Exploring the capabilities of Methylotuvimicrobium alcaliphilum 20Z to produce exopolymeric substances from methane.

Extracellular polymeric substances (EPS) form the main matrix of microbial biofilms and play a crucial role in maintaining microbial life. However, factors influencing EPS concentration and production in soil are poorly understood. Here we show that EPS are closely related to microbial communities and nutrient acquisition in tropical forest and cropland soils with varying iron-aluminum-manganese concentrations and total reserve in base cations. We found under homogenized moisture and temperature conditions that EPS concentration and production efficiency (i.e., EPS per unit of microbial biomass) depend more on land cover than on geochemical soil properties. EPS concentration and production efficiency were higher in cropland than in forest soil and were related to the higher relative abundance of microbial sequences identified as Paenibacillaceae, Ramlibacter, Chaetosphaeria, Burkholderiaceae, and Xanthobacteraceae, pointing to potential EPS producers. In contrast, lower EPS concentration in forest soil was related to the higher relative abundance of microbial sequences associated with e.g., Gemmatimonas and Massilia, suggesting potential EPS degradation. We also found that EPS production efficiency was positively related to microbial investment in nutrient acquisition, implying that EPS production likely follows the same principles as extracellular enzyme activity. That is, EPS production may increase when resources are scarce to facilitate nutrient acquisition, and decrease when resources are abundant. Overall, microbial community composition and resource demand seem to control EPS degradation and accumulation in tropical soils, which could influence microbially-driven carbon and nutrient cycling.

This study aimed to enhance the extracellular polymeric substances (EPS) production of Virgibacillus dokdonensis VITP14 and explore its antioxidant potential. EPS and biomass production by VITP14 strain were studied under different culture parameters and media compositions using one factor at a time method. Among different nutrient sources, glucose and peptone were identified as suitable carbon and nitrogen sources. Furthermore, the maximum EPS production was observed at 5% of inoculum size, 5 g/L of NaCl, and 96 h of fermentation. Response surface methodology was employed to augment EPS production and investigate the optimal levels of nutrient sources with their interaction. The strain was observed to produce actual maximum EPS of about 26.4 g/L for finalized optimum medium containing glucose 20 g/L, peptone 10 g/L, and NaCl 50 g/L while the predicted maximum EPS was 26.5 g/L. There was a nine fold increase in EPS production after optimization study. Additionally, EPS has exhibited significant scavenging, reducing, and chelating potential (>85%) at their higher concentration. This study imparts valuable insights into optimizing moderately halophilic bacterial EPS production and evaluating its natural antioxidant properties. According to findings, V. dokdonensis VITP14 was a promising isolate that will provide significant benefits to biopolymer producing industries.

Objective: Evaluation of Extracellular Polymeric Substance (EPS) induced heavy metal tolerance in Kocuria sp. BRI 36.Methods: Initially, the effect of different concentrations of glucose (1-10 %) on EPS production by BRI 36 was examined. At optimum glucose concentrations, EPS levels were measured by varying heavy metal concentrations (10-50 ppm) of Pb2+, Cd 2+and Cr3+. Maximum tolerable concentration (MTC) and survival percentage of BRI 36 were determined under conditions that support EPS synthesis. Comparative analysis of extracted crude EPS was performed by Fourier Transform Infrared Spectroscopy (FTIR) to establish functional groups involved in the metal interaction. Results: Kocuriasp. BRI 36 produced maximum EPS (1g/l) at 5% glucose. Increase in EPS production up to 89% (considering 1g/l as 100%) with an increase in concentrations of heavy metals up to 40 ppm. MTC levels of BRI 36 for heavy metals increased up to 700 ppm when it was cultivated in presence of 5% glucose indicating a major role of surface polymer in metal adsorption. The function of EPS as a protective cover was also evident from an increase in survival percentage of BRI 36 up to 39.4 at MTC. Comparative analysis of extracted crude EPS by FTIR revealed the involvement of O-H, C=O, and C-O-C groups in metal adsorptionConclusion: Antarctic oceanic isolate Kocuria sp. BRI 36 has an ability to produced EPS under stress conditions of heavy metals. Simultaneously, its MTC values increased due to increase in EPS levels. These observations suggest the possibility to develop gentle, environmentally safe and cost-effective method for heavy metal removal.

