Exopolysaccharide Production Research Articles

Coaggregative interactions between rhizobacteria are promoted by exopolysaccharides from Sinorhizobium meliloti.

Bacterial surface components and extracellular compounds such as exopolysaccharides (EPSs) are crucial for interactions between cells, tolerance to different types of stress, and host colonization. Sinorhizobium meliloti produces two EPSs: Succinoglycan (EPS I), which is involved in the establishment of symbiosis with Medicago sativa, and galactoglucan (EPS II), associated with biofilm formation and the promotion of aggregation. Here, we aimed to assess their role in aggregative interactions between cells of the same strain of a given species (auto-aggregation), and between genetically different strains of the same or different species (intra- or intergeneric coaggregation). To do this, we used S. meliloti mutants which are defective in the production of EPS I, EPS II, or both. Macroscopic and microscopic coaggregation tests were performed with combinations or pairs of different bacterial strains. The EPS II-producing strains were more capable of coaggregation than those that cannot produce EPS II. This was true both for coaggregations between different S. meliloti strains, and between S. meliloti and other common rhizobacteria of agricultural relevance, such as Pseudomonas fluorescens and Azospirillum brasilense. The exogenous addition of EPS II strongly promoted coaggregation, thus confirming the polymer's importance for this phenotype. EPS II may therefore be a key factor in events of physiological significance for environmental survival, such as aggregative interactions and biofilm development. Furthermore, it might be a connecting molecule with relevant properties at an ecological, biotechnological, and agricultural level.

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.

The Sinorhizobium meliloti NspS-MbaA system affects biofilm formation, exopolysaccharide production and motility in response to specific polyamines.

We previously showed that specific polyamines (PAs) present in the extracellular environment markedly affect extracellular polysaccharide (EPS) production, biofilm formation and motility in Sinorhizobium meliloti Rm8530. We hypothesized that extracellular PA signals were sensed and transduced by the NspS and MbaA proteins, respectively, which are homologs of the PA-sensing, c-di-GMP modulating NspS-MbaA proteins described in Vibrio cholerae. Here we show that the decrease in biofilm formation and EPS production in the quorum-sensing (QS)-deficient S. meliloti wild-type strain 1021 in cultures containing putrescine or spermine did not occur in a 1021 nspS mutant (1021 nspS). The transcriptional expression of nspS in strain 1021 was significantly increased in cultures containing either of these polyamines, but not by exogenous cadaverine, 1,3-diaminopropane (DAP), spermidine (Spd) or norspermidine (NSpd). Cell aggregation in liquid cultures did not differ markedly between strain 1021 and 1021 nspS in the presence or absence of PAs. The S. meliloti QS-proficient Rm8530 wild-type and nspS mutant (Rm8530 nspS) produced similar levels of biofilm under control conditions and 3.2- and 2.2-fold more biofilm, respectively, in cultures with NSpd, but these changes did not correlate with EPS production. Cells of Rm8530 nspS aggregated from two- to several-fold more than the wild-type in cultures without PAs or in those containing Spm. NSpd, Spd and DAP differently affected swimming and swarming motility in strains 1021 and Rm8530 and their respective nspS mutants. nspS transcription in strain Rm8530 was greatly reduced by exogenous Spm. Bioinformatic analysis revealed similar secondary structures and functional domains in the MbaA proteins of S. meliloti and V. cholerae, while their NspS proteins differed in some residues implicated in polyamine recognition in the latter species. NspS-MbaA homologs occur in a small subset of soil and aquatic bacterial species that commonly interact with eukaryotes. We speculate that the S. meliloti NspS-MbaA system modulates biofilm formation, EPS production and motility in response to environmental or host plant-produced PAs.

Genomic and physiological characterization of Novosphingobium terrae sp. nov., an alphaproteobacterium isolated from Cerrado soil containing a mega-sized chromid.

