Activity Of Exopolysaccharide Research Articles

Antioxidant and Immunomodulatory Properties of Partially purified Exopolysaccharide from Lactobacillus Casei Isolated from Chinese Northeast Sauerkraut

ABSTRACT Background Exopolysaccharides (EPS) from Lactobacillus spp. have been found to have biological activities. Our previous work demonstrated the antibiofilm activity of EPS from Lactobacillus casei NA-2 (L.casei NA-2) isolated from northeast Chinese sauerkraut (Suan Cai). The present study has focussed on the antioxidant and immunomodulatory activities of the EPS in vitro. Methods Antioxidant properties of the EPS were evaluated by the radical-scavenging activities in vitro. The immunomodulatory effects of EPS were assayed by measuring nitric oxide (NO), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), and reactive oxygen species (ROS) in RAW 264.7 macrophages, and the mechanism was investigated through NF-κB and JNK. Result EPS contains 88% total sugar, with the molecular weights (Mw) of 1.3 × 106 Da, 6.4 × 105 Da, 2.0 × 105 Da, and 1.4 × 104 Da. EPS showed antioxidant activity by scavenging hydroxyl radicals (42% at 1.2 mg/mL), superoxide radicals (76% at 100 µg/mL), and DPPH (80% at 10 mg/mL); and did not affect the proliferation of unstimulated or lipopolysaccharide (LPS)-induced RAW 264.7 cells at the concentrations ranging from 31.25 to 500 µg/mL. Results showed EPS promoted the production of ROS and TNF-α involved in NF-κB p65 and JNK signaling pathways in unstimulated RAW 264.7 cells. On the other hand, the levels of NO and iNOS were reduced after EPS treatment in LPS-induced RAW 264.7 cells. Conclusion Our results showed the protective effect against oxidative damage and potential immunomodulatory and anti-inflammatory properties of EPS from Lactobacillus casei NA-2.

Characterization and Biotechnological Functional Activities of Exopolysaccharides Produced by Lysinibacillus fusiformis KMNTT-10

In this study, the production and physicochemical characterization of exopolysaccharide (EPS) produced by Lysinibacillus fusiformis KMNTT-10 were investigated. Also, in vitro assays were conducted to investigate the biotechnological functional activities of EPS, including flocculation, emulsification, and antioxidant activity. Results showed that the maximum EPS produced by strain KMNTT-10 was 4.19 g/l after 120 h. The monosaccharides present in EPS were xylose, rhamnose, arabinose, galactose, and glucose in varying combinations. Characterization of EPS by FTIR and XRD analysis revealed the presence of hydroxyl, amino, and carboxyl functional groups and further, the EPS is an amorphous nature. SEM envisaged a highly porous web-like structure with an irregular surface in the EPS morphology. Further, the EPS had good flocculation activity with a maximum of 89.66% and also had potent emulsifying activity towards hydrocarbons with 1% EPS concentration. The EPS showed good antioxidant activity by potent scavenging actions on DPPH, ABTS, and nitric oxide free radicals. Overall results demonstrated that EPS of KMNTT-10 could be used in various industrial applications due to its excellent flocculation, emulsification potential, and good antioxidant activity.

Bioactivity assessment of exopolysaccharides produced by Pleurotus pulmonarius in submerged culture with different agro-waste residues

