Bioprospecting for new exopolysaccharide-producing microalgae of marine origin.

Microalgae are photosynthetic organisms that can produce biomolecules with industrial interest, including exopolysaccharides (EPS). Due to their structural and compositional diversity, microalgae EPS present interesting properties that can be considered in cosmetic and/or therapeutic areas. Seven microalgae strains from three different lineages, namely Dinophyceae (phylum Miozoa), Haptophyta, and Chlorophyta, were investigated as EPS producers. All strains were found to be EPS producers, though the highest EPS yield was obtained for Tisochrysis lutea, followed by Heterocapsa sp. (126.8 and 75.8 mg L-1, respectively). Upon assessment of the polymers' chemical composition, significant contents of unusual sugars, including fucose, rhamnose, and ribose, were found. Heterocapsa sp. EPS stood out due to its high content of fucose (40.9 mol%), a sugar known to confer biological properties to polysaccharides. The presence of sulfate groups (10.6-33.5 wt%) was also noticed in the EPS produced by all microalgae strains, thus contributing to the possibility that these EPS might have biological activities worth exploring.

Evaluation of two fungal exopolysaccharides as potential biomaterials for wound healing applications.

Microbial exopolysaccharides (EPSs) are mostly produced by bacteria and fungi and have potential use in the production of biomedical products such as nutraceuticals and in tissue engineering applications. The present study investigated the in vitro biological activities and in vivo wound healing effects of EPSs produced from a Sclerotium-forming fungus (Sclerotium glucanicum DSM 2159) and a yeast (Rhodosporidium babjevae), denoted as scleroglucan (Scl) and EPS-R, respectively. EPS yields of 0.9 ± 0.07 g/L and 1.11 ± 0.4 g/L were obtained from S. glucanicum and R. babjevae, respectively. The physicochemical properties of the EPSs were characterized using infrared spectroscopy and scanning electron microscopy. Further investigations of the biological properties showed that both EPSs were cytocompatible toward the human fibroblast cell line and demonstrated  hemocompatibility. Favorable wound healing capacities of the EPSs (10 mg/mL) were also established via in vivo tests. The present study therefore showed that the EPSs produced by S. glucanicum and R. babjevae have the potential use as biocompatible components for the promotion of dermal wound healing.

Effects of GSM 1800 band radiation on composition, structure and bioactivity of exopolysaccharides produced by yoghurt starter cultures.

In this study, the effects of GSM 1800 band radiation on composition, structure and bioactivity of exopolysaccharides (EPSs) produced by Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus were determined. For this, GSM 1800 band radiation was applied to both cultures and characteristics of EPSs extracted from the control groups (K) and the radiation stressed groups (R) were determined. An alteration in the chemical composition of the EPSs was observed and EPS production levels and molecular weights of the EPSs increased following the GSM 1800 band radiation application. Alterations in the functional groups, thermal and morphological characteristics of EPSs following the GSM 1800 band radiation application were confirmed by FTIR, TGA and SEM analysis, respectively. Importantly no alterations in the antioxidant and antibacterial activity of the EPSs were observed following the radiation application. These results suggested the effects of the GSM radiation on final characteristics of EPSs from yogurt starter cultures.

Exopolysaccharide Carbohydrate Structure and Biofilm Formation by Rhizobium leguminosarum bv. trifolii Strains Inhabiting Nodules of Trifoliumrepens Growing on an Old Zn-Pb-Cd-Polluted Waste Heap Area.

Heavy metals polluting the 100-year-old waste heap in Boleslaw (Poland) are acting as a natural selection factor and may contribute to adaptations of organisms living in this area, including Trifolium repens and its root nodule microsymbionts-rhizobia. Exopolysaccharides (EPS), exuded extracellularly and associated with bacterial cell walls, possess variable structures depending on environmental conditions; they can bind metals and are involved in biofilm formation. In order to examine the effects of long-term exposure to metal pollution on EPS structure and biofilm formation of rhizobia, Rhizobium leguminosarum bv. trifolii strains originating from the waste heap area and a non-polluted reference site were investigated for the characteristics of the sugar fraction of their EPS using gas chromatography mass-spectrometry and also for biofilm formation and structural characteristics using confocal laser scanning microscopy under control conditions as well as when exposed to toxic concentrations of zinc, lead, and cadmium. Significant differences in EPS structure, biofilm thickness, and ratio of living/dead bacteria in the biofilm were found between strains originating from the waste heap and from the reference site, both without exposure to metals and under metal exposure. Received results indicate that studied rhizobia can be assumed as potentially useful in remediation processes.

