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At least 469 records · Page 26Linked to original sources
PubMed1987

Second-step reconcentration of environmental samples by ammonium sulfate flocculation of beef extract.

Some enteric viruses are sensitive to the acid environment utilized during the concentration of viruses from water. The use of a neutral flocculant, neutralized ammonium sulfate at 50% saturation, permitted the recovery of 97% of the simian rotavirus SA-11, 87% of Coxsackievirus B-4, and 88% of poliovirus type 1. This method should permit a better recovery of enteric viruses from the environment.

Ammonium Sulfate↗
PubMed1992

Fluorescence study of lectinlike receptors involved in the flocculation of the yeast Saccharomyces cerevisiae.

Flocculation of some yeasts involves lectinlike receptors with two different patterns of inhibition by sugars: mannose sensitive (MS) and glucose-mannose sensitive (GMS). The visualization and quantification of these receptors were performed using neoglycoproteins fluorescent probes. Fluorescence microscopy showed a homogeneous distribution of surface receptors for the strain belonging to the MS group and a polar distribution for cells belonging to the GMS group. Affinity constants, estimated by fluorimetry, were shown to have different values (MS, 2.6 +/- 0.7 x 10(5) M-1; GMS, 2 +/- 1 x 10(6) M-1), but the number of sites was estimated to be smaller for strain NCYC 1195 which belongs to the GMS group than for strain NCYC 869 from the MS group (MS, 2.4 +/- 0.2 x 10(7) sites/cell; GMS, 3.9 +/- 0.8 x 10(6) sites/cell).

Flocculation↗
PubMed1975

Anti-DNA Investigated the DNA bentonite flocculation technique.

The DNA bentonite flocculation test was used to investigate the presence of antibody to DNA. In most sera a prozone-like phenomenon was found, caused by a non-specific inhibition of serum. Anti-DNA was found with extreme frequency in patients with SLE, chronic liver disease, acute hepatitis, infectious mononucleosis, and blood donors over the age of 60, but was found rarely or not at all in patients with some other disease or blood donors under 60 years of age.

Adolescent↗
PubMed2000

Enhancement of plant stem growth by flocculation of the antibiotic-producing bacterium, Pseudomonas fluorescens S272, on the roots.

The antibiotic-producing bacterium, Pseudomonas fluorescens, is assumed to be important in protecting plants from soilborne diseases. S. fluorescens S272, a hyper-producing strain of pyoluteorin (PT) and 2,4-diacetylphloroglucinol (DG), had previously been isolated from soil. The present paper reported that the growth of water-cultivated Kaiware radish was promoted to 120-140% of its normal level by the coaddition of an S272 culture broth (0.01-1% v/v) and a polysaccharide flocculant (1-100 ppm) from Klebsiella pneumoniae H12. Tight adhesion of S272 cells to the root tissue was microscopically observed. The growth promotion is assumed to have been caused by antibiotic effects for the following two reasons: 1) PT (4 mg/l) and DG (24 mg/l) addition to a radish culture enhanced stem growth to 130% of the normal level; 2) a culture solution containing the S272 culture broth (0.01-1% v/v) markedly inhibited the decomposition of hypersensitive chrysanthemum leaves. A soil-cultivation experiment with Gomphrena globosa under natural conditions also exhibited enhanced stem length (160%) by coaddition of the S272 culture broth and H12 polysaccharide. These results suggest that polysaccharide-enhanced adhesion of P. fluorescens S272 cells might be useful for promoting plant growth through the increased antibiotic effect.

Anti-Bacterial Agents↗
PubMed2003

Seasonal change in the number of Cryptosporidium parvum oocysts in water samples from the rivers in Hokkaido, Japan, detected by the ferric sulfate flocculation method.

An epidemiological study was carried out in natural water supplies of Hokkaido, one of the largest dairy prefectures in Japan. To investigate the prevalence of Cryptosporidium parvum (C. parvum) oocysts water samples were collected from three rivers in the eastern area of Hokkaido from August 1999 to October 2001, and C. parvum oocysts were collected and purified by the ferric sulfate flocculation method. The oocysts were detected using the immunofluorescent assay test (IFAT) and 4', 6-diamidino-2-phenylindole (DAPI) staining. The seasonal change in the number of oocysts detected was observed. Oocysts increased in numbers from the late summer to the early autumn (from August to November), thereafter, they exhibited a trend to decrease until December, when no oocysts could be detected. The maximum number of oocysts detected in the three rivers was 3.50, 5.00 and 3.33 oocysts/l, respectively. The oocyst density in river water changed in relation to the season in 1999, 2000 and 2001. This report first cleared up the seasonal changes in C. parvum oocysts number in river water.

