Characterization and removal of biofouling from reverse osmosis membranes (ROMs) from a desalination plant in Northern Chile,using Alteromonas sp. Ni1-LEM supernatant

Abstract

Biofouling control in reverse osmosis membranes (ROMs) is challenging due to the high cost of treatments, and reduction in the life of ROMs. This study characterizes the biofouling in the ROMs from a desalination plant and reports its effective removal using the supernatant obtained from Alteromonas sp. strain Ni1-LEM. The characterization of the bacterial community revealed that the most abundant taxa in ROMs were the genera Fulvivirga and Pseudoalteromonas, and unclassified species of the families Flavobacteriaceae and Sphingomonadaceae. This bacterial community significantly decreased upon treatment with the supernatant from Alteromonas sp. Ni1-LEM, resulting in the prevalence of the genus Pseudoalteromonas. Furthermore, this bacterial supernatant significantly inhibited cell adhesion of seven benthic microalgae isolated from ROMs as well as promoting cell detachment of the existing microbial biofilms. The study showed that the extracellular supernatant modified the conformation of extracellular polymeric substances (EPS) in the biofouling of ROMs without any biocidal effects.     

Isolation,characterization and localization of extracellular polymeric substances from the cyanobacterium Arthrospira platensis strain MMG-9

Arthrospira platensis is a cyanobacterium known for its nutritional value and secondary metabolites. Extracellular polymeric substances (EPS) are an important trait of most cyanobacteria, including A. platensis. Here, we extracted and analysed different fractions of EPS from a locally isolated strain of A. platensis. Three different fractions of EPS were distinguished. These were EPS released into the medium (REPS), EPS loosely bound to the organism (LEPS) and EPS tightly bound to the organism (TEPS), which were extracted by different procedures. The LEPS fraction was smaller than the other two fractions. The EPS of A. platensis exhibited high diversity. Total protein and carbohydrate content was determined in each of these fractions. The largest amount of total carbohydrates and total proteins was in the TEPS fraction. Eight sugar moieties were detected and analysed in all EPS fractions using HPAE-PAD. Fructose, mannose and ribose were rare sugar residues in all fractions of EPS. With the exception of fructose, all sugars tested for were detected in TEPS. The amount of sugars detected was significantly higher in TEPS compared with the two other fractions, especially for galactose, xylose and glucose. The EPS were localized by confocal laser scanning microscopy (CLSM) after staining with different fluorescent dyes and it was found that A. platensis possessed a thick and smooth layer of EPS around the spiral trichomes.     

Production and Characterization of the Intra‐ and Extracellular Carbohydrates and Polymeric Substances (EPS) of Three Sea‐Ice Diatom Species,and Evidence for a Cryoprotective Role for EPS

Diatoms and their associated extracellular polymeric substances (EPS) are major constituents of the microalgal assemblages present within sea ice. Yields and chemical composition of soluble and cell‐associated polysaccharides produced by three sea‐ice diatoms, Synedropsis sp., Fragilariopsis curta, and F. cylindrus, were compared. Colloidal carbohydrates (CC) contained heteropolysaccharides rich in mannose, xylose, galactose, and glucose. Synedropsis sp. CC consisted mainly of carbohydrates <8 kDa size, with relatively soluble EPS, compared to high proportions of less‐soluble EPS produced by both Fragilariopsis spp. F. curta colloidal EPS contained high concentrations of amino sugars (AS). Both Fragilariopsis species had high yields of hot bicarbonate (HB) soluble EPS, rich in xylose, mannose, galactose, and fucose (and AS in F. cylindrus). All species had frustule‐associated EPS rich in glucose–mannose. Nutrient limitation resulted in declines in EPS yields and in glucose content of all EPS fractions. Significant similarities between EPS fractions from cultures and different components of natural EPS from Antarctic sea ice were found. Increased salinity (52) reduced growth, but increased yields of EPS in Fragilariopsis cylindrus. Ice formation was inhibited byF. cylindrus, EPS, and by enhanced EPS content (additional xanthan gum) down to ?12°C, with growth rate reduced in the presence of xanthan. Differences in the production and composition of EPS between Synedropsis sp. and Fragilariopsis spp., and the association between EPS, freezing and cell survival, supports the hypothesis that EPS production is a strategy to assist polar ice diatoms to survive the cold and saline conditions present in sea ice.     

Detection, isolation, and characterization of exopolysaccharide produced by a strain of Phormidium 94a isolated from an arid zone of Mexico

Phormidium 94a, a cyanobacteria that produces extracellular polymeric substances (EPS), was isolated from arid soils of Mexico. Microscopic localization, using histochemical techniques like the Toluidine blue technique, was done in order to demonstrate the presence of EPS. Acetone was added to precipitate the EPS. In this study we characterized the EPS by GC, HPLC, and IR techniques. The highest fraction of EPS had a molecular weight of 2000 kDa. The sugar composition was galactose, mannose, galacturonic acid, arabinose, and ribose in the three main fractions, and the sugar ratio found was different in each fraction. The low EPS concentrations had a Newtonian behavior, when the concentrations were increased, the behavior changed to pseudoplastic. The EPS rheulogical behavior is similar to low viscosity arabic gum. Also, it was found that an increase in viscosity occurred at longer hydration time. More rheological and toxicological studies are required in order to analyze its possible application in food industries.     

