Yeast Suspension Research Articles

Polyamphoteric flocculants for the enhanced separation of cellular suspensions

The efficient concentration and separation of microorganisms from dilute culture suspensions is crucial to the success and productivity of many biotechnological processes. This article presents the design and characterization of polyamphoteric flocculants with a tunable, zwitterionic character for the enhanced separation of biocolloidal suspensions of yeast, wastewater, microalgae, and potentially other cellular systems. The polyamphoteric flocculants have overall molecular charges dependent upon the system pH, thereby providing a strong electrostatic attraction to the diverse but predominantly negatively-charged cellular surfaces of the biological suspensions. The polyamphoteric flocculants with tailored charge character are shown to have higher flocculation efficiencies than comparable cationic polyelectrolytes, and have an enhanced ability to 1) adsorb to the diverse range of charge character in cellular suspensions, 2) operate over an extended range of suspension pHs, and 3) operate at lower flocculant concentrations. These enhanced flocculation properties are shown to arise, perhaps counterintuitively, due to interactions between the negatively-charged functionality on the flocculant and the predominantly negatively-charged biocolloids. Statement of SignificanceThis article presents the design and characterization of polyamphoteric flocculants for the separations of biocolloidal suspensions of importance in the production of biopharmaceuticals, microalgal cultures for nutraceuticals and biofuels, and wastewater treatment. The polyamphoteric flocculants consist of tunable, mixed charges dependent upon system pH, thereby providing strong electrostatic attraction to the diversely-charged surfaces of cellular suspensions. Enhanced flocculation efficiencies are achieved, as compared to cationic polyelectrolyte flocculants, and result from the ability of polyampholytes to adsorb to a diverse range of charge character and operate over an extended range of pH conditions.

Modeling of filtration characteristics during submerged hollow fiber membrane microfiltration of yeast suspension under aeration condition

A modeling of filtration characteristics during the submerged hollow fiber membrane microfiltration of yeast suspension under aeration condition was developed on the basis of hydrodynamic mathematical equations that describe the local flux distribution, particle deposition and gas–liquid two-phase flow. The effects of average operating flux, fiber length, inner diameter and aeration rate on the distributions of local flux and filtration resistance were investigated using the developed model. The model was validated using the literature data. The simulated results showed that the asymmetry of initial local flux distribution was intensified with the increase of aeration rate. The local fluxes along the fiber experienced the self-adjustment and reconstruction due to the changes of filtration resistance as the filtration processed. Furthermore, the local flux distribution along the fiber with a short length and large fiber inner diameter at a high operating flux would tend to become relatively uniform at the initial period of filtration.

Stabilization mechanisms of oil-in-water emulsions by Saccharomyces cerevisiae

A multiphase system is commonly formed during the oil production by microbial route, which can lead to stable emulsions hindering product recovery. Thus, this study aimed to investigate the mechanisms of emulsion stabilization by the yeast Saccharomyces cerevisiae in order to contribute with processes development of oil production by fermentation. A model system using hexadecane as oil phase and yeast suspension as aqueous phase was used to prepare O/W emulsions. The yeast was subjected to different treatments as inactivation (autoclaving) and washing before to be resuspended in water. The washing water (water from the first washing) and suspension of commercial yeast (active) were also used as aqueous phase. After 24h of preparation, the emulsions separated into three phases: top (cream), intermediate, and bottom phase. The top or cream phase was a concentrated emulsion that kept stable during seven days, except for those prepared from washed yeast that were stable only for a short period of time. Emulsions prepared with washed yeast showed higher cell adhesion to the droplets interface, which implied in a higher amount of yeast into the cream phase in comparison to other formulations. Therefore, yeast cells adhesion plays a role on emulsion stability, but the greater contribution was provided by cell material dispersed into the aqueous phase, regardless of cell viability.