The exopolysaccharide-eDNA interaction modulates 3D architecture of Bacillus subtilis biofilm.

BACKGROUND: Bacterial biofilms are surface-adherent microbial communities in which individual cells are surrounded by a self-produced extracellular matrix of polysaccharides, extracellular DNA (eDNA) and proteins. Interactions among matrix components within biofilms are responsible for creating an adaptable structure during biofilm development. However, it is unclear how the interactions among matrix components contribute to the construction of the three-dimensional (3D) biofilm architecture. RESULTS: DNase I treatment significantly inhibited Bacillus subtilis biofilm formation in the early phases of biofilm development. Confocal laser scanning microscopy (CLSM) and image analysis revealed that eDNA was cooperative with exopolysaccharide (EPS) in the early stages of B. subtilis biofilm development, while EPS played a major structural role in the later stages. In addition, deletion of the EPS production gene epsG in B. subtilis SBE1 resulted in loss of the interaction between EPS and eDNA and reduced the biofilm biomass in pellicles at the air-liquid interface. The physical interaction between these two essential biofilm matrix components was confirmed by isothermal titration calorimetry (ITC). CONCLUSIONS: Biofilm 3D structures become interconnected through surrounding eDNA and EPS. eDNA interacts with EPS in the early phases of biofilm development, while EPS mainly participates in the maturation of biofilms. The findings of this study provide a better understanding of the role of the interaction between eDNA and EPS in shaping the biofilm 3D matrix structure and biofilm formation.

Utilization of kitchen waste for production of pullulan to develop biodegradable plastic.

Pullulan has many useful characteristics but, its high cost limits its potential applications. In the present work, kitchen waste (KW), which otherwise has zero commercial value, was evaluated for the economical production of pullulan. Before fermentation, the KW was hydrolyzed into free sugars using an in-house produced cocktail of enzymes. During hydrolysis, 46 ± 3.5 g/l and 31 ± 2.2 g/l of total reducing sugars and glucose were released, respectively. Hydrolyzed kitchen waste was then used as substrate for fermentation by Aureobasidium pullulans MTCC 2013 yielding 20.46 ± 2.01 g/l pullulan. Further, effect of different nitrogen sources was evaluated and yeast extract (3%) was found to be the best, yielding (24.77 ± 1.06 g/l) exopolysaccharide (EPS). The pullulan produced from KW was characterized in terms of organoleptic properties, physical strength, Fourier-transform infrared spectroscopy (FTIR), and H nuclear magnetic resonance (H NMR) analysis. The results corroborated well with commercial pullulan. The biodegradable nature and water solubility of the film developed from pullulan was also confirmed. To the best of our knowledge, this is the first report on the validation of the biodegradability of in-house produced pullulan. Thus, kitchen waste appears to be a promising option for economical pullulan production. Additionally, the method may also prove to be helpful for managing the increasing load of municipal solid waste in an eco-friendly and scientific way.

Health-promoting benefits of low-fat akawi cheese made by exopolysaccharide-producing probiotic Lactobacillus plantarum isolated from camel milk.

Lactic acid bacteria isolated from camel milk exhibit remarkable probiotic and exopolysaccharide (EPS)-producing characteristics. The health-promoting benefits of exopolysaccharide-producing probiotic Lactobacillus plantarum isolated from camel milk used for making low-fat akawi cheese were investigated. Three low-fat akawi cheeses were made using traditional culture (non-EPS-producing, EPS-), commercial EPS-producing (MEPS+), and camel milk EPS-producing (CEPS+) cultures. α-Amylase and α-glucosidase inhibitory activities, antioxidant activities, angiotensin-converting enzyme (ACE) inhibition, and antiproliferative activity were determined. Cheese made with CEPS+ culture exhibited comparable α-amylase inhibition to that of cheeses made with MEPS+. Scavenging rates of cheese made with EPS+ cultures were higher than those of cheese made with EPS- cultures. The percentage of α-glucosidase inhibition ranged from >45% at 0 d to ∼55% at 21 d of storage. After 7 d of storage, the scavenging rate in CEPS+ cheese increased >60% by ABTS assay [2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid)] and >20% by DPPH assay (1,1-diphenyl-2-picrylhydrazyl). Throughout storage, cheese made with EPS+ cultures showed higher ACE-inhibition activity compared with EPS- cultures. Cheese made with CEPS+ showed ACE inhibition >70% after 7 d of storage. Antiproliferation activity of CEPS+ cheese increased from 38 to 48% during 7 d of storage and was maintained above 45% with prolonged storage. Low-fat akawi cheese produced with these cultures exhibited similar or greater health-promoting benefits compared with cheese made using commercial starter cultures. Therefore, incorporation of these cultures in food is promising for commercial uses.

