Exopolysaccharide Yield Research Articles

Microbial Exopolysaccharides: A Promising Health Booster

Microbial exopolysaccharides (EPS) are long-chain polysaccharides that are synthesized and secreted by microorganisms into the external matrix. In bacteria, EPS can either be associated with the cell surface in the form of capsules or be secreted into the environment. The yield of EPS is influenced by various factors, including the growth conditions and composition of the growth media. EPSs are high molecular-weight carbohydrates that consist of a backbone of repeated subunits of monosaccharides in varying ratios. Recently, there has been an increasing interest in EPS-producing microbes with Generally Recognized as Safe (GRAS) status. These food-grade organisms have the potential to produce polymers that can control the rheological and functional properties of food systems. EPSs have also been reported to have prebiotic and immune-modulating functions like anticancer, antidiabetic, antiviral, etc. The increasing recognition of the association between EPS and health benefits suggests the potential of EPS-producing starters with functional characteristics in the production of value-added functional products. Such products align with consumer demand for natural and healthy alternatives with fewer additives. The exploration of functional means of EPS in Pharmacology will provide an opportunity to identify novel and robust microbial resources producing unique EPSs.

Optimization of Exopolysaccharide Produced by Lactobacillus plantarum R301 and Its Antioxidant and Anti-Inflammatory Activities.

In this study, the yield of exopolysaccharide (EPS) from Lactobacillus plantarum R301 was optimized using a single-factor experiment and response surface methodology (RSM). After optimization, the EPS yield was increased with a fold-change of 0.85. The significant factors affecting EPS production, as determined through a Plackett-Burman design and Central Composite Design (CCD), were MgSO4 concentration, initial pH, and inoculation size. The maximum yield was 97.85 mg/mL under the condition of 0.01% MgSO4, an initial pH 7.4, and 6.4% of the inoculation size. In addition, the EPS exhibited strong antioxidant activity, as demonstrated by its ability to scavenge DPPH, ABTS, and hydroxyl radicals. The scavenging rate was up to 100% at concentrations of 4 mg/mL, 1 mg/mL, and 2 mg/mL, respectively. Moreover, the EPS also exhibited reducing power, which was about 30% that of ascorbic acid when both tended to be stable with the increased concentration. These results suggest that L. plantarum R301 EPS possesses different antioxidant mechanisms and warrants further investigation. In addition to its antioxidant activity, the EPS also demonstrated good anti-inflammatory activity by inhibiting the inflammation induced by lipopolysaccharide (LPS) in RAW 264.7 cells, which could decrease nitric oxide (NO) production and expression of the proinflammatory cytokine Il-6. These findings suggest that L. plantarum R301 EPS could be used as a potential multifunctional food additive in the food industry.

Microbial exopolysaccharide: Sources, stress conditions, properties and application in food and environment: A comprehensive review

Microbial glucan or exopolysaccharides (EPS) have caught an eye of researchers from decades. The unique characteristics of EPS make it suitable for various food and environmental applications. This review overviews the different types of exopolysaccharides, sources, stress conditions, properties, characterization techniques and applications in food and environment. The yield and production condition of EPS is a major factor affecting the cost and its applications. Stress conditions are very important as it stimulates the microorganism for enhanced EPS production and affects its properties. As far as application is concerned specific properties of EPS such as, hydrophilicity, less oil uptake behavior, film forming ability, adsorption potential have applications in both food and environment sector. Novel and improved method of production, feed stock and right choice of microorganisms with stress conditions are critical for desired functionality and yield of the EPS.

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.

Proposal of Four New Aureobasidium Species for Exopolysaccharide Production.