Pleurotus spp. are white-rot fungi that utilize different agro-wastes to produce useful biologically active compounds. In this study, exopolysaccharides (EPS) were produced by Pleurotus pulmonarius in submerged culture supplemented with different agro-wastes. Functional groups in EPS were revealed using Fourier Transform-Infrared (FT-IR) spectroscopy. Antimicrobial activity of EPS was tested against microorganisms using agar well diffusion. Scavenging potentials of EPS was tested against 1, 1- diphenyl-2-picryhydrazyl (DPPH), hydroxyl (OH), iron (Fe2+) and nitric oxide (NO) radicals. In vitro prebiotic activity of EPS was carried out. The highest yield (5.60 g/L) of EPS was produced by P. pulmonarius in submerged culture supplemented with groundnut shell (20.0 g/L). The functional groups in EPS were hydroxyl (-OH), methyl (-CH3), ketone (-RCOH) and carbonyl group (-C=O). EPS displayed zones of inhibition (5.00–14.00 mm) against tested microorganisms. Scavenging activity of EPS ranged from 65.70-81.80% against DPPH. EPS supported the growth of Lactobacillus delbrueckii and Streptococcus thermophiles with values ranged from 3.04 × 104–3.40 × 104 cfu/ml and 2.50 × 104–2.81 × 104 cfu/ml, respectively. Submerged culture of P. pulmonarius with addition of agro-wastes enhanced yield of EPS. The EPS exhibited bio-functional properties like antimicrobial, antioxidant and prebiotic activities. Hence, agrowastes can be recycled in submerged fermentation with fungi to produce promising biomaterials for biopharmaceutical applications.

Effect of intense pulsed light on Lactobacillus bulgaricus exopolysaccharide yield, chemical structure and antioxidant activity

SummaryIn this work, IPL technology was used for improving the production of exopolysaccharide (EPS) in Lactobacillus bulgaricus. The effects of fluence per pulse, pulse number and pulse distance were investigated. Through GC–MS, Fourier transform infrared (FT‐IR), 1H nuclear magnetic resonance (1H NMR), X‐ray diffraction (XRD) and scanning electron microscopy (SEM) study the influence on EPS primary chemical structure and surface morphology. The antioxidant activity of EPS was evaluated by DPPH, Fe2+ chelating and reducing power assays. The findings demonstrate that IPL could be a novel environment protection method for improving the production of EPS. The research results provide a theoretical basis for whether IPL is a new type of environmental protection method and can be used to improve EPS production.

Study of antioxidant and α‐glucosidase inhibitory activities of exopolysaccharide and extracts from caterpillar fungus Ophiocordyceps sinensis cultured in olive oil‐supplemented broth

AbstractNatural remedies that can simultaneously inhibit α‐glucosidase and antioxidants have been becoming effective measures to prevent type 2 diabetes and its complications. Ophiocordyceps sinensis (O. sinensis) ‐ “Dong trung ha thao”, is a valuable medicinal mushroom containing many natural compounds such as cordycepin, d‐mannitol, polysaccharides with many important biological activities. O. sinensis has been used to treat a variety of diseases such as diabetes, high blood pressure, atherosclerosis, or to restore anti‐aging health. In this study, O. sinensis was cultured in 5 % olive oil‐supplemented broth to collect biomass and post‐culture medium. The exopolysaccharide (EPS) was then obtained from the medium and the mushroom biomass was fractionated with 96 % ethanol, 70 % ethanol, 50 % ethanol, and water. Finally, in vitro antioxidant and α‐glucosidase inhibitory activities of EPS and fractions were evaluated. The results revealed that the 70 % ethanol extract presented the greatest α‐glucosidase inhibitory activity (14.07±0.25 %). The supplement of olive oil helped improve the antioxidant capacity of EPS compared to the control (without supplement). The present study results have established the basis for conducting further experiments to enhance the antioxidant activity and α‐glucosidase inhibition on O. sinensis and clinical applications.

Potential Health Benefits of Ropy Exopolysaccharides Produced by Lactobacillus plantarum.

The ability of Lactobacillus plantarum to produce exopolysaccharides (EPS) of various structures and properties is effective in showing both starter and probiotic culture qualification. In this study, the potential health promoting functions of the ropy EPS produced by Lactobacillus plantarum strains isolated from tarhana were tested. A stimulation of the pro-inflammatory IL-12 and TNF-α cytokines was observed in the presence of the ropy EPS suggesting an in vitro immune modulation. Similarly, the tested EPS demonstrated promoted the growth of the probiotic strains in fermentation medium. A medium level of radical scavenging activities of ropy EPS was observed whereas the superoxide and hydroxyl scavenging activities were more effective. The ropy EPS also showed α-glucosidase inhibition and cholesterol removal characteristics depending on their concentration. These findings revealed the potential health-promoting functions of ropy EPS from L. plantarum strains and EPS from L. plantarum PFC311 and PFC310 strains demonstrated multiple health-improving effects that can be further evaluated in food and other industries.

