Dextrans produced by lactic acid bacteria exhibit antiviral and immunomodulatory activity against salmonid viruses

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

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

Analysis of the anti-PCV2 mechanism of Lactobacillus acidophilus based on non-target metabolomics and high-throughput molecular docking

Our previous studies have revealed that L. acidophilus possesses inhibitory effects on PCV2 proliferation in vivo, although the underlying mechanisms remain elusive. Probiotics like L. acidophilus are known to exert antiviral through their metabolites. Therefore, in this study, non-targeted metabolomics was used to detect the changes in metabolites of L. acidophilus after 24 h of proliferation. Subsequently, high-throughput molecular docking was utilized to analyze the docking scores of these metabolites with PCV2 Cap and Rep, aiming to identify compounds with potential anti-PCV2 effects. The results demonstrated that 128 compounds such as Dl-lactate were significantly increased. The results of high-throughput molecular docking indicated that compounds such as ergocristine, and telmisartan formed complexes with Cap and Rep, suggesting their potential anti-PCV2 properties. Furthermore, compounds like vitamin C, exhibit pharmacological effects consistent with L. acidophilus adding credence to the idea that L. acidophilus may exert pharmacological effects through its metabolites. These results will provide a foundation for the study of L. acidophilus.

Characterization and optimization of exopolysaccharide extracted from a newly isolated halotolerant cyanobacterium, Acaryochloris Al-Azhar MNE ON864448.1 with antiviral activity

Several antiviral agents lost their efficacy due to their severe side effects and virus mutations. This study aimed to identify and optimize the conditions for exopolysaccharide (EPS) production from a newly isolated cyanobacterium, Acaryochloris Al-Azhar MNE ON864448.1, besides exploring its antiviral activity. The cyanobacterial EPS was purified through DEAE-52 cellulose column with a final yield of 83.75%. Different analysis instruments were applied for EPS identification, including Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), and gas chromatographic-mass spectrometry (GC-MS). Plackett-Burman's design demonstrated that working volume (X1), EDTA (X2), inoculum size (X3), CaCl2 (X4), and NaCl (X5) are the most important variables influencing EPS production. Central composite design (CCD) exhibited maximum EPS yield (9.27 mg/mL) at a working volume of 300 mL in a 1 L volumetric flask, EDTA 0.002 g/L, inoculum size 7%, CaCl2 0.046 g/L, and NaCl 20 g/L were applied. EPS showed potent antiviral activities at different stages of herpes simplex virus type-1 and 2 (HSV-1, HSV-2), adenovirus (ADV) and coxsackievirus (A16) infections. The highest half-maximal inhibitory concentration (IC50) (6.477 µg/mL) was recorded during HSV-1 internalization mechanism, while the lowest IC50 (0.005669 µg/mL) was recorded during coxsackievirus neutralization mechanism.

Leuconostoc mesenteroides and Liquorilactobacillus mali strains, isolated from Algerian food products, are producers of the postbiotic compounds dextran, oligosaccharides and mannitol

Six lactic acid bacteria (LAB) isolated from Algerian sheep's milk, traditional butter, date palm sap and barley, which produce dextran, mannitol, oligosaccharides and vitamin B2 have been characterized. They were identified as Leuconostoc mesenteroides (A4X, Z36P, B12 and O9) and Liquorilactobacillus mali (BR201 and FR123). Their exopolysaccharides synthesized from sucrose by dextransucrase (Dsr) were characterized as dextrans with (1,6)-D-glucopyranose units in the main backbone and branched at positions O-4, O-2 and/or O-3, with D-glucopyranose units in the side chain. A4X was the best dextran producer (4.5 g/L), while the other strains synthesized 2.1-2.7 g/L. Zymograms revealed that L. mali strains have a single Dsr with a molecular weight (Mw) of ~ 145 kDa, while the Lc. mesenteroides possess one or two enzymes with 170-211 kDa Mw. As far as we know, this is the first detection of L. mali Dsr. Analysis of metabolic fluxes from sucrose revealed that the six LAB produced mannitol (~ 12 g/L). The co-addition of maltose-sucrose resulted in the production of panose (up to 37.53 mM), an oligosaccharide known for its prebiotic effect. A4X, Z36P and B12 showed dextranase hydrolytic enzymatic activity and were able to produce another trisaccharide, maltotriose, which is the first instance of a dextranase activity encoded by Lc. mesenteroides strains. Furthermore, B12 and O9 grew in the absence of riboflavin (vitamin B2) and synthesized this vitamin, in a defined medium at the level of ~ 220 μg/L. Therefore, these LAB, especially Lc. mesenteroides B12, are good candidates for the development of new fermented food biofortified with functional compounds.

Characterization of the heteropolysaccharides produced by Liquorilactobacillus sicerae CUPV261 and Secundilactobacillus collinoides CUPV237 isolated from cider

Some lactic acid bacteria (LAB) strains isolated from alcoholic beverages are able to produce exopolysaccharides (EPS). The present work focuses on the physico-chemical characterization of the heteropolysaccharides (HePS) produced by Liquorilactobacillus sicerae CUPV261T (formerly known as Lactobacillus sicerae) and Secundilactobacillus collinoides CUPV237 (formerly known as Lactobacillus collinoides) strains isolated from cider. Genome sequencing and assembly enabled the identification of at least four putative HePS gene clusters in each strain, which correlated with the ability of both strains to secrete EPS. The crude EPS preparation from CUPV261^T contained glucose, galactose and rhamnose, and that of CUPV237 was composed of glucose, galactose and N-acetylglucosamine. Both EPS were mixtures of HePS of different composition, with two major soluble components of average molecular weights (M_w) in the range of 10⁶ and 10⁴ g.mol^-1. These HePS were resistant to gastric stress conditions in an in vitro model, and they significantly reduced zebrafish larvae mortality in an in vivo model of inflammatory bowel disease.

