Preparation, partial characterization and bioactivity of exopolysaccharides from Lactobacillus casei LC2W

Antihyperglycemic, Antiaging, and L. brevis Growth-Promoting Activities of an Exopolysaccharide from Agrobacterium sp. FN01 (Galacan) Evaluated in a Zebrafish (Danio rerio) Model

Agrobacterium sp. are notable for their ability to produce substantial amounts of exopolysaccharides. Our study identified an exopolysaccharide (Galacan, 4982.327 kDa) from Agrobacterium sp. FN01. Galacan is a heteropolysaccharide primarily composed of glucose and galactose at a molar ratio of 25:1. The FT-IR results suggested that Galacan had typical absorption peaks of polysaccharide. The results of periodate oxidation, Smith degradation, and NMR confirmed the presence of structural units, such as β-D-Galp(→, →3)β-D-Galp(1→, →2,3)β-D-Glcp(1→, β-D-Glcp(1→, and →2)β-D-Glcp(1→. Galacan demonstrated significant biological activities. In experiments conducted with zebrafish, it facilitated the proliferation of Lactobacillus brevis in the intestinal tract, suggesting potential prebiotic properties. Moreover, in vivo studies revealed its antihyperglycemic effects, as evidenced by significant reductions in blood glucose levels and enhanced fluorescence intensity of pancreatic β cells in a streptozotocin (STZ)-induced hyperglycemic zebrafish model. Additionally, antiaging assays demonstrated Galacan's ability to inhibit β-galactosidase activity and enhance telomerase activity in a hydrogen peroxide (HP)-induced aging zebrafish model. These findings emphasized the potential of Galacan as a natural prebiotic with promising applications in diabetes prevention and antiaging interventions.

Cultivating the uncultured: Harnessing the "sandwich agar plate" approach to isolate heme-dependent bacteria from marine sediment

In the classical microbial isolation technique, the isolation process inevitably destroys all microbial interactions and thus makes it difficult to culture the many microorganisms that rely on these interactions for survival. In this study, we designed a simple coculture technique named the "sandwich agar plate method," which maintains microbial interactions throughout the isolation and pure culture processes. The total yield of uncultured species in sandwich agar plates based on eight helper strains was almost 10-fold that of the control group. Many uncultured species displayed commensal lifestyles. Further study found that heme was the growth-promoting factor of some marine commensal bacteria. Subsequent genomic analysis revealed that heme auxotrophies were common in various biotopes and prevalent in many uncultured microbial taxa. Moreover, our study supported that the survival strategies of heme auxotrophy in different habitats varied considerably. These findings highlight that cocultivation based on the "sandwich agar plate method" could be developed and used to isolate more uncultured bacteria.

Anti-Inflammatory and Anti-Oxidative Effects of Polysaccharides Extracted from Unripe Carica papaya L. Fruit

This study evaluated the antioxidative and anti-inflammatory activities of polysaccharides extracted from unripe Carica papaya L. (papaya) fruit. Three papaya polysaccharide (PP) fractions, namely PP-1, PP-2, and PP-3, with molecular weights of 2252, 2448, and 3741 kDa, containing abundant xylose, galacturonic acid, and mannose constituents, respectively, were obtained using diethylaminoethyl-Sepharose™ anion exchange chromatography. The antioxidant capacity of the PPs, hydroxyl radical scavenging assay, ferrous ion-chelating assay, and reducing power assay revealed that the PP-3 fraction had the highest antioxidant activity, with an EC50 (the concentration for 50% of the maximal effect) of 0.96 mg/mL, EC50 of 0.10 mg/mL, and Abs700 nm of 1.581 for the hydroxyl radical scavenging assay, ferrous ion-chelating assay, and reducing power assay, respectively. In addition, PP-3 significantly decreased reactive oxygen species production by 45.3%, NF-κB activation by 32.0%, and tumor necrosis factor-alpha and interleukin-6 generation by 33.5% and 34.4%, respectively, in H2O2-induced human epidermal keratinocytes. PP-3 exerts potent antioxidative and anti-inflammatory effects; thus, it is a potential biofunctional ingredient in the cosmetic industry.

