Brewer's Yeast Cells Research Articles

Effect of Yogurt Supplemented with Brewer's Yeast Cell Wall on Levels of Blood Lipids in Normal and Hypercholesterolemic Adults.

This study was designed to determine whether yogurt supplemented with insoluble dietary fibers would lower the levels of serum lipids in 89 normal and hyper-cholesterolemic adults. Yogurt supplemented with brewer’s yeast cell wall (BYC) was administered to 89 volunteers, and its effects on serum cholesterol levels were examined. The yoturt used contained 6g of BYC per 200ml, and an other batch without BYC served as control diet. The volunteers ingested 200ml of BYC-yogurt (BYC-Y) or control yogurt (CT-Y) everyday for four weeks in a crossover experiment. Blood samples were drawn from the subjects for analysis on five occasions two weeks before the start of the experimental period, and immediately before and after each dietary period. It was observed that the levels of the serum total cholesterol (TC), high-density lipoprotein (HDL) cholesterol and low-density lipoprotein (LDL) cholesterol significantly decreased following ingestion of BYC-Y compared with those before BYC-Y ingestion. Furthermore, the TC levels of the subjects (serum TC≥200mg/dl) taking the BYC-Y diet were found to be significantly lower than those taking the CT-Y diet. However, the HDL- and LDL-chloesterol levels of those taking the BYC-Y diet were not found to be significantly different from those taking the CT-Y diet. No abnormalities in serum biochemical parameters were observed during the experimental period in all the subjects. These results indicate that taking BYC-Y is effective in lowering the serum cholesterol levels in subjects with the tendency for hypercholesterolemia. The results suggest that BYC-Y may be utilized as a food for controlling hypercholesterolemia.

Effects of Brewer's Yeast Cell Wall on Fecal Steroid Excretion in Rats.

To reveal the mechanism(s) of the cholesterol-lowering effect of brewer’s yeast cell wall (BYC), we examined the effect of BYC on fecal steroid excretion in rats fed a high-cholesterol and -fat (HCF) diet or a cholesterol-free standard (STD) diet. Male Sprague-Dawley rats were fed an HCF diet or an HCF diet supplemented with 5% or 10% BYC for 14 days. The addition of BYC to the HCF diet dose-dependently reduced the increment of serum total cholesterol concentration and increased the fecal bile acid and neutral steroid(cholesterol and coprostanol) excretion levels. In this experiment, a negative correlation between serum total cholesterol concentration and fecal bile acid excretion level was observed; however, a correlation between serum total cholesterol concentration and fecal neutral steroid excretion level was not observed. Next, male Sprague-Dawley rats were fed an STD diet or an STD diet supplemented with 5% or 10% BYC for 14 days, to investigate whether BYC could lower serum total cholesterol concentration in the rats with normal serum cholesterol concentrations. The addition of BYC to the STD diet also slightly increased the fecal bile acid excretion level; however, it did not affect the serum cholesterol concentration. Furthermore, we examined whether BYC can reduce the serum total cholesterol concentration in Sprague-Dawley rats fed an HCF diet prior to the administration of BYC, to increase the serum total cholesterol concentration. In this experimental model, BYC reduced serum total cholesterol concentration and increased fecal total steroid excretion level, and a negative correlation between serum total cholesterol concentration and fecal bile acid excretion level was observed. These results suggest that BYC reduces serum total cholesterol concentration by increasing fecal bile acid excretion level.

Effects of Brewer's Yeast Cell Wall on Serum Lipid Levels in Rats Fed a High Cholesterol and Fat Diet.

We examined whether brewer’s yeast cell wall (BYC) is able to reduce serum lipid levels in rats fed a high cholesterol and fat (HCF) diet. Male Sprague-Dawley rats were fed a standard diet, an HCF diet or an HCF diet containing 2.5% or 5.0% BYC for 14days. The addition of 5.0% BYC to the HCF diet significantly reduced the increment of serum total cholesterol levels. On the basis of the results obtained, BYC may be utilized as a cholesterol-lowering foodstuff.

Iron absorption in rats increased by yeast glucan.

The effects of brewer's yeast cell walls and two of its components, glucan and mannan, on the absorption of 59Fe by anemic rats were investigated. After administration of the label, the percentage of 59Fe taken up into the blood of group given glucan was generally similar to that of a group given yeast cell walls, both values were higher than in controls. The incorporation of 59Fe into the small intestines was higher in the group given glucan than in the controls or a group given a glucan-mannan mixture. Glucan is the main substance in yeast cell walls that increases iron absorption.

Effects of yogurt supplemented with brewer's yeast cell wall on constipation and intestinal microflora in rats.

