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In the present work, bakers yeast catalyzed efficient synthesis of 2-amino-2-chromenes in methanol is presented. Here the ultrasonication has dual role i.e. as a source of energy for the reaction and tool for the disruption of the yeast cells. The cyclocondensation has been essentially carried under neutral conditions, thus reducing the possibility of unwanted side reactions.

Yeasts have been used for centuries for the leavening of bread. The main emphasis on the selection of yeast strains has been in relation to wheat products. This study is the first evaluation of different yeasts coming from the baking and brewing industry in a gluten-free system. Five different yeast strains (US-05, WB-06, T-58, S-23 and baker’s yeast) of the species Saccharomyces cerevisiae were evaluated for their suitability to leaven gluten-free dough. A wide range of dough quality characteristics such as the time and temperature-dependent rising behaviour, the chemical composition of the dough and the pH were determined. In addition to this, the bread quality attributes like, volume, texture, structure, aroma and flavour were evaluated. Obtained results indicated different activity levels between the selected yeast strains. Doughs prepared with US-05 showed a slower dough rise during proofing and a decreased height, in comparison to the baker’s yeast control. The application of WB-06 and T-58, however, resulted in a faster dough rise and increased dough height with greater gas cells (p < 0.05). These observations were also found in the baked breads, where these two yeasts reached a higher specific volume and a softer breadcrumb than the baker’s yeast bread (p < 0.05). Statistical analysis revealed strong correlations (p < 0.05) between activity level, dough properties and bread properties. Results obtained showed that the selected yeast strains reached different level of activity due to diverse preferences in temperature, time and sugars. Yeast strains which originated from the brewing industry were found to be suitable for gluten-free bread making.

Providing a project-based experience in an undergraduate biochemistry laboratory class can be complex with large class sizes and limited resources. We have designed a 6-week curriculum during which students purify and characterize the enzymes invertase and phosphatase from bakers yeast. Purification is performed in two stages via ethanol precipitation and anion exchange chromatography, and students perform both direct and coupled enzyme assays. By completion of the experimental series, students are able to identify which enzymes they have purified and have obtained kinetic parameters for one. This experimental series requires minimal instructor preparation time, is cost effective, and works with multiple sections of large groups of students. Students participating in this sequence showed increases in conceptual understanding of biochemical concepts as measured through in-class assessments and anonymous surveys.

Utilizing bakers’ yeast (Saccharomyces cerevisiae) as a biocatalyst, synthesis of α-aminophosphonates in one pot has been accomplished by the three-component reaction of an aldehyde, an amine, and diethyl phosphite in moderate to good yields under solvent-free reaction conditions. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

An environmentally friendly, one-pot synthesis of biologically important pyran derivatives in water is described herein. The advantages of this method are its simplicity, cost-effectiveness, and environmental friendliness. Water was exploited both as reaction media as well as activator of catalyst (fermentation of bakers' yeast). Compared with other methods for synthesis of pyran derivatives, satisfactory results were obtained with good yields under simple experimental procedure.

Bakers' yeast efficiently catalyzes synthesis of the benzimidazole and quinoxaline derivatives in aqueous media, via reaction of 1,2-phenylenediamine derivatives with aromatic aldehyde and 1,2-diketones respectively. The reactions proceed rapidly and the products are obtained through a facile and green procedure in good yields.

