Exopolysaccharide Yield Research Articles

Research Advance on Exopolysaccharides Synthesized by Lactic Acid Bacteria

Exopolysaccharides(EPS) of lactic acid bacteria(LAB) are natural polymers produced by LAB.As a new type of natural food additives,EPS of LAB catch the attention of researchers by its immense physiological function and industrial potential.But due to the differences between the composition and function of EPS,It is difficult to establish universal methods and criterions of detection.Also,how to improve the yield of EPS is a great challenge.The genetics of EPS,structure analysis,structure-function relationship,biological activity and further researches will be summarized.

The influence of fermentation condition on production and molecular mass of EPS produced by Streptococcus thermophilus 05-34 in milk-based medium

The yield of exopolysaccharide (EPS) produced by Streptococcus thermophilus 05-34 reached up to 250mg/L under the optimal fermentation condition, which was 4.2-fold higher than that produced under the non-optimal fermentation condition. Structure analysis showed that EPS produced under the optimal fermentation condition was composed of galactose and glucose in a molar ratio of 1.0:0.8. This EPS was with a molecular mass of 4.7×105Da, which was increased by 9 times compared with that in the non-optimal fermentation condition, while monosaccharide composition did not change. Furthermore, real-time quantitative PCR showed that the transcription level of epsC, which is responsible for chain-length determination, was up-regulated by 2.7-fold, suggesting that the increased molecular mass of EPS was resulted from improving polymerization degree of monosaccharide. These findings demonstrated that the optimized fermentation condition can improve EPS molecular mass, and may consequently modify the rheological properties of EPS.

The influence of rifampicin resistant mutations on the biosynthesis of exopolysaccharides by strain Escherichia coli K-12 lon

The influence of RNA polymerase (rif) mutations on the yield of capsular exopolysaccharide--colanic acid (CA) of Escherichia coli K-12 lon strain was studied. Five colanic acid isogenic producing strains were created by transduction transfer of rif alleles possessing pleiotropic effects. The obtained isogenic strains differed by specific growth rate, size and mucoidness of colonies, the dependence of growth on the medium composition and cultivation temperature, as well as by the adsorption rate of virulent bacteriophage M59, specifically lysing E. coli cells producing CA. Direct correlation between the yield of exopolysaccharides, growth rate and adsorption of bacteriophage M59 was revealed. Among rif recombinants strain AH203, which synthesized twice as much CA compared with the parental strain in submerged cultivation was selected.

In vitro probiotic characteristics of Lactobacillus plantarum ZDY 2013 and its modulatory effect on gut microbiota of mice

Lactobacillus plantarum ZDY 2013, a novel strain isolated from Chinese traditional fermented acid beans, was systematically evaluated for its survival capacity under stress conditions (pH, bile salt, simulated gastrointestinal tract, and antibiotics), production of exopolysaccharide and antagonism against 8 pathogens. Its effect on mice gut microbiota was also investigated by quantitative PCR and PCR-denaturing gradient gel electrophoresis. The results showed that ZDY 2013 can grow at pH 3.5 and survive at pH 2.0 for 6 h and at 0.45% bile salt for 3 h. The exopolysaccharide yield was up to 204±7.68 mg/L. The survival rate of ZDY 2013 in a simulated gastrointestinal tract was as high as 65.84%. Antagonism test with a supernatant of ZDY 2013 showed maximum halo of 28 mm against Listeria monocytogenes. The inhibition order was as follows: Listeria monocytogenes, Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa, Shigella sonnei, Enterobacter sakazakii, and Staphylococcus aureus. Lactobacillus plantarum ZDY 2013 was sensitive to some antibiotics (e.g., macrolide, sulfonamides, aminoglycoside, tetracyclines and β-lactams), whereas it was resistant to glycopeptides, quinolones, and cephalosporins antibiotics. Denaturing gradient gel electrophoresis profile demonstrated that ZDY 2013 administration altered the composition of the microbiota at various intestinal loci of the mice. Moreover, the quantitative PCR test showed that the administration of ZDY 2013 enhanced the populations of Bifidobacterium and Lactobacillus in either the colon or cecum, and reduced the potential enteropathogenic bacteria (e.g., Enterococcus, Enterobacterium, and Clostridium perfringens). Lactobacillus plantarum ZDY 2013 exhibited high resistance against low pH, bile salt, and gastrointestinal fluid, and possessed antibacterial and gut microbiota modulation properties with a potential application in the development of dairy food and nutraceuticals.