Brewer's yeast cell wall (BYC) is a valuable foodstuff that prevents constipation in rats. In this study, the effects of yogurt supplemented with brewer's yeast cell wall (BYC-Y) on constipated male Sprague-Dawley rats induced by loperamide (2 mg/kg body weight) were investigated. The preventive effect of BYC-Y on experimentally constipated rats was examined and compared with that of nonfiber diet (Control) and standard yogurt (Yogurt) as the control diets. The number of feces and fecal dry weight were greater in rats fed with BYC-Y than in those fed with Control or Yogurt. Moreover, the effect of BYC on the improvement of cecal microflora in constipated experimental model rats was evaluated. The number of Lactobacillus, Eubacterium, and total anaerobes per unit cecal contents increased (p<0.03) as a result of BYC ingestion. These findings indicate that BYC-Y or BYC is effective for the alleviation of constipation and bowel environment.

Effects of brewer's yeast cell wall on constipation and defecation in experimentally constipated rats.

Brewer's yeast cell wall (BYC) was tested on constipated male Sprague-Dawley rats that had been induced by loperamide (2 mg/kg of body weight). The preventive effect of BYC on constipation was examined and compared with that of a non-fiber diet (NF) as the control. The dose-response of BYC and the effect on defecation by constipated experimental rats were also compared with the characteristics of cellulose diet (CE) group which served as a control. Defecation was observed to be greater by the rats fed with BYC than by those fed with NF or CE. The fecal water content and level of volatile fatty acids (VFA) in the cecal contents were likewise higher in the rats fed with BYC. These results indicate that the administration of BYC was effective for improving defecation and other parameters related to defecation. These favorable effects of BYC supplemented to the diet are attributed to the fermentation ability, water holding capacity and swelling force in the large intestine.

Effects of Yogurt Supplemented with Brewer's Yeast Cell Wall on Intestinal Environment and Defecation in Healthy Female Adults

Effects of Yogurt Supplemented with Brewer's Yeast Cell Wall on Intestinal Environment and Defecation in Healthy Female Adults

Utilization of brewer's yeast cells for the production of food-grade yeast extract. Part 1: effects of different enzymatic treatments on solid and protein recovery and flavor characteristics

Yeast extract was produced from brewer's yeast of a beer factory by combined enzymatic treatments using endoprotease, exoprotease, 5 ′-phosphodiesterase, and adenosine monophosphate (AMP)-deaminase. Effects of enzyme combination, enzyme dosages and treatment sequence on the recovery of solid and protein, flavor and compositional characteristics were investigated. Exoprotease dosage strongly affected the recovery of protein and degree of hydrolysis (DH) and sensory characteristics. When the yeast cells were treated using optimal combination of endoprotease and exoprotease (0.6% Protamex TM and 0.6% Flavourzyme TM), high solid recovery (48.3–53.1%) and the best flavor profile were obtained. Among various treatment sequences using multiple enzymes, treatment with protease followed by nuclease resulted in the highest 5 ′-guanosine monophosphate (5 ′-GMP) content. The optimal concentrations of both 5 ′-phosphodiesterase and AMP-deaminase were found to be 0.03%. After treatments using optimal combination of enzyme, enzyme dosages and treatment sequence for four enzymes, a high solid yield of 55.1% and 5 ′-nucleotides content of 3.67% were obtained.

A rapid and selective assay for measuring cell surface hydrophobicity of brewer's yeast cells.

A rapid and selective assay was developed to measure cell surface hydrophobicity of brewer's yeast cells. During this so-called magnobead assay, bottom-fermenting yeast cells adhere to paramagnetic, polystyrene-coated latex beads which can easily be removed from the cell suspension by using a (samarium-cobalt) magnet. At pH 4 center dot 5, electrostatic repulsion between yeast cells and latex beads was found to be minimal and yeast cell adhesion was predominantly based on hydrophobic interactions. The percentage of cells adhering to the beads could be calculated and provided a measure for cell surface hydrophobicity. Cell surface hydrophobicity measured by the magnobead assay was found to yield similar results, as did determination of contact angles of water droplets on a layer of yeast cells, a standard method for measuring surface hydrophobicity. However, the magnobead assay has the following advantages: (i) it is a quick and simple method, and, more significantly, (ii) hydrophobicity can be measured under physiological conditions. Use of the magnobead assay confirmed that a higher level of cell surface hydrophobicity is correlated with stronger flocculence of brewer's lager yeast cells.

