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PubMed2004

Murine leukemia virus clearance by flocculation and microfiltration.

Clearance of murine leukemia virus from CHO cell suspensions by flocculation and microfiltration was investigated. Murine leukemia virus is a retrovirus that is recommended by the U.S. Food and Drug Administration for validating clearance of retrovirus-like particles. Due to biosafety considerations, an amphotropic murine leukemia virus vector (A-MLV) that is incapable of self-replication was used. Further, A-MLV is incapable of infecting CHO cells, thus ensuring that infection of the CHO cells in the feed did not result in a reduced virus titer in the permeate. The virus vector contains the gene for the enhanced green fluorescent protein (EGFP) to facilitate assaying for infectious virus particles. The virus particles are 80-130 nm in size. The feed streams were flocculated using a cationic polyelectrolyte. Microfiltration was conducted using 0.1 and 0.65 microm pore size hollow fiber membranes. The level of virus clearance in the permeate was determined. For the 0.1 microm pore size membranes a 1,000-fold reduction in the virus titer in the permeate was observed for feed streams consisting of A-MLV, A-MLV plus flocculant, A-MLV plus CHO cells, and A-MLV plus flocculant and CHO cells. While the flocculant had little effect on the level of virus clearance in the permeate for 0.1 microm pore size membranes, it did lead to higher permeate fluxes for the CHO cell feed streams. Virus clearance experiments conducted with 0.65 microm pore size membranes indicate little clearance of A-MLV from the permeate in the absence of flocculant. However, in the presence of flocculant the level of virus clearance in the permeate was similar to that observed for 0.1 microm pore size membranes. The results obtained here indicate that significant clearance of A-MLV is possible during tangential flow microfiltration. Addition of a flocculant is essential if the membrane pore size is greater than the diameter of the virus particles. Flocculation of the feed stream leads to an increase in the permeate flux.

Animals↗

PubMed1987

Yeast flocculation: kinetics and collision theory.

Flocculent yeast cells have an absolute requirement for mechanical energy input in order for flocculation to occur. Flocculation is arrested by cessation of energy input. The initial rate of flocculation increases as the square of the cell concentration. There is a minimum shaking speed to initiate flocculation and thereafter the initial rate of flocculation increases exponentially with the shaking speed. The minimum shaking speed for flocculation to occur increases with pH value. Activation energy for flocculation, derived from Arrhenius-like plots, varies with pH value. We propose that activation energy is required to overcome mutual repulsion between charged yeast cells and allow flocculent bonds to be formed.

Calcium↗

PubMed1993

Yeast flocculation: lectin synthesis and activation.

Yeast flocculation involves binding of surface lectins to carbohydrate receptors on neighbouring cell walls. Brewing strains of Saccharomyces cerevisiae normally become flocculent in the stationary phase of growth. This paper presents evidence that lectins are synthesized in exponential phase, inserted into the cell wall, and activated later at the time of flocculation onset. Cycloheximide failed to prevent flocculation unless it was added in early growth; with later additions progressively larger degrees of flocculation occurred. Flocculation onset was delayed by cycloheximide but was otherwise cycloheximide insensitive. Preflocculent cells could be artificially activated to full flocculation by heat. Artificial activation of samples from growing yeast cultures confirmed the progressive synthesis of lectins throughout exponential growth. Pronase E treatment of whole cells prior to heating prevented any activation of flocculation. It was concluded that lectins were synthesized continuously from an early stage of growth and rapidly inserted into the cell wall (accessible by pronase E), where they remained inactive for up to 14 h, before being activated at flocculation onset by an as-yet unknown mechanism. It was found that lectin synthesis and activation occurred in all brewing strains tested.

Beer↗

PubMed1991

Role of cations in the flocculation of Saccharomyces cerevisiae and discrimination of the corresponding proteins.

Asexual yeast flocculation was studied using strong flocculents of Saccharomyces cerevisiae. The inhibitory effect of cations on flocculation is considered to be caused by competition between those cations and Ca2+ at the binding site of the Ca(2+)-requiring protein that is involved in flocculation. Inhibition of flocculation by various cations occurred in the following order: La3+, Sr2+, Ba2+, Mn2+, Al3+, and Na+. Cations such as Mg2+, Co2+, and K+ promoted flocculation. This promoting effect may be based on the reduction of electrostatic repulsive force between cells caused by binding of these cations anionic groups present on the cell surface. In flocculation induced by these cations, trace amounts of Ca2+ excreted on the cell surface may activate the corresponding protein. The ratio of Sr2+/Ca2+ below which cells flocculated varied among strains: for strains having the FLO5 gene, it was 400 to 500; for strains having the FLO1 gene, about 150; and for two alcohol yeast strains, 40 to 50. This suggests that there are several different types of cell surface proteins involved in flocculation in different yeast strains.

