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At least 19 recordsLinked to original sources
PubMed1993

Yeast flocculation: flocculation onset and receptor availability.

Flocculent strains of brewing yeast grow and ferment as single cells and flocculate in the stationary phase of growth. The switch from single-celled yeast growth to multi-celled aggregation, flocculation onset, is of critical importance to the brewing industry. Yeast flocculation involves adhesion of surface-lectins on flocculent cells to carbohydrate receptors on neighbouring cell-walls. The presence of carbohydrate receptors, outer-chain mannan side-branches, was monitored throughout growth of flocculent and non-flocculent strains of Saccharomyces cerevisiae, with particular attention to the growth phases where flocculation is normally developed. Receptors were probed by coflocculation with flocculent strains and by aggregation with concanavalin A, a lectin shown to use the same receptors as flocculation. While considerable variation was found in coflocculation and concanavalin A aggregation between strains, little or no change in receptor availability was found throughout the growth of all yeast strains. Yeast cells could easily be coflocculated at any growth stage. It was concluded that receptor availability is not involved in the process of flocculation onset.

Adhesiveness↗
PubMed1996

Structure of the phosphopeptidomannans from flocculent and non-flocculent yeast Kluyveromyces lactis.

After extraction from whole cells, and purification by gel filtration, the chemical composition and molecular mass estimation of the cell-wall phosphopeptidomannan (PPM) showed no significant difference respectively between flocculent, weakly, very weakly and non-flocculent Kluyveromyces lactis yeast strains. However, when PPMs were tested as ligands of a lectin, extracted from the flocculent strain, the PPM isolated from the flocculent and weakly flocculent strain were recognized to a higher degree than those isolated from the non and very weakly flocculent strains. Acetolysis of PPM extracted from the four strains produced five oligosaccharide fractions corresponding to mono-, di-, tri-, penta-and hexa-saccharides. The flocculent strain was characterised by a high content of di-and penta-saccharides. The 1H NMR analysis of the oligosaccharides demonstrated that the flocculent strain contained equivalent levels of the two mannobioses: Man(alpha 1-->2)Man and Man(alpha 1-->3)Man and of the two mannotrioses Man(alpha 1-->2)Man(alpha 1-->2)Man and Man(alpha 1-->3)Man(alpha 1-->2)Man. In contrast, the non-flocculent and the very weakly flocculent strains contained a single type of mannobiose Man(alpha 1-->2)Man and one type of mannotriose Man(alpha 1-->2)Man(alpha 1-->2)Man.

Acetylglucosamine↗
PubMed2005

[Effect of flocculence of a self-flocculating yeast on its tolerance to ethanol and the mechanism].

Investigation was undertaken for the purpose of examining any possible correlation between flocculence of a self-flocculating fusant of Schizosaccharomyces pombe mutant and Saccharomyces cerevisiae mutant (called fusant SPSC for short) and the tolerance of this strain to ethanol. When exposed to 18% (V/V) ethanol for 7 h at 30 degrees C, 52%, 37% and 9% of viability levels remained for the cells of fusant SPSC and its two parental strains, Sch. pombe mutant and S. cerevisiae mutant respectively. Analysis of phospholipid fatty acid composition of plasma membrane showed that the content of palmitic acid of each flocculating yeast (fusant SPSC or Sch. pombe mutant) was around 2-fold higher than that of free S. cerevisiae mutant, with remarkably lower contents of palmitoleic and oleic acids than the latter. When 0.1 mol/L sodium citrate was initially included in the medium in which cells of each flocculating yeast were grown, free cells rather than aggregates were finally obtained. Furthermore, the content of palmitic acid in the phospholipid fatty acid composition of the plasma membranes of the free cells of each flocculating yeast was found to decrease significantly, with a marked increase in the contents of palmitoleic and oleic acids. As a result, the characteristics of the phospholipid fatty acid composition of the plasma membranes of the free cells of each flocculating yeast were similar to those of S. cerevisiae mutant. Meanwhile, the disappearance of flocculence of each flocculating yeast caused by the action of sodium citrate brought about a steeply decreased tolerance of the free cells to ethanol, thus being equivalent to that of S. cerevisiae mutant. These data suggest that the stronger ethanol tolerance of each flocculating yeast is related to the higher content of palmitic acid in the phospholipid fatty acid composition of the plasma membranes. Thus, the enhancement by flocculence on the tolerance of yeast cells to ethanol as well as its mechanism are first reported in this work.

Bioreactors↗
PubMed2006

Flocculation morphology: effect of particulate shape and coagulant species on flocculation.

