted polysaccharide and trypsin extracted polysaccharide concentrations were 200 μg mL^-1 , Raw264.7 proliferation rates were 101.69% and 159.41%, respectively.

CONCLUSION

The Lanzhou lily polysaccharide was identified as α-(1 → 6)-d-glucan. Consequently, the effects of both potential antioxidant and proliferative activity of trypsin are significant. © 2020 Society of Chemical Industry.

Structural characterization of exopolysaccharide from Streptococcus thermophilus ASCC 1275

In this study, we purified and characterized exopolysaccharide (EPS) produced by a high-EPS-producing dairy starter bacterium, Streptococcus thermophilus ASCC 1275. Crude EPS was extracted from S. thermophilus ASCC 1275 and partially purified using dialysis. Further purification and fractionation of exopolysaccharide was conducted using HPLC on a Superose 6 column (Cytiva/Global Life Sciences Solutions, Marlborough, MA). Glycosyl composition analysis, linkage analysis along with 1-dimensional and 2-dimensional nuclear magnetic resonance spectroscopy were performed to deduce the structure of EPS. Three fractions (F) obtained from gel permeation chromatography were termed F1 (2.6%), F2 (45.8%), and F3 (51.6%) with average molecular weights of approximately 511, 40, and 5 kDa, respectively. Monosaccharide composition analysis revealed the dominance of glucose, galactose, and mannose in all 3 fractions. Major linkages observed in F3 were terminal galactopyranosyl (t-Gal), 3-linked glucopyranosyl (3-Glc), 3-linked galactofuranosyl (3-Galf), and 3,6-linked glucopyranosyl (3,6-Glc) and major linkages present in F2 were 4-Glc (48 mol%), followed by terminal mannopyranosyl (t-Man), 2- + 3-linked mannopyranosyl (2-Man+3-Man), and 2,6-linked mannopyranosyl (2,6-Man; total ∼28 mol%). The 1-dimensional and 2-dimensional nuclear magnetic resonance spectroscopy revealed that F2 comprised mannans linked by (1→2) linkages and F3 consisted of linear chains of α-d-glucopyranosyl (α-d-Glcp), β-d-glucopyranosyl (β-d-Glcp), and β-d-galactofuranosyl (β-d-Galf) connected by (1→3) linkages; branching was through (1→6) linkage in F3. A possible structure of EPS in F2 and F3 was proposed.

Exopolysaccharides from Lactobacillus kiferi as adjuvant enhanced the immuno-protective against Staphylococcus aureus infection

Exopolysaccharides from lactic acid bacteria (LAB) have gained more attention due to their health benefits. Most research on LAB EPS focuses on antitumor and antioxidant activities. To our knowledge, the immunoadjuvant activity of LAB EPS has not been thoroughly studied. In this study, the EPS produced by Lactobacillus kiferi WXD029 were purified by ethanol precipitation and column chromatography fractionation. The molecular weight of the EPS was 3.423 × 10⁵ Da and was mainly composed of Glu, GlcN, and GalN in a molar ratio of 3.1:1:1. In vitro, EPS could significantly enhance the proliferation and phagocytic activity as well as induce the production of NO, TNF-α, IL-1β, and IL-6 in RAW264.7 cells. In vivo, the EPS adjuvant could increase the titers of S.aureus antigen-specific antibodies and markedly enhanced T cell proliferation. Notably, EPS adjuvant also induced a strong potential Th1, Th2 and Th17-cell mixture responses. Furthermore, immunization with S.aureus antigen plus EPS adjuvant induced a protective effect when compared with S.aureus antigen alone in murine bacteremia, pneumonia and mastitis model. Collectively, these results suggest that EPS derived from probiotic Lactobacillus kiferi strain is promising as an efficient adjuvant candidate for the prevention of S. aureus infections.