In this study, 99 strains of Aureobasidium species were isolated from various samples collected from different locations in China, among which 14 isolates showed different morphological characteristics to other strains identified as known Aureobasidium species. Based on morphological characteristics, those 14 strains were classified into four groups, represented by stains of KCL139, MDSC-10, XZY411-4, and MQL9-100, respectively. Molecular analysis of the internal transcriptional spacer (ITS) and part of the large ribosome subunit (D1/D2 domains) indicated that those four groups represent four new species in the Aureobasidium. Therefore, the names Aureobasidium insectorum sp. nov., A. planticola sp. nov., A. motuoense sp. nov., and A. intercalariosporum sp. nov. are proposed for KCL139, MDSC-10, XZY411-4, and MQL9-100, respectively. We also found that there were differences in the yield of exopolysaccharides (EPS) among and within species, indicating strain-related exopolysaccharide-producing diversity.

The protective effect of lactose on the bile salt stress response of Streptococcus thermophilus is strain dependent

Streptococcus thermophilus is generally considered to be sensitive to bile salt stimulation, and its bile salt tolerance is strain specific. In this study, the viable bacteria count, sugar utilization capacity, β-galactosidase activity, and extracellular polysaccharide synthesis capacity of 5 strains of Streptococcus thermophilus in bile salt with or without (w/o) lactose were measured to explore the protective ability of lactose to the strains. The changes in gene expression in stress and carbohydrate metabolism-related pathways were recorded. The results indicated that the protective effect of lactose on the bile salt stress response of Streptococcus thermophilus is strain dependent. The β-galactosidase activity of the strains was correlated with the yield of exopolysaccharides (EPS) significantly, and the strain with a high survival rate (4M6) showed higher lactose utilization, β-galactosidase activity and more EPS production in general.

Contribution of Quercetin to the Composition and Antioxidant Properties of Monascus Exopolysaccharides.

Exopolysaccharides are important metabolites of Monascus with healthy activities. However, the low production level limits their applications. Hence, the aim of this work was to increase the yield of exopolysaccharides (EPS) and optimize liquid fermentation by adding flavonoids. The EPS yield was optimized via both medium composition and culture conditions. The optional fermentation conditions achieved for EPS production of 7.018 g/L were 50 g/L sucrose, 3.5 g/L yeast extract, 1.0 g/L MgSO4·7H2O, 0.9 g/L KH2PO4, 1.8 g/L K2HPO4·3H2O, 1 g/L quercetin, and 2 mL/L Tween-80, with pH 5.5, inoculum size 9%, seed age 52 h, shaking speed 180 rpm, and fermentation culture 100 h, respectively. Furthermore, the addition of quercetin increased EPS production by 11.66%. The results also showed little citrinin residue in the EPS. The exopolysaccharides' composition and antioxidant capacity of quercetin-modified exopolysaccharides were then preliminarily investigated. The addition of quercetin changed the composition of the exopolysaccharides and the molecular weight (Mw). In addition, the antioxidant activity of Monascus exopolysaccharides was monitored using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS+), and -OH. Monascus exopolysaccharides have good scavenging ability of DPPH and -OH. Furthermore, quercetin increased the scavenging ABTS+ ability. Overall, these findings provide a potential rationale for the application of quercetin in improving the EPS yield.

Production and functional characteristics of exopolysaccharide by Lactobacillus plantarum co-cultivation with Saccharomyces cerevisiae

