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At least 91 records · Page 5Linked to original sources
PubMed1995

Development of biologically-controlled insulin pumps with glucose-dependent release.

An experimental insulin pump has been developed in which living microorganisms are used to measure glucose concentration and to produce the energy required to control the release of insulin. The insulin pump consists of a miniaturised bioreactor containing 50 mg freeze-dried yeast. 300 microL of glucose-containing liquid are injected into the bioreactor through a septum. When solutions containing 100 mg or 400 mg glucose in 100 mL are used, the amounts of insulin released differ significantly even within the first measuring interval of 15 min (t-test, p < 0.05). Within 120 min, 4 I.U. and 17 I.U. insulin respectively are released from the two glucose solutions.

Biosensing Techniques↗
PubMed2001

Gravitational field-flow fractionation for the characterisation of active dry wine yeast.

Gravitational field-flow fractionation (GrFFF) is applied to the fractionation of active dry wine yeast. An experimental approach to the analysis of the effects that field variation by changing mobile phase composition and flow-rate have on the fractionation process of standard particles (polystyrene) was first developed to further obtain effective fractionation of wine yeast by GrFFF. Scanning electron microscopy and Coulter counter particle size measurements were used to monitor the fractionation extent and capabilities of GrFFF to describe the distribution of yeast cells populations.

Chemical Fractionation↗
PubMed2000

[Technology for the whole utilization of brewer's yeast in food industry].

A flexible scheme for the fractionation of brewer's yeast was developed. The procedure allows the production of different products such as: dry yeast flakes, dry yeast pills, yeast-extract based table sauce, yeast protein concentrates and soy-like sauce. The investment required for the processing of one ton per day is below 2 million dollars with an overall profitability higher than 53%. Investment is recovered in 0.75 years. The production of food ingredients from yeast upgrades its biomass about 25 fold. Present procedure is compared with other biomass fractionation processes taking into account the utilization of all technological streams where the process becomes environmentally friendly since effluent production significantly lower than similar technologies.

Analysis of Variance↗
PubMed2005

Effects of cryoprotectants on the viability and activity of freeze dried recombinant yeasts as novel oral drug delivery systems assessed by an artificial digestive system.

The aim of this study was to investigate, in a gastric-small intestinal system TIM-1, the effect of cryoprotectants on the survival of freeze-dried Saccharomyces cerevisiae expressing the heterologous P450 73A1 and their ability to convert trans-cinnamic acid into p-coumaric acid. Yeasts were lyophilized in suspensions of trehalose, maltose, lactose, or a milk proteins/trehalose mix. Freeze-dried or native yeasts and trans-cinnamic acid were introduced simultaneously into TIM-1 at the beginning of digestion. Yeast survival rate was evaluated by cell counting in the ileal effluents. P450 73A1 activity was followed by HPLC assay of p-coumaric acid. Freeze-dried yeasts showed high tolerance to digestive conditions. Nevertheless, their survival rate was lower than that of non-dried cells (around 80% whatever the protective agent vs. 96%). The ability of recombinant freeze-dried S. cerevisiae to perform a bioconversion reaction in the digestive tract was shown with all the protectants. The highest trans-cinnamic acid conversion rate (24 vs. 41% for native yeasts) was obtained with the milk proteins/trehalose mix. These results show that freeze-drying might be considered for the pharmaceutical formulation of new drug delivery systems based on orally administered recombinant yeasts and that TIM-1 could be a helpful tool for the pre-screening of oral dosage forms.

Cryoprotective Agents↗
PubMed2000

Identification of impact odorants in Bordeaux red grape juice, in the commercial yeast used for its fermentation, and in the produced wine.

The aroma extract dilution analysis method was used to detect the impact odorants of Bordeaux Cabernet Sauvignon and Merlot wines extracts, as well as those of the extracts of the corresponding Cabernet Sauvignon juice and dry yeasts used for its fermentation. The wines and the yeasts were extracted using dichloromethane, and the juice was extracted using Amberlite XAD-2. Structural identification of the impact odorants using gas chromatography-mass spectrometry and atomic emission detection (sulfur acquisition) was achieved after enrichment of these extracts by silica gel and Affi-Gel 501 chromatography. The same odorants (with the exception of dimethyl sulfide among 48) were detected in both wine extracts, with about the same flavor dilution (FD) factors. The 18 impact odorants detected in the Cabernet Sauvignon juice and dry yeast extracts were also found in the wine extracts. The odorants with the highest FD factors were 3-(methylsulfanyl)propanal, (E,Z)-nona-2, 6-dienal, and decanal in the juice extract, 2-methyl-3-sulfanylfuran, 3-(methylsulfanyl)propanal, 2-/3-methylbutanoic acids, and phenylethanal in the dry yeast extract, and 2-/3-methylbutanols, 2-phenylethanol, 2-methyl-3-sulfanylfuran, acetic acid, 3-(methylsulfanyl)propanal, 2-/3-methylbutanoic acids, beta-damascenone, 3-sulfanylhexan-1-ol, Furaneol, and homofuraneol in the wine extracts. Determination of the odor thresholds of some of these impact odorants was carried out.