A rapid and selective assay for measuring cell surface hydrophobicity of brewer's yeast cells

A rapid and selective assay was developed to measure cell surface hydrophobicity of brewer's yeast cells. During this so-called magnobead assay, bottom-fermenting yeast cells adhere to paramagnetic, polystyrene-coated latex beads which can easily be removed from the cell suspension by using a (samarium-cobalt) magnet. At pH 4 center dot 5, electrostatic repulsion between yeast cells and latex beads was found to be minimal and yeast cell adhesion was predominantly based on hydrophobic interactions. The percentage of cells adhering to the beads could be calculated and provided a measure for cell surface hydrophobicity. Cell surface hydrophobicity measured by the magnobead assay was found to yield similar results, as did determination of contact angles of water droplets on a layer of yeast cells, a standard method for measuring surface hydrophobicity. However, the magnobead assay has the following advantages: (i) it is a quick and simple method, and, more significantly, (ii) hydrophobicity can be measured under physiological conditions. Use of the magnobead assay confirmed that a higher level of cell surface hydrophobicity is correlated with stronger flocculence of brewer's lager yeast cells.

A Rapid and Selective Assay for Measuring Cell Surface Hydrophobicity of Brewer's Yeast Cells

A Rapid and Selective Assay for Measuring Cell Surface Hydrophobicity of Brewer's Yeast Cells

Microbial cell disruption: role of cavitation

A novel technique of using hydrodynamic cavitation for the large-scale disruption of yeast cells is described. Baker's yeast and brewer's yeast cells in a pressed yeast form were used. Cell disruption was monitored in the form of increase in soluble protein content. Disruption by hydrodynamic cavitation is compared with that obtained by established techniques such as blade blender and acoustic cavitation (ultrasonication). The effect of cell concentration, time of treatment and number of passes in the flow loop system on the extent of cell disruption is reported. The energy efficiency of the hydrodynamic cavitation setup is compared with that of established techniques. Hydrodynamic cavitation was found to be at least an order of magnitude more energy efficient than established techniques such as ultrasonication or blade blender (mixer).

Isolation and partial purification of mannose-specific agglutinin from brewer's yeast involved in flocculation.

Yeast cell-agglutinating activity, designated agglutinin (possible lectin), was isolated from cell walls of both non-flocculent and flocculent brewer's yeast cells. Agglutinin-mediated aggregation of yeast cells in a manner similar to flocculation with respect to specific mannose-sensitivity, pH-dependence and calcium-dependence. Agglutinating activity was found to be heat-stable and protease-insensitive. Furthermore, addition of agglutinin to flocculent cells strongly stimulated the flocculation ability of the cells, whereas addition to non-flocculent cells rendered these cells weakly flocculent. Agglutinin was found to be released from flocculent cells during the course of a flocculation assay, but not from non-flocculent cells. Presence of mannose during the assay inhibited release of agglutinin. Our results suggest that (i) mannose-specific agglutinin is continuously synthesized during growth of brewer's yeast cells, (ii) agglutinin is present in cell walls of non-flocculent cells but is unable to bind its ligand on other cells, and (iii) the ability of yeast cells to flocculate in a flocculation assay depends, among other factors, on release of agglutinin from the cells. A 10-kDa polypeptide might represent one form of agglutinin.

Purification and partial characterization of a flocculin from brewer's yeast.

Analysis of a shear supernatant from flocculent, "fimbriated" Saccharomyces cerevisiae brewer's yeast cells revealed the presence of a protein involved in flocculation of the yeast cells and therefore designated a flocculin. The molecular mass of the flocculin was estimated to be over 300 kDa, as judged from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Gel permeation chromatography of the flocculin yielded an aggregate with an apparent molecular weight of > 2,000. The flocculin was found to be protease sensitive, and the sequence of its 16 N-terminal amino acids revealed at least 69% identity with the predicted N terminus of the putative protein encoded by the flocculation gene FLO1. The flocculin was isolated from flocculent S. cerevisiae cells, whereas only a low amount of flocculin, if any, could be isolated from nonflocculent cells. The flocculin was found to stimulate the flocculation ability of flocculent yeast cells without displaying lectinlike activity (that is, the ability to agglutinate yeast cells).

Production and properties of ∝-mannosidase from aspergillus sp.

Aspergillus sp NCIM 508 produced 22 U/L of extracellular ∝-mannosidase activity in a medium containing 8 % brewer's yeast cells. The optimum period and pH range for maximum production of the enzyme were 7 days and 4.0–6.0, respectively. The optimum pH and temperature for enzyme activity were 6.0 and 50°C, respectively. The enzyme was stable for 24 h at 28°C, in the pH range 6.0–7.0. The enzyme retained 100 and 65 % of its original activity after heating for 15 min at 45 and 55°C, respectively. The Km and Vmax for p-nitrophenyl-∝-D- mannoside (PNPM) were 71μM and 7.5 × 10−2 μmoles/min/mg, respectively. The enzyme was strongly inhibited by 1 mM Hg++ and Cu++ and partially by Co.++

Highly efficient bioconversion of glucose into fructose diphosphate with fed-batch-grown Saccharomyces cerevisiae cells

One of the methods commonly used for manufacturing fructose 1,6-diphosphate is based on the enzymatic phosphorylation of glucose with inorganic phosphate using permeabilized brewer's yeast cells. Our results demonstrate that a substantial improvement in the yield of bioconversion can be achieved using fed-batch-grown Saccharomyces cerevisiae cells. Under an appropriate glucose and phosphate to cell ratio the efficiency of bioconversion reaches 70% of the theoretical value.