ObjectiveTo formulate and evaluate acyclovir microcapsules using bakers yeast.MethodsAcyclovir, pretreated yeast and deionised water were taken at a volumetric ratio of 1:2:4 respectively. This suspension was agitated in a magnetic stirrer at 25°C, 30°C, 35°C, and 40°C for 4 hours. The suspension was then centrifuged for 10 minutes at 2 000 rpm. The supernatant solution was decanted and the cells were washed 5 times with deionised water. Then the suspended drug entrapped yeast cells were dried in a lyophillizer for 48 hours. The yield was noted.ResultsThe first four formulations were done with 200 mg of the drug, followed by 400 mg for the next four formulations and 800 mg the last four formulations. SEM showed that the surface of the microcapsules was intact, with no burst characteristics. FTIR showed no interaction between acyclovir and the cell wall. DSC showed that the peak was within the standard values. The mean particle size for all the samples was 8 μm in diameter. The dissolution studies were done for all the twelve samples and showed a Fickian model of diffusion.ConclusionsFrom the results it is inferred that the samples prepared at 40°C (FY-4, FY-8, FY-12) show better entrapment and release. So these samples are formulated in the form of a suspension and compared with marketed acyclovir suspension using HPLC technique. The formulated suspensions with FY-4, FY-8 and FY-12 shows drug content in accordance with the standards of the pharmacopoeial limits.

3-Aryl-2,1-benzisoxazoles and its salts underwent reductive cleavage of the N–O bond leading to 2-aminobenzophenones with bakers’ yeast under non-fermenting conditions in aqueous media. The procedure gives excellent yields of 2-alkylamino- and 2-aminobenzophenones.

A simple and inexpensive method for the reductive cleavage of N–O bond of benzofuroxans with bakers' yeast under nonfermenting condition in aqueous media was achieved. The procedure gives excellent yields of aryl-1,2-diamines.

The influence of whole yeast cells (0–15% w/v) on the protein adsorption performance in dye-ligand chromatography was explored. The adsorption of a model protein, bovine serum albumin (BSA), was selected to demonstrate this approach. The UpFront adsorbent (ρ=1.5 g/cm3) derivatised with Cibacron Blue 3GA and a commercially available expanded bed column (20 mm i.d.) from UpFront Chromatography, Denmark, were employed in the batch binding and expanded bed operation. The BSA binding capacity was demonstrated to not be adversely affected by the presence of yeast cells. The dynamic binding capacity of BSA at aC/C 0=0..1 biomass concentration of 5, 10, 15% w/v were 9, 8, and 7.5 mg/mL of settled adsorbent, respectively.

The adsorption of a model protein bovine serum albumin (BSA) in expanded bed chromatography was undertaken by exploiting a commercially available expanded bed column (20 mm i.d.) from Up Front Chromatography and Streamline DEAE (ρ=1.2 g/cm3) from Amersham Pharmacia Biotechnology. The influence of whole yeast cells on the adsorption capacity of column was explored by employing yeast cells in a concentration ranged of 0 to 15% (w/v). Equilibrium isotherms for adsorption of BSA on Streamline DEAE were correlated by using Langmuir equation. The presence of yeast cells resulted in decreased of BSA binding capacity in both batch binding and expanded bed chromatography. Results indicated that the yeast cells act as competitor for proteins to bind to the sites on adsorbents.

F.L. LOW, I.C. SHAW AND J.A. GERRARD. 2004. Aims: To investigate the ability of baker’s yeast (Saccharomyces cerevisiae) to degrade the herbicide glyphosateduring the fermentation cycle of the breadmaking process.Methods and Results: Aqueous glyphosate was added to bread ingredients and kneaded by commercially availablebreadmaking equipment into dough cultures. Cultures were incubated in the breadmaker throughout thefermentation cycle. The recovery of glyphosate levels following fermentation was determined, thus allowing anestimation of glyphosate degradation by yeast.Conclusions: It was shown, for the first time, that S. cerevisiae plays a role in metabolizing glyphosate during thefermentation stages of breadmaking. Approximately 21% was degraded within 1 h.Significance and Impact of the Study: As a result of projected increases in the glyphosate use on wheat and therole of bread as a dietary staple, this may contribute to more informed decisions being made relating to the use ofglyphosate on glyphosate-resistant wheat, from a public health/regulatory perspective.Keywords: bakers’ yeast, breadmaking, consumers, glyphosate, risk.