Evaluation of Fermentative Parameters for the Production of Botryosphaeran (a(1-->3;1-->6)-β-D-glucan) and Mycelial Biomass by Botryosphaeria rhodina MAMB-05

Botryosphaeran is an exopolysaccharide (EPS) of the (13;16)-β-D-glucan type produced by the fungus Botryosphaeria rhodina MAMB-05. In attempts to enhance its extracellular production, the quantitative effects of different nitrogen sources, fermentation time, inoculum size, C/N ratio, and initial pH were evaluated on the yields of botryosphaeran. Ammonium nitrate was selected as the best nitrogen source in examining these effects using a 2³-factorial central-composite experimental design, and analysis by the response surface method. According to a factorial design, the most important variables influencing both botryosphaeran and mycelium biomass production was inoculum concentration and the time of growth. Under these conditions, optimum botryosphaeran production occurred at 88 h of growth, 0.88 g of mycelium L -1 of nutrient mediumat C/N ratio of 30, and resulted in a 5.2 g L -1 yield of EPS in the fermentation broth. For production of the mycelium biomass, the optimum condition occurred at the same time of growth and inoculum concentration; however the best C/N ratio was 75, and resulted in a yield of 33.8 g L -1 of biomass. The results also indicated that the maximal mycelial growth is not associated to the yields of botryosphaeran production by Botryosphaeria rhodina MAMB-05. DOI: http://dx.doi.org/10.17807/orbital.v7i1.637

Screening and Identification of Exopolysaccharide-producing Bifidobacteria from Infant Gut

Exopolysaccharide (EPS) produced from lactic acid bacteria has many bioactivities and the role of prebiotic as reported. However, being a well-knowen probiotic, there is little report about EPS-producing bifidobacteria. In this study, several bifidobacteria strains were isolated from baby feces with mupirocin lithium salt improved medium and evaluated for the production of EPS. Culturing strains with MRS medium containing 2% sucrose, one EPS-producing bifidobacteria strain A19 was screened by ethanol precipitation, dialysis, phenol- sulfuric acid method and other methods. By the physiological and biochemical characteristics, 16S rDNA and tuf gene sequence analysis, strain A19 was identified as Bifidobacterium pseudocatenulatum. It was a novel EPS- producing bifidobacteria and the EPS yield was 55.546 mg/L in MRS broth with 2% sucrose. It could be a potential available strain for microecologic products and food starters.

Evaluation of biofilm formation by exopolysaccharide-producer strains of thermophilic lactic acid bacteria isolated from Algerian camel milk

Exploration of wild lactic acid bacteria from natural environments is the most suitable approach of search for the desired exopolysaccharide-phenotype. The significance of biofilm in food processing is a highly debated issue. The Biofilm represents the next major scientific challenge to microbiologists and food processors. A total of 30 thermophilic lactic acid bacteria strains were isolated from Algerian raw Camel milk. The isolation was carried on Chalmers agar, under aerobic and anaerobic conditions at 42 °C. The identification, based on the phenotypic characteristics showed high diversity of species and predominance of Lactobacillus and Enterococcus. Based on the mucoid type of the colonies, strains were screened for their ability to produce exopolysaccharides. The production of polymers was carried on modified MRS broth, then, the yields were quantified, using the colorimetric method. The results show that the tested strains produced large amounts of soluble exopolysaccharides, some strains have a potential to be used as culture starters for dairy products. These strains were examined for their ability to form biofilm, using the Biofilm Ring Test. The findings showed that all studied strains formed a biofilm. While, the Biofilm Ring Test with exopolysaccharide powder of different strains, showed positive result for only three Lactobacillus strains (La91, Lb116, La117) that Which suggest that there is no relationship between exopolysaccharide yield and biofilm formation.