Proteomic and in silico analyses of dextran synthesis influence on Leuconostoc lactis AV1n adaptation to temperature change

Leuconostoc lactis is found in vegetables, fruits, and meat and is used by the food industry in the preparation of dairy products, wines, and sugars. We have previously demonstrated that the dextransucrase of Lc. lactis (DsrLL) AV1n produces a high-molecular-weight dextran from sucrose, indicating its potential use as a dextran-forming starter culture. We have also shown that this bacterium was able to produce 10-fold higher levels of dextran at 20°C than at 37°C, at the former temperature accompanied by an increase in dsrLL gene expression. However, the general physiological response of Lc. lactis AV1n to cold temperature in the presence of sucrose, leading to increased production of dextran, has not been yet investigated. Therefore, we have used a quantitative proteomics approach to investigate the cold temperature-induced changes in the proteomic profile of this strain in comparison to its proteomic response at 37°C. In total, 337 proteins were found to be differentially expressed at the applied significance criteria (adjusted p-value ≤ 0.05, FDR 5%, and with a fold-change ≥ 1.5 or ≤ 0.67) with 204 proteins overexpressed, among which 13% were involved in protein as well as cell wall, and envelope component biosynthesis including DsrLL. Proteins implicated in cold stress were expressed at a high level at 20°C and possibly play a role in the upregulation of DsrLL, allowing the efficient synthesis of the protein essential for its adaptation to cold. Post-transcriptional regulation of DsrLL expression also seems to take place through the interplay of exonucleases and endonucleases overexpressed at 20°C, which would influence the half-life of the dsrLL transcript. Furthermore, the mechanism of cold resistance of Lc. lactis AV1n seems to be also based on energy saving through a decrease in growth rate mediated by a decrease in carbohydrate metabolism and its orientation toward the production pathways for storage molecules. Thus, this better understanding of the responses to low temperature and mechanisms for environmental adaptation of Lc. lactis could be exploited for industrial use of strains belonging to this species.

A methodology for the selection and characterization of riboflavin-overproducing Weissella cibaria strains after treatment with roseoflavin

Fermentative processes by lactic acid bacteria can produce metabolites of interest to the health and food industries. Two examples are the production of B-group vitamins, and of prebiotic and immunomodulatory dextran-type exopolysaccharides. In this study, three riboflavin- and dextran-producing Weissella cibaria strains (BAL3C-5, BAL3C-7 and BAL3C-22) were used to develop a new method for selection and isolation of spontaneous riboflavin-overproducing W. cibaria mutants. This method was based on the selection of strains resistant to roseoflavin. The DNA sequencing of the FMN riboswitch of bacterial cell populations treated with various roseoflavin concentrations, revealed the existence of at least 10 spontaneous and random point mutations at this location. Folding and analysis of the mutated FMN riboswitches with the RNA fold program predicted that these mutations could result in a deregulation of the rib operon expression. When the roseoflavin-treated cultures were plated on medium supporting dextran synthesis, the most promising mutants were identified by the yellow color of their mucous colonies, exhibiting a ropy phenotype. After their isolation and recovery in liquid medium, the evaluation of their riboflavin production revealed that the mutant strains synthesized a wide range of riboflavin levels (from 0.80 to 6.50 mg/L) above the wild-type level (0.15 mg/L). Thus, this was a reliable method to select spontaneous riboflavin-overproducing and dextran-producing strains of W. cibaria. This species has not yet been used as a starter or adjunct culture, but this study reinforces the potential that it has for the food and health industry for the production of functional foods or as a probiotic. Furthermore, analysis of the influence of FMN present in the growth medium, on rib mRNA and riboflavin levels, revealed which mutant strains produce riboflavin without flavin regulation. Moreover, the BAL3C-5 C120T mutant was identified as the highest riboflavin-overproducer. Determination of its chromosomal DNA sequence and that of BAL3C-5, revealed a total identity between the 2 strains except for the C120T mutation at the FMN riboswitch. To our knowledge, this work is the first demonstration that only a single alteration in the genome of a lactic acid bacteria is required for a riboflavin-overproducing phenotype.

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.

Characterization of Dextran Produced by the Food-Related Strain Weissella cibaria C43-11 and of the Relevant Dextransucrase Gene

A metabolic feature of lactic acid bacteria (LAB) is the production of exopolysaccharides (EPSs), which have technological and functional properties of interest to the food sector. The present study focused on the characterization of the Weissella cibaria strain C43-11, a high EPS producer in the presence of sucrose, in comparison with a low-producing strain (C2-32), and on possible genetic regulatory elements responsible for the modulation of dextransucrase (dsr) genes expression. NMR analysis of the polymeric material produced by the C43-11 strain indicated the presence of dextran consisting mainly of a linear scaffold formed by α-(1–6) glycosidic linkages and a smaller amounts of branches derived from α-(1–2), α-(1–3), and α-(1–4) linkages. Molecular analysis of the dsr genes and the putative transcriptional promoters of the two strains showed differences in their regulatory regions. Such variations may have a role in the modulation of dsr expression levels in the presence of sucrose. The strong upregulation of the dsr gene in the C43-11 strain resulted in a high accumulation of EPS. This is the first report showing differences in the regulatory elements of the dsr gene in W. cibaria and indicates a new perspective of investigation to identify the regulatory mechanism of EPS production.