Nucleotide sequence and expression of the Enterobacter aerogenes alpha-acetolactate decarboxylase gene in brewer's yeast.

The nucleotide sequence of a 1.4-kilobase DNA fragment containing the alpha-acetolactate decarboxylase gene of Enterobacter aerogenes was determined. The sequence contains an entire protein-coding region of 780 nucleotides which encodes an alpha-acetolactate decarboxylase of 260 amino acids. The DNA sequence coding for alpha-acetolactate decarboxylase was placed under the control of the alcohol dehydrogenase I promoter of the yeast Saccharomyces cerevisiae in a plasmid capable of autonomous replication in both S. cerevisiae and Escherichia coli. Brewer's yeast cells transformed by this plasmid showed alpha-acetolactate decarboxylase activity and were used in laboratory-scale fermentation experiments. These experiments revealed that the diacetyl concentration in wort fermented by the plasmid-containing yeast strain was significantly lower than that in wort fermented by the parental strain. These results indicated that the alpha-acetolactate decarboxylase activity produced by brewer's yeast cells degraded alpha-acetolactate and that this degradation caused a decrease in diacetyl production.

The change in the electro-rotation of yeast cells effected by silver ions

Pre-treatment of brewer's yeast ( Saccharomyces cerevisiae) cells with silver acetate or nitrate at concentrations of 20 nmol/l or higher caused a dramatic increase in the number of cells which rotated in the same direction as the field (‘Co-field rotation’). The change in rotation of single cells correlated very well with the chemically observed loss of potassium induced by Ag +. The sensitivity to Ag + was lowered by increasing the cell concentration, and the extent of this change can be used to estimate the binding of Ag + per cell and the limiting sensitivity of the method. The Ag + concentration required to induce a response was found to be increased significantly in the presence of alkali ions (especially K +) during the Ag + incubation. The Ag + sensitivity was, therefore, observed to be a function of the type and strength of buffer used in the incubation. Under certain conditions, 1 mM Ca 2+ increased the Ag + sensitivity. These observations show that the presence or absence of ions that are so common that they are often overlooked may have interesting consequences for the bio-assay of heavy metals.

Purification and characterization of a new peptide-mannan, SP-I, as a gastric secretion-inhibitory principle from autolysate of brewer's yeast.

A substance showing gastric secretion-inhibitory activity in rats was purified from defatted cell wall of brewer's yeast cells through extraction by autoclaving in distilled water, pepsin digestion, fractionation with ethanol, diethyl aminoethyl-Sephadex A-50 column chromatography and gel filtration on a Sepharose 6B column. The substance, named SP-I, markedly decreased gastric juice secretion in pylorus-ligated rats when administered intraperitoneally or intravenously at a dose of 2.5 mg/kg. SP-I reduced Shay ulceration by 81% (25 mg/kg×2, i.p.), aspirin ulceration by 56% (25 mg/kg, i.p.) and phenylbutazone ulceration by 82% (25mg/kg, i.p.). It was also shown that the decreases of hexosamine and sialic acid contents in gastric mucosa caused by aspirin administration in pylorus-ligated rats were significantly recovered by the administration of SP-I. SP-I, a new peptide-mannan (95% mannan, 3% peptide), showed a homogeneous pattern in ultracentrifugal analysis, and its molecular weight was estimated to be several hundred thousand daltons.

Enzymatic release of invertase from cell ghosts of Candida utilis.

1. The liberation of invertase (β-fructofuranosidase, EC3.2.1.26) from Candida utilis at autolysis of the cells was found to begin after the autolysis was almost completed. The autolysis residue at this stage consisted mainly of cell walls (ghosts). A suspension of washed cell ghosts released invertase on further incubation and this liberation was stimulated by the addition of reducing agents such as mercaptoethanol, or proteolytic enzymes such as papain, as has been known in the release of the invertase of Saccharomyces cerevisiae. 2. The invertase activity of the cell ghosts was not lost when the suspension was heated at 60°C. However, the invertase of the heated cell ghosts was not liberated even if the above stimulative agents were added. 3. Several commercial enzymes were shown to stimulate the liberation of invertase from the heated cell ghosts and "Zymolyase, " one of the effective enzymes, was fractionated. One fraction isolated from the preparation showed a striking effect on the liberation of invertase but this fraction did not show lytic activity on brewer's yeast cells.