Antioxidative Activity of Exopolysaccharide Extract from Fermented Wheat Distillers\'dried Grains Using UV-Irradiation Degradation Pretreatment by <em>Preussia aemulans</em>

A novel approach for utilizing wheat Dried Distillers' Grains with Solubles (DDGS) to produce exopolysaccharide by Preussia aemulans was explored. For degrading the insoluble polymer of wheat DDGS, the UV-irradiation method was used. After irradiation of 24 h, the soluble saccharide content of wheat DDGS medium was increased by 67%. The optimum fermentation conditions were: 5% (w/v) of fructose, 0.5% (w/v) of yeast extract, 7.5 of pH value, 5% (v/v) of the inoculum size, 60 rpm of shaking condition and 5 days of the fermentation time. The maximum exopolysaccharides yield of fermented broth under the optimum fermentation conditions was 3.51±0.24 g/L. Comparing with the unfermented wheat DDGS water extract, the exopolysaccharide yield of fermented broth was increased by 36%. The crude exopolysaccharide (EPS) indicated remarkable antioxidative activities though four antioxidant assays. Therefore, the crude EPS could be utilized as antioxidative food additives and functional feed in the future.

Correlation between the production of exopolysaccharides and oxalic acid secretion by Ganoderma applanatum and Tyromyces palustris.

The secretion of exopolysaccharides and oxalic acid in cultures of a white rot Ganoderma applanatum strain and a brown rot Tyromyces palustris strain were tested in terms of culture time, pH range, and temperature. The high yield of exopolysaccharides (EPS) required a moderate temperature of 28 °C for G. applanatum and 20 °C for T. palustris. G. applanatum and T. palustris accumulated more EPS when the concentration of the carbon source (maltose for G. applanatum and fructose for T. palustris) was 30 g/L. The results indicate that the production of oxalic acid by G. applanatum is correlated with the initial pH value of the culture medium and the concentration of oxalic acid increased to 1.66 ± 0.2 mM at the initial pH of 6.5 during the fungal growth. During the growth of T. palustris, the reduction of the initial pH value of the growing medium lowered the oxalic acid concentration from 7.7 ± 0.6 mM at pH 6.0 to 1.99 ± 0.2 mM at pH 3.5. T. palustris accumulated considerably more oxalic acid than G. applanatum and its presence did not affect significantly the production of exopolysaccharides. We also observed that the maximum amounts of exopolysaccharides secreted during cultivation of G. applanatum and T. palustris were 45.8 ± 1.2 and 19.1 ± 1.2 g/L, respectively.

Characterization of haloglycan, an exopolysaccharide produced by Halomonas stenophila HK30

We have conducted a thorough study of the exopolysaccharide (EPS) produced by strain HK30 of Halomonas stenophila, which we have named haloglycan. This strain was chosen during an ongoing research programme aimed at finding novel exopolysaccharide-producing halophilic bacteria in unexplored hypersaline habitats. Strain HK30 was isolated from a saline-wetland in Brikcha (Morocco) and identified as belonging to the species H. stenophila. It produced EPS mainly during the exponential growth phase and to a lesser extent during the stationary phase. Culture parameters influenced both bacterial growth and EPS production, EPS yield always being directly related to the quantity of biomass. Under optimum culture conditions, strain HK30 produced 3.89g of EPS per litre of medium. The polymer was a sulphated heteropolysaccharide composed of two fractions, with molecular masses of 8.2×104 and 1.4×106. The crude EPS contained 44±0.1% w/w carbohydrates and the following monosaccharide composition: glucose (24±1.73), glucuronic acid (7.5±0.37), mannose (5.5±0.17), fucose (4.5±0.36), galactose (1.2±0.17) and rhamnose (1±0.05) (%, w/w). It produced solutions of high viscosity and pseudoplastic behaviour that showed interesting flocculating and emulsifying activities and was also involved in forming biofilm.