Characterization of exopolysaccharide produced by Levilactobacillus brevis HDE-9 and evaluation of its potential use in dairy products

The bacterial strain HDE-9 was isolated from sauerkraut and identified as Levilactobacillus brevis. An exopolysaccharide (EPS) was isolated and purified from L. brevis HDE-9, and a preliminary investigation of its structural characteristics and biological activity was conducted. The molecular weight of the EPS was >1.0 × 10⁶ Da. Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy revealed that the EPS was composed of α-(1 → 6) linked d-glucopyranose units. X-ray diffraction (XRD) data on the EPS revealed its non-crystalline amorphous structure. Scanning electron microscopy (SEM) of the EPS revealed a smooth surface with sheet structures. The EPS exhibited the high value in thermal stability, water solubility, water holding capacity (WHC), and emulsification activity (EA). The water contact angle of the EPS revealed relatively high hydrophobicity in the presence of sucrose. The EPS also showed a strong milk solidification capacity in a dose-dependent manner. The EPS could significantly improve the texture of yoghurt, indicating its potential application as a functional starter in the production of fermented dairy products.

Extracellular Polymeric Substances: Still Promising Antivirals

Sulfated polysaccharides and other polyanions have been promising candidates in antiviral research for decades. These substances gained attention as antivirals when they demonstrated a high inhibitory effect in vitro against human immunodeficiency virus (HIV) and other enveloped viruses. However, that initial interest was followed by wide skepticism when in vivo assays refuted the initial results. In this paper we review the use of sulfated polysaccharides, and other polyanions, in antiviral therapy, focusing on extracellular polymeric substances (EPSs). We maintain that, in spite of those early difficulties, the use of polyanions and, specifically, the use of EPSs, in antiviral therapy should be reconsidered. We base our claim in several points. First, early studies showed that the main disadvantage of sulfated polysaccharides and polyanions is their low bioavailability, but this difficulty can be overcome by the use of adequate administration strategies, such as nebulization of aerosols to gain access to respiratory airways. Second, several sulfated polysaccharides and EPSs have demonstrated to be non-toxic in animals. Finally, these macromolecules are non-specific and therefore they might be used against different variants or even different viruses.

Structural Characterization of Exopolysaccharide Produced by Leuconostoccitreum B-2 Cultured in Molasses Medium and Its Application in Set Yogurt

Sugarcane molasses is an agricultural by-product containing sucrose. In this study, the exopolysaccharide (M-EPS) produced by Leuconostoc citreum B-2 in molasses-based medium was characterized, optimized, and its application in set yogurt was investigated. The structure analysis, including gel permeation chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance, revealed that the M-EPS was a linear dextran composed of D-glucose units, which were linked by α-(1→6) glycosidic bonds with 19.3% α-(1→3) branches. The M-EPS showed a lower molecular weight than that produced from sucrose. The M-EPS was added into the set yogurt, and then the water holding capacity, pH, and microstructure of set yogurt were evaluated. Compared with the controls, the addition of M-EPS improved the water holding capacity and reduced the pH of set yogurt. Meanwhile, the structure of the three-dimensional network was also observed in the set yogurt containing M-EPS, indicating that M-EPS had a positive effect on the stability of set yogurt. The results provide a theoretical basis for the cost-effective utilization of sugarcane molasses.

Biological Functions of Exopolysaccharides from Lactic Acid Bacteria and Their Potential Benefits for Humans and Farmed Animals

Lactic acid bacteria (LAB) synthesize exopolysaccharides (EPS), which are structurally diverse biopolymers with a broad range of technological properties and bioactivities. There is scientific evidence that these polymers have health-promoting properties. Most commercialized probiotic microorganisms for consumption by humans and farmed animals are LAB and some of them are EPS-producers indicating that some of their beneficial properties could be due to these polymers. Probiotic LAB are currently used to improve human health and for the prevention and treatment of specific pathologic conditions. They are also used in food-producing animal husbandry, mainly due to their abilities to promote growth and inhibit pathogens via different mechanisms, among which the production of EPS could be involved. Thus, the aim of this review is to discuss the current knowledge of the characteristics, usage and biological role of EPS from LAB, as well as their postbiotic action in humans and animals, and to predict the future contribution that they could have on the diet of food animals to improve productivity, animal health status and impact on public health.

Polysaccharides and Their Derivatives as Potential Antiviral Molecules

In the current context of the COVID-19 pandemic, it appears that our scientific resources and the medical community are not sufficiently developed to combat rapid viral spread all over the world. A number of viruses causing epidemics have already disseminated across the world in the last few years, such as the dengue or chinkungunya virus, the Ebola virus, and other coronavirus families such as Middle East respiratory syndrome (MERS-CoV) and severe acute respiratory syndrome (SARS-CoV). The outbreaks of these infectious diseases have demonstrated the difficulty of treating an epidemic before the creation of vaccine. Different antiviral drugs already exist. However, several of them cause side effects or have lost their efficiency because of virus mutations. It is essential to develop new antiviral strategies, but ones that rely on more natural compounds to decrease the secondary effects. Polysaccharides, which have come to be known in recent years for their medicinal properties, including antiviral activities, are an excellent alternative. They are essential for the metabolism of plants, microorganisms, and animals, and are directly extractible. Polysaccharides have attracted more and more attention due to their therapeutic properties, low toxicity, and availability, and seem to be attractive candidates as antiviral drugs of tomorrow.

Characterization and Biological Activity of a Novel Exopolysaccharide Produced by Pediococcus pentosaceus SSC-12 from Silage

In this study, 22 strains of exopolysaccharides-producing lactic acid bacteria were isolated from silage, and the strain SSC–12 with the highest exopolysaccharide (EPS) production was used as the test strain. The SSC–12 was identified as Pediococcus pentosaceus, based upon 16S rDNA gene sequencing and Neighbor Joining (NJ) phylogenetic analysis. The analysis of the kinetic results of EPS generation of SSC–12 showed that the EPS generation reached the maximum value at 20 h of culture. The characterization study showed the EPS produced by SSC–12 was a homogeneous heteropolysaccharide comprising glucose (42.6%), mannose (28.9%), galactose (16.2%), arabinose (9.4%), and rhamnose (2.9%). The EPS had good antioxidant activity, especially the activity of scavenging hydroxyl free radicals. At the same time, the EPS also had strong antibacterial ability and could completely inhibit the growth of Staphylococcus aureus. The EPS produced by the Pediococcus pentosaceus SSC–12 can be used as a biologically active product with potential application prospects in the feed, food, and pharmaceutical industries.