Abundance, Annual Survival, and Recruitment of Unexploited and Exploited Lake Charr, Salvelinus Namaycush, Populations at the Experimental Lakes Area, Northwestern Ontario

We studied abundance, annual survival, and recruitment of nine lake charr, Salvelinus namaycush, populations at the Experimental Lakes Area, Ontario, for periods of 9–24 years. We used the Jolly–Seber mark-recapture method to evaluate abundance and annual survival in all populations, and total catches of individual year classes to evaluate recruitment. Seven populations were unexploited and unaffected by whole-lake experiments. One population was exploited prior to mark-recapture study and another was affected by experimental acidification. Abundance ranged from 8 to 24 fish ha^–1 in the unaffected populations. Annual survival ranged from 78% to 93%yr^–1 in all populations except the exploited population. This population may have been additionally affected by northern pike, Esox lucius, predation. Yearly recruitment was relatively constant in all populations and related to lake charr abundance. Lake charr abundance did not recover in populations affected by exploitation or acidification. Unexploited lake charr populations were characterized by relatively constant abundance, high annual survival, and relatively constant annual recruitment.     

The Postglacial History of Lake Flarken,Southern Sweden,Interpreted from Subfossil Insect Remains

A correlation of changes in the composition of chironomid and chaoborid remains and changes in sediment chemical composition, floristic, and other faunistic information indicate that a decreasing productivity and an increasing humic level characterized the development of the small Lake Flarken, Southern Sweden, during the postglacial period. Pronounced changes in the fauna were correlated with fluctuations of the water level in the lake, which was caused by changes in the humidity of the climate. Significant human influence on the lake has only occurred in recent years, during which a rapid acidification has caused the most dramatic change in the fauna, by far, in the whole history of the lake.     

The new alkaliphilic bacteriochlorophyll <Emphasis Type="Italic">a</Emphasis>-containing bacterium <Emphasis Type="Italic">Roseinatronobacter monicus</Emphasis> sp. nov. from the hypersaline Soda Mono Lake (California,United States)

Two strains of pink-colored aerobic bacteriochlorophyll a-containing bacteria were isolated from aerobic (strain ROS 10) and anaerobic (strain ROS 35) zones of the water column of Mono Lake (California, United States). Cells of the bacteria were nonmotile oval gram-negative rods multiplying by binary fission by means of a constriction. No intracellular membranes were detected. Polyphosphates and poly-β-hydroxybutyric acid were the storage compounds. Pigments were represented by bacteriochlorophyll a and carotenoids of the spheroidene series. The strains were obligately aerobic, mesophilic (temperature optimum of 25–30°C), alkaliphilic (pH optimum of 8.5–9.5), and moderately halophilic (optimal NaCl concentration of 40 g/l). They were obligately heterotrophic and grew aerobically in the dark and in the light. Respiration was inhibited by light at wavelengths corresponding to the absorption of the cellular pigments. The substrate utilization spectra were strain-specific. In the course of organotrophic growth, the bacteria could oxidize thiosulfate to sulfate; sulfide and polysulfide could also be oxidized. The DNA G+C content was 59.4 mol % in strain ROS 10 and 59 mol % in strain ROS 35. In their phenotypic properties, the new strains were close but not identical to the alkaliphilic bacterium Roseinatronobacter thiooxidans. The distinctions in the nucleotide sequences of the 16S rRNA genes (2%) and low DNA-DNA hybridization level with Rna. thiooxidans (22–25%) allow the new strains to be assigned to a new species of the genus Roseinatronobacter, Roseinatronobacter monicus sp. nov. with the type strain ROS 35^T (=UNIQEM U-251^T = VKM B-2404^T).     

A comparison of the fatty acid composition of Gammarus lacustris and its food sources from a freshwater reservoir, Bugach, and the saline Lake Shira in Siberia, Russia

We studied fatty acid (FA) composition in samples from bodies and intestinal contents of the littoral amphipod Gammarus lacustris Sars, from the Bugach freshwater reservoir. Simultaneously, samples of seston and bottom sediments were also collected from the reservoir during early August. There were no differences in FA composition of gut contents, seston and sediments of pebbly bottom. Seston was the main food source of Gammarus but some FAs Gammarus got from sediments. The FA composition of G. lacustris and seston from the Bugach freshwater reservoir were compared with those of the animals from the saltwater Lake Shira (Siberia). While FA composition of the two Gammarus populations differed significantly, those of seston were practically similar: the composition of long-chain unsaturated fatty acids, 20:53, 22:63 and 20:46, were significantly higher in animals from saline Shira Lake, whereas 16:1 and 16:0 were higher in the freshwater populations of amphipods from the Bugach freshwater reservoir. Taking into account the relevant literature data, we hypothesise that this difference in C16 acid might be a distinguishing characteristic of FA composition of freshwater and saltwater crustaceans.     

Agkihpin,a Distinct SVTLE from the Venom of Gloydius halys Pallas: Purification,Characterization and Structure–Activity Determination

Blood clots produced by snake‐venom thrombin‐like enzymes (SVTLEs) are cleared rapidly, which makes SVTLEs attractive as potential candidates for antithrombotic therapy. We isolated a SVTLE, agkihpin, from the venom of Gloydius halys Pallas . Agkihpin was confirmed to a single‐chain TLE with molecular mass of 25.5 kD, pI of 7.43, optimal pH of 8.0 (hydrolyzing TAME), linked carbohydrate absent, and weak fibrinogen clotting activity. It was also found that (i) G. halys might be the latest species in SVTLEs phylogenetic tree; (ii) different level of conservation was shown among the SVTLEs from the Viperidae snakes. Some of those site may account for different activities exhibited by those SVTLEs, especially position 181, at which a fibrinogenolytic activity increase was found when a basic and larger amino acid substituted by a neutral and smaller one; (iii) an extra α‐helix constructed with a ‘Pro + acidic amino acid + aromatic amino acid’ pattern was found in the SVTLEs from Gloydius and Agkistrodon snakes, although it does not necessarily imply an effect on the fibrinogenolytic activity of the SVTLEs. This study provided some new insight into the activity of SVTLE.