Effects of carbohydrate sources on biosorption properties of the novel exopolysaccharides produced by Arthrobacter ps-5

The crude exopolysaccharides (EPSs) were obtained from Arthrobacter ps-5 fermentation using various carbohydrate sources followed by centrifugation, ethanol precipitation, and the isolated EPSs were further deproteinized and lyophilized. Carbohydrates from various sources resulted in different yield of EPSs from the fermentation and different molecular weight of EPSs. A maximum yield of 0.27mg/g was achieved by using the culture medium supplemented with sucrose. The EPS produced by glucose-supplemented medium had the maximum content of acidic polysaccharides, subsequently presented the highest biosorption capacity for Cu2+ and Pb2+ at 257.9mg/g and 331.8mg/g, respectively. The ratio of acidic to neutral polysaccharides presented in EPSs was a key factor to explicate the biosorption mechanism, the higher the ratio, the stronger the biosorption capacity.

Sulfated exopolysaccharide produced by Labrenzia sp. PRIM-30, characterization and prospective applications

Exopolysaccharides (EPS) are biopolymers produced by bacteria, having potential industrial applications. An EPS produced by a bacterium designated as PRIM-30 isolated from the deep seawater collected from offshore region of Cochin, India was studied. The isolate was identified as Labrenzia sp. based on 16S rRNA gene sequencing. Under optimum conditions for EPS production, the EPS yield was 840mgL−1 culture medium. The average molecular weight of the EPS was 269kDa and composed of glucose, arabinose, galacturonic acid and mannose in the ratio 14.4:1.2:1:0.6. Importantly, the purified EPS contained 4.76% (w/w) sulfate groups. Viscosity of the (1% w/v) EPS was 3.92cP (shear rate 300s−1, 25°C). Anodic peak potential (Epa) of the EPS by cyclic voltametric measurement was −0.7V. The EPS showed antioxidant activities with IC50 values of 640 and 190μgmL−1, respectively, for the inhibition of DPPH and superoxide radicals. The EPS displayed a linear dose dependent increase in total antioxidant capacity and ferric reducing power activities. To date, only a very few marine alphaproteobacterial representatives have been reported for EPS production and this study for the first time, shows the production of a sulfated EPS by a member of the genus Labrenzia.

Optimization of medium composition for exopolysaccharide production by Phellinus nigricans

Using Plackett–Burman design, steepest ascent method, and Box–Behnken design, we carried out sequential statistical optimization of the Phellinus nigricans culture medium for maximizing the production of exopolysaccharides. The concentrations of the constituents of culture medium as optimized by this method were: 51.67g/L glucose, 6.96g/L peptone, 1.0g/L yeast extract, 5mg/L thiamine, 1.0g/L KH2PO4, and 0.5g/L MgSO4. The yield of exopolysaccharides obtained using the optimized culture medium was 1.89±0.13g/L—2.3-fold higher than that obtained when unoptimized culture medium was used. The exopolysaccharide of P. nigricans (PNEP) is comprised by glucose and mannose with the molar ratio 1:2.63. PNEP thus produced scavenged superoxide anion radical, 1,1-diphenyl-2-picrylhydrazyl radical, and hydroxyl radical; showed antioxidant properties; and had reducing power.

Exopolysaccharide Production by a Lactic Acid Bacteria, Leuconostoc lactis Isolated from Ethnically Fermented Beverage

Ethnic tribals of Northeast India are known to prepare local beverages using indigenous technology. Exopolysaccharide (EPS) producing lactic acid bacteria are responsible for the alteration of wine and other fermented beverages. Isolated from ethnically fermented beverage (Kyiad pyrsi), Leuconostoc lactis in the present study, was investigated for EPS production. EPS productions were evaluated on MRS sucrose media and Ruthenium red milk agar plate. It was found that L. lactis had the yield of EPS (340.82 mg/l) which was found to be lower than Leuconostoc mesenteroides reported from wine which produced 904 mg/l. Microtiter plate assay on biofilm of the isolates was used for optimization of EPS production. Fructose, glucose, galactose, mannose, lactose, sucrose and ribose were used as carbohydrate sources, while pH of 5.0, 5.5, 6.0, 6.5 7.0, 8.0 and temperatures of 28, 37 and 45 °C were considered for production optimization. Sucrose, pH 6.5 and incubation temperature of 28 °C were found to be optimal conditions for EPS production by the isolate.