Exopolysaccharides (EPS) are well-known biopolymers secreted by several lactic acid bacteria with combination of various strains. The aim of this study is to increase EPS production by co-culturing Lactobacillus plantarum ATCC 8014 with Saccharomyces cerevisiae ICA-Y01 and study the changes in the functional characteristics of the EPS from both cultivations. In this study, the production and functional characteristics of EPS from co-cultivation culture of L. plantarum ATCC 8014 with S. cerevisiae ICA-Y01 were evaluated. The co-cultivation of L. plantarum ATCC 8014 with S. cerevisiae ICA-Y01was markedly increased EPS production up to 55.84% with 6.8 g/l yield after 20 hours cultivation. The pH of the co-cultivation culture was remained constantly at 5.2 until the end of cultivation. Furthermore, co-cultivation under pH 6 in the 16L bioreactor showed a higher growth rate of 0.214 h-1 and EPS production increased up to 104.44% when compared with single cultivation of L. plantarum ATCC 8014. This result clearly indicates the importance of growing the cells in the controlled pH condition when cultivated with S. cerevisiae ICA-Y01 to enhance EPS production. The functional characteristics of EPS secreted from both cultivation strategies were also evaluated. FT-IR spectroscopy confirmed EPS presence from both cultivations, indicating functional group of the polysaccharide with D-glucose units bound by α-(1→6). The EPS production from single cultivation showed a higher DPPH radical scavenging activity (88.21%) and IC50 (19.57%) as compared to EPS produced from co-cultivation with DPPH scavenging exhibited 32.45% with no IC50 value detected. Furthermore, solubility and water uptake of EPS from single cultivation are higher in comparison to co-cultivation. In conclusion, higher efficiency in the bioactivity of EPS from the single cultivation of L. plantarum ATCC 8014 was confirmed even though the EPS yield is low as compared to EPS synthesis through inter-kingdom cultivation.

Arsenic Adsorption and Toxicity Reduction of An Exopolysaccharide Produced by Bacillus licheniformis B3-15 of Shallow Hydrothermal Vent Origin

Exopolysaccharide (EPS) production represents an adaptive strategy developed by extremophiles to cope with environmental stresses. The EPS-producing Bacillus licheniformis B3-15, of shallow marine vent origin (Vulcano Island, Italy), was previously reported as tolerant to arsenate (AsV). In this study, we evaluated: (i) the increasing production of EPS by Bacillus licheniformis B3-15 in the novel SG17 medium; (ii) the arsenic absorption capacity of the EPS by mass spectroscopy; (iii) the functional groups of EPS interacting with As by ATR-FTIR spectroscopy; and (iv) the ability of EPS to prevent arsenic toxicity by the bioluminescent assay. The EPS yield (240 mg L−1) was 45% higher than previously reported. The EPS was mainly constituted of disaccharide repeating units with a manno-pyranosidic configuration and low protein content, attributed to the poly-gamma glutamic acid component as evidenced by NMR analysis. ATR-FTIR spectra indicated that the functional groups of the EPS (O–H, C=O, C–O and C=C and N–O) were involved in the adsorption of the arsenic cations, with greater interactions between EPS and arsenate (AsV) than arsenite (AsIII). Consequently, the EPS at increasing concentration (100 and 300 µg mL−1) adsorbed AsV more efficiently (20.5% and 34.5%) than AsIII (0.7% and 1.8%). The bioluminescence assay showed that the EPS was not toxic, and its addition reduced the toxicity of both As forms by more than twofold. The crude EPS B3-15 could be used in arsenic bioremediation as a possible eco-friendly alternative to other physical or chemical methods.

Effect of salinity on the biochemical characteristics and antioxidant activity of exopolysaccharide of Porphyridium purpureum FACHB 806

Porphyridium exopolysaccharide (EPS) is a kind of high-value biopolymer with various biological activities secreted by microalgae belonging to Porphyridium genus. Salinity is one of the important environmental factors affecting the growth of microalgae. In order to study the effect of salinity, the yield, biochemical characteristics and antioxidant activity of EPS in Porphyridium purpureum FACHB 806 cultured at four salinity levels (5‰, 20‰, 35‰ and 50‰) were investigated in this study. The results demonstrated that P. purpureum FACHB 806 could grow at all salinity levels. The highest cell density and EPS yield per cell were 6.6 × 107 cells·mL-1 and 29.1 pg·cell-1, which were obtained in the 20‰ and 50‰ salinity, respectively. With the increase of salinity, the percentage of xylose and galactose decreased while the percentage of glucose increased. Among all salinity levels, the 5‰ salinity group achieved the maximum contents of total carbohydrate and uronic acid of EPS, and the 50‰ salinity obtained the highest protein content of EPS. Compared to the 20‰ and 35‰ salinity groups, EPS of the 5‰ and 50‰ salinity showed stronger hydroxyl radical scavenging ability. These results indicated that salinity could influence the yield, biochemical composition and antioxidant activity of EPS, which will provide a new strategy to improve the yield and antioxidant activity of EPS.