Flocculation morphology is a new concept that investigates the morphological characteristics of colloidal particles and coagulants in water during the flocculation process, and the influence that these characteristics have on flocculation process efficiency. This paper is a summary of advances in research on this topic over several years. Morphological characteristics of colloids in natural waters and different kinds of hydrolysed coagulants are investigated, and their effect on colloid stability, flocculation kinetics and efficiency is analysed. It is confirmed that the traditional theory has some deviations in coagulation of nonspherical particles, and these deviations are revised by the flocculation morphology model. Flocculation morphology can not only promote research about flocculation theory, but also instruct the production, application and flocculation control. It can be foreseen that more progress will be made in research and application of flocculation morphology in the near future.

Colloids↗
PubMed1989

Characterization of non-flocculent cells isolated from a culture of flocculent Saccharomyces cerevisiae NCYC 1001.

During cultivation of a flocculent yeast, Saccharomyces cerevisiae 1001, two cell fractions, flocs and free cells, appeared in the medium. Free cells contained cells with a normal ability to flocculate, less flocculent cells and not-flocculent cells. When the non-flocculent cells and not-flocculent cells. When the non-flocculent cell fraction from the postexponential phase of growth was collected and used as an inoculum, the culture showed synchronous growth. The floc forming ability of the yeast cells from this culture increased gradually with the number of divisions.

Chemical Precipitation↗
PubMed1988

Yeast flocculation: factors affecting the measurement of flocculence.

The physical meaning of the residual absorbance of a yeast suspension after flocculation and settling has been investigated. Starting with a dispersed suspension, agitation accelerates flocculation by increasing the probability of collision between particles. As flocculation advances, agitation also breaks the flocs. A stationary state is reached when flocculence (tendency to flocculate) is counterpoised by agitation. If the intensity of agitation is maintained constant, the free cell concentration reflects the flocculence, provided the stationary state is reached. The residual absorbance, determined after settling of the flocs, is a measure of the free cell concentration and represents an adequate parameter to characterize yeast flocculence.

Cell Adhesion↗
PubMed2004

Flocculation performance of a novel synthesized flocculant with low ecological risk.

Combined flocculants with low ecological risk are urgently required in water supply and wastewater treatment in China. A novel flocculant was thus developed under the condition of low ecological risk (noted as CAS). The experiments to examine wastewater treatment performance of the new product showed that there was favourable performance in the flocculation process in contrast to commercial flocculants in treating kaolin suspensions, municipal effluent and domestic wastewater. Flocculation performance included the turbidity removal rate, sediment character and a decrease in COD (chemical oxygen demand). The sediment time of flocculation is short and the removal rate of turbidity treated by CAS is high compared with PAC (polyaluminum-chloride), PAM (polyacrylamide) and the combined addition of PAC and PAM. The optimal concentration required to affect flocculation processes is dependent on kaolin concentration and the character of the wastewater within the range examined. It also showed that CAS is effective to treat wastewater with high turbidity.

China↗
PubMed2001

Production of a biopolymer flocculant from Bacillus licheniformis and its flocculation properties.

Bacillus licheniformis CCRC 12826 produced extracellularly an excellent biopolymer flocculant in a large amount when it was grown aerobically in a culture medium containing citric acid, glutamic acid and glycerol as carbon sources. The biopolymer flocculant was an extremely viscous material with a molecular weight over 2 x 10(6) by gel permeation chromatography. It could be easily purified from the culture medium by ethanol precipitation. It was shown to be a homopolymer of glutamic acid by amino acid analysis and thin layer chromatography and presumed to be poly-glutamic acid (PGA). This bioflocculant efficiently flocculated various organic and inorganic suspensions. It flocculated a suspended kaolin suspension without cations, although its flocculating activity was synergistically stimulated by the addition of bivalent or trivalent cations Ca2+, Fe3+ and Al3+. However, the synergistic effects of metal cations were most effective at neutral pH ranges. The comparison of the flocculating activity between the present biopolymer and a commercial lower molecular weight product showed that the biopolymer of the present study had much higher activity. The high productivity and versatile applications of PGA make its development as a new biodegradable, harmless, biopolymer flocculant economical and advantageous.

Aerobiosis↗
PubMed1998

Distribution of the flocculation protein, flop, at the cell surface during yeast growth: the availability of flop determines the flocculation level.