The beauty of biocatalysis: sustainable synthesis of ingredients in cosmetics

Covering: 2015 up to July 2021The market for cosmetics is consumer driven and the desire for green, sustainable and natural ingredients is increasing. The use of isolated enzymes and whole-cell organisms to synthesise these products is congruent with these values, especially when combined with the use of renewable, recyclable or waste feedstocks. The literature of biocatalysis for the synthesis of ingredients in cosmetics in the past five years is herein reviewed.

Lactic Acid Bacteria Isolated from Fermented Doughs in Spain Produce Dextrans and Riboflavin

Many lactic acid bacteria (LAB) produce metabolites with applications in the food industry, such as dextran-type exopolysaccharides (EPS) and riboflavin (vitamin B₂). Here, 72 bacteria were isolated from sourdoughs made by Spanish bread-makers. In the presence of sucrose, colonies of 22 isolates showed a ropy phenotype, and NMR analysis of their EPS supported that 21 of them were dextran producers. These isolates were identified by their random amplified polymorphic DNA (RAPD) patterns and their rrs and pheS gene sequences as LAB belonging to four species (Weissella cibaria, Leuconostoc citreum, Leuconostoc falkenbergense and Leuconostoc mesenteroides). Six selected strains from the Leuconostoc (3) and Weissella (3) genera grew in the absence of riboflavin and synthesized vitamin B₂. The EPS produced by these strains were characterized as dextrans by physicochemical analysis, and the L. citreum polymer showed an unusually high degree of branching. Quantification of the riboflavin and the EPS productions showed that the W. cibaria strains produce the highest levels (585–685 μg/and 6.5–7.4 g/L, respectively). Therefore, these new LAB strains would be good candidates for the development of fermented foods bio-fortified with both dextrans and riboflavin. Moreover, this is the first report of riboflavin and dextran production by L. falkenbergense.

Rediscovering bacterial exopolysaccharides of terrestrial and marine origins: novel insights on their distribution, biosynthesis, biotechnological production, and future perspectives

Bacteria exist in colonies as aggregates or associated with surfaces forming biofilms rather than planktonic cells. Living in such a unique manner is always mediated via a matrix of extracellular polymeric substances, which are composed mainly of polysaccharides or specifically exopolysaccharides (EPS). Biofilm formation and hence EPS production are affected by biotic and abiotic factors inducing/inhibiting several involved genes and other molecules. In addition, various aspects of bacterial EPS regarding: physiological functions, molecular weight, and chemical composition were demonstrated. Recent investigations have revealed a wide spectrum of EPS chemical and physicochemical properties showing promising applications in different industrial sectors. For instance, lactic acid bacteria (LAB)- and marine-derived EPS exhibit: immunomodulatory, antioxidant, antitumor, bioremediation of heavy metals, as well as thickening and viscosity modifiers in the food industry. However, bacterial EPS have not yet been commercially implemented, in contrast to plant-derived analogues. The current review aims to rediscover the EPS structural and biosynthetic features derived from marine and terrestrial bacteria, and applications as well.

An overview of functional genomics and relevance of glycosyltransferases in exopolysaccharide production by lactic acid bacteria

There are many reports on exopolysaccharides of lactic acid bacteria (LAB EPS) such as isolation, production and applications. The LAB EPS have been proved to exhibit significantly improved texture and rheological properties in order to prevent syneresis of fermented foods. Furthermore, they are known to have many biological properties such as mouthwatering flavors, antioxidant activity, cholesterol lowering and antimicrobial activities. Considering their GRAS status, LAB EPS need to be explored for better titre and improved biological properties, where strain improvement by genetic engineering has a major role for making tailor-made EPS. The genetic overview of the EPS production by LAB is an auxiliary area of interest as the process and the biosynthetic pathway involves numerous genes and their proteins. Among them Glycosyltransferases (gtfs) are the key enzymes involved in EPS biosynthesis. Current knowledge of gtfs of LAB and its manipulation is limited. The present review spotlights the importance of glycosyltransferases and their specific role on the biosynthesis of LAB EPS and addresses the functionality and applicability of these enzymes and their products. It enfold the available literature including some patents in recent past to underline the fact that glycosyltransferases are un-reluctantly the key proteins involved in the EPS biosynthesis.

Challenges and Solutions to Viral Diseases of Finfish in Marine Aquaculture

Aquaculture is the fastest food-producing sector in the world, accounting for one-third of global food production. As is the case with all intensive farming systems, increase in infectious diseases has adversely impacted the growth of marine fish farming worldwide. Viral diseases cause high economic losses in marine aquaculture. We provide an overview of the major challenges limiting the control and prevention of viral diseases in marine fish farming, as well as highlight potential solutions. The major challenges include increase in the number of emerging viral diseases, wild reservoirs, migratory species, anthropogenic activities, limitations in diagnostic tools and expertise, transportation of virus contaminated ballast water, and international trade. The proposed solutions to these problems include developing biosecurity policies at global and national levels, implementation of biosecurity measures, vaccine development, use of antiviral drugs and probiotics to combat viral infections, selective breeding of disease-resistant fish, use of improved diagnostic tools, disease surveillance, as well as promoting the use of good husbandry and management practices. A multifaceted approach combining several control strategies would provide more effective long-lasting solutions to reduction in viral infections in marine aquaculture than using a single disease control approach like vaccination alone.