Mechanisms of electron transfer between a styrylquinolinium dye and yeast in biofuel cell

In the present study, the influence of the recently synthesized styrylquinolinium dye 4-{(E)-2-[4-(dimethylamino)naphthalen-1-yl]ethenyl}-1-methylquinolinium iodide (DANSQI) on the intracellular processes as well as the electrical outputs of Candida melibiosica 2491 yeast-based biofuel cell was investigated. The addition of nanomolar quantities of DANSQI to the yeast suspension results in an increase of the current outputs right after the startup of the biofuel cells, associated with an electrooxidation of the dye on the anode. After that, the formed cation radical of the dye penetrates the yeast cells, provoking a set of intracellular changes. Studies of the subcellular anolyte fractions show that 1μM dye increased the peroxisomal catalase activity 30-times (1.15±0.06Unit/mg protein) and over twice the mitochondrial cytochrome c oxidase activity (92±5Unit/mg protein). The results obtained by electrochemical and spectrophotometric analyses let to the supposition that the dye acts as subcellular shuttle, on account of its specific intramolecular charge transfer properties. The transition between its benzoid, quinolyl radical and ion forms and their putative role for the extracellular and intracellular charge transfer mechanisms are discussed.

Effect of ultrasonic treatment on the physico-chemical parameters of kvass

In this paper, for the intensification of production kvass process are encouraged to use the installation "Wave-M" UZTA-1/22-OM sonication product. The aim of the experiment was to study the effect of treatment of process water and the yeast suspension with ultrasound in the production of kvass. To achieve its objectives for the Department of technological machinery and equipment ITMO University experimental setup was designed. In the course of the experiment we studied the effect of ultrasonic treatment on the physico-chemical characteristics of the finished beverage, made in different formulations, depending on the tiered effect of ultrasound. Organoleptic evaluation of the product was carried out, and active acidity measured amount of dry matter in the finished beverage. When processing kvass ultrasound power of 60 and 90 W at a tasting in the product became noticeable pleasant caramel flavor. Due to this effect may be replaced in the production of soft drinks expensive equipment used for cooking in sugar syrup tinting siropovarochnyh, kolerovarochnyh boilers cheaper ultrasonic unit. The acidity of the samples increased within acceptable limits. On the amount of solids in kvass ultrasonic treatment did not significantly affected. To increase the shelf life of the beverage used microfiltration. Anticipated acceleration of the process of obtaining fermented kvass 2 times. It is shown that the filtration using the dosing of ultrasound in the production of kvass not only reduce the cost of the equipment and remove some of the tra-ditional processes, but also provide with the cold sterilization of kvass with higher quality indicators.

Magnesium capability to attenuate the toxicity of aluminum on the growth of Saccharomyces cerevisiae PE-2

Summary The magnesium (Mg) capability to attenuate the toxicity of aluminum (Al) for the trehalose content, anaerobic growth, viability and budding rate of Saccharomyces cerevisiae, was studied in this work. Fermentations were carried out in triplicate with sterilized and diluted sugar cane media (4% total reducing sugars/pH 4.0) containing different Al (0.0, 50, 100 and 150 mg L-1) and Mg (0.0, 50 and 100 mg L-1) concentrations. The media were inoculated with 1 mL of 1% (wet basis) yeast suspension and incubated at 30ºC, 70 rpm for 20 hours in orbital shaker. At specific times during fermentation portions of cell suspension were taken out and the biomass concentration, yeast viability, budding rate and trehalose content on cells determined. The increase of Al levels, from 0.0 up to 150 mg L-1, showed a reduction on the yeast growth of approximately 95%, 55% and 18% as Mg increased from 0.0 to 50 and 100 mg L-1, respectively. The trehalose content experienced its lowest reduction when greater amounts of Mg were added to the fermentation process. Cell viability showed greater reductions as the content of Al in the media increased. Magnesium effectively protected yeast cells against the deleterious effects of Al on cell growth, viability, budding and trehalose content.

Optimization of the flux values in multichannel ceramic membrane microfiltration of Baker`s yeast suspension

The objective of this work was to estimate the effects of the operating parameters on the baker's yeast microfiltration through multichannel ceramic membrane. The selected parameters were transmembrane pressure, suspension feed flow, and initial suspension concentration. In order to investigate the influence and interaction effects of these parameters on the microfiltration operation, two responses have been chosen: average permeate flux and flux decline. The Box-Behnken experimental design and response surface methodology was used for result processing and process optimization. According to the obtained results, the most important parameter influencing permeate flux during microfiltration is the initial suspension concentration. The maximum average flux value was achieved at an initial concentration of 0.1 g/L, pressure around 1.25 bars and a flow rate at 16 L/h.