An empirical equation is proposed to correlate the dough volume and the incubation time during cylinder tests using thin flour dough carried out to evaluate the gassing power of compressed yeast. The above equation permitted to correlate the gassing power of the yeast and the proof time, as well as to calculate the specific rate of the dough volume variation at any time. It provided more information regarding the fermentation power of the yeast than the sole value of its gas-producing power. A physical interpretation of the proposed equation is presented.Propõe-se uma equação empírica que correlaciona o volume da pasta com o tempo de incubação na medida, pelo método do cilindro graduado e pasta de baixa concentração, da capacidade do fermento prensado de aumentar o volume da pasta (usualmente denominada "poder de levantamento" ou "poder de fermentação" do fermento). A equação proposta permite não apenas correlacionar o valor daquela capacidade com o tempo de incubação, mas também calcular a velocidade específica de aumento do volume da pasta em cada instante, fornecendo assim muito mais informações sobre o desempenho do fermento. Apresenta-se, também, uma possível explicação da fórmula empírica proposta.

Baker's yeast (Saccharomyces cerevisiae) reductions were applied to the synthesis of the paclitaxel C-13 side-chain analogue. An easily synthesized alpha-keto-beta-lactam (1-(4-methoxyphenyl)-4-tert-butylazetidin-2,3-dione, 4) was reduced by yeast cells to give a mixture of enantiomerically pure cis and trans isomers. Both compounds were isolated and characterized, and their absolute configurations were confirmed by X-ray crystallographic analysis.Key words: Taxol®, C-13 side-chain, paclitaxel analogues, optically pure alpha-hydroxy-beta-lactams, baker's yeast-catalyzed reductions.

A green protocol for one-pot synthesis of pharmacologically important indolyl chromenes and bis(indolyl)alkanes was achieved using Saccharomyces cerevisiae (commonly known as bakers' yeast) as catalyst under room temperature stirring condition. This method is relatively simple, efficient, inexpensive, and environment-friendly.

The purpose of this study was to investigate the use of a horizontal packed bed bioreactor, named Biopack, to treat high strength wastewater, such as bakers yeast wastewater. The Biopack system (RBC P ) is a modified rotating biological contactor and the system was applied for secondary treatment. The RBC P system produced high treatment efficiencies, COD removal was 94.9% when COD was 472 mg/l and surface organic loading=0.187 kg COD/m 2 per day and surface hydraulic loading=6 l/m 2 per day. Variations of surface hydraulic loading from 6 to 11.9 l/m 2 per day produced a decrease in COD removal efficiency from 94.9 to 58.6%. Other factors, such as shock load, retention time and rotational speed were also investigated.

Commercial baker's yeast cells were immobilized through adhesion on jute fabric using polyethylenimine. Optimal binding was seen when the yeast cells were contacted with jute fabric treated with 2% polyethylenimine. The adhesion was strong and the cells were not eluted even under extreme conditions of pH (3–10) and ionic concentration of 0.5 M NaCl. No change in pH or temperature optimum for invertase present in the cell was seen on immobilization. The thermostability of the enzyme was enhanced on immobilization. An annular reactor was designed for sucrose inversion, in which the jute fabric was attached to a stainless steel mesh on the inner side and was rolled into a cylinder, after which the yeast cells were adhered on it. This yeast cell bound module was used in a temperature controlled tubular reactor for the inversion of concentrated (60–80%) sucrose syrups. The column could be operated at 45°C for a study period of over 45 days without loss in efficiency.