A novel bacterial strain, designated GeG2T, was isolated from soils of the native Cerrado, a highly biodiverse savanna-like Brazilian biome. 16S rRNA gene analysis of GeG2T revealed high sequence identity (100%) to the alphaproteobacterium Novosphingobium rosa; however, comparisons with N. rosa DSM 7285T showed several distinctive features, prompting a full characterization of the new strain in terms of physiology, morphology, and, ultimately, its genome. GeG2T cells were Gram-stain-negative bacilli, facultatively anaerobic, motile, positive for catalase and oxidase activities, and starch hydrolysis. Strain GeG2T presented planktonic-sessile dimorphism and cell aggregates surrounded by extracellular matrix and nanometric spherical structures were observed, suggesting the production of exopolysaccharides (EPS) and outer membrane vesicles (OMVs). Despite high 16S rDNA identity, strain GeG2T showed 90.38% average nucleotide identity and 42.60% digital DNA-DNA hybridization identity with N. rosa, below species threshold. Whole-genome assembly revealed four circular replicons: a 4.1Mb chromosome, a 2.7Mb extrachromosomal megareplicon, and two plasmids (212.7 and 68.6kb). The megareplicon contains a few core genes and plasmid-type replication/maintenance systems, consistent with its classification as a chromid. Genome annotation shows a vast repertoire of carbohydrate-active enzymes and genes involved in the degradation of aromatic compounds, highlighting the biotechnological potential of the new isolate. Chemotaxonomic features, including polar lipid and fatty acid profiles, as well as physiological, molecular, and whole-genome comparisons showed significant differences between strain GeG2T and N. rosa, indicating that it represents a novel species, for which the name Novosphingobium terrae is proposed. The type strain is GeG2T (= CBMAI 2313T = CBAS 753T).

Mitigation of water scarcity with sustained growth of Rice by plant growth promoting bacteria.

Climate change augments the risk to food security by inducing drought stress and a drastic decline in global rice production. Plant growth-promoting bacteria (PGPB) have been known to improve plant growth under drought stress. Here in the present study, we isolated, identified, and well-characterized eight drought-tolerant bacteria from the rice rhizosphere that are tolerant to 20% PEG-8000. These strains exhibited multiple plant growth-promoting traits, i.e., 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, exopolysaccharide production, phosphate (P)-solubilizing activity (51-356 µg ml-1), indole-3 acetic acid (IAA) production (14.3-46.2 µg ml-1), and production of organic acids (72-178 µg ml-1). Inoculation of bacterial consortium (Bacillus subtilis NM-2, Brucella haematophilum NM-4, and Bacillus cereus NM-6) significantly improved seedling growth and vigor index (1009.2-1100) as compared to non-inoculated stressed plants (630-957). Through rhizoscanning, efficiency of the consortium was validated by improved root parameters such as root length (17%), diameter, and surface area (18%) of all tested genotypes as compared with respective non-inoculated stressed treatments. Furthermore, the response of consortium inoculation on three rice genotypes was positively correlated with improved plant growth and drought stress ameliorating traits by the accumulation of osmoprotectant, i.e., proline (85.8%-122%), relative water content (51%), membrane stability index (64%), and production of antioxidant enzymes to reduce oxidative damage by reactive oxygen species. A decrease in temperature and improved chlorophyll content of inoculated plants were found using infrared thermal imaging and soil plant analyzer development (SPAD), respectively. The key supporting role of inoculation toward stress responses was validated using robust techniques like infrared thermal imaging and an infrared gas analyzer. Furthermore, principal component analysis depicts the contribution of inoculation on stress responses and yield of tested rice genotypes under water stress. The integration of drought-tolerant rice genotype (NIBGE-DT02) and potential bacterial strains, i.e., NM-2, NM-4, and NM-6, can serve as an effective bioinoculant to cope with water scarcity under current alarming issues related to food security in fluctuating climate.

Genome analysis of novel Apilactobacillus sp. isolate from butterfly (Pieris canidia) gut reveals occurrence of unique glucanogenic traits and probiotic potential.