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

Exopolysaccharides (EPS) from lactic acid bacteria (LAB) as edible and safe bioproducts with health benefits have become an interesting topic. In this study, aqueous two-phase system (ATPS) was established using ethanol and (NH₄)₂SO₄ as phase-forming substances to separate and purify LAB EPS from Lactobacillus plantarum 1.0665. The operating conditions were optimized by a single factor and response surface method (RSM). The results indicated that an effectively selective separation of LAB EPS was achieved by the ATPS consisted of 28 % (w/w) ethanol and 18 % (w/w) (NH₄)₂SO₄ at pH 4.0. Under optimized conditions, the partition coefficient (K) and recovery rate (Y) were well matched with the predicted value of 3.83 ± 0.019 and 74.66 ± 1.05 %. The physicochemical properties of purified LAB EPS were characterized by various technologies. According to the results, LAB EPS was a complex polysaccharide with a triple helix structure mainly composed of mannose, glucose and galactose in the molar ratio of 1.00: 0.32: 0.14, and it proved that the ethanol/(NH₄)₂SO₄ system had good selectivity for LAB EPS. In addition, LAB EPS displayed excellent antioxidant activity, antihypertension activity, anti-gout capacity and hypoglycemic activity in vitro analysis. The results suggested that LAB EPS could be a dietary supplement applied in functional foods.

Biological activities and applications of exopolysaccharides produced by lactic acid bacteria: a mini-review

Exopolysaccharides (EPSs) are naturally occurring high-molecular-weight carbohydrates that have been widely studied for their biological activities, including antioxidant, immunomodulatory, anticancer and gut microbiota regulation activities. Polysaccharides are abundant in nature and can be derived from animals, plants, algae, and microorganisms, but among polysaccharides with potential uses, EPSs from microorganisms have the advantages of a short production cycle, high yield, and independence of production from season and climate and thus have broad prospects. While the safety of the producing microorganism can represent a problem in application of microbial EPSs, lactic acid bacteria (LAB) have been used by humans for thousands of years, and they and their products are generally recognized as safe. This makes LAB excellent sources for exopolysaccharides. EPS-producing LAB are readily found in nature. Through screening of strains, optimization of culture conditions, and improvement of the growth medium, the yield of EPSs from LAB can be increased and the scope of application broadened. This review summarizes EPSs from LAB in terms of structure, function and applications, as well as yield optimization, and introduces recent research on the biological activities and practical applications of LAB EPSs, aiming to provide references for researchers in related areas.

Novel exopolysaccharide derived from probiotic Lactobacillus pantheris TCP102 strain with immune-enhancing and anticancer activities

Probiotics are gaining attention due to their functions of regulating the intestinal barrier and promoting human health. The production of exopolysaccharide (EPS) is one of the important factors for probiotics to exert beneficial properties. This study aimed to screen exopolysaccharides-producing lactic acid bacteria (LAB) and evaluate the probiotic potential. we obtained three exopolysaccharide fractions (EPS1, EPS2, and EPS3) from Lactobacillus pantheris TCP102 and purified by a combination of ion-exchange chromatography and gel permeation chromatography. The structures of the fractions were characterized by FT-IR, UV, HPLC, and scanning electron microscopy (SEM) analysis. The Mw of EPS1, EPS2, and EPS3 were approximately 20.3, 23.0, and 19.3 kDa, and were mainly composed of galactose, glucose, and mannose, with approximate molar ratios of 2.86:1:1.48, 1.26:1:1, 1.58:1.80:1, respectively. Furthermore, SEM analysis demonstrated that the three polysaccharide fractions differ in microstructure and surface morphology. Additionally, preliminary results for immune-enhancing and anticancer activities reveal that these EPSs significantly induced the production of nitric oxide (NO), TNF-α, and IL-6 in Ana-1 cells and peritoneal macrophage cells. Meanwhile, the EPSs also significantly suppressed the proliferation of HCT-116, BCG-803, and particularly A-2780 cells. The results suggest that the three novel EPSs isolated from Lactobacillus pantheris TCP102 can be regarded as potential application value in functional food and natural antitumor drugs.

Exopolysaccharides of Lactic Acid Bacteria: Production, Purification and Health Benefits towards Functional Food

Lactic acid bacteria (LAB) are capable of synthesising metabolites known as exopolysaccharides (EPS) during fermentation. Traditionally, EPS plays an important role in fermented dairy products through their gelling and thickening properties, but they can also be beneficial to human health. This bioactivity has gained attention in applications for functional foods, which leads them to have prebiotic, immunomodulatory, antioxidant, anti-tumour, cholesterol-lowering and anti-obesity activity. Understanding the parameters and conditions is crucial to optimising the EPS yields from LAB for applications in the food industry. This review provides an overview of the functional food market together with the biosynthesis of EPS. Factors influencing the production of EPS as well as methods for isolation, characterisation and quantification are reviewed. Finally, the health benefits associated with EPS are discussed.