Adsorption↗

PubMed2000

Initial Stage Dynamics of Bridging Flocculation of Polystyrene Latex Spheres with Polyethylene Oxide.

The kinetics of bridging flocculation of polystyrene latex (PSL) particles induced by addition of excess polyethylene oxide (PEO) in the initial stage was studied using standardized mixing flow generated in an end-over-end rotation apparatus. To clarify the effect of the rate of polymer supply, flocculation experiments were performed by changing polymer concentration (C(p)). As was found in previous investigation, the progress of flocculation is divided into two stages. The first stage is characterized by an enhancement of the rate of flocculation by polymer addition. The increase in polymer concentration results in a higher enhancement but in a shorter duration for this stage. In the second stage, the flocculation is essentially stopped due to the appearance of steric stabilization. It was found that the ultimate degree of flocculation goes through a maximum against C(p). That is, when C(p)>==1.0 ppm, the ultimate degree of flocculation decreases with increased C(p). In this region, a clear crossover from the first stage to the second stage was observed. In the extreme case, evidence of a slight setback of flocculation was confirmed, which implies the breakup of metastable bridges by the application of additional fluid shear. When C(p)<==1.0 ppm, the ultimate degree of flocculation decreases with decreased C(p). The crossover from the first stage to the second stage appears more gradual at lower C(p). These results were observed irrespective of ionic strength. This result was interpreted as the elimination of a bare surface due to the spreading of a steric layer of adsorbed polymer. The characteristic time for reconformation of the polymer at a bare colloidal surface was estimated to be a few seconds. Copyright 2000 Academic Press.

Journal Article↗

PubMed1985

Quantitative analysis of mitochondrial flocculent densities in rat hepatocytes during normothermic and hypothermic ischemia in vitro.

The development of flocculent densities in mitochondria as a sign of irreversible cell injury in rat hepatocytes has been studied by quantitative electron microscopy during in vitro ischemia under both normothermic (37 degrees C) and hypothermic (4 degrees C) conditions. At 37 degrees C flocculent densities first appear after 1 h ischemia; at this stage they are small in diameter (170 nm) and occur in only 8% of mitochondria. After 1.5 hour ischemia, flocculent densities increase in diameter (207 nm) and are seen in 37% of mitochondria. Death of the majority of hepatocytes seems to occur between 1.5 and 2 h ischemia since at this stage the percentage of mitochondria containing flocculent densities reaches a maximum (48%). However, flocculent densities continue to increase in size (to 337 nm diam.) up to between 2 and 4 h ischemia (the prenecrotic phase). In contrast, at 4 degrees C signs of ischemic damage to hepatocytes are considerably delayed. Flocculent densities of comparable size and frequency to those observed after 1 h ischemia at 37 degrees C are not seen till as late as 4 days at 4 degrees C. At the latter temperature, only after 7 days ischemia a substantial rise (to about 25%) in the proportion of mitochondria containing flocculent densities occurs. A further slow increase in size and in the percentage of mitochondria containing densities occurs up to 14 days ischemia at 4 degrees C. It is concluded that the development of flocculent densities may be used only as a parameter of irreversible damage in cells with a sufficient number of mitochondria, such as hepatocytes, under normothermic conditions. With ischemia at 4 degrees C, possibly due to a different protein denaturation pattern, the development of flocculent densities is of much less value as an indication of irreversible cell damage and cannot, therefore, be considered as a reliable sign of cellular damage in organs stored at 4 degrees C for transplantation purposes.

Animals↗

PubMed2003

The influence of PEO/poly(vinyl phenol-co-styrene sulfonate) aqueous complex structure on flocculation.