This study was conducted with a perception that fructose-rich niches may inhabit novel species of lactic acid bacteria that are gaining importance as probiotics and for the production of exopolysaccharides that have applications in food and pharmaceuticals. Recently, some Lactobacillus species have been reclassified as fructophilic lactic acid bacteria due to their preference for fructose over glucose as a carbon source. These bacteria are likely to be found in fructose rich niches such as flower nectar and insects that feed on it. We explored the butterfly gut and acquired a new isolate, designated as F1, of fructophilic lactic acid bacteria, which produces a glucan-type exopolysaccharide. Whole genome sequencing and in silico analysis revealed that F1 has significantly lower average nucleotide identity and DNA-DNA hybridization values as compared to its closest Apilactobacillus neighbors in phylogenetic analysis. Therefore, we declare the isolate F1 as a novel Apilactobacillus species with the proposed name of Apilactobacillus iqraium F1. Genome mining further revealed that F1 harbors genes for exopolysaccharide synthesis and health-promoting attributes. To this end, F1 is the only Apilactobacillus species harboring three diverse α-glucan-synthesis genes that cluster with different types of dextransucrases in the dendrogram. Moreover, many nutritional marker genes, as well as genes for epithelial cell adhesion and antimicrobial synthesis, were also detected suggesting the probiotic attributes of F1. Overall analysis suggests A. iqraium sp. F1 be a potential candidate for various health beneficial and pharmaceutical applications.

Weissella and the two Janus faces of the genus

The genus Weissella belongs to the lactic acid bacteria group. It occurs naturally in foods and is a component of the human microbiome. A few Weissella species are candidate probiotics due to their potential for survival under the harsh conditions present in the gastrointestinal tract of humans and animals. Various species have also shown potential for treating and preventing periodontal disease, skin pathologies, and atopic dermatitis; some are used as starters for the fermentation of foods due to their production of exopolysaccharides; and others are used as protective cultures due to their production of weissellicin, a bacteriocin. However, a few Weissella species are opportunistic pathogens, such as W. ceti, which is the etiological agent of weissellosis, a disease in rainbow trout. Additionally, most Weissella species are intrinsically vancomycin-resistant. Thus, the Weissella genus is important from both medical and industrial points of view, and the Janus faces of this genus should be considered in any expected biotechnological applications. In this review, we present an overview of the probiotic potential and pathogenic cases of the Weissella genus reported in the literature.

Two novel genes identified by large-scale transcriptomic analysis are essential for biofilm and rugose colony development of Vibrio vulnificus.

Many pathogenic bacteria form biofilms to survive under environmental stresses and host immune defenses. Differential expression (DE) analysis of the genes in biofilm and planktonic cells under a single condition, however, has limitations to identify the genes essential for biofilm formation. Independent component analysis (ICA), a machine learning algorithm, was adopted to comprehensively identify the biofilm genes of Vibrio vulnificus, a fulminating human pathogen, in this study. ICA analyzed the large-scale transcriptome data of V. vulnificus cells under various biofilm and planktonic conditions and then identified a total of 72 sets of independently co-regulated genes, iModulons. Among the three iModulons specifically activated in biofilm cells, BrpT-iModulon mainly consisted of known genes of the regulon of BrpT, a transcriptional regulator controlling biofilm formation of V. vulnificus. Interestingly, the BrpT-iModulon additionally contained two novel genes, VV1_3061 and VV2_1694, designated as cabH and brpN, respectively. cabH and brpN were shared in other Vibrio species and not yet identified by DE analyses. Genetic and biochemical analyses revealed that cabH and brpN are directly up-regulated by BrpT. The deletion of cabH and brpN impaired the robust biofilm and rugose colony formation. CabH, structurally similar to the previously known calcium-binding matrix protein CabA, was essential for attachment to the surface. BrpN, carrying an acyltransferase-3 domain as observed in BrpL, played an important role in exopolysaccharide production. Altogether, ICA identified two novel genes, cabH and brpN, which are regulated by BrpT and essential for the development of robust biofilms and rugose colonies of V. vulnificus.