Biological responses of symbiotic Rhizobium radiobacter strain VBCK1062 to the arsenic contaminated rhizosphere soils of mung bean.

The rationale could be that mung bean is cultivated in areas of arsenic contamination and therefore it is worth investigating how Rhizobium is impacted by arsenic exposure. The objective(s) of the study deals with relationship between Rhizobium metal tolerance and its adaptations to metal stressed environment. The selected strain was recovered from root nodules of Vigna radiata, based on viscous EPS production and arsenic tolerant capacity, identified as R. radiobacter by 16S rDNA sequencing. Batch studies were performed to evaluate toxic effects of heavy metal ions in decreasing order of MIC As(V) (10mM), Cu(1.5mM), Pb(0.18mM), Cr(0.1mM), Ni(0.08mM) and Cd(0.04mM). Scanning electron microscopy analysis of Arsenic resistant strain revealed evident changes in cell morphology. SDS-PAGE results showed altered expression of proteins in response to arsenate. One unique protein of approximately 21kDa was highly expressed in 5mM arsenate, but same protein was down regulated in 10mM arsenate. The exopolysaccharide components such as total carbohydrates, proteins and uronic acids were significantly enhanced by 41%, 25% and 33% (P Value <0.05) and also produced EPS under Arsenic stressed conditions. Fourier transformed spectroscopy analysis demonstrated arsenic metal ion-EPS interactions. The results obtained from SEM-EDS analysis clearly revealed mucous nature of Rhizobial-EPS surrounding bacterial cells and confirmed the role of EPS in arsenate sequestration (10% as weight). Interestingly total arsenate uptake by strain VBCK1062 in whole-cell pellet and EPS were 0.045mg and 0.068mgg-1 of biomass respectively. Thus these results significantly contribute to better understanding of plant-metal-microbe interactions, cellular-metabolic changes and As-enhanced EPSs, hence can serve as potential bioremediation agent for As-contaminated agrogeoecosystems.

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

BACKGROUND: 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. RESULTS: 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. CONCLUSION: 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.

Structure and properties of the exopolysaccharide isolated from Flavobacterium sp. Root935.

Flavobacterium strains exert a substantial influence on roots and leaves of plants. However, there is still limited understanding of how the specific interactions between Flavobacterium and their plant hosts are and how these bacteria thrive in this competitive environment. A crucial step in understanding Flavobacterium - plant interactions is to unravel the structure of bacterial envelope components and the molecular features that facilitate initial contact with the host environment. Here, we have revealed structure and properties of the exopolysaccharides (EPS) produced by Flavobacterium sp. Root935. Chemical analyses revealed a complex and interesting branched heptasaccharidic repeating unit, containing a variety of sugar moieties, including Rha, Fuc, GlcN, Fuc4N, Gal, Man and QuiN and an important and extended substitution pattern, including acetyl and lactyl groups. Additionally, conformational analysis using molecular dynamics simulation showed an extended hydrophobic interface and a distinctly elongated, left-handed helicoidal arrangement. Furthermore, properties of the saccharide chain, and likely the huge substitution pattern prevented interaction and recognition by host lectins and possessed a low immunogenic potential, highlighting a potential role of Flavobacterium sp. Root935 in plant-microbial crosstalk.

Effects of genes required for exopolysaccharides biosynthesis in Lacticaseibacillus paracasei S-NB on cell surface characteristics and probiotic properties.