Exopolysaccharides Produced by Lactic Acid Bacteria: From Biosynthesis to Health-Promoting Properties

The production of exopolysaccharides (EPS) by lactic acid bacteria (LAB) has attracted particular interest in the food industry. EPS can be considered as natural biothickeners as they are produced in situ by LAB and improve the rheological properties of fermented foods. Moreover, much research has been conducted on the beneficial effects of EPS produced by LAB on modulating the gut microbiome and promoting health. The EPS, which varies widely in composition and structure, may have diverse health effects, such as glycemic control, calcium and magnesium absorption, cholesterol-lowering, anticarcinogenic, immunomodulatory, and antioxidant effects. In this article, the latest advances on structure, biosynthesis, and physicochemical properties of LAB-derived EPS are described in detail. This is followed by a summary of up-to-date methods used to detect, characterize and elucidate the structure of EPS produced by LAB. In addition, current strategies on the use of LAB-produced EPS in food products have been discussed, focusing on beneficial applications in dairy products, gluten-free bakery products, and low-fat meat products, as they positively influence the consistency, stability, and quality of the final product. Highlighting is also placed on reports of health-promoting effects, with particular emphasis on prebiotic, immunomodulatory, antioxidant, cholesterol-lowering, anti-biofilm, antimicrobial, anticancer, and drug-delivery activities.

Molecular and Cellular Mechanisms Influenced by Postbiotics

In recent years, commensal bacteria colonizing the human body have been recognized as important determinants of health and multiple pathologic conditions. Among the most extensively studied commensal bacteria are the gut microbiota, which perform a plethora of functions, including the synthesis of bioactive products, metabolism of dietary compounds, and immunomodulation, both through attenuation and immunostimulation. An imbalance in the microbiota population, i.e., dysbiosis, has been linked to many human pathologies, including various cancer types and neurodegenerative diseases. Targeting gut microbiota and microbiome-host interactions resulting from probiotics, prebiotics, and postbiotics is a growing opportunity for the effective treatment of various diseases. As more research is being conducted, the microbiome field is shifting from simple descriptive analysis of commensal compositions to more molecular, cellular, and functional studies. Insight into these mechanisms is of paramount importance for understanding and modulating the effects that microbiota, probiotics, and their derivatives exert on host health.

Lactic Acid Bacteria Exopolysaccharides Producers: A Sustainable Tool for Functional Foods

Lactic acid bacteria (LAB) used in the food industry, mainly for the production of dairy products, are able to synthetize exopolysaccharides (EPS). EPS play a central role in the assessment of rheological and sensory characteristics of dairy products since they positively influence texture and organoleptic properties. Besides these, EPS have gained relevant interest for pharmacological and nutraceutical applications due to their biocompatibility, non-toxicity and biodegradability. These bioactive compounds may act as antioxidant, cholesterol-lowering, antimicrobial and prebiotic agents. This review provides an overview of exopolysaccharide-producing LAB, with an insight on the factors affecting EPS production, their dairy industrial applications and health benefits.

Naturally Occurring Exopolysaccharide Nanoparticles: Formation Process and Their Application in Glutathione Detection

Naturally occurring nanoscale exopolysaccharide (EPS) has attracted much attention in recent years. In this research, we obtained a new kind of naturally occurring spherical EPS nanoparticles (EPS-R503) from Lactobacillus plantarum R503. The secretion, self-assembly process, morphological structure, and surface characteristics of the as-prepared nanoparticles were comprehensively revealed with transmission electron microscopy (TEM) and atomic force microscope (AFM) for the first time. It was found that the EPS-R503 nanoparticles consist of negatively charged heteropolysaccharide composed of mannose, glucose, galactose, and glucuronide with several functional groups including -OH, -COOH, and -NH₂. When different solvents were used to treat the EPS-R503 nanoparticles, the morphological structure and surface properties could be changed or manipulated. The forming mechanism of EPS-R503 was elucidated based on the aggregation processes from a fundamental point of view. Furthermore, EPS-R503 can serve as reducing and stabilizing agents for the biosynthesis of manganese dioxide nanosheets (MnO₂ NSs), leading to EPS-MnO₂ nanocomposite. The as-prepared nanocomposites can absorb fluorescein (FL) to form EPS-MnO₂-FL, which can be used to detect glutathione (GSH) with a low limit of detection (0.16 μM) and a wide detection range from 0.05 to 4 mM. The excellent biocompatibility of EPS-MnO₂-FL endows the feasibility of in vivo detection of GSH as well. Overall, the findings from this work not only benefit the exploitation of naturally occurring EPS nanomaterials but also provide a novel strategy for the green synthesis of metal-containing nanosheets for GSH detection.