Ultrasound stimulated production of exopolysaccharide with anti-UV radiation activity by increasing cell permeability of Paenibacillus polymyxa

Exopolysaccharide (EPS) produced by Paenibacillus polymyxa PYQ1 may be a promising agent used in the cosmetic field for skin care because of its protective benefits against short-wave ultraviolet (UVC, 100–280 nm) radiation, which induces cytotoxicity in HaCaT cells. We attempted to use low-intensity ultrasound to enhance its fermentation, and the yield of EPS increased by 24 % under the optimum ultrasonic treatment (90 W, 45 s in 9 h). Results of further experiments show that low-intensity ultrasound will kill a few bacterial cells. Therefore, the remaining bacterial cells have more space and more nutrients, growing faster and producing EPS more efficiently. The recoverable physical damage caused by ultrasound increased the cell permeability, and for the first time, we found that low-intensity ultrasound up-regulated the expression of membrane transporters involved with the transport of sucrose and polysaccharides. Owing to these changes, the utilization of carbon sources was accelerated, and the transport of EPS was promoted to the outside of bacterial cells such that the production of EPS was enhanced.

POTENTIAL OF LACTIC ACID BACTERIA FROM MOROCCAN GOAT’S MILK FOR STARTER CULTURE DEVELOPMENT

Goat milk, a highly nutritious product is widely used in cheese making. In order to properly select suitable milk samples for production, fifty-five samples of raw goat’s milk were collected from eight farms in the North-West of Morocco to analyze their counts of various mesophilic bacteria and determining the physicochemical characteristics during different seasons of the year. Lactic acid bacteria (LAB) were isolated, identified, and screened for several technological properties. Overall mean values for mesophilic aerobic flora were above 7.10 log cfu/mL in spring and 5.80 log cfu/mL during winter with a statistically significant difference found between all the microorganisms except for coagulase-positive staphylococci. The physical and chemical composition tests showed higher values for fat (4.9±1.01%), dry matter (13.98±0.95%), ash (1.3±0.12%), lactose (3.1±0.65 g/L), and protein (4.6±1.03 g/L) during the winter season which could be of great interest for cheese production. fatty acids (FA) composition mainly consisted of saturated fatty acids (SFA) in both seasons. Lactococci isolates were the most acidifying (pH6h=4.35–pH24h=4.08) while Lactobacillus paracasei produced the highest proteolytic activity (66.93±2.63 mgTyr.L-1) and diacetyl-acetoin (54.83±0.46 mg diacetyl/L). None of the tested isolates were lipolytic, however, several lactobacilli and lactococci exhibited a high salt tolerance and exopolysaccharide (EPS) production. Lactobacillus plantarum exhibited the highest lysis rate (67.34±1.76%) while the antibacterial profile ranged between 10.5±0.137 and 22.9±0.23 mm. The obtained results highlight the importance of Moroccan goat milk as a valuable component for cheese making due to its rich fat and protein contents alongside its abundance in LABs with biotechnological properties.

Microencapsulation in the chitosan-coated alginate-inulin matrix of Limosilactobacillus reuteri SW23 and Lactobacillus salivarius RBL50 and their characterization

The present study was undertaken for biosynthesis and in vitro evaluation of microencapsulated autochthonous probiotics, Limosilactobacillus reuteri SW23 and Lactobacillus salivarius RBL50 in the chitosan-coated alginate-inulin matrix. For this purpose, autochthonous potential probiotics of Sahiwal calf origin, L. reuteri SW-23, and L. salivarius RBL-50 were encapsulated in an alginate (Alg) matrix with or without inulin (Inu) incorporation and coated with chitosan (Cht) using the extrusion technique. The size of the microcapsules of both probiotics L. reuteri SW23 and L. salivarius RBL50 was largest in Alg-Inu-Cht microencapsulate followed by Alg-Cht, Alg-Inu, and smallest in Alg. The findings also revealed that after sequential exposure to simulated gastrointestinal conditions, the viable count in microencapsulates of both probiotics was higher (P < 0.05) in comparison to free cells. Among the microencapsulated groups, the highest viability was reported in alginate-inulin-incorporated chitosan-coated probiotics. The encapsulation process and encapsulating agents had no effect on the exopolysaccharide production and antibacterial activity. The beta-galactosidase activity after GI exposure was found to be highest in free cells and the lowest in inulin-added chitosan-coated probiotics. Overall, the best response was seen in probiotic microcapsules that were coated in alginate-chitosan and co-encapsulated with inulin.