Exploring the Identity and Properties of Two Bacilli Strains and their Potential to Alleviate Drought and Heavy Metal Stress

Naturally available plant growth-promoting rhizobacteria (PGPR) have 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzymes, and are capable of processing the plant-borne ACC by converting it into α-ketobutyrate and ammonia. Thus, the PGPRs help in the depletion of ethylene levels, and enhance abiotic stress tolerance in plants. In the present study, two rhizobacterial strains, i.e., Bacillus cereus and B. haynesii, isolated from Vigna mungo and Phaseolus vulgaris, were used. These strains were taxonomically identified by 16S rDNA sequencing as B. cereus and B. haynesii, with NCBI accession numbers LC514122 and LC 514123, respectively. The phylogeny of these strains has also been worked out based on homology, with data available on NCBI GenBank. The strains were screened for their plant growth-promoting traits, and quantified in the same way. The enzymatic activity and molecular weight of the ACC deaminase obtained from both bacterial strains have also been determined. An in vitro drought tolerance study was done by using PEG 6000. These bacterial strains exhibited higher ACC deaminase activity (~5 to 6 µmol/mL), exopolysaccharide yield (15 to 18 mg/10 mL protein), and indole acetic acid (27–32 µg/mL). These characteristics indicate that the bacterial strains under present study may be helpful in enhancing the drought tolerance of the crops with enhanced yield. Bacillus cereus has been found to be a tolerant strain to As, Ba, and Ni, based on the plate assay method, and so it has the potential to be used as biofertilizer in fields affected by these metals.

L. A. Ulakhanova, S. V. Gomboeva, V. Zh. Tsyrenov

Silicate bacteria have a wide biotechnological potential, they produce a large number of biologically active substances: enzymes that destroy silicates; fungicidal and antimicrobial compounds; phytohormones and exopolysaccharides (EPS). At the same time, they are able to use silicon-containing minerals as a source of additional energy. The literature provides studies on the destruction of polysilicon compounds by silicate bacteria of the speciessilicate bacteria. They are capable of destroying quartz, aluminosilicates with the release of Si, K and other elements. There is also information about stimulating the reproduction of silicate bacteria when growing on mineral media with the addition of silicon-containing components. At the same time, the influence of polysilicon compounds on the synthesis of exopolysaccharides by silicate bacteria is not considered. The exoglycans released by them are used in various industries: mining, oil production, pharmaceutical, food and cosmetic. The studies used isolated pure cultures of silicate bacteria, the biosynthetic activity of which was compared with strains of Paenibacillus mucilaginosus B7519 and B4901 (VKPM, GosNIIgenetics). Bacteria were isolated from the soils and sand of the Baikal region. The influence of silicon-containing components (bentonite, quartz sand) of the nutrient medium on crop growth and EPS synthesis was investigated. The positive effect of silicate minerals on the growth of isolated strains and museum cultures of P. mucilaginosus has been confirmed. Strain B-4901 had the highest amount of CFU/ml on nutrient media with both quartz sand and bentonite. The influence of siliconcontaining components on the EPS yield of the studied microorganisms has been established. The highest EPS yield was observed in the VSGUTU-2 strain on a nutrient medium with the addition of quartz sand, and the B7519 strain had the best synthesis on a medium with the addition of bentonite. The VSGUTU-1 strain showed the same yield of exopolysaccharides on two variants of media with silicon-containing components, whereas the amount of EPS in the B4901 strain did not increase with the addition of bentonite and quartz sand. The lowest EPS yields were on nutrient media without the addition of a silicon source.