Colloidal suspensions were flocculated with complexes formed from high molecular weight polyethylene oxide (PEO) and a cofactor. Poly(vinyl phenol-co-potassium styrene sulfate) (PKS) or poly(styrene-co-styrene sulfonate) (PS-co-SSS) copolymers were used as the cofactors for this work. The larger the PEO/cofactor complex species, the better the initial flocculation. Factors such as increasing temperature or ionic strength that gave smaller complexes also gave poorer flocculation. Cofactor performance was sensitive to the balance of hydrophobic phenolic groups and hydrophilic styrene sulfonates. If there are too few phenolic groups, the PEO/PSK complexes are large but are too weak to give shear-resistant flocs, whereas complexes formed with high phenolic content PSK are relatively small, giving poorer flocculation but more shear-resistant flocs. Both phenyl and phenol groups are effective as the hydrophobic component in the cofactor. The hydrogen-bonding potential of phenolic cofactors does not seem to offer much advantage relative to phenyl groups. A crucial step in the flocculation is the adsorption of PEO/cofactor complex onto the target colloids. Thus, flocculation is sensitive to the target colloid surface chemistry. Positively charged precipitated calcium carbonate and surfactant-free polystyrene latex are particularly easy to flocculate because adsorption is driven by electrostatic and hydrophobic interactions, respectively. By contrast, the latex coated with hydrophilic poly(N-isopropylacrylamide) (PNIPAM) does not flocculate because the PEO/cofactor complex does not bind to PNIPAM. Finally, the flocculation of highly negatively charged, dextran sulfate coated calcium carbonate seems to be stimulated by the presence of soluble calcium ions that make the complex less soluble and more likely to adsorb.

Journal Article↗

PubMed2003

The effect of pretreatment of calcite dispersions with anionic sodium polyacrylate on their flocculation behavior induced by cationic starch.

The flocculation performance of cationic starches on calcite pretreated with anionic sodium polyacrylate (NaPA) was investigated by measuring the mean particle size and the dynamic mobility of the calcite dispersions. Cationic starches of different molecular weight and degree of substitution were used. By varying the amount of anionic sodium polyacrylate, which has a strong affinity to the calcium carbonate surface, one is able to anionically modify the particles and reverse the charge character of the originally cationic calcium carbonate. By such modification of the charge character of the calcium carbonate dispersion, it is possible to approach the mechanisms of flocculation caused by cationic macromolecules like starch. The importance of different mechanisms of flocculation, such as bridging, charge neutralization, and flocculation induced by polyelectrolyte complexes (PEC), was further investigated in this work. It was found that when the NaPA is completely absorbed at the calcite surfaces the mechanism of the flocculation induced by the starch is mainly bridging flocculation. Excess NaPA in the calcium carbonate dispersion will result in polyelectrolyte complexes formed between the non-absorbed NaPA and the oppositely charged starch polymers. These complexes will in most cases strongly enhance the flocculation due to mainly charge neutralization. Depending on the ratio of non-absorbed NaPA and the starch in the aqueous phase, the calcite dispersion is either re-stabilized or more strongly flocculated due to the formed polyelectrolyte complexes. Both the mobility and the particle size measurements support the mechanisms described. It was further demonstrated that the molecular weight and degree of substitution of the starches might be adjusted to control the flocculation behavior.

Journal Article↗

PubMed2004

Scaling behavior of delayed demixing, rheology, and microstructure of emulsions flocculated by depletion and bridging.

This paper describes an experimental comparison of microstructure, rheology, and demixing of bridging- and depletion-flocculated oil-in-water emulsions. Confocal scanning laser microscopy imaging showed that bridging-flocculated emulsions were heterogeneous over larger length scales than depletion-flocculated emulsions. As a consequence, G' as determined from diffusing wave spectroscopy (DWS) corresponded well with G' as measured macroscopically for the depletion-flocculated emulsions, but this correspondence was not found for the bridging-flocculated emulsions. The heterogeneity of bridging-flocculated emulsions was confirmed by DWS-echo measurements, indicating that their structure breaks up into large fragments upon oscillatory shear deformation larger than 1%. Depletion- and bridging-flocculated emulsions showed a different scaling of the storage modulus with the volume fraction of oil and a difference in percolation threshold volume fraction. These differences will be discussed on the basis of the two types of droplet-droplet interactions studied. Gravity-induced demixing occurred in both emulsions, but the demixing processes differed. After preparation of bridging-flocculated emulsions, serum immediately starts to separate, whereas depletion-flocculated systems at polysaccharide concentrations in the overlap regime usually showed a delay time before demixing. The delay time was found to scale with the network permeability, B; the viscosity, eta, of the aqueous phase; and the density difference between oil and water, Deltarho, as tdelay approximately B(-1)etaDeltarho(-1). The results are in line with the mechanism proposed by Starrs et al. (J. Phys.: Condens. Matter 2002, 14, 2485-2505), where erosion of the droplet network leads to widening of the channels within the droplet networks, facilitating drainage of liquid.