The cell surface of lactic acid bacteria (LAB) plays an essential role in cell-cell and cell-host interactions. Exopolysaccharides (EPSs) are produced on the cell surface of LAB or in the surrounding medium and are considered to be in favor of the strain- specific probiotic surface characteristics. In this work, the structure features of EPS from Lacticaseibacillus paracasei S-NB were analyzed preliminarily, and the genes involved in EPS biosynthesis of S-NB strain were hypothesized and annotated, and their role in phenotypic characteristics were demonstrated by gene deletion analysis. Four mutant strains with deletion of crucial genes involved in EPS synthesis were analyzed for strain characteristics that are closely related to their ability to interact with the host intestinal epithelium cells, including strain surface characteristics and viability under the gastrointestinal stress conditions (both acid and bile stress). Furthermore, the adherence and immunomodulatory properties of wild-type S-NB and its mutant strains were compared using Caco-2 and RAW 264.7 cell lines, respectively. Taken together, the results indicated the importance of genes associated with EPS biosynthesis in L. paracasei S-NB as a determinant in strain surface characteristics and cell-host interaction, especially for S-NB_2176 (responsible for EPS polymerization) and S-NB_2175 (responsible for CpsD/CapB family tyrosine-protein kinase).

Effects of the Exopolysaccharide from Lactiplantibacillus plantarum HMX2 on the Growth Performance, Immune Response, and Intestinal Microbiota of Juvenile Turbot, Scophthalmus maximus.

In this study, the exopolysaccharide (EPS) from Lactiplantibacillus plantarum (HMX2) was isolated from Chinese Northeast Sauerkraut. Its effects on juvenile turbot were investigated by adding different concentrations of HMX2-EPS (C: 0 mg/kg, H1: 100 mg/kg, H2: 500 mg/kg) to the feed. Compared with the control group, HMX2-EPS significantly improved the growth performance of juvenile turbot. The activities of antioxidant enzymes, digestive enzymes, and immune-related enzymes were significantly increased. HMX2-EPS could also increase the secretion of inflammatory factors and enhance the immune response of turbot by regulating the IFN signal transduction pathway and exhibit stronger survival rates after the A. hydrophila challenge. Moreover, HMX2-EPS could improve the diversity of intestinal microbiota in juvenile fish, increase the abundance of potential probiotics, and reduce the abundance of pathogenic bacteria. The function of gut microbes in metabolism and the immune system could also be improved. All results showed better effects with high concentrations of HMX2-EPS. These results indicated that HMX2-EPS supplementation in the diet could promote growth, improve antioxidant activity, digestive capacity, and immunity capacity, and actively regulate the intestinal microbiota of juvenile turbot. In conclusion, this study might provide basic technical and scientific support for the application of L. plantarum in aquatic feed.

Exopolysaccharide from the yeast Papiliotrema terrestris PT22AV for skin wound healing.

INTRODUCTION: Exopolysaccharides (EPSs) are high-value functional biomaterials mainly produced by bacteria and fungi, with nutraceutical, therapeutic and industrial potentials. OBJECTIVES: This study sought to characterize and assess the biological properties of the EPS produced by the yeast Papiliotrema terrestris PT22AV. METHODS: After extracting the yeast's DNA and its molecular identification, the EPS from P. terrestris PT22AV strain was extracted and its physicochemical properties (structural, morphological, monosaccharide composition and molecular weight) were characterized. The EPS's in vitro biological activities and in vivo wound healing potential were also evaluated. RESULTS: The obtained EPS was water-soluble and revealed an average molecular weight (Mw) of 202 kDa. Mannose and glucose with 97% and 3% molar percentages, respectively, constituted the EPS. In vitro antibacterial activity analysis of the extracted EPS exhibited antibacterial activity (>80%) against Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis at a concentration of 2 mg/mL. The EPS showed cytocompatibility against the human fibroblast and macrophage cell lines and the animal studies showed a dose-dependent wound healing capacity of the EPS with higher wound closure at 10 mg/mL compared to negative and positive control after 14 days. CONCLUSION: The EPS from P. terrestris PT22AV could serve as a promising source of biocompatible macromolecules with potential for skin wound healing.

Structural and Functional Characterization of Exopolysaccharide Produced by a Novel Isolate Bacillus sp. EPS003.