Production, characterization, and biological activity of a chitin-like EPS produced by Mortierella alpina under submerged fermentation

The production of a chitin-like exopolysaccharide (EPS) was optimized through experimental design methods, evaluating the influence of urea, phosphate, and glucose. Under optimized conditions, up to 1.51 g/L was produced and its physicochemical characteristics were evaluated by chromatography, NMR, and FTIR spectroscopy, and rheological techniques. The results showed a homogeneous EPS (Mw 4.9 × 105 g mol−1) composed of chitin, linear polymer of β-(1→4)-linked N-acetyl-d-glucosamine residues. The acetylation degree as determined by 13C CP-MAS NMR spectroscopy was over 90 %. The EPS biological activities, such as antioxidant effect and antitumor properties, were evaluated. To the best of our knowledge, this is the first study on the production of a new alternative of extracellular chitin-like polysaccharide with promising bioactive properties from the filamentous fungus M. alpina.

Purified exopolysaccharides from Weissella confusa 11GU-1 and Propionibacterium freudenreichii JS15 act synergistically on bread structure to prevent staling

Exopolysaccharides (EPS) can act beneficially on bread texture and prevent staling. Homopolysaccharides such as dextran have been extensively investigated in cereal products, but fewer studies have adressed heteropolysaccharides (HePS). We investigated the functional interactions of the EPS types produced by Weissella confusa 11GU-1 (dextran and ropy cell-associated polymer) and Propionibacterium freudenreichii JS15 (HePS) produced by co-fermentation process on dough and wheat bread characteristics. Purified EPS powders obtained by ultrafiltration of fermentates from Weissella single culture and co-culture with Propionibacterium supplemented at 2.5 or 5 g/kg flour increased loaf volumes by about 10% and reduced moisture loss during baking compared to control bread. Synergistic activities of Weissella and Propionibacterium EPS led to improvement with respect to crumb-firming properties. For the lower addition of co-culture EPS powder (2.5 g/kg flour, corresponding to approximately 1.5 g pure EPS/kg dough), bread crumb firmness was reduced by 30 and 36% after 72 h and 1 week storage, respectively, compare to unsupplemented control bread. Our study revealed that Weissella-Propionibacterium co-culture EPS improved bread characteristics and decreased bread staling at a low level of addition compared to Weissella single culture EPS and unsupplemented bread.

Genetic and Biochemical Characterization of an Exopolysaccharide With in vitro Antitumoral Activity Produced by Lactobacillus fermentum YL-11.

In the present study, the whole genome sequence of Lactobacillus fermentum YL-11, a novel exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) strain isolated from fermented milk, was determined. Genetic information and the synthetic mechanism of the EPS in L. fermentum YL-11 were identified based on bioinformatic analysis of the complete genome. The purified EPS of YL-11 mainly comprised galactose (48.0%), glucose (30.3%), mannose (11.8%), and arabinose (6.0%). In vitro, the EPS from YL-11 exhibited inhibition activity against HT-29 and Caco-2 colon cancer cells, suggesting that EPS from strain YL-11 might be used as an antitumoral agent. EPS at 600 and 800 μg/mL achieved inhibition rates of 46.5 ± 3.5% and 45.6 ± 6.1% to HT-29 cells, respectively. The genomic information about L. fermentum YL-11 and the antitumoral activity of YL-11 EPS provide a theoretical foundation for the future application of EPS in the food and pharmaceutical industries.

Isolation, Optimization of Fermentation Conditions, and Characterization of an Exopolysaccharide from Pseudoalteromonas agarivorans Hao 2018.