NADP(H)-specific Bakers yeast glucose 6-phosphate dehydrogenase (BYG6PDH) was paired, in turn, with each of three different source glutamate dehydrogenases (GDHs): NAD(P)-specific bovine liver (BLGDH), NADP-specific Candida utilis (CUGDH) and NADP-specific Proteus sp. (PSGDH) to constitute three enzyme cycling systems; (i) BYG6PDH/BLGDH; (ii) BYG6PDH/CUGDH; and (iii) BYG6PDH/PSGDH. When incorporated into an enzymatic cycling/amplification system for NAD kinase and run on a centrifugal fast analyzer (CFA), the microbial source enzyme CUGDH gave rise to a seven-fold greater amplification rate [21.5 × 103 cycles−1 (cph)] relative to that realized (3 × 103 cph) using the BYG6PDH/BLGDH cycling pair previously reported. Either of these cycling systems can be used as a flexible and general-purpose module for robotic amplification and data collection of NADP(H) linked enzymes as a user’s requirements dictate. Although the BYG6PDH/PSGDH cycling pair produced a respectable cycling rate (14.4 × 103 cph), for reasons discussed the PSGDH enzyme was not considered a suitable replacement for BLGDH in an NADP(H) cycling system.

We examined the freeze tolerance of bakers' yeast loaded with exogenous trehalose. Freeze-tolerant and freeze-sensitive compressed bakers' yeast samples were soaked at several temperatures in 0.5 M and 1 M trehalose and analyzed. The intracellular trehalose contents in both types of bakers' yeast increased with increasing soaking period. The initial trehalose-accumulation rate increased with increasing exogenous trehalose concentration and soaking temperature. The maximum trehalose content was almost identical (200-250 mg/g of dry cells) irrespective of the soaking temperature and the type of bakers' yeast, but depended on the exogenous trehalose concentration. The leavening ability of both types of bakers' yeast loaded with trehalose was almost identical to that of the respective original cells, irrespective of the soaking conditions. The freeze-tolerant ratio (FTR) of both types of bakers' yeast increased with increasing intracellular trehalose content. However, FTR decreased during over-soaking after the maximum amount of trehalose had accumulated. FTR of the freeze-sensitive bakers' yeast was more efficiently improved than that of the freeze-tolerant type.

Enantiomerically pure 2-(1-hydroxyalkyl)pyridines were prepared via reaction of 2-lithiopyridine with (R)-2,3-O-isopropylideneglyceraldehyde, methyl (S)-2-methoxypropionate and methyl (S)-2-methoxy-2-phenylacetate, obtained from D-mannitol, L-lactic acid and L-mandelic acid, respectively. 6,6′-Bis(1-hydroxyalkyl)-2,2′-bipyridines were obtained from the same naturally occurring chiral compounds and 2-bromo-6-lithiopyridine with subsequent Ni-catalysed coupling.

The cyclocondensation of 2-aminothiophenol and aldehydes has been carried out in dichloromethane using bakers’ yeast as a catalyst for obtaining 2-aryl/heteryl benzothiazoles in good yields.

Improvement of the enantioselectivity and enhancement of the reactivity were achieved in the bakers' yeast reduction of the α- and β-keto ester derivatives by the addition of a sulfur compound. High enantioselectivity in the bakers' yeast reduction of keto esters was accomplished by using combination of an addition of a sulfur compound with an appropriate selection of the alcohol part of the ester.

The bakers' yeast reduction of trifluoroacetyl derivatives was examined in the presence of various esters of methanethiosulfonate. The yeast reduction of 4-bromo-4′-trifluoroacetylbiphenyl using the cyclohexylmethyl methanethiosulfonate resulted in the R product with the highest enantiomeric excess of 96% ee, which is compared with the reduction without the additive to give the corresponding alcohol with 84% ee. On the other hand, in the case of 4-hyrdoxy-4′-trifluoroacetylbiphenyl, the highest enantioselectivity was observed also using cyclohexylmethyl methanethiosulfonate to give the R-product with 90% ee, in contrast with the reduction without the additives to give the same product with 77% ee.

Optically pure α-hydroxy esters and α-hydroxy ketones have been synthesized by the reduction of the corresponding ketones with a keto ester reductase isolated from bakers’ yeast (YKER-I). The reduction of α-keto esters affords the corresponding (S)- or (R)-hydroxy esters selectively, where the stereochemical course depends on the chain length of the alkyl substituent on the carbonyl group. An α-keto short alkanoic ester affords the corresponding (S)-hydroxy ester, whereas a long alkanoate yields the corresponding (R)-hydroxy ester. The reduction of α-diketones affords the corresponding (S)-2-hydroxy ketones regio- and stereoselectively.