An exopolysaccharide (EPS)-producing soil bacterium was isolated and characterized using 16S rRNA as Bacillus sp. EPS003. EPS was precipitated using ethanol and % composition of total carbohydrate, and protein was determined. Monosaccharide composition was identified using thin layer chromatography (TLC), and it was found to be a levan. Fourier transform infrared (FTIR) spectrum revealed the peaks for carboxyl, hydroxyl, and amide functional groups. 1H nuclear magnetic resonance (NMR) spectrum further confirmed the presence of fructose monomer. Field emission scanning electron microscopic images (FE-SEM) revealed porous and amorphous characteristics of EPS which was further confirmed with broad peaks in X-ray diffraction (XRD) spectrum. Elemental composition was determined using energy-dispersive X-ray analysis (EDAX). Thermogravimetric analysis (TGA) of EPS resulted in a residual mass of 33.81% at 548 °C indicating high thermal stability. In addition, solubility index and water-holding capacity of EPS were found to be 56% and 264%, respectively, making EPS suitable for various applications. Further, antioxidant potential of EPS was studied using hydroxyl and DPPH radical scavenging assays. In vitro cytotoxicity assessment using L929 cells and SK-MEL-3 cell lines clearly indicated that the EPS produced by the novel isolate Bacillus sp. EPS003 could serve as a potential anticancer agent.

Selenium Bio-Nanocomposite Based on Alteromonas macleodii Mo169 Exopolysaccharide: Synthesis, Characterization, and In Vitro Antioxidant Activity.

In this study, the novel exopolysaccharide (EPS) produced by the marine bacterium Alteromonas macleodii Mo 169 was used as a stabilizer and capping agent in the preparation of selenium nanoparticles (SeNPs). The synthesized nanoparticles were well dispersed and spherical with an average particle size of 32 nm. The cytotoxicity of the EPS and the EPS/SeNPs bio-nanocomposite was investigated on human keratinocyte (HaCaT) and fibroblast (CCD-1079Sk) cell lines. No cytotoxicity was found for the EPS alone for concentrations up to 1 g L-1. A cytotoxic effect was only noticed for the bio-nanocomposite at the highest concentrations tested (0.5 and 1 g L-1). In vitro experiments demonstrated that non-cytotoxic concentrations of the EPS/SeNPs bio-nanocomposite had a significant cellular antioxidant effect on the HaCaT cell line by reducing ROS levels up to 33.8%. These findings demonstrated that the A. macleodii Mo 169 EPS can be efficiently used as a stabilizer and surface coating to produce a SeNP-based bio-nanocomposite with improved antioxidant activity.

Preparation of Porous Scaffold Based on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) and FucoPol.

This work focused on the development of porous scaffolds based on biocomposites comprising two biodegradable and biocompatible biopolymers: a terpolyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (PHBHVHHx), and the bacterial polysaccharide FucoPol. The PHBHVHHx terpolymer was composed of 3-hydroxybutyrate (55 wt%), 3-hydroxyvalerate (21 wt%), and 3-hydroxyhexanoate (24 wt%). This hydrophobic polyester has low crystallinity and can form elastic and flexible films. Fucopol is a fucose-containing water-soluble polysaccharide that forms viscous solutions with shear thinning behavior and has demonstrated emulsion-forming and stabilizing capacity and wound healing ability. Emulsion-templating was used to fabricate PHA-based porous structures in which FucoPol acted as a bioemulsifier. Compared with the scaffolds obtained from emulsions with only water, the use of FucoPol aqueous solutions resulted in structures with improved mechanical properties, namely higher tensile strength (4.4 MPa) and a higher Young's Modulus (85 MPa), together with an elongation at break of 52%. These features, together with the scaffolds' high porosity and pore interconnectivity, suggest their potential to sustain cell adhesion and proliferation, which is further supported by FucoPol's demonstrated wound healing ability. Therefore, the developed PHBHVHHx:FucoPol scaffolds arise as innovative porous bioactive structures with great potential for use in tissue engineering applications.

Characterisation of Films Based on Exopolysaccharides from Alteromonas Strains Isolated from French Polynesia Marine Environments.

This work assessed the film-forming capacity of exopolysaccharides (EPS) produced by six Alteromonas strains recently isolated from different marine environments in French Polynesia atolls. The films were transparent and resulted in small colour alterations when applied over a coloured surface (ΔEab below 12.6 in the five different colours tested). Moreover, scanning electron microscopy showed that the EPS films were dense and compact, with a smooth surface. High water vapour permeabilities were observed (2.7-6.1 × 10-11 mol m-1 s-1 Pa-1), which are characteristic of hydrophilic polysaccharide films. The films were also characterised in terms of barrier properties to oxygen and carbon dioxide. Interestingly, different behaviours in terms of their mechanical properties under tensile tests were observed: three of the EPS films were ductile with high elongation at break (ε) (35.6-47.0%), low tensile strength at break (Ꞇ) (4.55-11.7 MPa) and low Young's modulus (εm) (10-93 MPa), whereas the other three were stiffer and more resistant with a higher Ꞇ (16.6-23.6 MPa), lower ε (2.80-5.58%), and higher εm (597-1100 MPa). These properties demonstrate the potential of Alteromonas sp. EPS films to be applied in different areas such as biomedicine, pharmaceuticals, or food packaging.