Initial Analysis on the Characteristics and Synthesis of Exopolysaccharides from Sclerotium rolfsii with Different Sugars as Carbon Sources

Scleroglucan is widely used in the food and chemical industries because of its good rheological property, stability, and emulsification activity. To investigate the influence of different carbon sources on the properties and synthesis of exopolysaccharides (EPS), the three EPSs (GEPS, glucose was used as the carbon source; LEPS, lactose was used as the carbon source; and SEPS, sucrose was used as the carbon source) were determined, respectively. It was found that the yield and viscosity of exopolysaccharides were different. When sucrose and glucose were used as the carbon sources, the viscosity and yield of EPS were both higher than lactose. The scanning electron microscopy (SEM) images showed that the three EPSs had different morphologies, but the monosaccharide analysis showed that they were all composed of glucose units. Fourier transform infrared spectroscopy (FT-IR) proved that there were no additional substituents for the three EPSs. Furthermore, the high performance liquid chromatography (HPLC) results showed that SEPS and LEPS had two fractions. Through the analysis of proteomics data, there were few differences in the metabolic pathways between GEPS and SEPS, but a significant difference between LEPS and SEPS. Our study provides a theoretical basis and reference for understanding the biosynthesis of exopolysaccharides and the development of different types of EPS products.

Anti-elastase and anti-collagenase potential of Lactobacilli exopolysaccharides on human fibroblast

Polysaccharides could be used as biodegradable and biocompatible polymers for scaffolds and carriers matrix. Numerous algal, fungi and herbal polysaccharides can attenuate degradation of skin matrix by the inhibition of elastase, collagenase and matrix metalloproteinases (MMPs). In this study, we investigate anti-elastase and anti-collagenase potential of Lactobacilli exopolysaccharides (LEPS) on normal human fibroblast. Among 60 Lactobacilli isolated from herbal plants and dairy products, selected LEPS showed high anti-collagenase (up to 100%), anti-elastase (up to 87%) and antioxidant activity (up to 60%). Most of them had no cytotoxicity effect on fibroblast, and some of them promote cell proliferation (up to 10%). In scratch assay, all the investigated EPS_s stimulated wound healing process in fibroblast (up to 99%). MMP1, MMP2, MMP3, MMP9 and MMP10 were down-regulated significantly and TIMP1 and TIMP2 were up-regulated slightly in LEPS of B9-1 from L. casei with high anti-collagenase and anti-elastase activity; however, no meaningful alteration was observed in MMP_s expression level for LEPS of P35 from L. plantarum with low anti-collagenase and anti-elastase activity. By consideration of high anti-collagenase, anti-elastase, antioxidant activity and wound healing of LEPS, they could be considered as good candidate of skin anti-aging agents for tissue engineering and skin regeneration scaffolds.

Structural elucidation of a pectin-type polysaccharide from Hovenia dulcis peduncles and its proliferative activity on RAW264.7 cells

In this paper, an acidic polysaccharide HDP3A was isolated from Hovenia dulcis peduncles with 45.9% of uronic acid content. Structure of HDP3A was elucidated by chemical and spectroscopic analysis. HDP3A was mainly contained of galacturonic acid, galactose, rhamnose and arabinose with a small quantity of xylose, fucose, mannose, glucose. The structural analysis indicated that HDP3A was a pectin-type polysaccharide with HG and RG-I regions and hairy regions. HG was linear homopolymer with repeating units of (1→4)-α-d-galactopyranosyl uronic (GalA) residues. The GalpA residues in HG domain may be acetylated and/or methyl-esterified. The backbone of RG-I contains repeating units of [→α-GalpA-1,2)-α-Rhap-1,4→]_n and the hairy regions attached in the Rha at position O-4. Hairy regions were mainly composed of galactans, arabinans, arabinogalactans, glucans, mannans and xylans. The immunomodulatory activities of HDP3A and its reduced (HDP3A-R) and hydrolyzed product (HDP3A-0.1) in vitro on macrophages were determined. The three polysaccharide fractions all stimulated the proliferation of RAW264.7 cells and the order of the proliferative effects was HDP3A>HDP3A-R>HDP3A-0.1, indicating that the immune effects of pectin-type polysaccharides were related to branches and molecular weight. Consequently, HDP3A could be as a potential source for the proliferative activity.