Exopolysaccharide of Anoxybacillus pushchinoensis G11 has antitumor and antibiofilm activities

Exopolysaccharides (EPS/EPSs) possess several various applications in the food and pharmaceutical industries. This study was performed to investigate the biological (antibiofilm and antitumor), rheological (temperature, shear rate, and density) and chemical (solubility, carbohydrate and protein content, composition, molecular weight, functional group analysis, thermal analysis, X-ray diffraction pattern and scanning electron microscopy) properties of the EPS, which was purified from the locally isolated thermophilic bacterium Anoxybacillus pushchinoensis G11 (MN720646). EPS was found to have antibiofilm and antitumor [lung (A-549) and colon (Caco-2 and HT-29) cancer] activities. The viscosity of EPS showing Newtonian flow was temperature dependent. As chemical properties, the EPS was found to be a heteropolysaccharide containing arabinose (57%), fructose (26%), glucose (12%), and galactose (5%). EPS contained 93% carbohydrates and 1.08% protein. The molecular weight of EPS was determined as 75.5 kDa. The FTIR analysis confirmed the presence of sulfate ester (band at 1217 cm^-1), an indication of the antitumor effect. The EPS was semi-crystalline. It could maintain 36% of its weight at 800 °C and crystallization and melting temperatures were 221 and 255.6 °C. This is the first report on the EPS production potential and the biological activity of A. pushchinoensis.

The effect of optimized carbon source on the synthesis and composition of exopolysaccharides produced by Lactobacillus paracasei

This study aimed to predict the optimal carbon source for higher production of exopolysaccharides (EPS) by Lactobacillus paracasei TD 062, and to evaluate the effect of this carbon source on the production and monosaccharide composition of EPS. We evaluated the EPS production capacity of 20 strains of L. paracasei under the same conditions. We further investigated L. paracasei TD 062, which showed the highest EPS-producing activity (0.609 g/L), by examining the associated biosynthesis pathways for EPS. Genomics revealed that fructose, mannose, trehalose, glucose, galactose, and lactose were carbon sources that L. paracasei TD 062 could use to produce EPS. We identified an EPS synthesis gene cluster that could participate in transport, export, and sugar chain synthesis, and generate 6 sugar nucleotides. Experimental results showed that the sugar content of the EPS produced using fermentation with the optimized carbon source (fructose, mannose, trehalose, glucose, galactose, and lactose) increased by 115%. Furthermore, use of the optimized carbon source changed the monosaccharide content of the associated EPS. The results of enzyme activity measurements showed significant increases in the activity of 2 key enzymes involved in the glycoside synthesis pathway. Our study revealed that optimizing the carbon source provided for fermentation not only increased the production of EPS, but also affected the composition of the monosaccharides by increasing enzyme activity in the underlying synthesis pathways, suggesting an important role for carbon source in the production of EPS by L. paracasei TD 062.

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

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.

Structural characterization and effect on leukopenia of fucoidan from Durvillaea antarctica

Fucoidans from brown seaweed shows various bioactive properties and promising prospects in biomedical field. Here, a novel fucoidan (F-4) was extracted and purified from Durvillaea antarctica. The structure of F-4 was characterized by HPLC, HPGPC, GC-MS, together with IR and NMR spectral analysis. F-4 is a sulfated polysaccharide mainly composed of fucose (Fuc), galactose (Gal), and glucose (Glc) in a molar ratio of 26.4: 7.1: 1.0. The backbone of F-4 is composed of (1→3) and (1→4)-linked-α-L-Fucp residues, which sulfated at C-4 or C-2 positions and branched with α-L-Fuc, β-D-Gal, and β-D-Glc residues. Furthermore, F-4 can effectively promote the growth of leukocyte in a mouse model induced by cyclophosphamide, possibly by activating hematopoietic progenitor cells and regulating the hematopoietic microenvironment of bone marrow. Our data provide useful information for further investigation of fucoidan in the treatment of chemotherapy-induced leukopenia.