Characterization and Immunological Activity of Exopolysaccharide from Lacticaseibacillus paracasei GL1 Isolated from Tibetan Kefir Grains.

Two exopolysaccharide fractions (GL1-E1 and GL1-E2) of Lacticaseibacillus paracasei GL1 were isolated with the molecular weights of 3.9 × 105 Da and 8.2 × 105 Da, respectively. Both fractions possessed mannose, glucose, and galactose in molar ratios of 1.16:1.00:0.1, and 3.81:1.00:0.12, respectively. A structural arrangement of two fractions was proposed by methylation, one-dimensional and two-dimensional nuclear magnetic resonance experiments. The backbone of GL1-E1 consisted of →4)-α-D-Glcp(1→, →3,4)-α-D-Manp(1→, →3,6)-α-D-Manp(1→, →6)-α-D-Manp(1→, and →6)-α-D-Galp(1→ with α-D-Glcp at branching point. The backbone of GL1-E2 consisted of →4)-α-D-Glcp(1→, →3,4)-α-D-Manp(1→, →3,6)-α-D-Manp(1→, →6)-α-D-Manp(1→, →6)-α-D-Galp(1→, and →4)-ß-D-Manp(1→, and the side chain also consisted of α-D-Manp residue. In addition, the differential scanning calorimetry (DSC) analysis indicated that both GL1-E1 and GL1-E2 had good thermal stability. Furthermore, the two fractions could promote the viability of RAW264.7 cells and exert an immunomodulatory role by enhancing phagocytosis, increasing nitric oxide (NO) release and promoting the expression of cytokines.

EPS-Producing Lactobacillus plantarum MC5 as a Compound Starter Improves Rheology, Texture, and Antioxidant Activity of Yogurt during Storage

This study evaluated the effects of probiotic Lactobacillus plantarum MC5 on the quality, antioxidant activity, and storage stability of yogurt, to determine its possible application as a starter in milk fermentation. Four groups of yogurt were made with different proportions of probiotic L. plantarum MC5 and commercial starters. The yogurt samples' rheological properties, texture properties, antioxidant activity, storage stability, and exopolysaccharides (EPS) content during storage were determined. The results showed that 2:1 and 1:1 yogurt samples (supplemented with L. plantarum MC5) attained the highest EPS content (982.42 mg/L and 751.71 mg/L) during storage. The apparent viscosity, consistency, cohesiveness, and water holding capacity (WHC) of yogurt samples supplemented with L. plantarum MC5 were significantly higher than those of the control group (p < 0.05). Further evaluation of antioxidant activity revealed that yogurt samples containing MC5 starter significantly increased in DPPH, ABTS, OH, and ferric iron-reducing power. The study also found that adding MC5 can promote the growth of Streptococcus thermophilus. Therefore, yogurt containing L. plantarum MC5 had favorable rheological properties, texture, and health effects. The probiotic MC5 usage in milk fermentation showed adequate potential for industrial application.

Analysis of Myxococcus xanthus Vegetative Biofilms With Microtiter Plates.

The bacterium Myxococcus xanthus forms both developmental and vegetative types of biofilms. While the former has been studied on both agar plates and submerged surfaces, the latter has been investigated predominantly on agar surfaces as swarming colonies. Here we describe the development of a microplate-based assay for the submerged biofilms of M. xanthus under vegetative conditions. We examined the impacts of inoculation, aeration, and temperature to optimize the conditions for the assay. Aeration was observed to be critical for the effective development of submerged biofilms by M. xanthus, an obligate aerobic bacterium. In addition, temperature plays an important role in the development of M. xanthus submerged biofilms. It is well established that the formation of submerged biofilms by many bacteria requires both exopolysaccharide (EPS) and the type IV pilus (T4P). EPS constitutes part of the biofilm matrix that maintains and organizes bacterial biofilms while the T4P facilitates surface attachment as adhesins. For validation, we used our biofilm assay to examine a multitude of M. xanthus strains with various EPS and T4P phenotypes. The results indicate that the levels of EPS, but not of piliation, positively correlate with submerged biofilm formation in M. xanthus.