A series of batch experiments was undertaken to explore the influence of growth conditions on the extracellular polymeric substances (EPS) production of five representative strains of trichloroethylene (TCE) degrading toluene oxidizing bacteria of importance to in situ bioremediation. EPS production for three distinct carbon sources (i.e., lactate, glucose, and toluene) was examined under starvation and non-starvation conditions. EPS extraction was accomplished using DOWEX™ (cation exchange resin; CER), and total carbohydrate, protein, and uronic acid were quantified as the main EPS constituents. Experimental results reveal that most bacteria grown on toluene synthesized more EPS per colony forming unit (CFU) than those grown on other substrates and that EPS production is enhanced with increasing length of starvation. These observations suggest that EPS may be produced under conditions of environmental stress and may be linked to enzyme deactivation. The results from this work additionally indicate that the mutant strain of Ralstonia pickettii PKO1 with the lack of gene encoding TbuX (an outer membrane protein) is more hydrophobic due to less EPS synthesis ability. The relatively lower amount of EPS synthesis in the mutant strain of R. pickettii PKO1 suggests that TbuX, an outer membrane protein encoded a part of the toluene catabolic regulation of R. pickettii PKO1, has a role in bacterial EPS production.

The kinetic study of Arthrospira platensis extracellular polymeric substances (EPS) production under different trophic modes-photoautotrophy (100 μmol photons m(-2) s(-1)), heterotrophy (1.5 g/L glucose), and mixotrophy (100 μmol photons m(-2) s(-1) and 1.5 g/L glucose)-was investigated. Under photoautotrophic and heterotrophic conditions, the maximum EPS production 219.61 ± 4.73 and 30.30 ± 1.97 mg/L, respectively, occurred during the stationary phase. Under a mixotrophic condition, the maximum EPS production (290.50 ± 2.21 mg/L) was observed during the early stationary phase. The highest specific EPS productivity (433.62 mg/g per day) was obtained under a photoautotrophic culture. The lowest specific EPS productivity (38.33 mg/g per day) was observed for the heterotrophic culture. The effects of glucose concentration, light intensity, and their interaction in mixotrophic culture on A. platensis EPS production were evaluated by means of 32 factorial design and response surface methodology. This design was carried out with a glucose concentration of 0.5, 1.5, and 2.5 g/L and at light levels of 50, 100, and 150 μmol photons m(-2) s(-1). Statistical analysis of the model demonstrated that EPS concentration and EPS yield were mainly influenced by glucose concentration and that conditions optimizing EPS concentration were dissimilar from those optimizing EPS yield. The highest maximum predicted EPS concentration (369.3 mg/L) was found at 150 μmol photons m(-2) s(-1) light intensity and 2.4 g/L glucose concentration, while the highest maximum predicted EPS yield (364.3 mg/g) was recorded at 115 μmol photons m(-2) s(-1) light intensity and 1.8 g/L glucose concentration.

Influence of shear on the production of extracellular polymeric substances in membrane bioreactors

Shear, in the form of vigorous aeration, is used to control fouling in membrane bioreactor (MBR) systems. However, shear also influences the physicochemical and biological properties of MBR biomass. The current study examines the relationship between the aeration intensity and extracellular polymeric substance (EPS) production in MBRs. Two identical submerged MBRs were operated in parallel but the aeration rate was three times greater in one of the MBRs. The concentrations of floc-associated and soluble EPS were monitored for the duration of the experiment. Microscopic images and floc-size measurements were also collected regularly. The membrane fouling potential of the biomass was quantified using the flux-step method. Increased aeration did not have a direct effect on soluble or floc-associated EPS production in the microfiltration MBRs. However, aeration intensity had a significant effect on predatory organisms. Large aquatic earthworms, Aeolosoma hemprichi, proliferated under lower shear conditions but were never observed in the high shear reactor. Predation by A. hemprichi resulted in increased floc-associated and soluble EPS production. Thus, the mixing conditions in the low shear MBR indirectly resulted in increased soluble EPS concentrations and higher fouling potential. This research suggests that predation can have a significant impact on the production rates of floc-associated and soluble EPS – key parameters driving membrane fouling in MBRs.