The effects of exopolysaccharides and exopolysaccharide-producing Lactobacillus on the intestinal microbiome of zebrafish (Danio rerio)

BACKGROUND

Numerous studies have reported the health-promoting effects of exopolysaccharides (EPSs) in in vitro models; however, a functional evaluation of EPSs will provide additional knowledge of EPS-microbe interactions by in vivo intestinal microbial model. In the present study, high-throughput amplicon sequencing, short-chain fatty acid (SCFAs) and intestinal inflammation evaluation were performed to explore the potential benefits of exopolysaccharides (EPSs) and EPS-producing Lactobacillus (HNUB20 group) using the healthy zebrafish (Danio rerio) model.

RESULTS

The results based on microbial taxonomic analysis revealed that the abundance of four genera, Ochrobactrum, Sediminibacterium, Sphingomonas and Sphingobium, were increased in the control group in comparison to HNUB20 group. Pelomonas spp. levels were significantly higher and that of the genera Lactobacillus and Brachybacterium were significantly decreased in EPS group compared with control group. PICRUSt based functional prediction of gut microbiota metabolic pathways indicated that significantly lower abundance was found for transcription, and membrane transport, whereas folding, sorting and degradation and energy metabolism had significantly higher abundance after HNUB20 treatment. Two metabolic pathways, including metabolism and endocrine functions, were more abundant in the EPS group than control group. Similar to the HNUB20 group, transcription was also decreased in the EPS group compared with the control group. However, SCFAs and immune indexes indicated EPS and HNUB20 performed limited efficacy in the healthy zebrafish.

CONCLUSIONS

The present intestinal microbial model-based study indicated that EPSs and high-yield EPS-producing Lactobacillus can shake the structure of intestinal microbiota, but cannot change SCFAs presence and intestinal inflammation.

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.

Antibacterial potential of a novel Lactobacillus casei strain isolated from Chinese northeast sauerkraut and the antibiofilm activity of its exopolysaccharides

Lactobacillus spp., as probiotics, have shown efficacy in the inhibition of pathogenic bacteria in the intestinal tract. In this study, we investigated the antibacterial activity of Lactobacillus casei NA-2, which was isolated from northeast sauerkraut in China. The results of co-culture suggested that L. casei NA-2 could inhibit the growth of Bacillus cereus, Staphylococcus aureus, Salmonella typhimurium and Escherichia coli O157:H7. Moreover, L. casei NA-2 could adhere to the four pathogenic bacteria potentially associated with its exopolysaccharide (EPS). EPS from L. casei NA-2 was then isolated and its activity determined. The results showed that EPS inhibited the biofilms of B. cereus, S. aureus, S. typhimurium and E. coli O157:H7, with the highest inhibition ratios of 95.5% ± 0.1%, 30.2% ± 3.3%, 14.3% ± 0.6%, and 16.9% ± 5.4%, respectively. Moreover, EPS was able to disperse B. cereus, S. aureus, S. typhimurium and E. coli O157:H7 by 94.1% ± 1.2%, 31.8% ± 8.6%, 40.8% ± 3.3% and 49.6% ± 3.8%, respectively. Results showed that EPS from L. casei NA-2 have potential antibacterial properties by inhibiting biofilm formation and dispersing pathogenic bacteria. In conclusion, the antibiofilm property of the EPS on the surface of L. casei NA-2 is one of the possible reasons for antibacterial activity of L. casei NA-2.

A novel exopolysaccharide produced by Lactobacillus coryniformis NA-3 exhibits antioxidant and biofilm-inhibiting properties in vitro

Background

Exopolysaccharides (EPSs) secreted from lactic acid bacteria are carbohydrate polymers with reported biological activities. In this study, we extracted and characterized the composition as well as antioxidant and biofilm-inhibitory properties of EPS from Lactobacillus coryniformis NA-3 isolated from northeast Chinese sauerkraut (Suan Cai).

Methods

Lactobacillus coryniformis NA-3 was identified with 16S rDNA amplification and Neighbor Joining (NJ) phylogenetic analysis. EPS derived from Lactobacillus coryniformis NA-3 (EPS-NA3) was analyzed, including compositions by high-performance liquid chromatography (HPLC), functional groups by Fourier-transform infrared spectroscopy (FT-IR) and glycosidic bond configuration by Hydrogen-1 Nuclear Magnetic Resonance (¹H NMR). Antioxidant activity of EPS was evaluated with hydroxyl and superoxide radical-scavenging. Anti-biofilm activities of EPS-NA3 were checked through inhibition and dispersion.