Journal Article↗

PubMed1992

Flocculence of Saccharomyces cerevisiae cells is induced by nutrient limitation, with cell surface hydrophobicity as a major determinant.

Initiation of flocculation ability of Saccharomyces cerevisiae MPY1 cells was observed at the moment the cells stop dividing because of nitrogen limitation. A shift in concentration of the limiting nutrient resulted in a corresponding shift in cell division and initiation of flocculence. Other limitations also led to initiation of flocculence, with magnesium limitation as the exception. Magnesium-limited S. cerevisiae cells did not flocculate at any stage of growth. Cell surface hydrophobicity was found to be strongly correlated with the ability of the yeast cells to flocculate. Hydrophobicity sharply increased at the end of the logarithmic growth phase, shortly before initiation of flocculation ability. Treatments of cells which resulted in a decrease in hydrophobicity also yielded a decrease in flocculation ability. Similarly, the presence of polycations increased both hydrophobicity and the ability to flocculate. Magnesium-limited cells were found to be strongly affected in cell surface hydrophobicity. A proteinaceous cell surface factor(s) was identified as a flocculin. This heat-stable component had a strong emulsifying activity, and appears to be involved in both cell surface hydrophobicity and in flocculation ability of the yeast cells.

Amino Acids↗

PubMed2001

Isolation and biochemical characterization of cell wall tight protein complex involved in self-flocculation of Kluyveromyces bulgaricus.

Flocculation of yeasts is a cell-cell aggregation phenomenon which is driven by interactions between cell wall lectins and cell wall heteropolysaccharides. In Sabouraud medium, Kluyveromyces bulgaricus was highly flocculent. Incubation of flocculent K. bulgaricus cells with EDTA or Hecameg led to extracts showing hemagglutinating and flocculating properties. Purification of the extracts by native PAGE gave two bands which allowed flocculation of deflocculated K. bulgaricus. Both bands with specific reflocculating activity were composed of five subunits, of which only three possessed weak reflocculating activity upon deflocculated yeast. The mixture of these three proteins allow the recovery of initial specific reflocculating activity of the complex. These three proteins, denoted p28, p36 and p48, presented, in their first 15 amino acids, homologies with glycolysis enzymes, i.e., 3-phosphoglycerate mutase, glyceraldehyde-3-phosphate dehydrogenase and enolase, respectively. However, no such enzymatic activity could be detected in the crude extract issued from treatment with EDTA and Hecameg of flocculent yeast cells. When yeasts had grown in glucose poor medium, flocculation was drastically affected. The EDTA and Hecameg crude extracts showed weak reflocculating activity. After PAGE, the protein complexes did not appear in the EDTA extract, but they did appear in the Hecameg crude extract. These results suggest that: (i) self-flocculation of K. bulgaricus depends on the expression of different floc-forming protein complex, (ii) these proteins are galactose specific lectins showing homologies in their primary structure with glycolysis enzymes.

Amino Acid Sequence↗

PubMed1990

Selective flocculation with chitosan in Escherichia coli disintegrates: effects of pH and nuclease treatment.

The flocculation of cell debris from a beta-galactosidase constitutive E. coli with chitosan as a flocculant was studied to investigate the possibility of obtaining a selective flocculation in cell disintegrates with high product recoveries. The flocculation removed 98% of the cell debris by 30 min sedimentation under gravity, which should be compared to a separation of the cell debris without flocculation of only 70% by centrifugation at 15,000 g. Optimal flocculation dosages varied between 12 and 43 mg chitosan g-1 dry weight of cells, depending on pH. The yield of the product beta-galactosidase reached 60% at optimal pH. Hydrolysis of the nucleic acids by DNAase and RNAase decreased the optimal flocculation dosages considerably. The study showed that the flocculation is somewhat selective, since chitosan also removed 85% of the nucleic acids and 50% of the proteins, which contributed to the purification of the protein solution.

Bacterial Proteins↗

PubMed1996

Induction of flocculation in brewing yeasts by change in pH value.

Most brewing strains of Saccharomyces cerevisiae flocculate following growth in beer wort. However, many do not flocculate in laboratory culture media, because their initial pH and buffering capacity do not correspond to the pH range within which these yeasts flocculate. Many, though not all, NewFlo phenotype brewing yeasts flocculate within a narrow pH range only; this is indicative of the existence of more than one NewFlo flocculation phenotype. Such strains may be flocculated by small alterations of pH to within the flocculation range. Induction of flocculation by pH change may be used to separate cells from media at any stage during fermentation.