Oxygen Consumption by Postfermentation Wine Yeast Lees: Factors Affecting Its Rate and Extent under Oenological Conditions.

Postfermentation wine yeast lees show antioxidant properties based on their ability to consume dissolved oxygen. The oxygen consumption capacity of suspended yeast lees obtained after fermentations with six commercial active dry yeast strains was investigated in model, white and red wines using fluorescence-based oxygen sensors operating in a nondestructive way. In model solution, the oxygen consumption rate of yeast lees was shown to depend on their amount, yeast strain, sulfur dioxide and temperature. It is slightly lower in red than in white wines. It is strongly decreased by current levels of free sulfur dioxide, thus excluding the complementary use of both as antioxidants in wine. However, in 25 randomly sampled white wines produced under commercial conditions, the rate and extent of oxygen consumption during the first six months of postfermentation had no significant correlation with any of these interacting factors, making it difficult to predict the actual antioxidant effect of yeast lees. In these wines, yeast lees consumed 0 to 47% of the dissolved oxygen. Although total oxygen consumption capacity of yeast lees is not a limiting factor under commercial winemaking conditions, their oxygen consumption proceeds at a limited rate that reduces but cannot totally prevent concomitant chemical oxidation of the wine.

Paracetamol like antipyretic activity of lyophilized succulent of Aloe vera leaves in rats

Aims: To evaluate the antipyretic activity of lyophilized succulent of Aloe vera (AVS) as well as its interaction with conventional antipyretic drug paracetamol (PCM) against experimentally induced pyrexia in rats. Materials and Methods: Pyrexia was induced experimentally by either Brewer’s yeast or misoprostol injection after recording basal rectal temperature in rats. Animals were treated with lyophilized AVS at the dose of 100, 200, and 300 mg kg and standard drug PCM 150 mg/kg, 18 h after injection of Brewer’s yeast suspension in one set of experiment and combination of sub‑effective dose of AVS with that of PCM 1 h after injecting misoprostol in other set of experiment. Rectal temperature was recorded at different time intervals after drug administration. AVS was also phytochemically screened for the presence of tannins, saponins, flavonoids, coumarins, sterols, reducing sugar, glycosides, starch, alkaloids, and triterpenoids. Results: Pyrexia was observed at 18 h and at 1 h after Brewer’s yeast and misoprostol injection subcutaneous, respectively. AVS (200 and 300 mg/kg) treated groups showed significant fall in rectal temperature (P 0.05) with standard drug PCM at 150 mg/kg. The combination of sub‑effective dose of AVS (100 mg/kg) with that of PCM (50 mg/kg) produced significant (P < 0.05) antipyretic activity against misoprostol‑induced pyrexia at different time intervals as compared with control, AVS 100 mg/kg and PCM 50 mg/kg treated groups when used alone. Phytochemical tests showed the presence of flavonoids, saponins, tannins, reducing sugar, glycoside, starch, and steroids. Conclusion: Lyophilized AVS possesses antipyretic activity. It enhances the antipyretic activity of PCM suggesting its role in inhibition of prostaglandin synthesis.

EVALUATION OF THE BAKER'S YEAST SACCHAROMYCES CERVISIAE AS A FOOD SUPPLEMENT FOR THE CLAM VENERUPIS AUREA

Bivalve aquaculture, that includes the cultivation of clams, is a growing source of food production all worldwide. No previous study has reported the relative food value of the yeast for the clam Venerupis aurea. The present study investigates the use of cheap and non-algal food (the baker's yeast Saccharomyces cervisiae) as a manipulated diet for the clam used in the study. A preliminary experiment was conducted to evaluate graded levels of dried baker's yeast as a supplement diet of the clam. This trial elucidated that the yeast with a ratio of 5% of the bivalve weight was suitable to enhance the growth of clams larger than 9 mm shell length. As the chemical treatment improves food value of the yeast (due to its homogenous yeast suspension), this level of yeast was added with and without chemical treatment in the basic experiment. The results exhibited obvious daily growth rate over the control in the largest size in case of the non-treated yeast. On the other hand, manipulation of the chemically treated yeast was suitable for small and moderate clam size. This may explain the clam behavior to get its nourishment. Hence, the present study proved that small clams are suspension feeders while the larger ones are deposit feeders.