Development of a genetic system for the deep-sea psychrophilic bacterium Pseudoalteromonas sp. SM9913

BackgroundPseudoalteromonas species are a group of marine gammaproteobacteria frequently found in deep-sea sediments, which may play important roles in deep-sea sediment ecosystem. Although genome sequence analysis of Pseudoalteromonas has revealed some specific features associated with adaptation to the extreme deep-sea environment, it is still difficult to study how Pseudoalteromonas adapt to the deep-sea environment due to the lack of a genetic manipulation system. The aim of this study is to develop a genetic system in the deep-sea sedimentary bacterium Pseudoalteromonas sp. SM9913, making it possible to perform gene mutation by homologous recombination.ResultsThe sensitivity of Pseudoalteromonas sp. SM9913 to antibiotic was investigated and the erythromycin resistance gene was chosen as the selective marker. A shuttle vector pOriT-4Em was constructed and transferred into Pseudoalteromonas sp. SM9913 through intergeneric conjugation with an efficiency of 1.8 × 10-3, which is high enough to perform the gene knockout assay. A suicide vector pMT was constructed using pOriT-4Em as the bone vector and sacB gene as the counterselective marker. The epsT gene encoding the UDP-glucose lipid carrier transferase was selected as the target gene for inactivation by in-frame deletion. The epsT was in-frame deleted using a two-step integration–segregation strategy after transferring the suicide vector pMT into Pseudoalteromonas sp. SM9913. The ΔepsT mutant showed approximately 73% decrease in the yield of exopolysaccharides, indicating that epsT is an important gene involved in the EPS production of SM9913.ConclusionsA conjugal transfer system was constructed in Pseudoalteromonas sp. SM9913 with a wide temperature range for selection and a high transfer efficiency, which will lay the foundation of genetic manipulation in this strain. The epsT gene of SM9913 was successfully deleted with no selective marker left in the chromosome of the host, which thus make it possible to knock out other genes in the same host. The construction of a gene knockout system for Pseudoalteromonas sp. SM9913 will contribute to the understanding of the molecular mechanism of how Pseudoalteromonas adapt to the deep-sea environment.

Influence of casein hydrolysates on exopolysaccharide synthesis byStreptococcus thermophilusandLactobacillus delbrueckiissp.bulgaricus

A lot of interesting research has been undertaken to enhance the yield of exopolysaccharides (EPS) produced by lactic acid bacteria (LAB). The objective of this study was to determine the influence of casein hydrolysates (CH) with molecular weight less than 3 kDa on cell viability, EPS synthesis and the enzyme activity involved in EPS synthesis during the co-culturing of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus in MRS broth for 72 h at 37 ± 0.1 °C. The highest EPS yield (150.1 mg L⁻¹) was obtained on CH prepared with papain (CHP) at 48 h. At 24 h, EPS were composed of galactose, glucose and rhamnose in a molar ratio of 1.0:2.4:1.5. The monosaccharide composition changed with extension of the fermentation time. The activities of α-phosphoglucomutase, uridine 5'-diphosphate (UDP)-glucose pyrophosphorylase and UDP-galactose 4-epimerase were associated with EPS synthesis. Moreover, the activities of β-phosphoglucomutase and deoxythymadine 5'-diphosphate (dTDP)-glucose pyrophosphorylase involved in rhamnose synthesis were very low at the exponential growth phase and could not be detected during other given periods. The influence of different CH (<3 kDa) on LAB viability, EPS production, EPS monomeric composition and activity levels of key metabolic enzymes was distinct. Besides, their influence was related to the distribution of amino acids.