Results

The monosaccharide composition of EPS included α-rhamnose, α-mannose, α-galactose, and α-glucose in a ratio of 2.6:1.0:5.0:3.3. The free radical-scavenging abilities of EPS-NA3 were 37.77% ± 1.56% and 78.87% ± 3.07% on hydroxyl and superoxide reactive oxygen species respectively. Moreover, EPS-NA3 attenuated the formation of Bacillus cereus and Salmonella typhimurium biofilms by inhibition ratios of approximately 80% and 40% respectively. Additionally, treatment with EPS-NA3 dispersed established biofilms of B. cereus and S. typhimurium by approximately 90% and 20% respectively.

Conclusion

These results suggest that EPS-NA3 may be developed as antioxidant and anti-biofilm agents for industrial and clinical applications due to its capacity of scavenging free radicals, inhibition of bacterial biofilm formation, and dispersion of established biofilms.

Physical and functional characterization of succinoglycan exopolysaccharide produced by Rhizobium radiobacter CAS from curd sample

Identification and rheological behaviour of succinoglycan exopolysaccharide (EPS) from Rhizobium radiobacter CAS isolated from curd was published in earlier reports. In current investigation physicochemical and functional properties of CAS EPS has been studied. SEC-MALLS revealed molecular weight (Mw), number molecular weight (Mn) and polydispersity index (PDI) of CAS EPS as 4.05×10⁶g·mol^-1, 3.82×10⁶g·mol^-1 and, 1.06 respectively. Thermogravimetric analysis showed the high thermal stability of CAS polymer where approximately 77% of CAS hydrocolloid maintain physical integrity and stability with temperature degradation (T_d) at 290°C. Scanning electron microscopy and particle size analysis confirmed the porous and hygroscopic nature and 2.049μm size of CAS EPS respectively. Equally important functional properties such as water activity (0.55), water solubility (95%), water contact angle (54.83°), water binding capacity (101g/g), water holding capacity (68.19g/g), oil binding ability (soybean and groundnut oils were found 4.35g/g and 3.68g/g) and swelling index (17.5mL/g) were examined for CAS EPS. Prevention of syneresis has been studied at 1% CAS EPS concentration which significantly prohibited the degree of syneresis of starch. These physico-functional properties make CAS EPS a prominent candidate for food processing and product development sector.

Bioactive compound from Aspergillus terreusDMTMGK004 synergistically contributes towards potential anti-pathogenicity

This study focused on the evaluation of fungal compound for their anti-pathogenic potential against respiratory pathogens. Soil samples were collected from various geographical regions in Madurai, fungal strain was isolated and identified as Aspergillus terreusDMTMGK004 (MGK004). Secondary metabolites were extracted and evaluated for antioxidant potential. It exhibited significantly high anti-proliferative property against gastric adenocarcinoma (AGS) cell lines. Antimicrobial activity against Gram positive (Streptococcus pneumoniae) and Gram negative (Klebsiella pneumoniae and Haemophilus influenzae) respiratory pathogens were analysed and the minimum inhibitory concentration (MIC) values were determined. Furthermore, the time-killing assay illustrated that the metabolite eliminates 50% of the vegetative cells within few hours of the treatment. From the spectral data, the major functional groups present in the compound were determined as carbonyl group and phenolic hydroxyl group which contribute towards its bioactivity. The compound significantly depreciates the production of extracellular polysaccharides which results in the weakening of biofilm architecture and resistance towards serum killing and phagocytosis. It also induced cell membrane damage which leads to protein and nucleic acid leakage. Hence, the results of the present study could provide a better insinuation towards the formulation of new drug targeting respiratory pathogens. SIGNIFICANCE AND IMPACT OF THE STUDY: The ubiquitous fungi Aspergillus terreus is well known for its secondary metabolite production. The fungus was evaluated for production of antagonistic molecule to reduce the growth of infectious agents causing respiratory infections. It exhibited the biological means of antioxidant, anti-proliferative and anti-pathogenic compound production. The compound exhibits killing effect against respiratory pathogens within two hours. It induced cell membrane damage leading to protein and nucleic acid leakage. It significantly reduced the production of extracellular polysaccharides. The results provide needed information to design innovative strategies for targeting pathogenic factors of the respiratory pathogens instead of killing it precisely.