Effect of EPS production on the performance of membrane-based biofilm reactors

We have simulated a nitrifying biofilm with one ammonia and one nitrite oxidising species in order to elucidate the effect of various extracellular polymeric substance (EPS) production scenarios on biofilm structure and function. The individual-based model (IbM) BacSim simulates diffusion of all substrates on a two-dimensional lattice. Each bacterium is individually simulated as a sphere of given size in a continuous, three-dimensional space. EPS production kinetics was described by a growth rate dependent and an independent term (Leudeking-Piret equation). The structure of the biofilm was dramatically influenced by EPS production or capsule formation. EPS production decreased growth of producers and stimulated growth of non-producers because of the energy cost involved. For the same reason, EPS accumulation can fall as its rate of production increases. The patchiness and roughness of the biofilm decreased and the porosity increased due to EPS production. EPS density was maximal in the middle of the vertical profile. Introduction of binding forces between like cells increased clustering.

Production and fate of extracellular polymeric substances produced by benthic diatoms and bacteria: A laboratory study

An axenic culture of Cylindrotheca closterium and a natural community of benthic diatoms were used to study the effect of temperature and irradiance on the production of extracellular polymeric substances (EPS). In the culture, results depended on the growth stage of the algae and on whether absolute values or biomass-related values were considered. The highest amount of EPS (standing stock) was produced at 15 and 25°C during early stationary growth phase. When EPS concentrations were normalized to chlorophyll a (chl a), maximum values were measured at 4 and 10°C. Independent of temperature the ratios (EPS:chl a) decreased with increasing age of the culture. Additionally, differences between the investigated temperatures were less pronounced in older cultures. A field sample of benthic diatoms was used to study: (1) the combined effect of temperature and irradiance on primary production and excretion of EPS; and (2) the partitioning of photosynthetically fixed carbon (C) into different fractions of intracellular and extracellular C pools by using a short-term 14C incorporation. Again highest values of primary production and EPS (production rates) were measured at 25°C. At lower irradiances, the temperature of 35°C had an inhibitory effect on the production rates of all fractions. In the culture as well as in the natural sample, the fraction of EPS that was closely bound to the cells (attached EPS) and the soluble fraction (colloidal EPS) were produced in different amounts at the different temperatures. This suggested that the production of the 2 operationally defined fractions of EPS might serve different functions, e.g. for migration or for storage of reserve products [KEYWORDS: Benthic diatoms; Cylindrotheca closterium; Extracellular polymeric substances; EPS; Irradiance; Temperature]

The production processes of the pulp and paper industry often run in campaigns, leading to large variations in the composition of wastewaters and waste sludges. During anaerobic digestion (AD) of these wastes, the viscosity or the production of extracellular polymeric substances (EPS) and soluble microbial products (SMP) may be affected, with the risk of foam formation, inefficient digester mixing or poor sludge dewaterability. The aim of this study was to investigate how viscosity and production of EPS and SMP during long-term AD of pulp and paper mill sludge is affected by changes in organic loading rate (OLR) and hydraulic retention time (HRT). Two mesophilic lab-scale continuous stirred tank reactors (CSTRs) were operated for 800 days (R1 and R2), initially digesting only fibre sludge, then co-digesting fibre sludge and activated sludge. The HRT was lowered, followed by an increase in the OLR. Reactor fluids were sampled once a month for rheological characterization and analysis of EPS and SMP. The production of the protein fraction of SMP was positively correlated to the OLR, implicating reduced effluent qualities at high OLR. EPS formation correlated with the magnesium content, and during sulphate deficiency, the production of EPS and SMP increased. At high levels of EPS and SMP, there was an increase in viscosity of the anaerobic sludges, and dewatering efficiency was reduced. In addition, increased viscosity and/or the production of EPS and SMP were important factors in sludge bulking and foam formation in the CSTRs. Sludge bulking was avoided by more frequent stirring.