Antiviral activity of fermented foods and their probiotics bacteria towards respiratory and alimentary tracts viruses

The recent COVID-19, a viral outbreak calls for a high demand for non-conventional antiviral agents that can reduce the risk of infections and promote fast recovery. Fermented foods and their probiotics bacteria have recently received increasing interest due to the reported potential of high antiviral activity. Several probiotics strains demonstrated broad range of antiviral activities and different mechanisms of action. This article will review the diversity, health benefits, interaction with immune system and antiviral activity of fermented foods and their probiotics bacteria. In addition, the mechanisms of action will be reviewed to determine the broad range potential antiviral activity against the respiratory and alimentary tracts viruses. The probiotics bacteria and bioactive compounds in fermented foods demonstrated antiviral activities against respiratory and alimentary tracts viruses. The mechanism of action was reported to be due to the stimulation of the immune system function via enhancing natural killers cell toxicity, enhance the production of pro-inflammatory cytokines, and increasing the cytotoxic of T lymphocytes (CD3⁺, CD16⁺, CD56⁺). However, further studies are highly recommended to determine the potential antiviral activity for traditional fermented foods.

Evaluation of an O2-Substituted (1-3)-β-D-Glucan, Produced by Pediococcus parvulus 2.6, in ex vivo Models of Crohn's Disease

1,3-β-glucans are extracellular polysaccharides synthesized by microorganisms and plants, with therapeutic potential. Among them, the O2-substituted-(1–3)-β-D-glucan, synthesized by some lactic acid bacteria (LAB), has a prebiotic effect on probiotic strains, an immunomodulatory effect on monocyte-derived macrophages, and potentiates the ability of the producer strain to adhere to Caco-2 cells differentiated to enterocytes. In this work, the O2-substituted-(1–3)-β-D-glucan polymers produced by GTF glycoyltransferase in the natural host Pediococcus parvulus 2.6 and in the recombinant strain Lactococcus lactis NZ9000[pNGTF] were tested. Their immunomodulatory activity was investigated in an ex vivo model using human biopsies from patients affected by Crohn’s disease (CD). Both polymers had an anti-inflammatory effect including, a reduction of Interleukine 8 both at the level of its gene expression and its secreted levels. The overall data indicate that the O2-substituted-(1–3)-β-D-glucan have a potential role in ameliorating inflammation via the gut immune system cell modulation.

Dual and mutual interaction between microbiota and viral infections: a possible treat for COVID-19

All of humans and other mammalian species are colonized by some types of microorganisms such as bacteria, archaea, unicellular eukaryotes like fungi and protozoa, multicellular eukaryotes like helminths, and viruses, which in whole are called microbiota. These microorganisms have multiple different types of interaction with each other. A plethora of evidence suggests that they can regulate immune and digestive systems and also play roles in various diseases, such as mental, cardiovascular, metabolic and some skin diseases. In addition, they take-part in some current health problems like diabetes mellitus, obesity, cancers and infections. Viral infection is one of the most common and problematic health care issues, particularly in recent years that pandemics like SARS and COVID-19 caused a lot of financial and physical damage to the world. There are plenty of articles investigating the interaction between microbiota and infectious diseases. We focused on stimulatory to suppressive effects of microbiota on viral infections, hoping to find a solution to overcome this current pandemic. Then we reviewed mechanistically the effects of both microbiota and probiotics on most of the viruses. But unlike previous studies which concentrated on intestinal microbiota and infection, our focus is on respiratory system's microbiota and respiratory viral infection, bearing in mind that respiratory system is a proper entry site and residence for viruses, and whereby infection, can lead to asymptomatic, mild, self-limiting, severe or even fatal infection. Finally, we overgeneralize the effects of microbiota on COVID-19 infection. In addition, we reviewed the articles about effects of the microbiota on coronaviruses and suggest some new therapeutic measures.

Isolation and characterization of an exopolymer produced by Bacillus licheniformis: In vitro antiviral activity against enveloped viruses

The exopolymer (EPSp) produced by the strain B. licheniformis IDN-EC was isolated and characterized using different techniques (MALDI-TOF, NMR, ATR-FTIR, TGA, DSC, SEM). The results showed that the low molecular weight EPSp contained a long polyglutamic acid and an extracellular teichoic acid polysaccharide. The latter was composed of poly(glycerol phosphate) and was substituted at the 2-position of the glycerol residues with a αGal and αGlcNH₂. The αGal O-6 position was also found to be substituted by a phosphate group. The antiviral capability of this EPSp was also tested on both enveloped (herpesviruses HSV, PRV and vesicular stomatitis VSV) and non-enveloped (MVM) viruses. The EPSp was efficient at inhibiting viral entry for the herpesviruses and VSV but was not effective against non-enveloped viruses. The in vivo assay of the EPSp in mice showed no signs of toxicity which could allow for its application in the healthcare sector.

The role of dextran production in the metabolic context of Leuconostoc and Weissella Tunisian strains

High molecular weight dextrans improve the rheological properties of fermented products and have immunomodulatory and antiviral activity. We report on 5.84 × 10⁷-2.61 × 10⁸ Da dextrans produced by Leuconostoc lactis AV1n, Weissella cibaria AV2ou and Weissella confusa V30 and FS54 strains. Dextransucrases catalyze dextran synthesis by sucrose hydrolysis concomitant with fructose generation. The four bacteria have dextransucrases with molecular weight of about 160 kDa detected by zymograms. Each bacterium showed different interplay of dextran production and metabolic fluxes. All bacteria produced lactate, and AV2ou apart, synthesized mannitol from fructose. FS54 hydrolyzed dextran blue and the concentration of dextran produced by this bacterium decreased during the stationary phase. The AV1n binding to Caco-2 cells and polystyrene plates was higher under conditions for dextran synthesis. Thus, this is the first instance of a Weissella dextranase, associated with a dextransucrase ability, and of a positive influence of dextran on adhesion and aggregation properties of a bacterium.