In recent years, the wide application of exopolysaccharides (EPSs) in food, cosmetics, medicine, and other fields has drawn tremendous attention. In this study, an EPS produced by Pseudoalteromonas agarivorans Hao 2018 was isolated and purified, and its fermentation conditions were optimized. Its structure and biological functions were also studied. The purity and molecular weight of EPS were determined by high performance liquid chromatography (HPLC), and the EPS exhibited a number average of 2.26 × 105 and a weight average of 2.84 × 105. EPS has good adsorption for Cu2+ and Pb2+. The adsorption rates can reach up to 69.79% and 82.46%, respectively. The hygroscopic property of EPS was higher than that of chitosan, but slightly lower than that of sodium hyaluronate. However, the water-retaining activity of EPS was similar to that of chitosan and sodium hyaluronate. EPS has strong ability to scavenge free radicals, including OH radical and O2− radical. Further, its activity on O2− radicals has similarities with that of vitamin C. EPS has broad application prospects in many fields, such as cosmetics, environmental protection.

Preparation of a sulfated exopolysaccharide (S-EPS) from Ophiocordyceps sinensis fungus and its antioxidant effects

Sulfated exopolysaccharides have been well-known to enhance biological activities. Exopolysaccharide (EPS) produced by Ophiocordyceps sinensis fungus is a source of natural compounds. The aim of our study is to improve the EPS biological activities by its sulfated modification using the chlorosulfonic acid (CSA)-pyridine (Pyr) method. The appropriate conditions of the sulfation reaction were explored, including CSA/Pyr ratio (v/v) of 1:3 and 6h. The degree of substitution (DS) of S-EPS11 was the highest (DS = 1.59). The total contents of polysaccharides and SO42- of S-EPS11 were 52.25% and 47.15%, respectively. Besides, the FT-IR spectra analysis indicated the presence of CO-S (peak of 815 cm-1) and S=O (peak of 1129 cm-1) stretching vibrations, while the natural EPS did not appear. Importantly, OH• and ABTS• radical scavenging potential of S-EPS11 significantly increased compared with those of the natural EPS. Together, we successfully generated sulfated EPS extracted from O. sinensis fungus which enhanced antioxidant activities of natural EPS.

Preparation screening, production optimization and characterization of exopolysaccharides produced by Lactobacillus sanfranciscensis Ls-1001 isolated from Chinese traditional sourdough

The present study focused on preparation screening, production optimization and characterization of exopolysaccharides (EPS) produced by Lactobacillus sanfranciscensis isolated from a Chinese traditional sourdough sample. In addition, in vitro antioxidant activity of pure EPS was determined. A total of 51 strains of L. sanfranciscensis were screened, and L. sanfranciscensis Ls-1001 was proved as the most abundant crude EPS producing strain, which was selected for further EPS optimization and characterization. The optimized conditions resulted in around 31% increase in EPS production (final yield: 249.30 mg/L) and included: maltose 25 g/L, yeast peptone 10.24 g/L and fresh yeast extractives (FYE) 12.92 mL/L. HPLC analysis showed that pure EPS contained only glucose monomers, indicating that it was a kind of homopolysaccharides. FTIR spectroscopy revealed the presence of hydroxyl and carbonyl groups. NMR analysis confirmed that EPS contained α-glycosidic bond and pyranose residue. The EPS showed strong in vitro antioxidant activity.

Immunostimulatory and antibacterial activity of Leuconostoc mesenteroides and its purified exopolysaccharide against extended-spectrum beta-lactamase producing Burkholderia cepacia