Relationship Between Putative eps Genes and Production of Exopolysaccharide in Lactobacillus casei LC2W

Lactobacillus casei LC2W, a probiotic strain, can produce exopolysaccharide (EPS) with anti-hypertensive bioactivity. The relationship between eps genes and EPS synthesis in LC2W due to unclear regulation mechanism of EPS biosynthesis was investigated. The several relevant genes in EPS biosynthetic gene cluster were deleted, overexpressed and complemented. The results suggested that glucose-1-phosphate thymidyltranseferase gene (LC2W_2179), uncharacterized EPS biosynthesis protein (LC2W_2188), and EPS biosynthesis protein (LC2W_2189) were related to EPS biosynthesis. EPS titer decreased 15, 13, and 21% when the three genes were deleted, respectively. When they were overexpressed, EPS titer increased 16, 10, and 18%. When they were complemented, EPS titer was similar to the wild-type strain. This work showed the three eps genes from LC2W played important roles on EPS production.

Exopolysaccharides produced by Lactobacillus strains suppress HT-29 cell growth via induction of G0/G1 cell cycle arrest and apoptosis

In the present study, the effects of exopolysaccharides (EPS) from nine Lactobacillus strains with a high degree of bio-activity on human colon cancer cell line HT-29 were studied. The extracellular polymeric substances from 4 strains, namely K11, M5, SB27 and ×12, displayed desirable anti-proliferative activity against HT-29 cells. Crude and acidic EPS were purified from the 4 strains and the inhibitory effects were further investigated. The crude and acidic EPS from these 4 strains exerted anti-proliferation effects on HT-29 cells in a dose-dependent manner but were nontoxic to Vero cells. Treatment with EPS significantly induced G0/G1 cell cycle arrest and apoptosis of HT-29 cells. Hoechst 33258 staining of acidic EPS-treated HT-29 cells revealed different degrees of morphological changes within the nucleus and the formation of apoptotic bodies. Caspase-3 activity was markedly upregulated in HT-29 cells following treatment with acidic EPS. In addition, acidic EPS from the SB27 strain demonstrated the most robust inhibitory effect on HT-29 cells. The results of the present study suggest that as an inducer of apoptosis EPS has the potential to be applied in the treatment of colorectal cancer.

Characterization of a cryptic plasmid isolated from Lactobacillus casei CP002616 and construction of shuttle vectors based on its replicon

The cryptic plasmid pLC2W was isolated from Lactobacillus casei CP002616. Nucleotide sequence analysis revealed that 4 putative open reading frames (ORF) were responsible for DNA replication. Four Escherichia coli-Lactobacillus shuttle vectors were constructed using different lengths of the pLC2W replicon to identify the shortest functional replicon. The length of the pLC2W replicon did not affect the stability of the plasmids. Green fluorescent protein (GFP) as a reporter was expressed successfully in several lactobacilli using our constructed vectors. The results suggested that the expression vectors pUE-F0GFP and pUE-F1GFP are potential molecular tools for heterologous gene cloning and expression in lactobacilli. Moreover, 2 plasmid-curing methods were used to eliminate pLC2W from L. casei. We detected no difference between L. casei CP002616 and L. casei CP002616 pLC2WΔ-IC (mutant strain cured by plasmid incompatibility method) in production of exopolysaccharide (EPS) or acid. However, EPS and acid production were both reduced in L. casei CP002616 pLC2WΔ-HT (mutant strain cured by high-temperature heat treatment method), demonstrating a difference between these 2 curing methods. Sequence analysis of pLC2W and plasmid curing data suggest that plasmid pLC2W is not involved in EPS synthesis.

Gene editing and genetic engineering approaches for advanced probiotics: A review

The applications of probiotics are significant and thus resulted in need of genome analysis of probiotic strains. Various omics methods and systems biology approaches enables us to understand and optimize the metabolic processes. These techniques have increased the researcher's attention towards gut microbiome and provided a new source for the revelation of uncharacterized biosynthetic pathways which enables novel metabolic engineering approaches. In recent years, the broad and quantitative analysis of modified strains relies on systems biology tools such as in silico design which are commonly used methods for improving strain performance. The genetic manipulation of probiotic microorganisms is crucial for defining their role in intestinal microbiota and exploring their beneficial properties. This review describes an overview of gene editing and systems biology approaches, highlighting the advent of omics methods which allows the study of new routes for studying probiotic bacteria. We have also summarized gene editing tools like TALEN, ZFNs and CRISPR-Cas that edits or cleave the specific target DNA. Furthermore, in this review an overview of proposed design of advanced customized probiotic is also hypothesized to improvise the probiotics.