Characterization and in vitro anticancer potential of exopolysaccharide extracted from a freshwater diatom Nitzschia palea (Kütz.) W.Sm. 1856

Diatoms are photoautotrophic microalgae classified under class Bacillariophyceae, engulfed by hard silicate frustules, which give mechanical support and protection from bacterial infections. They exude polysaccharides extracellularly that help them with their gliding motion (locomotion). However, the bioactivity of such compounds was least explored from freshwater diatoms. In the present study, a single species of pennate diatom identified as Nitzschia palea was isolated and molecularly characterized by 18S rRNA smaller subunit gene (partial) sequencing and submitted to GenBank NCBI and accession number retrieved as ON360983. Based on logarithmic growth curve analysis, the exponential phase was obtained from 3rd to 4th day of diatom culture. The exopolysaccharide was extracted by the hot-water extraction method, and characterized by FT-IR. The total yield of exopolysaccharide from Nitzschia palea was estimated as 1.56 mg in 100 mL of culture after 7 days of incubation. The estimated carbohydrate content was 51.35 µg/100 µL. The monosaccharide constituents were determined by acid hydrolysis of exopolysaccharide, silylation (derivatization), followed by GC–MS analysis and tabulated. The extracted exopolysaccharide was evaluated for its anti-cancer potential against the Human Adenocarcinoma lung cancer cell line (A549) and the estimated IC50 value was 62.64 µg/mL. Acridine orange staining assay and DNA fragmentation assay also confirmed the apoptotic activity of exopolysaccharide derived from the diatom Nitzschia palea.

Optimization of the fermentation process, characterization and antioxidant activity of exopolysaccharides produced from Azotobacter As101

Azotobacter was selectively isolated and purified from the soil samples of Xinjiang Salt Lake Scenic spot, the fermentation technology of exopolysaccharides (EPS) by Azotobacter was optimized, and the antioxidant activity of exopolysaccharides (EPS) was studied. The bacteria were isolated and purified from the soil samples by the scribing method and the 16SrRNA gene was used for molecular identification. The carbon source, fermentation time, inoculation amount and pH of target bacteria in the exopolysaccharides (EPS) fermentation process were optimized through single-factor experiments and their antioxidant activity was measured. Eight types of Azotobacter were isolated and purified from the soil samples of Salt Lake scenic spot. Among them, As101, which showed 99.58% homology with Azotobacter salinestris, was selected as the target strain. Through single-factor experiments which used exopolysaccharides (EPS) yield and exopolysaccharides content as indexes, the optimal conditions for the As101 fermentation process were determined as follows: fermentation temperature 35, fermentation time 96h, pH 7 and mannitol as carbon source. Exopolysaccharides content from Azotobacter salinestris was 61.35% and the yield was 6.34 g/L. The results of the exopolysaccharides (EPS) antioxidant activity experiment under optimal conditions showed that As101 EPS had excellent scavenging ability against DPPH free radical, ABTS free radical and hydroxyl free radical, with IC50 values of 6.11 mg/ml, 2.42 mg/ml and 9.57 mg/ml, respectively. As101 with high yield and high exopolysaccharides content was isolated from saline soil in a special environment of Xinjiang, and the EPS obtained showed excellent antioxidant activity. The Azotobacter found in this study would provide the material basis for further opening up the adsorption of exopolysaccharides on heavy metals and the improvement of saline-alkali soil and contribute to further understanding of the structure and other activities of exopolysaccharides derived from Azotobacter.