The yeast FLO genes encode cell surface proteins which are expected to play a major role in the control of flocculation. We have assessed the availability of the Flo proteins at the cell surface during the growth of two flocculent strains, ABXL-1D (FLO1) and STX347-1D (FLO5) using immunological approaches, enzyme-linked immunosorbent assays and immunofluorescence. Our data show that they are not permanently present at the cell surface but that their amount increases during growth. With both strains the flocculation level is tightly correlated to the amount of Flop antigen detected, suggesting that it is the availability of the Flo proteins at the cell surface which determines the flocculation level. Our data are consistent with the idea that the Flo proteins correspond to the flocculation lectins. The differences of flocculation pattern among strains could originate from variations in the regulation of the expression of the FLO genes. Monitoring of the distribution of the Flo proteins during cellular development revealed that they are incorporated essentially in the cell wall of growing buds. Incorporation of the Flo proteins in the cell wall displays a highly polarized aspect, at the bud tip and at the mother-daughter neck junction, which can persist in mature cells. Such a localization could be relevant to constraints of the cell wall incorporation of the mannoproteins. Depending on the regulation of Flop expression and on the incorporation of the proteins in the cell wall, a yeast population can be highly heterogeneous in Flo protein equipment.

Cell Wall↗
PubMed2003

Characteristics of coagulation-flocculation of humic acid with effective performance of polymeric flocculant and inorganic coagulant.

Ferric chloride and aluminium sulphate as coagulants and positive charged flocculants PDDMAC ((PDDMAC = poly (diallyldimethylammonium chloride) were used for pre-treatment of water and wastewater for removing humic substance prior to RO membrane filtration. It was found that a combination of flocculant and coagulant enhanced the coagulation-flocculation process and humic acid removal. The optimum conditions of coagulation-flocculation were established in reference to the ratio of humic acid and coagulant. Zeta potential and the ratio of E4/E6 were investigated to explore the possible micro-mechanisms of coagulation-flocculation. The ratios of E4/E6 show the molecular size variations using different coagulants and flocculants, which are expected to benefit membrane-fouling control.

Dimethylamines↗
PubMed1990

Acetolysis and 1H NMR studies on mannans isolated from very flocculent and weakly flocculent cells of Pichia pastoris IFP 206.

Growth of the yeast Pichia pastoris IFP 206 in methanol- and glucose-containing media led respectively to very and weakly flocculent cells. Mannans from both kinds of cells were extracted and compared. Chemical analysis and molecular mass estimation showed some differences between the mannans from very and weakly flocculent cells, especially in quantitative amino acid content. 1H NMR analysis showed that both kinds of mannan contained alpha-1,2 and beta-1,2 linkages. Two acetolysis conditions, combined with 1H NMR analysis, revealed that mannans from both kinds of cells were composed of mannose, mannobiose, mannotriose, mannotetraose and mannopentaose side-chains with the following respective structures: Man; Man alpha 1---2Man; Man alpha 1----2Man alpha 1----2Man; Man beta 1----2Man alpha 1----2Man; Man beta 1----2Man beta 1----2Man alpha 1----2Man; Man alpha 1----2Man beta 1----2Man beta 1----2Man alpha 1----2Man. Additionally the beta-1,2 linkages of the non-reducing terminal residues of the mannotetraose were shown to be acetolysis-labile. The mannans from very flocculent cells were richer in mannopentaose than the mannans from weakly flocculent cells. According to these results, the extended conformations in the branching moieties of the mannan could be the basis of the higher degree of flocculation of the methanol-grown cells.

Carbohydrate Conformation↗
PubMed2000

A mannose-binding protein from the cell surface of flocculent Saccharomyces cerevisiae (NCIM 3528): its role in flocculation.

A cell surface lectin was isolated and purified to homogeneity from the cell walls of a highly flocculent strain of Saccharomyces cerevisiae (NCIM 3528) by chromatography on DEAE-cellulose, phenyl Sepharose and Sephacryl S-300. It showed a molecular mass of 40 kDa on SDS-PAGE. It is an acidic protein with a pI of 4.0 and contains 44% hydrophobic amino acids. The N-terminal sequence up to 10 amino acid residues showed at least 70% homology with the predicted N-terminal sequence of the putative FLO1 as well as FLO5 gene products. The mannose-binding nature of the lectin was indicated by its high affinity and specificity towards the branched trisaccharide of mannose, a ligand which also inhibits the flocculation of yeast cells. Immunofluorescence studies confirmed the presence of lectin on the yeast cell surface and lectin-specific IgGs prevented flocculation of the cells. This cell surface mannose-specific lectin probably plays an important role in flocculation, with the branched trimannoside on the cell wall being the apparent carbohydrate receptor. The N-terminal sequence data gives a primary indication that the lectin could be a product of one of the FLO genes.

Amino Acid Sequence↗
PubMed2004

Effect of point-of-use disinfection, flocculation and combined flocculation-disinfection on drinking water quality in western Kenya.