<strong class="journal-contentHeaderColor">Abstract.</strong> Extracellular polymeric substances (EPS) are an important organic carbon reservoir in many pelagic and benthic environments. The production of EPS is intimately associated with the growth of phyto- and picoplankton. EPS plays a critical role in carbonate precipitation through the binding of cations and by acting as a nucleation site for minerals. Large-scale episodes of fine-grained calcium carbonate precipitation in the water column (whiting events) have been linked to cyanobacterial blooms, including of <em>Synechococcus</em> spp.,. The mechanisms that trigger these precipitation events are still debated. We pose that the cyanobacterial EPS, produced during exponential and stationary growth phases plays a critical role in the formation of whitings. The aim of this study was to investigate the production of EPS during a two-month cyanobacterial growth, mimicking a bloom. We further evaluated the potential role of EPS in carbonate precipitation. The production and properties of EPS produced at different <em>Synechococcus</em> spp. growth stages were investigated and carbonate mineral formation within these EPS matrices was determined in forced precipitation experiments. EPS produced during the early and late stationary phase contained a larger amount of negatively charged groups than present in EPS produced during the exponential phase. Consequently, a higher Ca²⁺ binding affinity of the stationary phase-EPS led to the formation of a larger amount of smaller carbonate minerals (&lt;50 &micro;m) compared to crystals formed in exponential phase-EPS, which were less and larger (&gt; 50 &micro;m). These findings were used to establish a conceptual model for picoplankton bloom-mediated CaCO₃ precipitation that can explain the role of EPS in whitings (see graphical abstract).

<strong class="journal-contentHeaderColor">Abstract.</strong> Extracellular polymeric substances (EPS) are an important organic carbon reservoir in many pelagic and benthic environments. The production of EPS is intimately associated with the growth of phyto- and picoplankton. EPS plays a critical role in carbonate precipitation through the binding of cations and by acting as a nucleation site for minerals. Large-scale episodes of fine-grained calcium carbonate precipitation in the water column (whiting events) have been linked to cyanobacterial blooms, including of <em>Synechococcus</em> spp.,. The mechanisms that trigger these precipitation events are still debated. We pose that the cyanobacterial EPS, produced during exponential and stationary growth phases plays a critical role in the formation of whitings. The aim of this study was to investigate the production of EPS during a two-month cyanobacterial growth, mimicking a bloom. We further evaluated the potential role of EPS in carbonate precipitation. The production and properties of EPS produced at different <em>Synechococcus</em> spp. growth stages were investigated and carbonate mineral formation within these EPS matrices was determined in forced precipitation experiments. EPS produced during the early and late stationary phase contained a larger amount of negatively charged groups than present in EPS produced during the exponential phase. Consequently, a higher Ca²⁺ binding affinity of the stationary phase-EPS led to the formation of a larger amount of smaller carbonate minerals (&lt;50 &micro;m) compared to crystals formed in exponential phase-EPS, which were less and larger (&gt; 50 &micro;m). These findings were used to establish a conceptual model for picoplankton bloom-mediated CaCO₃ precipitation that can explain the role of EPS in whitings (see graphical abstract).

<strong class="journal-contentHeaderColor">Abstract.</strong> Extracellular polymeric substances (EPS) are an important organic carbon reservoir in many pelagic and benthic environments. The production of EPS is intimately associated with the growth of phyto- and picoplankton. EPS plays a critical role in carbonate precipitation through the binding of cations and by acting as a nucleation site for minerals. Large-scale episodes of fine-grained calcium carbonate precipitation in the water column (whiting events) have been linked to cyanobacterial blooms, including of <em>Synechococcus</em> spp.,. The mechanisms that trigger these precipitation events are still debated. We pose that the cyanobacterial EPS, produced during exponential and stationary growth phases plays a critical role in the formation of whitings. The aim of this study was to investigate the production of EPS during a two-month cyanobacterial growth, mimicking a bloom. We further evaluated the potential role of EPS in carbonate precipitation. The production and properties of EPS produced at different <em>Synechococcus</em> spp. growth stages were investigated and carbonate mineral formation within these EPS matrices was determined in forced precipitation experiments. EPS produced during the early and late stationary phase contained a larger amount of negatively charged groups than present in EPS produced during the exponential phase. Consequently, a higher Ca²⁺ binding affinity of the stationary phase-EPS led to the formation of a larger amount of smaller carbonate minerals (&lt;50 &micro;m) compared to crystals formed in exponential phase-EPS, which were less and larger (&gt; 50 &micro;m). These findings were used to establish a conceptual model for picoplankton bloom-mediated CaCO₃ precipitation that can explain the role of EPS in whitings (see graphical abstract).