Pharmacological effects of ethanol extract of Egyptian Artemisia herba-alba in rats and mice

ObjectiveTo investigate some pharmacological effects including gastroprotective, anti-inflammatory, analgesic, antipyretic and in vitro antioxidant effects of Artemisia herba-alba extract in different experimental models. MethodsInflammation was induced in rat paw by subcutaneous injection of 1% (v/v) carrageenan solution. Writhes was induced in mice by intraperitoneal injection of 0.6% (v/v) acetic acid solution. Pyrexia was induced using Brewer's yeast suspension. Gastric lesion was induced in rats by oral administration of 99% ethanol. The anti-inflammatory, analgesic, antipyretic and gastroprotective activities of Artemisia herba-alba extract were investigated respectively. In vitro antioxidant effect was investigated using DPPH free radical. ResultsThe plant extract showed anti-inflammatory effect in carrageenan-induced paw edema in rats, analgesic effect against acetic acid-induced writhing, and antipyretic activity in Brewer's yeast model of pyrexia. Besides, it was shown to be a gastroprotective agent against ethanol-induced gastric ulcers. The plant also exhibited a free radical scavenging potential in an in vitro antioxidant study using DPPH. ConclusionsThe results validate the use of the investigated plant in traditional medicine for different ailments.

Antipyretic and antioxidant activities of Eleucine indica

Eleucine indica is a medicinal plant used by the Ibibios of southern Nigeria in the treatment of malaria fever and also as a tonic. This study was to evaluate the antipyretic activities of the ethanol extract and the antioxidant activities of the extract, n-hexane, chloroform, ethyl acetate, butanol and aqueous fractions of the whole plant. Basal rectal temperatures of adult albino rats of both sexes were recorded and the animals fasted for 24 h but allowed access to water ad libitum. They were then treated with DNP (10 mg/kg) and amphetamine (5 mg/kg) intraperitoneally. Within 30 min following the administration of amphetamine, animals with increased temperature of 1◦C were selected and randomized into five groups of six animals each. Group 1 received 10 ml/kg of distilled water orally. Group’s 2 - 4 animals were administered 200 – 600 mg/kg of the extract intraperitoneally respectively. Group 5 animals received 100 mg/kg of acetyl salicylic acid orally. Yeast-induced pyrexia was achieved using 10 ml/kg of Brewer’s yeast suspension injected subcutaneously in the back below the neck. Rectal temperatures were then obtained at 0.5 h and thereafter hourly for 5h. Superoxide dismutase, reduced glutathione, catalase, free radical scavenging with 1, 2-diphenyl-2- picrylhydrazyl, lipid peroxidation and methaemoglobin were measured in rats using standard methods. The result showed a significant (p &lt; 0.05 – 0.001) and dose-dependent reduction in the elevated body temperature in rats pre-treated with the extract compared to control. There were also significantly high levels of superoxide dismutase and increased levels of reduced glutathione, catalase, free radical scavenging activity with DPPH, lipid peroxidation and methaemoglobin in both serum samples and liver homogenates of rats relative to control. These results corroborate with the ethno botanical use of the plant as antipyretic and depicts that the plant has both antioxidant ad pro-oxidant properties.