Beer↗

PubMed1981

[Characterization of cell wall constituents involved in the flocculation of Saccharomyces uvarum yeast strains].

Cell walls of flocculent strains (0006) and non flocculent strains (0019) of Saccharomyces uvarum (Carlsbergensis), grown in different media and taken in both growth and stationary phases, were treated with water and with 2 per cent (W/V) potassium hydroxide. This treatment yielded four fractions (FI, FII, FIII and FR). The fractions FI isolated from the flocculent cell walls contained more mannose and less protein than the corresponding fractions FI isolated from the non flocculent cell walls. The amino-acid composition was also different between the two types of fractions. A radioactive labelling technique revealed that the FI and the walls from flocculent cells bound on average two to three times as much 45Ca as did the FI and the walls from non flocculent yeast. The substitution of carboxyl groups in FI and walls with glycine methyl ester led to a great drop of the 45Ca binding capacity. This result suggests that carboxyl groups of the cell walls are involved in the flocculation process. But flocculation seems to be a phenomenon more complex than the simple formation of a Ca2+ bridge, the involvement of "lectin like" components easily removed from the cell walls, should not be rejected.

Amino Acids↗

PubMed2001

Screening of chitosans and conditions for bacterial flocculation.

Chitosans with different chemical compositions and molecular weights have been evaluated as flocculants of Escherichia coli suspensions. The flocculation performance of chitosans at different conditions (pH, ionic strength) was followed by residual turbidity measurements. For precise comparison, the chitosan concentrations corresponding to 75% flocculated bacteria (x(75)) were calculated from a mathematical function fitted to the measured data. At all conditions, an increase in the fraction of acetylated units (F(A)) resulted in lower x(75) and thereby better flocculation efficiency. Especially the most acetylated chitosans (F(A) 0.49 and F(A) 0.62) were excellent flocculants. An increase in F(A) from 0.002 to 0.6 caused a 10-fold reduction in necessary concentrations, at both pH 5 and 6.8. pH was a rather insignificant factor in the range 4-7.4, further pH increase led to either increase of necessary doses at low F(A) or sudden ceasing of flocculation at high F(A). The chitosans flocculated in a broad range of molecular weights, although an increase in molecular weight was a favorable factor. Increase in ionic strength caused a severalfold reduction in x(75) for all chitosans and considerable broadening of flocculation intervals.

Biopolymers↗

PubMed1976

Role of wall phosphomannan in flocculation of Saccharomyces cerevisiae.

Treatment with 60% hydrofluoric acid (HF) removed most of the phosphorus and small amounts of mannan, glucan and protein from walls of two non-flocculent strains (NCYC366 and NCYC1004) and two flocculent strains (NCYC1005 and NCYC1063) of Saccharomyces cerevisiae. Organisms of all strains showed increased flocculating ability following HF treatment. Flocculation of untreated organisms of NCYC1005 and NCYC1063, and of HF-treated organisms of all four strains, declined appreciably when they were washed in deionized water, with or without EDTA, and the flocculation was measured in deionized water instead of in 0-05 M-sodium acetate containing Ca2+. Treatment with 1,2-epoxypropane also caused a decrease in the flocculating ability of these organisms. Extracting the lipids from organisms of strains NCYC366 and NCYC1004 had no effect on their flocculating ability, but decreased the flocculating ability of organisms of strains NCYC1005 and NCYC1063. pH-electrophoretic mobility curves of untreated and HF-treated organisms confirmed the loss of wall phosphate by HF treatment, and indicated that HF treatment had little effect on the content of protein carboxyl groups in the outer wall layers. Mannose at 0-22 M completely prevented floc formation by organisms of strain NCYC1063; but, even at 0-33 M, it had very little effect on floc formation by HF-treated organisms of strains NCYC366 and NCYC1063. Organisms of all four strains bound fluorescein-conjugated concanavalin A to the same extent after treatment with HF as before, but this treatment led to a greatly diminished binding of of fluorescein-conjugated antiserum raised against organisms of strain NCYC366. The results indicate that phosphodiester linkages in yeast-wall mannan are not involved in bride formation through Ca2+ during floc formation and that this arises principally through carboxyl groups.

Binding Sites, Antibody↗

PubMed2026

Moderate expression and activity of flocculins underlie the characteristic flocculation phenotype of Saccharomyces pastorianus.