Animals↗
PubMed2006

Extracellular polymers in partly ozonated return activated sludge: impact on flocculation and dewaterability.

The purpose of this study was to evaluate the influence of partial ozonation of return activated sludge on settling properties and dewaterability of sludge. Sequencing batch reactors with two sets of aerobic and alternating anoxic/aerobic conditions were used. In each set, one reactor served as a control and the other was subject to the ozone treatment (doses in the range of 0.016-0.080 mg O3/mg TSS of initial excess sludge). The level of total suspended solids (TSS) in each reactor was controlled at 1,800 mg/l. To evaluate settleability and dewaterability, settling kinetic studies, sludge volume index (SVI) and capillary suction time test (CST) were used. For extraction and quantifying sludge biopolymers, thermal-ethanolic extraction was employed. The ratio of bound-to-total extracellular polymer substances (EPS) was higher for the strictly aerobic reactor than for the alternating anoxic/aerobic one, indicating the stronger structure of the aerobic flocs. After ozone treatment, the fraction of bound EPS was released and solubilized, increasing soluble EPS. Increased apparent food-to-microorganism (F/M) ratio favoured production of EPS in ozonated reactors, enhancing flocculation, which had potential to improve settling. Dewaterability, measured by CST test, was better in alternating anoxic/aerobic reactors than in aerobic ones, indicating that incorporation of an anoxic zone for biological nutrient removal leads to improvement in sludge dewatering. The negative impact of ozonation on dewaterability was minimal in terms of the long-term operation.

Aerobiosis↗
PubMed1998

Particle size determination of a flocculated suspension using a light-scattering particle size analyzer.

Microscopy is a useful and direct method for measuring the particle size of a suspension because, in addition to the particle size and size distribution, it provides visual detection of the shape and state of aggregation of the particles in the suspension. However, this method suffers from the shortcomings of being tedious and time consuming. In this study, a light-scattering particle size analyzer was used to determine the particle size and size distribution of a flocculated suspension. The sonication of the sample prior to and during measurement was found to be critical in ensuring that data are representative of the size distribution of the primary particles of the suspension. The light-scattering results were further confirmed by data generated using a polarized light microscope equipped with an image analyzer.

Benzocaine↗
PubMed1976

Preliminary observations on the use of the capillary flocculation test for the diagnosis of heartwater (Cowdria ruminantium infection).

A capillary flocculation test was developed to diagnose heartwater disease of ruminants. Antigen was prepared from the brains of cattle and goats highly infected with Cowdria ruminantium. Sera were obtained from experimentally infected ruminants which either recovered naturally or with the aid of oxytetracycline treatment. Antibodies were first detected one to two weeks after clinical recovery or after treatment, and persisted for periods varying between one and four weeks. Control sera collected from cattle (sheep) and goats in the Netherlands where heartwater does not occur, or from animals serologically positive for Anaplasma marginale or Eperythrozoon ovis infections, did not react to the test.

Animals↗
PubMed2004

[Removal of turbidity and effect of humic acid in flocculation by polyferric chloride].

The removals of humic acid and turbidity by polyferric chloride under different coagulation conditions were studied (pH = 4, 7, 10). Zeta potential, turbidity and humic acid removal efficiency were analyzed. Experimental results showed that the dosage and scope of polyferric chloride (PFC) is the narrowest and the residual turbidity is biggest when pH = 4, the dosage and scope of PFC is the broadest and the residual turbidity is the least when pH = 10; Fe(III) can complex with humic acid under acidic condition; The effect of flocculation is not influenced by the presence of humic acid.

Chlorides↗
PubMed2003

A novel technology to improve drinking water quality: a microbiological evaluation of in-home flocculation and chlorination in rural Guatemala.

An estimated 1 billion persons in low-income countries do not have access to improved drinking water. Chlorine, a useful water treatment agent, is less effective in turbid water, and lacks a visible effect, limiting its acceptability. A product incorporating precipitation, coagulation, flocculation, and chlorination technology (combined product) to reduce microbial, organic and heavy metal contaminants in water was evaluated. The combined product's microbiological efficacy in Guatemalan villagers' households was evaluated. One hundred randomly selected households from four neighboring Guatemalan villages were enrolled. Three groups received the combined product and either the Centers for Disease Control (CDC) water storage vessel, a covered bucket with spigot, or no vessel. One group received chlorine bleach and the CDC water storage vessel, and one group no intervention. Household water samples were collected for 4 weeks and Escherichia coli, chlorine, and turbidity levels were measured. Potable water was defined as having less than one E. coli per 100 ml. Eight (8%) baseline water samples were potable. Follow-up water samples were more likely to be potable than control samples (combined product and traditional vessel 83%; combined product and CDC vessel 92%; combined product and covered bucket with spigot 93%; chlorine and CDC vessel 92%; versus control 5%). Among combined product users, 98% reported improved water clarity compared with 45% of chlorine bleach users (p < 0.0001). The combined product technology improved water potability as effectively as chlorine bleach; improved water clarity could motivate more persons to effectively treat their water.