Bioconversion of Fish Discards through the Production of Lactic Acid Bacteria and Metabolites: Sustainable Application of Fish Peptones in Nutritive Fermentation Media

In the current work, we study the capacity of 30 peptones obtained by enzyme proteolysis of ten discarded fish species (hake, megrim, red scorpionfish, pouting, mackerel, gurnard, blue whiting, Atlantic horse mackerel, grenadier, and boarfish) to support the growth and metabolite production of four lactic acid bacteria (LAB) of probiotic and technological importance. Batch fermentations of Lactobacillus plantarum, L. brevis, L. casei, and Leuconostoc mesenteroides in most of the media formulated with fish peptones (87% of the cases) led to similar growths (quantified as dry-weight biomass and viable cells) and metabolites (mainly lactic acid) than in commercial control broth (MRS). Comparisons among cultures were performed by means of the parameters obtained from the mathematical fittings of experimental kinetics to the logistic equation. Modelling among experimental and predicted data from each bioproduction was generally accurate. A simple economic assessment demonstrated the profitability achieved when MRS is substituted by media formulated with fish discards: a 3-4-fold reduction of costs for LAB biomass, viable cells formation, and lactic and acetic acid production. Thus, these fish peptones are promising alternatives to the expensive commercial peptones as well as a possible solution to valorize discarded fish biomasses and by-products.

Structural characterization of a homopolysaccharide with hypoglycemic activity from the roots of Pueraria lobata

A water-soluble neutral homopolysaccharide (PLP-1) was obtained from the roots of Pueraria lobata by DEAE cellulose and Sephadex G-200 gel chromatography purification. The average molecular weight of PLP-1 was 16.2 kDa. Monosaccharide composition analysis showed that PLP-1 was composed of glucose as a glucan. The structure of PLP-1 was characterized on the basis of extensive physical and chemical analysis, which indicated that the backbone of PLP-1 was mainly composed of →3)-α-d-Glcp(1→ and →4)-β-d-Glcp(1→ with a molar ratio of 7.0 : 1.0. Moreover, the hypoglycemic activity of PLP-1 was investigated by palmitic acid and high glucose induced insulin resistant HepG2 cells. The results elucidated that PLP-1 could decrease the glucose concentration by up-regulating the expression of PI3K and AKT, and down-regulating the expression of FoxO1, PCK2, and G6Pase in insulin resistant cells. Therefore, PLP-1 could serve as a dietary supplement to ameliorate insulin resistance for diabetic patients.

Isolation of a Leuconostoc mesenteroides Strain With Anti-Porcine Epidemic Diarrhea Virus Activities From Kefir Grains

Swine grown under commercial conditions are vulnerable to environmental exposure to several viruses, which may cause infectious diseases and spread easily and rapidly, resulting in significant economic losses in animal husbandry. Previous studies have suggested that probiotics seem to be a new and promising alternative to vaccinations to protect animals against potential viral infections. In this study, we used the Vero cell culture model of infection to study porcine epidemic diarrhea virus (PEDV). We screened lactic acid bacteria (LAB) with anti-PEDV potential from kefir grains, which are starter cultures used to ferment milk into kefir. Twenty-nine LAB strains were isolated and identified as Enterococcus durans, Lactobacillus kefiri, Lactococcus lactis, and Leuconostoc mesenteroides, according to 16S ribosomal RNA (rRNA) and rpoA gene sequence analyses. The anti-PEDV activities of the LAB intracellular extracts were compared, and the intracellular extracts of Ln. mesenteroides showed higher anti-PEDV activities than that of the other species. Among the Ln. mesenteroides strains, a strain designated YPK30 showed a higher growth rate than that of the other strains and was further evaluated for its anti-PEDV activity. The results showed that the intracellular extracts of Ln. mesenteroides YPK30 possessed in vitro prophylactic, therapeutic, and direct-inhibitory effects against PEDV in the Vero cell model. The expression levels of Type 1 interferon (IFN)-dependent genes, including Myxovirus resistance 1 (MX1) and interferon-stimulated gene 15 (ISG15), were significantly increased after treatment with intracellular extracts of Ln. mesenteroides YPK30 for 24 h. Such expression suggests that the anti-PEDV activity of Ln. mesenteroides YPK30 could be attributed to its up-regulatory effect on the expression of MX1 and ISG15 genes. These results suggested that Ln. mesenteroides YPK30 has the potential to provide some levels of host protection against PEDV infections.

Bifidobacteria cell wall-derived exo-polysaccharides, lipoteichoic acids, peptidoglycans, polar lipids and proteins - their chemical structure and biological attributes

A variety of health benefits has been documented to be associated with the consumption of probiotic bacteria, namely bifidobacteria and lactobacilli. Thanks to the scientific advances in recent years we are beginning to understand the molecular mechanisms by which bacteria in general and probiotic bacteria in particular act as host physiology and immune system modulators. More recently, the focus has shifted from live bacteria towards bacteria-derived defined molecules, so called postbiotics. These molecules may represent safer alternative compared to the live bacteria while retaining the desired effects on the host. The excellent source of effector macromolecules is the bacterial envelope. It contains compounds that are pivotal in the adhesion phenomenon, provide direct bacteria-to-host signaling capacity and the associated physiological impact and immunomodulatory properties of bacteria. Here we comprehensively review the structure and biological role of Bifidobacterium surface and cell wall molecules: exopolysaccharides, cell wall polysaccharides, lipoteichoic acids, polar lipids, peptidoglycans and proteins. We discuss their involvement in direct signaling to the host cells and their described immunomodulatory effects.