Flocculation is a key technological trait in lager brewing, governing fermentation performance, yeast recovery, and beer quality. In the allo-aneuploid hybrid yeast Saccharomyces pastorianus, the genetic basis of flocculation remains poorly resolved due to its complex dual sub-genome architecture. Here, we systematically re-annotated and functionally characterized the complete FLO gene repertoire of the Group II strain CBS 1483. Thirteen FLO genes were identified, including allelic variants and a previously uncharacterized adhesin, Flo12, containing a Hyphal_reg_CWP domain instead of the canonical PA14 lectin-binding domain. Structural modeling revealed strong conservation of Ca²+-binding residues in PA14 domains, alongside repeat-region diversification likely contributing to functional variability. Using optogenetic expression in a FLO-null background, we demonstrated that SpcI-FLO9-1 and SpcI-FLO9-2_1 are the strongest drivers of flocculation, exhibiting NewFlo-like sugar sensitivity. Transcriptomic analysis during 17°P wort fermentation showed dynamic induction of these genes coinciding with flocculation onset. Surprisingly, deletion of both loci in CBS 1483 did not abolish but only delayed sedimentation in wort, accompanied by improved maltose utilization and attenuation. These findings reveal functional redundancy and compensatory mechanisms within the FLO network of lager yeast, highlighting the genetic complexity underlying flocculation, and providing a molecular framework to inform yeast selection, strain development, and optimization of the lager fermentation processes.IMPORTANCEFlocculation, the process by which yeast cells aggregate and settle, is essential for producing clear, high-quality lager beer, and for efficient yeast recovery during brewing. However, the genetic basis of this trait in lager yeast has remained poorly understood because these strains possess unusually complex hybrid genomes. In this study, we systematically identified and characterized the complete set of flocculation genes in the industrial lager yeast Saccharomyces pastorianus CBS 1483. We demonstrated that lager yeast flocculation is not controlled by a single dominant gene, but instead emerges from the combined action of several moderately active adhesion proteins that are expressed at low levels during fermentation. Surprisingly, deleting the two strongest candidate genes only delayed, rather than eliminated, sedimentation, revealing a robust compensatory network that preserves brewing performance. These findings refine the current understanding of yeast flocculation and provide a molecular framework for developing brewing strains with improved fermentation efficiency, product consistency, and flavor quality.

Saccharomyces pastorianus↗

PubMed2005

Household based treatment of drinking water with flocculant-disinfectant for preventing diarrhoea in areas with turbid source water in rural western Kenya: cluster randomised controlled trial.

OBJECTIVE: To compare the effect on prevalence of diarrhoea and mortality of household based treatment of drinking water with flocculant-disinfectant, sodium hypochlorite, and standard practices in areas with turbid water source in Africa. DESIGN: Cluster randomised controlled trial over 20 weeks. SETTING: Family compounds, each containing several houses, in rural western Kenya. PARTICIPANTS: 6650 people in 605 family compounds. INTERVENTION: Water treatment: flocculant-disinfectant, sodium hypochlorite, and usual practice (control). MAIN OUTCOME MEASURES: Prevalence of diarrhoea and all cause mortality. Escherichia coli concentration, free residual chlorine concentration, and turbidity in household drinking water as surrogates for effectiveness of water treatment. RESULTS: In children < 2 years old, compared with those in the control compounds, the absolute difference in prevalence of diarrhoea was -25% in the flocculant-disinfectant arm (95% confidence interval -40 to -5) and -17% in the sodium hypochlorite arm (-34 to 4). In all age groups compared with control, the absolute difference in prevalence was -19% in the flocculant-disinfectant arm (-34 to -2) and -26% in the sodium hypochlorite arm (-39 to -9). There were significantly fewer deaths in the intervention compounds than in the control compounds (relative risk of death 0.58, P = 0.036). Fourteen per cent of water samples from control compounds had E coli concentrations < 1 CFU/100 ml compared with 82% in flocculant-disinfectant and 78% in sodium hypochlorite compounds. The mean turbidity of drinking water was 8 nephelometric turbidity units (NTU) in flocculant-disinfectant households, compared with 55 NTU in the two other compounds (P < 0.001). CONCLUSIONS: In areas of turbid water, flocculant-disinfectant was associated with a significant reduction in diarrhoea among children < 2 years. This health benefit, combined with a significant reduction in turbidity, suggests that the flocculant-disinfectant is well suited to areas with highly contaminated and turbid water.

Adolescent↗