Beverages↗
PubMed1998

Effect of specific growth rate on fermentative capacity of baker's yeast.

The specific growth rate is a key control parameter in the industrial production of baker's yeast. Nevertheless, quantitative data describing its effect on fermentative capacity are not available from the literature. In this study, the effect of the specific growth rate on the physiology and fermentative capacity of an industrial Saccharomyces cerevisiae strain in aerobic, glucose-limited chemostat cultures was investigated. At specific growth rates (dilution rates, D) below 0.28 h-1, glucose metabolism was fully respiratory. Above this dilution rate, respirofermentative metabolism set in, with ethanol production rates of up to 14 mmol of ethanol . g of biomass-1 . h-1 at D = 0.40 h-1. A substantial fermentative capacity (assayed offline as ethanol production rate under anaerobic conditions) was found in cultures in which no ethanol was detectable (D < 0.28 h-1). This fermentative capacity increased with increasing dilution rates, from 10.0 mmol of ethanol . g of dry yeast biomass-1 . h-1 at D = 0.025 h-1 to 20.5 mmol of ethanol . g of dry yeast biomass-1 . h-1 at D = 0.28 h-1. At even higher dilution rates, the fermentative capacity showed only a small further increase, up to 22.0 mmol of ethanol . g of dry yeast biomass-1 . h-1 at D = 0.40 h-1. The activities of all glycolytic enzymes, pyruvate decarboxylase, and alcohol dehydrogenase were determined in cell extracts. Only the in vitro activities of pyruvate decarboxylase and phosphofructokinase showed a clear positive correlation with fermentative capacity. These enzymes are interesting targets for overexpression in attempts to improve the fermentative capacity of aerobic cultures grown at low specific growth rates.

Acetates↗
PubMed2006

Nonlinear predictive control of a drying process using genetic algorithms.

A nonlinear predictive control technique is developed to determine the optimal drying profile for a drying process. A complete nonlinear model of the baker's yeast drying process is used for predicting the future control actions. To minimize the difference between the model predictions and the desired trajectory throughout finite horizon, an objective function is described. The optimization problem is solved using a genetic algorithm due to the successful overconventional optimization techniques in the applications of the complex optimization problems. The control scheme comprises a drying process, a nonlinear prediction model, an optimizer, and a genetic search block. The nonlinear predictive control method proposed in this paper is applied to the baker's yeast drying process. The results show significant enhancement of the manufacturing quality, considerable decrease of the energy consumption and drying time, obtained by the proposed nonlinear predictive control.

Journal Article↗
PubMed1979

Reduction of hepatic lipid deposition in laying hens by dietary selenium-yeast interaction.

Experiments were conducted to study the effect of chromiun and selenium on liver lipid deposition and incidence of liver hemorrhage in caged layers. Commercial strains of layers were fed ad libitum equicaloric and isonitrogenous diets. Corn-torula dried yeast diets containing added selenium (.1 microgram/g) with or without supplementary chromium (10 microgram/g) significantly reduced total liver lipid and liver hemorrhage. The effects of protein source (soybean meal vs. yeast) and selenium were separated in a factorial experiment which showed that the hepatic lipid response to selenium results from an interaction of selenium with an unidentified factor in torula yeast. The addition of selenium to diets with each protein source significantly elevated glutathione peroxidase (GSHPx) activity. Inclusion of 5% brewers yeast in the corn-soy diet or vitamin E (50 IU/kg) to the corn-torula dried yeast reduced liver lipid similar to that seen in birds fed the torula-yeast diet containing .1 microgram Se/g. Comparison of oral glucose tolerance of birds fed corn-soy and corn-soy brewers yeast diets showed no significant difference. None of the dietary treatments significantly altered body weight, egg production, egg weight, or feed consumption. The results indicate that the metabolic role of selenium in relation to its role in hepatic lipid metabolism is mediated through an interaction with a dietary factor(s) present in yeast.