Lactic acid bacteria (LAB) have reported as antifungal, antibacterial, and immunostimulatory agents. Exopolysaccharide (EPS) of lactic acid bacteria effectively could stimulate the production of cytokines by macrophages. This study was aimed to extract, purified, and characterize the EPS from Leuconostoc mesenteroides subsp. Cremoris and to evaluate the immunostimulatory and antibacterial activities of EPS against extended-spectrum beta-lactamase (ESBL) producing Burkholderia cepacia strains. Nine EPSs producing L. mesenteroides subsp. cremoris strains were isolated from local dairy products and the isolated bacteria were identified by using API 50. Eight B. cepacia strains were isolated from different specimens in the hospitals of Medical city, Baghdad. Furthermore, genotypic and phenotypic detection of antibiotic resistance were determined including ESBL genes. EPS of L. mesenteroides subsp. Cremoris was extracted and purified by gel filtration chromatography. EPS physical and chemical analysis were performed to characterize it. Antibacterial and immunomodulatory effect of EPS were studied in vivo using mice and ELISA was used to determine the levels of IL-10 in the mice sera. The extracted EPS was found to have a maximum relative viscosity in water (3.51 dl/g) and maximum specific viscosity (2.93 dl/g), while the intrinsic viscosity recorded 1.41 dl/g. The chemical analysis of the extracted polysaccharide was found to contain the following components, carbohydrates, protein, uronic acids, hexosamines, acetyl groups, ketal linked pyruvate groups, phosphate groups, and sulfate groups, also show the following functional groups under infrared (IR) spectra (hydroxyl, alkanes, carbonyl, carbonyl of carboxylic acid, phosphates, and aliphatic amines). HPLC analysis revealed the presence of mannose as a major component with a calculated molecular weight of 1.71 × 103 g/mol. Genotypic detection of the blaPER-1 gene among ESBL producing B. cepacia strains showed the presence of blaPER-1 gene in three (42.86%) strains. Furthermore, to confirm the biological potential, the EPS was evaluated for its antibacterial activity against multidrug resistance B. cepacia strains in vitro and the result showed that the purified EPS was more effective than crude EPS in all concentrations. The protective activities of L. mesenteroides and EPS were observed when administered 7 days before and after B. cepacia infection, whereas therapeutic activities were monitored by administering EPS for 7 days after B. cepacia induction. This results revealed that the administration of L. mesenteroides and EPS significantly decreased the number of B. cepacia in liver, spleen, and lung (P < 0.05). Furthermore, they enhanced production of IL-10. In conclusion, the L. mesenteroides and its EPSs possess antibacterial and immunostimulator properties and are nontoxic with medicinal importance. Therefore, further studies in human participants should determin the role of L. mesenteroides and its EPS as an immunomodulatory and its relationship in the host protection to pathogens.

Exploring two contrasting surface-active exopolysaccharides from a single strain of Ochrobactrum utilizing different hydrocarbon substrates.

During production and characterization of exopolysaccharides (EPS) of Ochrobactrum pseudintermedium C1, it was observed that an experimental change in the basic hydrocarbon type of substrate for bacterial utilization led to elicitation of different surface-active properties in the EPS produced. In the sugar substrate, it elicited surfactant property, while in oil substrates it elicited emulsifying property, which indicated that the EPS might be different. Consequently, attention was focused on a detailed analysis of this substrate-specific EPS. Utilizing waste sugar, edible, and mineral oil substrates, EPS produced in each situation was characterized. Besides estimating surface activity and thermostability, each substrate-specific EPS was analyzed by Fourier-transform infrared spectroscopy, gas chromatography-mass spectroscopy, 1 H-nuclear magnetic resonance, and matrix-assisted laser desorption/ionization-time of flight mass spectroscopy to find any structural difference. The results were significantly contrasting although the similarity in molecular mass suggested a basic similarity in polysaccharide structure. Morphological differences were also evident both macroscopically and microscopically with scanning electron microscopy. As the surface-active property of EPS was dependent on the substrate utilized, their structural differences might account for it. These diverse surface activities of EPS produced by a single bacterial strain simply by changing the nature of substrate would also augment their bioapplications. Moreover, utilization of waste and easily available substrates should make such applications convenient, ecofriendly, and cost-worthy.

Exopolysaccharide from a commensal bacterium improves outcome of graft versus host disease by decreasing donor T cell activation

Abstract We previously showed that exopolysaccharide (EPS) produced by a commensal bacterium, Bacillus subtilis, induces alternatively-activated, anti-inflammatory M2 macrophages that protect mice from T cell-dependent inflammatory disease, induced by the enteric pathogen Citrobacter rodentium. Here, we show that EPS induces clinical improvement in another T cell-mediated disease, graft versus host disease (GVHD). GVHD is a common complication of allogenic bone marrow transplantation and is caused by the activation of alloreactive donor T cells. To monitor the inflammatory response of allogeneic bone marrow cells in recipient mice, we used donor cells from transgenic mice that express a luciferase-based biosensor that is cleaved by caspase-1, a protein activated during inflammation. We found that donor inflammatory responses and T cell activation was decreased in EPS-treated mice. Our previous data indicate that EPS does not have a direct effect on T cells. To identify the cell type affected by EPS, we tested the activity of EPS on bone marrow-derived dendritic cells (BMDCs) and found that these cells have upregulated expression of the inhibitory molecule, PD-L1, and the cells inhibited alloreactive T cell activation and proliferation in mixed lymphocyte reactions (MLR). We also found that in vivo injection of EPS resulted in the upregulation of PD-L1 expression on splenic dendritic cells. We conclude that EPS ameliorates clinical manifestations of GVHD by decreasing the activation of donor T cells, and we suggest that EPS affects T cells by inducing inhibitory dendritic cells.