PROBIOTIC CHARACTERIZATION OF SACCHAROMYCES CEREVISIAE Y196 AND Y197 ISOLATED FROM RICE CHHANG- A FERMENTED BEVERAGE OF LAHAUL SPITI

Fermented foods and beverages are rich source of probiotic microorganisms and yeasts are the most common microorganisms found in these fermented products. Fermented beverages are less explored for probiotics, therefore; the present study was focused on isolation, screening and characterization of probiotic yeast from rice Chhang, a fermented beverage of Lahaul Spiti. Ten yeast isolates were initially isolated from rice Chhang and out of which two isolates Saccharomyces cerevisiae Y196 and Saccharomyces cerevisiae Y197 were selected based on their antimicrobial activity. These two yeast isolates were examined for various probiotic properties such as survival at low pH, bile tolerance, microbial adhesion to hydrocarbons, cholesterol assimilation, exopolysaccharide production and haemolytic activity. Both isolates showed antimicrobial activity against all the tested pathogens used in this study, also showed high acid tolerance at pH 2 and pH 3 and can withstand high bile concentration as compared to control. Percentage of hydrophobicity was found to be 57 % and 41 % in Saccharomyces cerevisiae Y196 and Saccharomyces cerevisiae Y197, respectively. Both isolates were able to show high cholesterol assimilation with a maximum of 90 % in case of Saccharomyces cerevisiae Y197 with taurocholate. They were also found to be positive for exopolysaccharide production and showed no haemolytic activity. Hence, keeping in view the results of present study, these isolates can be proposed for preparation of various probiotic food products.

Rhizobial migration toward roots mediated by FadL-ExoFQP modulation of extracellular long-chain AHLs

Migration from rhizosphere to rhizoplane is a key selecting process in root microbiome assembly, but not fully understood. Rhizobiales members are overrepresented in the core root microbiome of terrestrial plants, and here we report a genome-wide transposon-sequencing of rhizoplane fitness genes of beneficial Sinorhizobium fredii on wild soybean, cultivated soybean, rice, and maize. There were few genes involved in broad-host-range rhizoplane colonization. The fadL mutant lacking a fatty acid transporter exhibited high colonization rates, while mutations in exoFQP (encoding membrane proteins directing exopolysaccharide polymerization and secretion), but not those in exo genes essential for exopolysaccharide biosynthesis, led to severely impaired colonization rates. This variation was not explainable by their rhizosphere and rhizoplane survivability, and associated biofilm and exopolysaccharide production, but consistent with their migration ability toward rhizoplane, and associated surface motility and the mixture of quorum-sensing AHLs (N-acylated-L-homoserine lactones). Genetics and physiology evidences suggested that FadL mediated long-chain AHL uptake while ExoF mediated the secretion of short-chain AHLs which negatively affected long-chain AHL biosynthesis. The fadL and exoF mutants had elevated and depleted extracellular long-chain AHLs, respectively. A synthetic mixture of long-chain AHLs mimicking that of the fadL mutant can improve rhizobial surface motility. When this AHL mixture was spotted into rhizosphere, the migration toward roots and rhizoplane colonization of S. fredii were enhanced in a diffusible way. This work adds novel parts managing extracellular AHLs, which modulate bacterial migration toward rhizoplane. The FadL-ExoFQP system is conserved in Alphaproteobacteria and may shape the “home life” of diverse keystone rhizobacteria.

Xanthomonas campestris VemR enhances the transcription of the T3SS key regulator HrpX via physical interaction with HrpG.

VemR is a response regulator of the two-component signalling systems (TCSs). It consists solely of a receiver domain. Previous studies have shown that VemR plays an important role in influencing the production of exopolysaccharides and exoenzymes, cell motility, and virulence of Xanthomonas campestris pv. campestris (Xcc). However, whether VemR is involved in the essential pathogenicity determinant type III secretion system (T3SS) is unclear. In this work, we found by transcriptome analysis that VemR modulates about 10% of Xcc genes, which are involved in various cellular processes including the T3SS. Further experiments revealed that VemR physically interacts with numerous proteins, including the TCS sensor kinases HpaS and RavA, and the TCS response regulator HrpG, which directly activates the transcription of HrpX, a key regulator controlling T3SS expression. It has been demonstrated previously that HpaS composes a TCS with HrpG or VemR to control the expression of T3SS or swimming motility, while RavA and VemR form a TCS to control the expression of flagellar genes. Mutation analysis and in vitro transcription assay revealed that phosphorylation might be essential for the function of VemR and phosphorylated VemR could significantly enhance the activation of hrpX transcription by HrpG. We infer that the binding of VemR to HrpG can modulate the activity of HrpG to the hrpX promoter, thereby enhancing hrpX transcription. Although further studies are required to validate this inference and explore the detailed functional mechanism of VemR, our findings provide some insights into the complex regulatory cascade of the HpaS/RavA-VemR/HrpG-HrpX signal transduction system in the control of T3SS.