Animal Feed↗
PubMed2004

The presence of Enterococcus, coliforms and E. coli in a commercial yeast manufacturing process.

This study evaluated a typical commercial yeast manufacturing process for bacterial contamination. Product line samples of a commercial yeast manufacturing process and the corresponding seed yeast manufacturing process were obtained upstream from the final compressed and dry yeast products. All samples were analysed before (non-PI) and after preliminary incubation (PI) at 37 degrees C for 24 h. The PI procedure was incorporated for amplification of bacterial counts below the lower detection limit. Enterococcus, coliform and Escherichia coli counts were quantified by standard pour-plate techniques using selective media. Presence at all stages and progressive increases in counts of Enterococcus, coliforms and E. coli during processing in the commercial manufacturing operation suggested that the primary source of contamination of both compressed and dry yeast with these bacteria was the seed yeast manufacturing process and that contamination was amplified throughout the commercial yeast manufacturing process. This was confirmed by surveys of the seed yeast manufacturing process which indicated that contamination of the seed yeast with Enterococcus, coliforms and E. coli occurred during scale up of seed yeast biomass destined as inoculum for the commercial fermentation.

Colony Count, Microbial↗
PubMed2005

A human papillomavirus type 16 vaccine by oral delivery of L1 protein.

To establish an edible HPV16 vaccine, we constructed a recombinant HPV16 L1-expressing Schizosaccharomyces pombe yeast strain (HPV16L1 yeast). A preliminary study revealed that freeze-dried yeast cells could be delivered safely, and were digested in the mouse intestine. The freeze-dried HPV16 L1 yeast was administered orally as an edible vaccine, with or without the mucosal adjuvant heat-labile toxin LT (R192G), to 18 female BALB/c mice. After the third immunization, none of the mice that received the edible HPV16 vaccine showed specific antibody responses, whereas all of the positive controls that were administered intranasally with 5 microg of HPV16-virus-like particles (VLP) had serum IgG, and genital IgA and IgG that reacted with HPV16-VLP in enzyme-linked immunosorbent assays (ELISAs). When a suboptimal dose (1 microg) of HPV16-VLP was administered to all the mice, including the negative control mice, 50% of the mice that were pre-immunized with the edible HPV16 vaccine showed positive serum IgG responses, while none of the negative controls showed any response. Vaginal IgG and IgA antibodies were also elicited in 33 and 39%, respectively, of the mice that were given with the edible HPV16 vaccine and the intranasal boost. All of the antibodies reacted more strongly to intact HPV16-VLP than to denatured HPV16-L1 protein suggesting that the edible vaccine primes for antibody responses against conformation-dependent epitopes. The inclusion of adjuvant in the vaccine formulation marginally increased the genital IgA response (P=0.06). HPV16-L1 protein in the yeast might induce tolerance in the vaccinated animals that could be recovered by intranasal boosting with a suboptimal dose of HPV-VLP. This freeze-dried yeast system may be useful as an oral delivery of HPV 16 L1 protein.

Adjuvants, Immunologic↗
PubMed2006

Use of the industrial yeast Candida utilis for cadmium sorption.

The sorption ability of Candida utilis biomass for cadmium ions with accumulating competence of dried cells and cells in alginate was compared. After an optimization of process conditions (pH 5.5, biomass concentration 1 g/L and c0 50 mg/L), the cadmium sorption capacity of dried yeast biomass was perceptibly higher than that of the other tested adsorbents. Considering the sorption of the dried yeast biomass equal to 100 %, the cells in alginate reached 86 % while native cells showed only 42 %.

Adsorption↗
PubMedDate not supplied

[Effect of protein synthesis inhibitors on the activity of mitochondrial enzymes of Saccharomyces cerevisiae during desiccation].

The work deals with the effect of carbon sources, presence of protein synthesis inhibitors (cycloheximide and chloramphenicol) and dehydration regime on the enzyme activity of the dried yeast Saccharomyces cerevisiae. The yeast grown on molasses and dried by aeration demonstrated a notable increase of the NADH-dehydrogenase and succinate dehydrogenase activities as compared with the analogously treated yeast grown on ethanol. The latter showed a notable rise only in the activity of NADH-dehydrogenase during slow drying. Addition of protein synthesis inhibitors into the cultivation medium caused no decrease of activities of the above mentioned enzymes of the dried yeasts in any variant under study.

Desiccation↗