Bakers’ yeast (Saccharomyces cerevisiae) efficiently catalyzes the three-component Biginelli reaction of aldehydes, β-keto esters, and urea/thiourea to form 3,4-dihydropyrimidin-2-(1H)-ones in good to excellent yields.

Asymmetric synthesis of methyl 2-alkyl-3-hydroxybutanoate having three consecutive chiral centers with a reductase from bakers' yeast has been investigated. When the enzyme is employed in the reduction of a β-keto ester substituted by a secondary alkyl group at α-position, the reaction affords the corresponding β-hydroxy ester in excellent stereoselectivity.

In an organic solvent system, 3-oxo-3-arylpropanenitriles are C-alkylated by bakers yeast. The reported mechanism for bakers yeast alkylation of ethyl cyanoacetate ( 13 ), in an aqueous system, has been revised.

The bakers' yeast reduction of (trifluoroacetyl)biphenyl derivatives produces (R)-trifluoromethyl biphenylyl carbinols in high enantioselectivity, whereas the reduction of the same derivatives with Geotrichum candidum acetone powder gives the corresponding (S)-carbinols in excellent yields and enantioselectivity.

Improvement of the enantioselectivity and enhancement of the reactivity were achieved in the bakers' yeast reduction of the β-keto ester derivatives by the addition of a sulfur compound. © 1997 Elsevier Science Ltd. All rights reserved.

Reduction of the piperidine keto esters 16–19 using fermenting bakers’ yeast provides high yields of the corresponding hydroxy esters 20, 26, 32 and 37 respectively, exclusively as the cis-diastereoisomers and with good levels (80%) of enantiomeric enrichment. The relative stereochemistries of the products were deduced from NMR data while the absolute configurations were determined by degradation to known piperidinemethanol derivatives or, in the case of hydroxy ester 37, by homologation to (R)-3-quinuclidinol 41b.

Piperidine carboxylic acids and 4-hydroxypiperidine-3-carboxylic acid, the latter obtained from bakers yeast reduction of the corresponding piperidone, were coupled in solid-phase synthesis to form simplified oligosaccharide analogues. A split-and-mix synthesis approach was used to create small combinatorial libraries which were characterised by LC-MS and screened as inhibitors of glycosidases.

Reduction of the ketone 1 with Bakers’ yeast gives the alcohol (R)-2 with high enantiomeric excess, and this upon subsequent epoxidation and alkylation with Grignard reagents provides the alcohols (S)-4 without racemisation. Tosylation of the alcohols (S)-4 under common conditions yields the tosylates (toluene-p-sulfonates) (S)-5, whilst under Mitsunobu conditions inversion of configuration takes place giving the tosylates (R)-5. Subsequent treatment of the tosylates (S)-5 and (R)-5 with lithium diisopropylamide leads to cyclization affording the enantiomerically pure cyclopropanes (S,S)-6 and (R,R)-6 in high yields, respectively. The diastereoisomeric alcohol (S)-4f, obtained by methylation of the alcohol (S)-4e, can also be converted into the single stereoisomer (R,R)-6f in enantiomerically pure form.

Bakers' yeast-mediated reduction of (RS)-2-(4-methoxyphenyl)-1,5-benzothiazepin-3,4(2H,5H)-dione [(RS)-1] to (2S,3S)-2,3-dihydro-3-hydroxy-2-(4-methoxyphenyl)-1,5-benzo-thiazepin-4(5H)-one, a key intermediate in the synthesis of diltiazem hydrochloride, was investigated for industrial application. We found that an aggregate of (RS)-1, formed by the addition of its DMF solution to water, was soluble in an aqueous medium at about 20 mg/l. Thus, the asymmetric reduction using the (RS)-1 aggregate successively proceeded in the presence of ethanol under aerobic conditions. In this procedure, 100 g of the substrate was reduced in 1 l of the aqueous medium to produce the desired chiral intermediate with over 99% enantiomeric excess in 80% yield.