Structural Analysis of Exopolysaccharides from Lactic Acid Bacteria

Production of exopolysaccharides by lactic acid bacteria is a common phenomenon. Structural information of these widely diverse biopolymers is rendered by the monosaccharide composition, the anomeric configurations, the type of glycosidic linkages, the presence of repeating units and noncarbohydrate substituents, and finally the presentation of a chemical molecular structure or composite model. The detailed structural analysis of polysaccharides is a time-consuming pursuit, including the use of different techniques, such as chemical degradation methods (e.g., hydrolysis), separation methods (e.g., SEC-chromatography and HPLC/HPAEC), and identification methods (e.g., GLC-EIMS and ¹H/¹³C NMR spectroscopy). In this chapter, some analytical methods are described and demonstrated for two different exopolysaccharides from lactic acid bacteria.

Different Modes of Regulation of the Expression of Dextransucrase in Leuconostoc lactis AV1n and Lactobacillus sakei MN1

Leuconostoc lactis AV1 strain isolated from a Tunisian avocado was characterized as a dextran producer. The promoter P dsrLL and the dsrLL gene encoding the DsrLL dextransucrase responsible for the dextran synthesis were transcriptionally fused to the mCherry coding gene generating the pRCR20 plasmid. Upon plasmid transfer, both AV1n and the dextran non-producing Leuconostoc mesenteroides CM70 became red due to expression of the mCherry from the P dsrLL-dsr-mrfp transcriptional fusion. Characterization of the polymers present in cultures supernatants revealed that the DsrLL encoded from pRCR20 in the recombinant bacteria was able to synthesize dextran. The production of dextran by the DsrLL in AV1n increased in response to low temperature, reaching 10-fold higher levels at 20°C than at 37°C (4.15 g/L versus 0.41 g/L). To analyze if this stress response includes activation at the transcriptional level and if it was only restricted to Leuconostoc, AV1n was transformed with plasmids carrying either the P dsrLL -mrfp fusion or the P dsrLS of Lactobacillus sakei MN1 fused to the mrfp gene, and the influence of temperature and carbon source on expression from the Dsr promoters was monitored by measurement of the mCherry levels. The overall expression analysis confirmed an induction of expression from P dsrLL upon growth at low temperature (20°C versus 30°C and 37°C) in the presence of sugars tested (sucrose, glucose, maltose, and fructose). In addition, the presence of sucrose, the substrate of Dsr, also resulted in activation of expression from P dsrLL . A different behavior was detected, when expression from P dsrLS was evaluated. Similar levels of fluorescence were observed irrespectively of the carbon source or temperature, besides a sequential decrease at 30°C and 20°C, when sucrose was present in the growth medium. In conclusion, the two types of regulation of expression of Dsr presented here revealed two different mechanisms for environmental adaptation of Leuconostoc and Lactobacillus that could be exploited for industrial applications.

Current status of biotechnological production and applications of microbial exopolysaccharides

Microbial exopolysaccharides (EPS) are an abundant and important group of compounds that can be secreted by bacteria, fungi and algae. The biotechnological production of these substances represents a faster alternative when compared to chemical and plant-derived production with the possibility of using industrial wastes as substrates, a feasible strategy after a comprehensive study of factors that may affect the synthesis by the chosen microorganism and desirable final product. Another possible difficulty could be the extraction and purification methods, a crucial part of the production of microbial polysaccharides, since different methods should be adopted. In this sense, this review aims to present the biotechnological production of microbial exopolysaccharides, exploring the production steps, optimization processes and current applications of these relevant bioproducts.

Sucrose-Induced Proteomic Response and Carbohydrate Utilization of Lactobacillus sakei TMW 1.411 During Dextran Formation

Lactobacillus (L.) sakei belongs to the dominating lactic acid bacteria in indigenous meat fermentations, while diverse strains of this species have also been isolated from plant fermentations. We could recently show, that L. sakei TMW 1.411 produces a high molecular weight dextran from sucrose, indicating its potential use as a dextran forming starter culture. However, the general physiological response of L. sakei to sucrose as carbohydrate source has not been investigated yet, especially upon simultaneous dextran formation. To address this lack of knowledge, we sequenced the genome of L. sakei TMW 1.411 and performed a label-free, quantitative proteomics approach to investigate the sucrose-induced changes in the proteomic profile of this strain in comparison to its proteomic response to glucose. In total, 21 proteins were found to be differentially expressed at the applied significance criteria (FDR ≤ 0.01). Among these, 14 were associated with the carbohydrate metabolism including several enzymes, which enable sucrose and fructose uptake, as well as, their subsequent intracellular metabolization, respectively. The plasmid-encoded, extracellular dextransucrase of L. sakei TMW 1.411 was expressed at high levels irrespective of the present carbohydrate and was predominantly responsible for sucrose consumption in growth experiments using sucrose as sole carbohydrate source, while the released fructose from the dextransucrase reaction was more preferably taken up and intracellularly metabolized than sucrose. Genomic comparisons revealed, that operons coding for uptake and intracellular metabolism of sucrose and fructose are chromosomally conserved among L. sakei, while plasmid-located dextransucrase genes are present only in few strains. In accordance with these findings, all 59 different L. sakei strains of our strain collection were able to grow on sucrose as sole carbohydrate source, while eight of them exhibited a mucous phenotype on agar plates indicating dextran formation from sucrose. Our study therefore highlights the intrinsic adaption of L. sakei to plant environments, where sucrose is abundant, and provides fundamental knowledge regarding the use of L. sakei as starter culture for sucrose-based food fermentation processes with in-situ dextran formation.