Application of exopolysaccharide directionally synthesized by Xanthomonas campestris as the green selective depressant for the clean flotation of talc: Statistical optimization and mechanism analysis

During froth flotation, the more non-polar, friable talc (Mg3(Si2O5)2(OH)2) usually adheres to the surface of sulfide ore and floats up, causing difficulties in flotation separation and subsequent industrial treatment. Microbial flotation as a green separation method avoids chemical contamination due to the limited selectivity and high agent consumption of the currently used inhibitors. Recent studies have found that exopolysaccharides produced by Xanthomonas campestris (X.c) could be used as inhibitors for the efficient flotation separation of talc from chalcopyrite. Therefore, this paper is the first attempt to optimize the molecular structure of exopolysaccharides and the optimal culture parameters of this strain to synthesize a green depressant for efficient flotation of talc, and also to explore in depth the mechanism of its selective inhibition of talc. Results of fermentation condition experiments and Fourier transform infrared analysis showed that the exopolysaccharides with the presence of polar groups (—OH and –COOH) significantly inhibited the floatability of talc. 1H Nuclear magnetic resonance further identified the active components of polar groups in the polysaccharide structure as hydroxyl groups, glucuronic acid, and pyruvic acid. Furthermore, the fermentation parameters were optimized by response surface methodology and increased the yield of exopolysaccharides by 5.55 g/L compared with before optimization. Flotation experiments on mixed ore confirmed the excellent selective inhibition of the synthesized exopolysaccharide at pH 7 and a 60 mg/L concentration. The contact angle test showed a significant decrease from 65.04° to 51.77° on the talc surface after the reaction with 60 mg/L concentration of exopolysaccharides. Atomic force microscopy characterization directly revealed the multilayer adsorption of exopolysaccharides on the talc surface, as well as a high coverage of 50.88%.

Effects of galactosyltransferase on EPS biosynthesis and freeze-drying resistance of Lactobacillus acidophilus NCFM

Galactosyltransferase (GalT) is an important enzyme in synthesizing exopolysaccharide (EPS), the major polymer of biofilms protecting cells from severe conditions. However, the contribution to, and regulatory mechanism of GalT, in stressor resistance are still unclear. Herein, we successfully overexpressed GalT in Lactobacillus acidophilus NCFM by genetic engineering. The GalT activity and freeze-drying survival rate of the recombinant strain were significantly enhanced. The EPS yield also increased by 17.8%, indicating a positive relationship between freeze-drying resistance and EPS. RNA-Seq revealed that GalT could regulate the flux of the membrane transport system, pivotal sugar-related metabolic pathways, and promote quorum sensing to facilitate EPS biosynthesis, which enhanced freeze-drying resistance. The findings concretely prove that the mechanism of GalT regulating EPS biosynthesis plays an important role in protecting lactic acid bacteria from freeze-drying stress.

Probiotic Properties of Weissella confusa PP29 on Hibiscus sabdariffa L. Media

To date, there are very few data regarding new efficient probiotics’ development with their own prebiotic substrate. All commercial products contain prebiotic substrate that was previously purified from external sources and added to the final product. The present study describes Weissella confusa strain fermentations in media with different anthocyanin concentrations from Hibiscus sabdariffa L., in order to increase the exopolysaccharide (EPS) yield, leading to augmented probiotic and prebiotic properties. The extracted and purified EPS were characterized by Gel permeation chromatography, Fourier-transform infrared, and nuclear magnetic resonance spectroscopy; thermal analysis measurements and the whole fermented media’s probiotic properties were evaluated by testing low pH and bile salt resistance, along with hydrophobicity and auto-aggregation capacity. The anthocyanins increased biomass and EPS yields and the high EPS molecular mass improved nutrient access by allowing a good microbial suspension in media. The confirmed dextran structure provides media biocompatibility and very good probiotic properties compared with existing literature. Simultaneously, the anthocyanins in media protected the strain cells against low pH and bile salt compared with the control fermentation. These very good results show that the whole fermented culture media is suitable for further in-vitro and in-vivo studies regarding its probiotic and prebiotic activity.

Study of the Polysaccharide Production by the Microalga Vischeria punctata in Relation to Cultivation Conditions.