A study was carried out on yeast fermentation of carica papaya (pawpaw) agricultural waste using dried active baker's yeast and brewer's yeast strain (Sacchromyces cerevisiae). The pawpaw considered as an agricultural waste was the tapped ripe pawpaw fruit harvested after the tapping of papain. Effect of different yeast strains on the percentage yield of ethanol was investigated. The effects of yeast concentration, saccharification and different nutrient supplements as they relate to the optimization of the ethanol yield were also carried out. The fermented pawpaw yielded ethanol contents of 3.83 to 5.19% (v/v). The reducing sugar in the pawpaw was determined before and after saccharification. The reducing sugar was highest after 48 h of saccharification using Aspergillus niger. The value recorded was 7.6 to 13.6 g/100g. Brewers yeast gave a higher ethanol yield than bakers yeast. Saccharification for 48 h coupled with nutrient supplements significantly increased the ethanol yield. Key words: Paw-paw agrowaste, bakers yeast, brewers yeast, fermentation, pH, temperature, saccharification.

Utilizing bakers’ yeast (Saccharomyces cerevisiae) as a biocatalyst, synthesis of α-aminophosphonates in one pot has been accomplished by the three-component reaction of an aldehyde, an amine, and diethyl phosphite in moderate to good yields under solvent-free reaction conditions. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

Over the past 20 years, the yeast cell wall has been thoroughly investigated by genetic and biochemical methods, leading to remarkable advances in the understanding of its biogenesis and molecular architecture as well as to the mechanisms by which this organelle is remodeled in response to environmental stresses. Being a dynamic structure that constitutes the frontier between the cell interior and its immediate surroundings, imaging cell surface, measuring mechanical properties of cell wall or probing cell surface proteins for localization or interaction with external biomolecules are among the most burning questions that biologists wished to address in order to better understand the structure-function relationships of yeast cell wall in adhesion, flocculation, aggregation, biofilm formation, interaction with antifungal drugs or toxins, as well as response to environmental stresses, such as temperature changes, osmotic pressure, shearing stress, etc. The atomic force microscopy (AFM) is nowadays the most qualified and developed technique that offers the possibilities to address these questions since it allows working directly on living cells to explore and manipulate cell surface properties at nanometer resolution and to analyze cell wall proteins at the single molecule level. In this minireview, we will summarize the most recent contributions made by AFM in the analysis of the biomechanical and biochemical properties of the yeast cell wall and illustrate the power of this tool to unravel unexpected effects caused by environmental stresses and antifungal agents on the surface of living yeast cells.

Efficient kinetic resolution of 2-benzenesulfonylcyclopentanones 1 , bearing 3-alkyl, 3-aryl, or 3-benzyl substituents, has been achieved by bakers' yeast mediated reduction. With the unsubstituted 2-benzenesulfonylcyclopentanone 1a , efficient asymmetric reduction to form (1 S ,2 R )- cis -2-benzenesulfonylcyclopentanol 2a is observed under the same conditions. Excellent enantioselectivities (up to > 95% ee) are obtained.

The bakers' yeast reduction of ethyl 3-oxo-4-phenylthiobutanoate gave ethyl (R)-3-hydroxy-4-phenylthiobutanoate with >99%ee. The resultant enantiomerically pure alcohol was easily transformed into β-lactam without loss of its enatiomeric purity via the oxamate derivative.

The effect of homogeniser impact distance on the disruption efficiency of stationary and growth-phase Escherichia coli is examined. Disruption efficiency decreases as impact distance increases as seen previously for yeasts. However, the dependence on impact distance is considerably less than previously reported for yeast. Results suggest that homogeniser performance can be improved by decreasing impact distance. This effect is modelled.