Modulation of macro and micronutrients to enhance lipid production by Scenedesmus abundans in a flat-panel photobioreactor under outdoor natural sunlight

The present study investigates the effect of macro- and micronutrients on photoautotrophic lipid production from Scenedesmus abundans. An optimized lipid medium has been formulated using one-at-a-time variation of macronutrients and a study of micronutrient interactions. Both single-stage and two-stage strategies were used for simultaneous production of lipid and exopolysaccharide (EPS) in medium-scale photobioreactors (PBRs) using the optimized lipid medium. In the single-stage cultivation 32% fatty acid methyl ester (FAME, biodiesel) was achieved, whereas only 12.6% FAME was observed in two-stage PBR. A FAME titer of 1.16 g/L with overall FAME productivity of 32 mg/L/day and 280 mg/L EPS was achieved using the single-stage strategy. Further, under diurnal natural sunlight and outdoor conditions, a FAME content of 46%, with 1.28 g/L of FAME and 27 mg/L/day FAME productivity, and 155 mg/L EPS were achieved using the single-stage strategy in 2 L medium-scale flat-panel PBRs. Apart from high biodiesel and EPS production, this microalgal strain also has the ability to carry out natural autoflocculation with high efficiency. The strain could be exploited for high lipid content under outdoor cultivation without photoinhibition. Highlights Micronutrients have effects on lipid accumulation in Scenedesmus abundans. Scenedesmus abundans produced high biodiesel content (46% of DCW) under natural sunlight. Simultaneous synthesis of multiproducts by this candidate paves the way for biorefining.

Study of morphological features and growth parameters of psychrophilic microalgae and cyanobacteria

Recently, a question of producing a complex of biologically active substances from microalgae has aroused widespread interest. It is known that microalgae are able to produce a significant amount of exopolysaccharides. The aim of this work was to study morphological features and growth parameters of psychrophilic microalgae and cyanobacteria for the subsequent production of exopolysaccharides. The morphology of microalgae was observed using a binocular microscope. Growth parameters were studied by spectrophotometry; parameters of the culture medium were determined using a pH-meter. Exponential dependency graphs that show the dynamics and expected growth rate of microalgae were built. A rate of growth and polysaccharide biosynthesis in microalgae was determined upon changing the light intensity from 50 to130 mmol/m2/s. The highest level of cell counts in the logarithmic growth phase was up to 0.8 for Scenedesmus obtusiusculus Chod IPPAS S-329. A level of cells also varied in the deceleration phase from 0.25 for Ankistrodesmus acicularis Korsch IPPAS А-218 to 1.8 for Scenedesmus obtusiusculus Chod IPPAS S-329. Microalgae showed a high level of biomass accumulation under alkalophylic conditions. Eukaryotic algae actively photosynthesized at a pH of more than 8.0 and a temperature of 30 °C.The maximum activity at the level of pH 3.0/3.2 in the lag phase was 100% in C-1509 Nannochloris sp. Naumann. Microalga C-1509 Nannochloris sp. Naumann showed a high level of biomass accumulation under alkalophylic conditions; it photosynthesized at a pH of more than 8.0 and a temperature of 30 °C. It has been proved that neutrophiles can grow at pH lower than 3.0; this corresponds to the results of the experiments with the collection strains of microalgae with biomass productivity of 27.3%. At the alkaline pH values of 8.3-9.0, biomass productivity reduced from 46.0 to 37.2%. It is especially interesting that at the alkaline pH values of 7.5 and 8.0 biomass productivity of microalgae increased, which indicates the optimal growth conditions at this narrow pH range. An ability of microalgae to produce exopolysaccharides opens prospects of their use for practical purposes.