Hop proanthocyanidins for the fining of beer

Fining agents are used in the clarification of beers; they help to reduce the time required to sediment suspended yeast cells and ensure the clarity and colloidal stability of beer. Following an adventitious observation during dry-hopping experiments, we identified a fining activity associated with Saaz hops. Extracts of hop cones were subsequently shown to have the capacity to flocculate yeast and result in their sedimentation. This activity has since been identified in extracts of many different hop varieties and, significantly in spent hops, the co-product resulting from commercial extraction of hops with either CO2 or ethanol. Here we illustrate the activity of the novel finings extracted from spent hops following CO2 extraction of Galena hops. The sediments formed on fining were compact, relative to those obtained when commercial isinglass was used to fine the same beers. The hop extracts were also effective in reducing 90° haze in beers under conditions designed to mimic both cask ale (12 °C) and lager (4 °C) type applications. The compounds responsible for the fining activity appear to be large (30–100 kDa, or more) polyphenols. Analysis of the polyphenols using colourimetric tests indicated the presence of proanthocyanidins. On acidic hydrolysis these generated cyanidin, which would be derived from a polymer composed of catechin and epicatechin subunits. The presence of these materials in spent hops offers the possibility to develop commercial products, with desirable fining properties, from an existing co-product stream. Furthermore, the finings are derived from a traditional ingredient of the brewing process.

A new folded plate membrane module for hydrodynamic characteristics improvement and flux enhancement

Abstract To intensify the air scouring efficiency and reduce the membrane fouling, a new folded plate membrane module (FPMM) was designed by modifying the configuration of conventional flat sheet membrane module (FSMM). The hydrodynamic characteristics near the folded plate membrane surface, and its filtration performance in different operating conditions were studied. The particle image velocimetry (PIV) measurement results showed that, the higher flow velocity, the stronger turbulence, and more vortices existed near the folded plate membrane surface. The stable flux of the FPMMs had an increase of 17.8–57.7% over that of the FSMM, and the optimal vertical inclination angle was 15°. Moreover, in the filtration process, the flux enhancement of the FPMM was affected by the aeration intensity, yeast suspension concentration and trans-membrane pressure (TMP).

Experimental analysis of an effect of the nutrient type and its concentration on the rheological properties of the baker’s yeast suspensions

Abstract The aim of the study presented was to experimentally analyze an effect of the nutrient type and its concentration on the variability of rheological properties of the baker’s yeast suspensions for different time periods. Aqueous suspensions of the baker’s yeast of various concentration (solution I, without nutrient) and yeasts suspended in aqueous solution of sucrose or honey as nutrients with different concentration (solution II or solution III) were tested. Experiments were carried out using rotational rheoviscometer of type RT10 by a company HAAKE. The measurements were conducted for different time periods (from 1 h up to 144 h) at given fluid temperature. On the basis of the obtained data, rheological characteristics of the aqueous solution of baker’s yeast suspensions without and with nutrients of different sucrose or honey concentration were identified and mathematically described.

Concentration measurement of yeast suspensions using high frequency ultrasound backscattering

This work proposes the use of an ultrasound based technique to measure the concentration of yeasts in liquid suspension. This measurement was achieved by the detection and quantification of ultrasonic echoes backscattered by the cells. More specifically, the technique was applied to the detection and quantification of Saccharomyces cerevisiae. A theoretical approach was proposed to get the average density and sound speed of the yeasts, which were found to be 1116kg/m3 and 1679m/s, respectively. These parameters were needed to model the waves backscattered by each single cell. A pulse-echo arrangement working around 50MHz, being able to detect echoes from single yeasts was used to characterize experimentally yeast solutions from 102 to 107cells/ml. The Non-negative Matrix Factorization denoising technique was applied for data analysis. This technique required a previous learning of the spectral patterns of the echoes reflected from yeasts in solution and the base noise from the liquid medium. Comparison between pulse correlation (without denoising) and theoretical and experimental pattern learning was made to select the best signal processing. A linear relation between ultrasound output and concentration was obtained with correlation coefficient R2=0.996 for the experimental learning. Concentrations from 104 to 107cells/ml were detected above the base noise. These results show the viability of using the ultrasound backscattering technique to detect yeasts and measure their concentration in liquid cultures, improving the sensitivity obtained using spectrophotometric methods by one order of magnitude.