Sulfonation of Lactobacillus plantarum WLPL04 exopolysaccharide amplifies its antioxidant activities in vitro and in a Caco-2 cell model

Exopolysaccharide (EPS) of Lactobacillus plantarum WLPL04 and its sulfated EPS were systematically investigated for their antioxidant activities and effects on protecting the oxidative damage of Caco-2 cells from H2O2. Exopolysaccharide was successfully sulfonated from purified EPS as confirmed by Fourier-transform infrared spectroscopy, and the degree of sulfonation was 0.30. Both EPS and sulfated EPS showed antioxidant activities in vitro determined by 1,1-diphenyl-2-picrylhydrazyl, superoxide, and hydroxyl radical scavenging tests, and those activities of sulfated EPS were significantly enhanced at 1,000 μg/mL. Cell viabilities of Caco-2 in the range of 1 to 100 μg/mL of EPS and sulfated EPS showed no significant difference. In H2O2-damaged Caco-2 cells models, EPS and sulfated EPS significantly inhibited the enhancement of reactive oxygen species and malondialdehyde levels, and sulfated EPS enhanced the effects by 40.86% and 61.11% when compared with the purified EPS at the same concentration of 100 μg/mL, respectively. For the activities of antioxidant-related enzymes (superoxide dismutase, catalase, and glutathione peroxidase) and expression of genes (SOD2, GPX2, MT1M) on Caco-2 cells, strong protection abilities against the oxidative stress were displayed from both EPS and sulfated EPS, and sulfated EPS exhibited significant enhancement as compared with either EPS or control groups. In summary, sulfonation is an effective strategy for improving the antioxidant activities of EPS fromL.plantarumWLPL04 in vitro and on Caco-2 cells.

Production of antioxidative exopolysaccharides of Cordyceps militaris with Vernonia amygdalina leaves in substrate

Cordyceps militaris exopolysaccharides (EPS) have many pharmacological activities such as boosting immunity and antifatigue. To obtain EPS efficiently, we added moderate Vernonia amygdalina leaf powder as inducer to the fermentation medium to promote the production of Cordyceps militaris EPS and studied the infrared absorption spectrum and antioxidant activities of the EPS after optimization. The optimum liquid fermentation conditions were as follows: addition of Vernonia amygdalina leaf powder of 8 g/L, fermentation duration of 9 d, initial pH of 6.5, inoculation quantity of 5.0 mL. Under such a condition, the yield of Cordyceps militaris EPS reached (5.24±0.28) mg/mL, increased by 205.20% compared to the control group without adding Vernonia amygdalina leaf powder. Results of infrared analysis and antioxidant activity showed that the Vernonia amygdalina leaves had little effect on the structure and activities of Cordyceps militaris EPS. The results of this research suggest that Vernonia amygdalina leaf can enhance the production of Cordyceps militaris EPS effectively, and provides a novel method for efficient production of EPS in Cordyceps militaris.