Characterization of a Lipase From the Silkworm Intestinal Bacterium Bacillus pumilus With Antiviral Activity Against Bombyx mori (Lepidoptera: Bombycidae) Nucleopolyhedrovirus In Vitro

To investigate whether Bombyx mori Linnaeus (Lepidoptera: Bombycidae) intestinal microorganism play a role in the host defence system against viral pathogens, a lipase gene from the silkworm intestinal bacterium Bacillus pumilus SW41 was characterized, and antiviral activity of its protein against B. mori nucleopolyhedrovirus (BmNPV) was tested. The lipase gene has an open-reading frame of 648 bp, which encodes a 215-amino-acid enzyme with a 34-amino-acid signal peptide. The recombinant lipase (without signal peptide) was expressed and purified by using an Escherichia coli BL21 (DE3) expression system. The total enzyme activity of this recombinant lipase reached 277.40 U/mg at the optimum temperature of 25°C and optimum pH value of 8.0. The antiviral test showed that a relative high concentration of the recombinant lipase reduced BmNPV infectivity in vitro, which resulted in decreased viral DNA abundance and viral occlusion bodies. Besides, the preincubation method also suggested that the lipase probably directly acting on the budded virions. The results suggest that the lipase from intestinal bacterium B. pumilus SW41 is a potential antiviral factor for silkworm against BmNPV.

Characterization of the SN35N Strain-Specific Exopolysaccharide Encoded in the Whole Circular Genome of a Plant-Derived Lactobacillus plantarum

Lactobacillus plantarum SN35N, which has been previously isolated from pear, secretes exopolysaccharide (EPS). The aim of the present study is to characterize the EPS chemically and to find the EPS-biosynthesizing gene cluster. The present study demonstrates that the strain produces an acidic EPS carrying phosphate residue, which is composed of glucose, galactose, and mannose at a molecular ratio of 15.0 : 5.7 : 1.0. We also show that acidic EPS strongly inhibits the catalytic activity of hyaluronidase (EC 3.2.1.35), promoting an inflammatory reaction. In the present study, we also determined the complete genome sequence of the SN35N strain, demonstrating that the genome is a circular DNA with 3267626 bp, and the number of predicted coding genes is 3146, with a GC content of 44.51%. In addition, the strain harbors four plasmids, designated pSN35N-1, -2, -3, and -4. Although four EPS-biosynthesizing genes, designated lpe1, lpe2, lpe3, and lpe4, are present in the SN35N chromosomal DNA, another EPS gene cluster, lpe5, is located in the pSN35N-3 plasmid, composed of 35425 bp. EPS low-producing mutants, which were obtained by treating SN35N cells with novobiocin, lost the lpe5 gene cluster in the plasmid-curing experiment, suggesting that the gene cluster for the biosynthesis of acidic EPS is present in the plasmid. The present study shows the chemical characterization of the acidic EPS and its inhibitory effect to the hyaluronidase.

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.

β-Glucan-Producing Pediococcus parvulus 2.6: Test of Probiotic and Immunomodulatory Properties in Zebrafish Models

Lactic acid bacteria synthesize exopolysaccharides (EPS), which could benefit the host's health as immunomodulators. Furthermore, EPS could protect bacteria against gastrointestinal stress, favoring gut colonization, thus protecting the host against pathogenic infections. Pediococcus parvulus 2.6, produces a 2-substituted (1,3)-β-D-glucan and, in this work, its probiotic properties as well as the immunomodulatory capability of its EPS have been investigated using Danio rerio (zebrafish). To this end and for a comparative analysis, P. parvulus 2.6 and its isogenic β-glucan-non-producing 2.6NR strain were fluorescently labeled by transfer of the pRCR12 plasmid, which encodes the mCherry protein. For the in vivo studies, there were used: (i) a gnotobiotic larvae zebrafish model for bacterial colonization, pathogen competition, and evaluation of the β-glucan immunomodulation capability and (ii) a transgenic (mpx:GFP) zebrafish model to determine the EPS influence in the recruitment of neutrophils under an induced inflammation. The results revealed a positive effect of the β-glucan on colonization of the zebrafish gut by P. parvulus, as well as in competition of the bacterium with the pathogen Vibrio anguillarum in this environment. The larvae treatment with the purified β-glucan resulted in a decrease of expression of genes encoding pro-inflammatory cytokines. Moreover, the β-glucan had an anti-inflammatory effect, when it was evaluated in an induced inflammation model of Tg(mpx:GFP) zebrafish. Therefore, P. parvulus 2.6 and its EPS showed positive health properties in in vivo fish models, supporting their potential usage in aquaculture.

Bioprospecting of indigenous resources for the exploration of exopolysaccharide producing lactic acid bacteria

Exploration of biodiversity lead towards the discovery of novel exopolysaccharide (EPS) producing microbes that have multiple applications. The safety compatibility status of lactic acid bacteria (LAB) makes it an attractive candidate for the production of EPS in industries. Therefore, new bacterial isolates are continuously being identified from different habitats. Current research was conducted to explore indigenous biodiversity for the production of dextransucrase, which is involved in the synthesis of dextran. Dextran is an EPS which is used in different industries. In this study, thirty-nine LAB were isolated from different food samples. The isolates were identified as genus Leuconostoc, Weissella and Streptococcus based on genotypic and phenotypic characteristics. Screening revealed that only eight isolates can produce dextransucrase in high titres. Fermentation conditions of dextran producing LAB was optimized. The results indicated that Weissella confusa exhibited maximum specific activity (1.50 DSU mg-1) in 8 h at 25 °C with pH 7.5. Dextran produced from Weissella proved to be a useful alternative to commercially used dextran produced by Leuconostoc mesenteroides in industries for various applications.