Exopolysaccharide production by Anabaena sp. PCC 7120: physicochemical parameter optimization and two-stage cultivation strategy to maximize the product yield

Exopolysaccharide production by Anabaena sp. PCC 7120: physicochemical parameter optimization and two-stage cultivation strategy to maximize the product yield

Maltose-Enhanced Exopolysaccharide Synthesis of Lactiplantibacillus plantarum through CRP-like Protein

Carbon sources alter the synthesis of exopolysaccharides (EPS) in Lactiplantibacillus plantarum. Maltose increased the EPS production of L. plantarum 163 6.5-fold. Subsequently, EPS production, transcriptome, and proteome were analyzed using glucose or maltose to further clarify the regulatory mechanism. A cAMP receptor protein (UniProtKB: F9UNI5) has been identified to control EPS synthesis in the presence of cAMP by binding to the EPS synthesis promoter Pcps4A-J. Overexpression of the cAMP synthesis gene cyaA increased cAMP content and EPS production 4.5- and 2.2-fold, respectively. Furthermore, yogurt produced with L. plantarum 163-cyaA had a similar viscosity to that of commercial Greek yogurt; it had 20 and 83.7% greater viscosity than that produced with L. plantarum 163 with maltose and glucose, respectively. These findings indicated that L. plantarum 163-cyaA has potential applications in the production of functional fermented dairy products.

Exo-polysaccharide producing bacteria can induce maize plant growth and soil health under saline conditions

ABSTRACT Salt tolerant plant growth boosting rhizobacteria can play an important function in plant salinity stress mitigation. In the current investigation, only two rhizobacterial isolates out of 68 produced exo-polysaccharide at the fastest rate and exhibited plant growth promoting properties such as IAA, CAT, APX production, and phosphate solubilization at 6% NaCl (w/v) concentration. Both isolates had synergistic PGP features and were compatible with one another. Isolate SP-20 was identified as Kluyvera sp. and SP-203 was identified as Enterobacter sp. -by 16SrDNA sequencing. After 30, 60, and 90 days, the combination of SP-20 and SP-203 enhanced the physicochemical parameters in the maize plant in comparison to the control. By increasing soil enzymes like DHA and PPO, both isolates significantly improved the soil health matrix. When a group of these isolates were inoculated into 1% and 2% NaCl (w/v) supplemented soil, the absorption of Na in the shoot and root of maize plants was inhibited by around 50%. The BCF values for all treatments were less than TF, and the values of BCF and TF were less than one. Therefore, the present study illustrated that the novel native isolates play a remarkable role to mitigate salinity stress in maize plant.

Feeding Lactic Acid Bacteria with Different Sugars: Effect on Exopolysaccharides (EPS) Production and Their Molecular Characteristics.

Exopolysaccharides (EPS) are complex molecules produced by some microorganisms and used in foods as texturizers and stabilizers, their properties depending on their chemical structure. In this work, three different lactic acid bacteria (LAB), were tested for their ability to produce EPS, by using five different mono- and disaccharides as their sole carbon source. The growth and acidifying ability were analysed, the EPSs were quantified by the official method AOAC 991.43, and their chemical structure was investigated. The amount of EPS varied from 0.71 g/L to 2.38 g/L, and maltose was the best sugar for EPS production by Lacticaseibacillus paracasei 2333. Lacticaseibacillus rhamnosus 1019 produced the highest amount when fed with lactose, whereas the EPS amount of Lactobacillus bulgaricus 1932 was not significantly different depending on the sugar type. The EPS chains consisted of fructose, galactose, glucose, mannose, ribose, glucosamine, galactosamine, and in some cases rhamnose in different proportions, depending on the strain and carbon source. The molecular weight of EPS ranged from &lt;10 KDa to &gt;500 KDa and was again highly dependent on the strain and the sugar used, suggesting the possibility of growing different strains under different conditions to obtain EPS with different potential applications in the food system.