Isolation and characterization of a high molecular mass β-glucan from Lactobacillus fermentum Lf2 and evaluation of its immunomodulatory activity

When grown in a semi-defined medium, L. fermentum Lf2 synthesizes significant quantities (∼2 g/L) of two exopolysaccharides (EPS). The two EPS were separated by preparative size exclusion chromatography to give a high molecular mass β-glucan (1.23 × 106 Da) and a medium molecular mass heteroglycan (8.8 × 104 Da). The structure of the high molecular mass β-glucan was determined using a combination of NMR spectroscopy, monomer and linkage analysis. The EPS has the following structure:▪The immunomodulatory activity of the high molecular mass EPS was studied in peripheral blood mononuclear cells (PBMC). Exposure of PBMC to an aqueous solution of the EPS for 24 h led to increased cell proliferation, changes in expression of the cytokines CD14 and TLR2, and to an increase in production of TNF-α compared to controls. In contrast, when cells that had been treated with EPS for 24 h and from which the EPS had been removed, were subsequently exposed to the bacterial antigen LPS very low levels of TNF-α production were observed. This result indicates that the EPS imparts immunotolerance in PBMC. An ability to modulate the release of the proinflammatory mediators, such as TNF-α, is an important goal in the development of therapies for the treatment of diseases, such as Crohn's disease and ulcerative colitis, associated with excessive release of inflammatory mediators.

Effect of γ-irradiation on physico-chemical and antioxidant properties of galactan exopolysaccharide from Weissella confusa KR780676.

Exopolysaccharide (EPS) produced by Weissella confusa KR780676 from an Indian fermented food (Idli) has been characterized as galactan in earlier report. In this study, the galactan EPS was irradiated at different doses (0, 4, 8, and 16kGy) using 60Co as γ-source and effect of γ-irradiation on physico-chemical and antioxidant potential of galactan EPS was studied. Color and flow properties showed moderate change after the γ-irradiation treatment. Particle size analysis and scanning electron microscopy exhibited significant breakdown of the EPS particles into smaller average hydrodynamic diameter size from 495.54 to 198.44nm with increasing irradiation doses. Overall, pH showed decrease, while the water activity showed an increasing trend with the increasing irradiation dose. No significant effect was observed in the functional groups of EPS as revealed in the FT-IR spectroscopic analysis. After the treatment, semi-crystalline nature of the EPS changed to amorphous as shown in XRD analysis due to the breakdown. Antioxidant activities of galactan EPS increased marginally after the treatment. However, hydroxyl radical scavenging activity increased significantly from 48 to 67%. Changes in physico-chemical and antioxidant properties of galactan EPS with γ-irradiation treatment altered the functional properties of EPS positively, making it more suitable for wider application in the food industry.

Optimization of exopolysaccharide production by probiotic yeast Lipomyces starkeyi VIT-MN03 using response surface methodology and its applications

In the present study, the cultural conditions for exopolysaccharide (EPS) production from probiotic yeast Lipomyces starkeyi VIT-MN03 were optimized using response surface methodology (RSM) to maximize the yield of EPS. Interactions among the various factors viz. sucrose concentration (1–3 g%), NaCl concentration (2–4 g%), pH (3–5), temperature (20–30 °C), and incubation period (20–40 days) during EPS production were studied using Box-Behnken design (BBD). The EPS was purified and characterized using various instrumental analyses. The properties like adhesion, antioxidant, biosurfactant, cholesterol removal, and binding ability to mutagens were also tested for EPS produced. Sixfold increase in EPS production (4.87 g L−1) by L. starkeyi VIT-MN03 was noted under optimized condition. EPS showed a high viscosity (1.8 Pa S−1) and good shear-thinning properties. Instrumental analysis showed that EPS was heteropolysaccharide composed of glucan, mannan, and rhamnan. Lipomyces starkeyi VIT-MN03 exhibited good self-adhesion (95%) and co-aggregation ability (93%). Adhesion efficiency for yeast inoculum containing 5.5 × 107 CFU mL−1 per 9.2 cm2 of Caco-2 cell (colorectal adenocarcinoma) was noted. The probiotic EPS displayed strong antioxidant ability to scavenge hydroxyl radical and DPPH by 58% and 71% respectively. In addition, biosurfactant activity (86%) and cholesterol removal (90%) ability of probiotic EPS was also tested. EPS bound cells of L. starkeyi VIT-MN03 showed good binding ability to mutagens. These results support the effectiveness of using RSM for maximum EPS production. To the best of our knowledge, this is the first report on optimization of EPS production by probiotic yeast.