Vischeria punctata is a unicellular microalga that has industrial potential, as it can produce substances with beneficial properties. Among them, endopolysaccharides (accumulated in cells) and exopolysaccharides (released by cells into the culture medium) are of particular interest. This study aimed to investigate the effect of nutrient medium composition on the growth of V. punctata biomass and the synthesis of polysaccharides by microalgae. The effect of modifying a standard nutrient medium and varying cultivation parameters (temperature, time, and extractant type) on the yield of exopolysaccharides produced by the microalgae V. punctate was investigated. The methods of spectrophotometry, ultrasonic extraction, and alcohol precipitation were used in the study. It was found that after 61 days of cultivation, the concentration of polysaccharides in the culture medium was statistically significantly higher (p <0.05) when using a Prat nutrient medium (984.9 mg/g d.w.) than BBM 3N (63.0 mg/g d.w.). It was found that the increase in the V. punctata biomass when cultivated on different nutrient media did not differ significantly. The maximum biomass values on Prat and BBM 3N media were 1.101 mg/g d.w. and 1.120 mg/g d.w., respectively. Neutral sugars and uronic acids were found in the culture media. It follows on from the obtained data that the modified PratM medium was more efficient for extracting polysaccharides from V. punctata. The potential of microalgae as new sources of valuable chemicals (polysaccharides), which can be widely used in technologies for developing novel functional foods, biologically active food supplements, and pharmaceutical substances, was studied.

Rhizobia exopolysaccharides: promising biopolymers for use in the formulation of plant inoculants.

Inoculants with beneficial microorganisms comprise both selected strains and carriers that ensure a favorable microenvironment for cell survival and stability. Formulations of inoculants using synthetic polymers as carriers are common. However, only a few studies are available in the literature regarding the formulation of inoculants using natural biomolecules as carriers. Exopolysaccharides (EPS) are biomolecules produced by a vast array of microbial species, including symbiotic nitrogen-fixing bacteria, commonly known as rhizobia. EPS perform several functions, such as the protection against the deleterious effects of diverse environmental soil stresses. Two Rhizobium tropici strains and one Paraburkholderia strain were selected after semiquantitative analysis by scanning electron microscopy (SEM) of their EPS production in liquid YMA medium. Their EPS were characterized through a series of analytical techniques, aiming at their use in the formulation of plant inoculants. In addition, the effect of the carbon source on EPS yield was evaluated. Multi-stage fragmentation analysis showed the presence of xylose, glucose, galactose, galacturonic acid, and glucuronic acid in EPS chemical composition, which was confirmed by FT-IR spectra and 13C NMR spectroscopy. Thermal stability (thermogravimetric) was close to 270°C and viscosity ranged from 120 to 1053.3mPa.s. Surface morphology (SEM) was rough and irregular, with a cross-linked spongy matrix, which, together with the hydrophilic functional groups, confers water holding capacity. The present study showed that the three EPS have potential as microorganism carriers for formulation of microbial inoculants to be applied in plants.

Efficient biosynthesis of exopolysaccharide in Candida glabrata by a fed-batch culture.

Polysaccharides are important natural biomacromolecules. In particular, microbial exopolysaccharides have received much attention. They are produced by a variety of microorganisms, and they are widely used in the food, pharmaceutical, and chemical industries. The Candida glabrata mutant 4-C10, which has the capacity to produce exopolysaccharide, was previously obtained by random mutagenesis. In this study we aimed to further enhance exopolysaccharide production by systemic fermentation optimization. By single factor optimization and orthogonal design optimization in shaking flasks, an optimal fermentation medium composition was obtained. By optimizing agitation speed, aeration rate, and fed-batch fermentation mode, 118.6 g L−1 of exopolysaccharide was obtained by a constant rate feeding fermentation mode, with a glucose yield of 0.62 g g−1 and a productivity of 1.24 g L−1 h−1. Scaling up the established fermentation mode to a 15-L fermenter led to an exopolysaccharide yield of 113.8 g L−1, with a glucose yield of 0.60 g g−1 and a productivity of 1.29 g L−1 h−1.