Numerical and experimental study of microorganism disruption using shock treatment

The use of shock waves to destroy microorganisms is considered one of the newly developed methods in the field of cell disruption. This simulation part of this research work aims to determine the required shock pressure to disrupt a single yeast cell and the rupture location on the cell wall. As a step towards understanding the physical response of the microorganisms to dynamic pressure and shock treatments a Finite Element (FE) model has been developed using commercial software ABAQUS. Von Mises theory of failure is adopted in this work and the properties of Saccharomyces cerevisiae (S. cerevisiae) reported in the literature were used in the numerical and experimental work. The simulation results demonstrate that maximum dynamic σv/Pe (0.85) was found to be over three times that of the static σv/Pe (0.25) values. This suggests a location of the rupture within the cell wall when shock pressure loading is applied; such a result has not been previously reported in current literatures. In the experimental work, a gas gun tunnel was used to generate 100–400 MPa external pressure loading on a yeast suspension. The experimental results showed that the maximum yeast reduction of 95.7% resulted when a 336 Mpa pressure rise was applied.

Ultrafiltration by a super-hydrophilic regenerated cellulose membrane

Ultrafiltration (UF) has received tremendous attention in concentration and purification of proteins in biotechnology, biomedicine and food production industries. Accordingly, in the present work innovated super-hydrophilic UF membranes were fabricated by the phase inversion technique, from a special casting solution formulation consisting of cellulose acetate in different solvents/additives, followed by complete deacetylation to form a regenerated cellulose membrane. Variables investigated included time of evaporation of as-cast membrane, temperature of coagulation water bath and post annealing of membrane. The membranes were used in ultrafiltrating yeast suspensions and examined by scanning electron microscopy (SEM), Fourier transform infrared, contact angle, porosity and pore size. The membrane performance was found to be strongly affected by each variable, and the best membrane gave a consistently high flux (27 kg/m2h) on prolonged operation, with almost zero salt rejection (%SR), when subjected to 5 bar operating pressure. The super-hydrophilic membrane morphologies indicated an asymmetric structure by SEM examination.

English

Portulaca tuberosa Roxb belongs to family of Portulacaceae. Plant’s infusion is given internally in dysuria; externally applied to erysipelas traditionally. The herb shows diuretic, calculolythic, analgesic and antipyretic properties. The aerial parts contain diterpenoids, pilosanone A and B. Previously studies showed that thePortulaca tuberosa has good effect against diuretic, analgesic , however no work was carried out for in vivo antipyretic activity. The present study was made to investigate the ethanolic extract of Portulaca tuberosa leaves for antipyretic activity, compared to that of Aspirin as a reference drug.Pyrexia was induced by s/c injection of aqueous suspension of yeast 20% w/v in normal saline at the rate of 10ml/kg body weight. The experiment was done at the doses of 200 mg/kg, 400mg/kg and 800 mg/kg B/w. Rectal temperatures were recorded for 4 hrs by digital thermometer (Holden medical B.V, Netherlands). The result showed that Portulaca tuberosa Roxb has strong p< 0.01 antipyretic activity and this strongly support the ethanophrmacological uses of Portulaca tuberosa Roxb as antipyretic agent.

A free-standing calcium alginate/polyacrylamide hydrogel nanofiltration membrane with high anti-fouling performance: Preparation and characterization

An anti-fouling, free-standing membrane was synthesized through the polymerization of acrylamide in the presence of sodium alginate using N,N′-methylene-bisacrylamide as the covalent crosslinker and CaCl2 as the ionic crosslinker. The membranes were characterized via field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FT-IR), and Thermal Gravity (TG). Bovine serum albumin (BSA) solution and yeast suspension were used to investigate the anti-fouling performance of the hydrogel filtration membrane. The calcium alginate/polyacrylamide (CA/PAM) filtration membrane exhibited 89.06% and 85.84% water flux recovery for yeast suspension and BSA solution, respectively, without washing the filtration membrane. The hydrogel filtration membrane showed limited adsorption and adhesion for BSA and yeast, and the rejection of BSA and yeast reached 98.53% and 99.64%, respectively. The results of dye rejection studies demonstrated potential applications of this material as a nanofiltration membrane. The free-standing CA/PAM hydrogel filtration membrane exhibits excellent anti-fouling properties and has promising application prospects in the fields of protein separation, microorganism filtration and removal of dyes.