Regulation of EPS production in Lactobacillus casei LC2W through metabolic engineering

Lactobacillus casei LC2W is an exopolysaccharide(EPS)-producing strain with probiotic effects. The low efficiency and unclear regulation mechanism of EPS biosynthesis have become main constraints for its application in food industry. To investigate the major rate-limiting factors of EPS biosynthesis and to improve its yield, metabolic engineering was applied to this strain. Eight relevant genes related to central metabolism, sugar-nucleotides supply, glycosyltransferase and cofactor engineering were cloned and overexpressed. The results suggested that nox, pfk, rfbB and galT genes were the largest contributors to EPS biosynthesis in this study, which elevated EPS yield by 46·0, 20, 17·4 and 19·6% respectively. Notably, under aerobic condition which was not a suitable condition for lactobacilli to grow in, recombinant strain LC-nox achieved the highest EPS yield of 263·7 mg l(-1) , which was increased by 75% compared to that of the starting strain. The oxygen stress was excluded since the phenomenon was not observed in the control strain under the same condition. Therefore, it was probably that higher NADH oxidase activity led to a decreased NADH availability and reduced lactate concentration, which resulted in the elevation of EPS yield.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study contributed to the understanding of EPS biosynthesis in Lact. casei through metabolic engineering and provided a starting point for introducing cofactor engineering into this strain. Overexpression of NADH oxidase was found to have a most significant effect on the EPS production. It is the first report that EPS could be accumulated to such a high level under aerobic condition in lactobacilli. Our results provided a novel strategy for the improvement of EPS production in lactic acid bacteria.

Chemical characterization and immunomodulatory properties of polysaccharides isolated from probiotic Lactobacillus casei LOCK 0919

The Lactobacillus casei strain, LOCK 0919, is intended for the dietary management of food allergies and atopic dermatitis (LATOPIC® BIOMED). The use of a probiotic to modulate immune responses is an interesting strategy for solving imbalance problems of gut microflora that may lead to various disorders. However, the exact bacterial signaling mechanisms underlying such modulations are still far from being understood. Here, we investigated variations in the chemical compositions and immunomodulatory properties of the polysaccharides (PS), L919/A and L919/B, which are produced by L. casei LOCK 0919. By virtue of their chemical features, such PS can modulate the immune responses to third-party antigens. Our results revealed that L919/A and L919/B could both modulate the immune response to Lactobacillus planatarum WCFS1, but only L919/B could alter the response of THP-1 cells (in terms of tumor necrosis factor alpha production) to L. planatarum WCFS1 and Escherichia coli Nissle 1917. The comprehensive immunochemical characterization is crucial for the understanding of the biological function as well as of the bacteria-host and bacteria-bacteria cross-talk.

Lactobacillus-produced exopolysaccharides and their potential health benefits: a review

Lactic acid bacteria, such as those of the Lactobacillus genus, naturally reside within the microbiota of the human body and have long been used as starter cultures and probiotic enhancers in fermented foods, such as fermented drinks, yoghurts and cheeses. Many of the beneficial qualities of these bacteria have traditionally been associated with the bacteria themselves, however, a recent spate of studies have demonstrated a wide variety of biological effects exhibited by lactobacilli-produced exopolysaccharides which could, theoretically, confer a range of local and systemic health benefits upon the host. In this review, we discuss the production of exopolysaccharides within the Lactobacillus genus and explore their potential as beneficial bioactive compounds.

Cracking Streptococcus thermophilus to stimulate the growth of the probiotic Lactobacillus casei in co-culture

Lactobacillus casei, a probiotic, and Streptococcus thermophilus, a fast acidifying lactic acid bacterial strain, are both used in the food industry. The aim of this study was to investigate the interaction between L. casei and S. thermophilus in the presence or absence of S. thermophilus-specific bacteriophage during milk fermentation. The acidification capability of L. casei co-cultured with S. thermophilus was significantly higher than that observed for L. casei or S. thermophilus cultured alone. However, the probiotic content (i.e., L. casei cell viability) was low. The fastest acidification and the highest viable L. casei cell count were observed in co-cultures of L. casei and S. thermophilus with S. thermophilus phage. In these co-cultures, S. thermophilus compensated for the slow acid production of L. casei in the early exponential growth phase. Thereafter, phage-induced lysis of the S. thermophilus cells eliminated the competition for nutrients, allowing L. casei to grow well. Additionally, the ruptured S. thermophilus cells released intracellular factors, which further promoted the growth and function of the probiotic bacteria. Crude cellular extract isolated from S. thermophilus also significantly accelerated the growth and propagation of L. casei, supporting the stimulatory role of the phage on this micro-ecosystem.