Anti-Bacterial Agents↗
PubMed2004

Turbidity-based monitoring of particle concentrations and flocculant requirement in wastewater pre-treatment.

The removal of particulate organic material in the first step of wastewater treatment may result in significant savings of reactor volume and energy at wastewater treatment plants, because the organic loading to pursuing unit operations can be reduced. This article describes experiments into the possibility of using turbidity measurements as a tool to quantify the concentration of particles in raw wastewater and, based on the result, assess the organic polymer requirement. A feed forward polymer dosing strategy based on a fixed polymer to influent-turbidity ratio was developed and tested. The experimental work confirms that turbidity measurements can be used to quantify particulate COD. For the investigated wastewater (both untreated and flocculated samples) a linear relationship was found in a wide range of particulate COD (100-900 mg O2 x l(-1)) and turbidity (50-450 NTU). On-line turbidity measurements showed that the particle concentrations in the tested municipal wastewater varied significantly. During dry weather conditions the turbidity fluctuated from 100 to 400 NTU, while in rainy periods fluctuations of 100 to >1,000 NTU were measured. The tested turbidity-related polymer dosing method could be used to create different, constant levels of particle removal, despite large particle concentration variations in the influent. Moreover, it resulted in higher removal efficiencies and a more stable operation compared to the dosing of fixed polymer dose per unit of volume.

Chemical Precipitation↗
PubMed2004

Temperature effects on flocculation, using different coagulants.

Temperature is known to affect flocculation and filter performance. Jar tests have been conducted in the laboratory, using a photometric dispersion analyser (PDA) to assess the effects of temperature on floc formation, breakage and reformation. Alum, ferric sulphate and three polyaluminium chloride (PACI) coagulants have been investigated for temperatures ranging between 6 and 29 degrees C for a suspension of kaolin clay in London tap water. Results confirm that floc formation is slower at lower temperatures for all coagulants. A commercial PACl product, PAX XL 19, produces the largest flocs for all temperatures; and alum the smallest. Increasing the shear rate results in floc breakage in all cases and the flocs never reform to their original size. This effect is most notable for temperatures around 15 degrees C. Breakage, in terms of floc size reduction, is greater for higher temperatures, suggesting a weaker floc. Recovery after increased shear is greater at lower temperatures implying that floc break-up is more reversible for lower temperatures.

Alum Compounds↗
PubMed2004

[Effect of growth phase on the flocculation of algal cells using clays].

Four different growth phases, late lag phase, middle logarithmic phase, late logarithmic phase and early senescence phase of Microcystis aeruginosa 469 were studied for their surface hydrophobicity (xylene-water system) and surface charge (Zeta potential), followed by flocculation tests with sepiolite of 0.2 g/L. The results showed that the values of hydrophobicity were 64%, 48%, 58% and 70%, and the algal removal efficiencies after 60 min were 97%, 87%, 81% and 99% respectively, indicating a good relationship between surface hydrophobicity and removal efficiency (R = 0.7-0.8), but not the surface charge. Surface hydrophobicity and removal efficiency for the algal cells of Microcystis aeruginosa both varied with growth phase in a sequence of senescence phase > lag phase > logarithmic phase.

Aluminum Silicates↗
PubMed2005

[Continuous ethanol fermentation using self-flocculating yeast strain and bioreactor system composed of multi-stage tanks in series].