The beneficial effect of exopolysaccharides from Bifidobacterium bifidum WBIN03 on microbial diversity in mouse intestine

The structure of exopolysaccharides (EPS) produced by Bifidobacterium and their beneficial effects on human health have been fully studied, but only a few studies have investigated their influence on microbial diversity in the human/animal intestine. The strain named Bifidobacterium bifidum WBIN03 with high growth rate and exopolysaccharide (EPS) yield was selected to study the effect of its EPS on modifying the intestinal microbiota of mice. The results indicated that EPS significantly increased the growth of lactobacilli and total anaerobic bacteria, and exerted their inhibition effect on the growth of enterobacteria, enterococci and Bacteroides fragilis. Denaturing gradient gel electrophoresis (DGGE) analysis indicated that the EPS significantly increased the diversity of total bacteria and lactobacilli, but significantly decreased the diversity of enterobacteria. When receiving a low dose of EPS, Bacteroidales sp./Lactobacillus sp. occupied the dominant position, and L. johnsonii, L. animalis and L. reuteri were identified as the dominant strains when receiving a high concentration of EPS. The combination of viable cell count, DGGE and sequencing was used as an effective method to assess the microbial diversity in mouse intestine, and the benefit effect of EPS from B. bifidum WBIN03 on probiotics and antagonistic effect against pathogens would guaranteed the health of their hosts.

Enzymatic and bacterial conversions during sourdough fermentation

Enzymatic and microbial conversion of flour components during bread making determines bread quality. Metabolism of sourdough microbiota and the activity of cereal enzymes are interdependent. Acidification, oxygen consumption, and thiols accumulation by microbial metabolism modulate the activity of cereal enzymes. In turn, cereal enzymes provide substrates for bacterial growth. This review highlights the role of cereal enzymes and the metabolism of lactic acid bacteria in conversion of carbohydrates, proteins, phenolic compounds and lipids.Heterofermentative lactic acid bacteria prevailing in wheat and rye sourdoughs preferentially metabolise sucrose and maltose; the latter is released by cereal enzymes during fermentation. Sucrose supports formation of acetate by heterofermentative lactobacilli, and the formation of exopolysaccharides. The release of maltose and glucose by cereal enzymes during fermentation determines the exopolysaccharide yield in sourdough fermentations.Proteolysis is dependent on cereal proteases. Peptidase activities of sourdough lactic acid bacteria determine the accumulation of (bioactive) peptides, amino acids, and amino acid metabolites in dough and bread.Enzymatic conversion and microbial metabolism of phenolic compounds is relevant in sorghum and millet containing high levels of phenolic compounds. The presence of phenolic compounds with antimicrobial activity in sorghum selects for fermentation microbiota that are resistant to the phenolic compounds.

Paenibacillus polymyxa Rhizobacteria and Their Synthesized Exoglycans in Interaction with Wheat Roots: Colonization and Root Hair Deformation

We examined the ability of several Paenibacillus polymyxa strains to colonize wheat roots and the ability of P. polymyxa exoglycans to induce root hair deformation. For the first time, exopolysaccharides isolated from P. polymyxa were found to produce, with different intensities, various morphological changes in the root hairs of wheat seedlings, which are some of the earliest responses of plants to bacteria in the surrounding milieu. P. polymyxa 1465, giving the highest exopolysaccharide yield and the highest viscosity of aqueous exopolysaccharide solutions, was best able to colonize wheat seedling roots, and its exopolysaccharide proved to be the best in producing root hair deformation. It is suggested that P. polymyxa exoglycans have an active role in the establishment of plant-microbe associations.

Statistical modeling and optimization for exopolysaccharide production by Lactobacillus confusus in submerged fermentation under high salinity stress

In the last two decades, many studies have been reported that a high concentration of NaCl suppresses exopolysaccharide (EPS) production in lactic acid bacteria. In the present study, however, the enhancement of EPS production by Lactobacillus confusus under high salinity stress in submerged fermentation was demonstrated using response surface methodology via a full factorial design. Under the optimized conditions of 3.33% NaCl, 20 g/L sucrose, and 35 h of incubation, the EPS yield was 10.87 g/ L with 178% higher than the maximum yield (6.12 g/L of EPS) produced from the modified MRS medium without NaCl. Biomass production was independent of EPS production. A high yield of biomass was obtained in the culture with 0.23% NaCl. This results indicate that high salinity stress by NaCl can enhance EPS production in submerged fermentation in uncontrolled pH cultivations by inducing the production of cell-associated dextransucrase.