AIMS: Point-of-use drinking water disinfection with sodium hypochlorite has been shown to improve water quality and reduce diarrhoeal disease. However, the chlorine demand of highly turbid water may render sodium hypochlorite less effective. METHODS AND RESULTS: We evaluated a novel combined flocculant-disinfectant point-of-use water treatment product and compared its effect on drinking water quality with existing technologies in western Kenya. In water from 30 sources, combined flocculant-disinfectant reduced Escherichia coli concentrations to <1 CFU100 ml(-1) for 29 (97%) and reduced turbidity to <5 nephelometric turbidity units (NTU) for 26 (87%). By contrast, water from 30 sources treated with sodium hypochlorite reduced E. coli concentrations to <1 CFU 100 ml(-1) for 25 (83%) and turbidity to <5 NTU for 5 (17%). CONCLUSIONS: For source waters over a range of turbidities in western Kenya, combined flocculant-disinfectant product effectively reduces turbidity to <5 NTU and reduces E. coli concentrations to <1 CFU 100 ml(-1). SIGNIFICANCE AND IMPACT OF THE STUDY: The novel flocculant-disinfectant product may be acceptable to consumers and may be effective in reducing diarrhoeal disease in settings where source water is highly turbid.

Alum Compounds↗
PubMed1999

[Distinction of yeast flocculent phenotypes and studies of the physiological and biochemical characteristics of yeast flocculation].

More than 400 yeast strains were examined for their flocculation, and five of them displayed strong flocculation. The 5 strains were divided into two groups which are Flo 1 and NewFlo phenotypes on the basis of their response to sugar inhibition. Related physiological and biochemical characteristics of the two phenotypes' strains were studied. The results showed that the flocculation of Flo 1 phenotype was only inhibited by mannose; it was sensitive to high temperature (70 degrees C), pronase E, trypsin, whereas tolerant to pronase K, chymotrypsin, Ca2+, pH; the flocculation of NewFlo was inhibited by many sugars, such as glucose, maltose, sucrose, mannose; it was sensitive to high temperature (70 degrees C), pronase, Ca2+, pH. The Calcium concentration and pH value of the optimum flocculaton of the Flo1 and NewFlo phenotypes strains were respectively 10 mmol/L-1 mol/L; 3.0-4.5.

Culture Media↗
PubMed2004

[Flocculating mechanism of microbial flocculant MBFTRJ21].

The bioflocculant MBFTRJ21 for nature soda was exploited in our lab, and its flocculating mechanism was studied. The bioflocculant produced by Lactobacillus, has some advantages, such as less dosage, better flocculating effects, and etc. MBFTRJ21 is mainly composed of polysaccharide, which is determined by Anthrone reaction, Coomassie blue reaction and Elson-Morgan method. The acting force between bioflocculant and nature soda is hydrogen bond, which is determined by xi electric potential, hydrogen bond and electrovalent bond determination. The bioflocculant is treated by heat and KIO4, which indicate the active ingredient of bioflocculant is protein and osamine. Bridge occur during flocculation process, which is determined by particle size distribution. The results showed that the flocculating mechanism of MBFTRJ21 resulted from the combination of nature soda with MBFTRJ21 by hydrogen bond at the active position of glycosaminoglycan.

Flocculation↗
PubMed2004

Screening of flocculant-producing microorganisms and flocculating activity.

A strain saccharomycete STSM-1 with high flocculanting activity was isolated from activated sludge with conventional methods. The high production rate and the low cost STSM-1 medium was obtained by selecting different kinds of media, carbon source, nitrogen source and inorganic salt ion. The best flocculant-producing conditions were found by changing medium initial pH, culture temperature and ventilation flow. The best flocculating effect was obtained by changing positive ion types, density and concentration of flocculant.

Cost Control↗
PubMed1992

The flocculation of wine yeasts: biochemical and morphological characteristics in Zygosaccharomyces--flocculation in Zygosaccharomyces.

The floc-forming ability of flocculent strains of Zygosaccharomyces bailii and Z. fermentati, isolated from musts, was tested for susceptibility to proteinase and sugar treatments. Z. fermentati was found highly resistant to the proteolytic enzymes tested, whereas Z. baili was only trypsin-resistant. The inhibition of flocculation by sugars distinguished two types: in Z. fermentati flocculation was completely inhibited by mannose, in Z. bailli by various sugars. By SEM observation, the cell surface of Zygosaccharomyces revealed the presence of a column structure, resulting from fusion of vesicles present on the cell surface.

Cell Adhesion↗
PubMed2000

Influence of the flocculating agent in sedimentation and performance of a non flocculent strain of Zymomonas mobilis in the ethanol production process.

The influence of the flocculating agent was studied in the performance (measured by microbial growth and ethanol production) of a non flocculent strain of Zymomonas mobilis, as well as the potentiality of the sedimentation process in the separation of the biomass from the fermentation broth. Among the flocculating agents studied, it was verified that both tannin and the polyelectrolyte yielded good results with regard to cellular performance. However, with regard to sedimentation tannin is more adequate to be used in processes involving Zymomonas mobilis.

Acrylic Resins↗