A continuous ethanol fermentation system composed of four-stage tank fermentors in series and with a total working volume of 4000 mL was established. The first fermentor was designated as the seed fermentor and the others for ethanol fermentation. A self-flocculating yeast strain developed by protoplast fusion of Saccharomyces cerevisiae and Schizosaccharomyces pombe was applied. Two-stage corn powder enzymatic hydrolyzate containing reducing sugar 100 g/L, together with 2.0 g/L (NH4)2HPO4 and KH2PO4, was used as yeast seed culture medium and fed into the seed fermentor at the dilution rate of 0.017h (-1). Meanwhile, the hydrolyzate containing reducing sugar 220 g/L, added with 1.5 g/L (NH4)2HPO4 and 2.5 g/L KH2PO4, was used as ethanol fermentation substrate and fed into the second fermentor at the dilution rates of 0.017, 0.025, 0.033, 0.040 and 0.050 h(-1) (based on the total working volume of the three fermentors), respectively. The chemostat states on which all of the monitoring parameters, including residual sugar, ethanol and yeast cell biomass concentrations, were maintained relatively constant were observed for seed cultivation and ethanol fermentations when the fermentation system was operated at the dilution rates of 0.017, 0.025, 0.033 and 0.050 h(-1). Yeast cells were observed being partly immobilized because significant yeast cell biomass concentration differences between the broth out of and inside the fermentors were detected. Moreover, the oscillations of residual sugar, ethanol and yeast cell biomass concentrations were observed when the fermentation system was operated at the dilution rate of 0.040 h(-1). The broth containing more than 12% (V/V) ethanol and less than 0.11% (W/V) residual reducing sugar and 0.35% (W/V) residual total sugar was produced when the dilution rate was controlled at no more than 0.033 h(-1). The ethanol productivity was calculated to be 3.32(g x L(-1) x h(-1)) for the dilution rate of 0.033 h(-1), which increased nearly 100% compared with that for conventional ethanol fermentation technologies using freely suspended yeast cells.

Bioreactors↗
PubMed2005

[Construction of flocculation selective vector and expression of beta-glucosidase gene in Saccharomyces cerevisiae].

Selective markers used in yeast vector for gene manipulation were usually drug resistance or autotrophy. Unfortunately, drug resistance selective marker requires drug sensitive host and most industrial strains were not autotrophy. In this paper, flocculation gene (FLO1) from Saccharomyces cerevisiae ABXL-1D was amplified by PCR, sequenced and cloned to construct an expression vector. The new vector was easy to manipulate and suitable for broad host of yeasts without either autotrophy or drugs. beta-glucosidase gene from Bacillus polymyxa was cloned with the vector and expressed in Saccharomyces cerevisiae. The specific activity of beta-glucosidase of the recombinant yeast cell-free extract was 3.91 u/mg protein. The residue glucose of the recombinant yeast was considerably reduced in mixed fermentation of glucose and cellobiose. It should be favorable for ethanol fermentation when utilize lignocellulosic biomass as raw material.

Bacillus↗
PubMed2005

Protein amino acid composition of plasma membranes affects membrane fluidity and thereby ethanol tolerance in a self-flocculating fusant of Schizosaccharomyces pombe and Saccharomyces cerevisiae.

A combination of three amino acids including 1.0 g/L isoleucine, 0.5 g/L methionine and 2.0 g/L phenylalanine was found to enhance ethanol tolerance of a self-flocculating fusant of Schizosaccharomyces pombe and Saccharomyces cerevisiae. When subjected to 20% (V/V) ethanol for 9 h at 30 degrees C, all cells died whereas 57% remained viable for the cells grown in the presence of the three amino acids. Based on the analysis of protein amino acid composition of plasma membranes and the determination of plasma membrane fluidity by measuring fluorescence anisotropy using diphenylhexatriene as a probe, it was found that the significantly increased ethanol tolerance of cells grown with the three amino acids was due to the incorporation of the supplementary amino acids into the plasma membranes, thus resulting in enhanced ability of the plasma membranes to efficiently counteract the fluidizing effect of ethanol when subjected to ethanol stress. This is the first time to report that plasma membrane fluidity can be influenced by protein amino acid composition of plasma membranes.

Amino Acids↗
PubMedDate not supplied

[Evaluation of the sanitary-and-epidemiological safety of flocculating agents used for portable water purification].

Polyelectrolytes used in the practice of water supply to the population were comparatively hygienically studied, by using a complex of hazard indices and a new approach to sanitary-and-epidemiological evaluation of the safety of water-soluble polymers is substantiated. The anionic and cationic flocculating agents from different chemical classes, such as Superflok A-100, Fennopol A 321E, Fennopol K 221E, Praestol 2530 TR, VPK-402, Superflok C-577, Saipan, KF-91, Ecosol-401, a low molecular-weight sodium polyacrylate were tested as model compounds. Moreover, the information already available in the scientific literature on the toxicity of synthetic polyelectrolytes was analyzed. The generalized maximum permissible concentrations were substantiated for individual chemical classes of synthetic polyelectrolytes: polyacrylamides, polyamines, polydiallyldimethylammonium chloride.

Acrylic Resins↗