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Baker's Yeast (baker + yeast)
Selected AbstractsRegio- and Stereo-selective Bioreduction of Diketo- n -butylphosphonate by Baker's YeastCHINESE JOURNAL OF CHEMISTRY, Issue 11 2002Ke Wang Abstract A regio- and stereo-selective reduction of diketo-n-butylphosphonates by baker's yeast was reported. The chemical yield and ee value of these reactions are highly dependent on the structure of substrates. The resulting optical active hydroxyalkanephosphonates can be used as chirons for the synthesis of polyfunctional organophosphorus compounds. As useful building block, a series of ,, ,-unsaturated ketones bearing chiral hydroxy group in addition to trifluoromethyl moiety was prepared via the Homer-Wadsworth-Emmons (HWE) reaction of the biotransformation products. [source] Baker's Yeast Reduction of ,-Hydroxy KetonesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2010Daniela Acetti Abstract Reduction of ,-hydroxy ketones to the corresponding 1,3-diols by baker's yeast was investigated, in order to develop methods for simultaneous control over the configurations of multiple stereogenic centres. The reactions were found to be enantiospecific and generally characterised by good diastereoselectivity. Substrates with a substituent at the carbon atom in the , position were also considered. When the substituent at the ,-carbon atom was part of a ring, higher selectivity was observed. [source] Effects of pressure on the activity and spectroscopic properties of carboxyl proteinasesFEBS JOURNAL, Issue 3 2001Apparent correlation of pepstatin-insensitivity, pressure response The pressure dependence of the activity and spectroscopic properties of four carboxyl proteinases were investigated. Two were pepstatin-sensitive carboxyl proteinases (porcine pepsin and proteinase A from baker's yeast) and two were pepstatin-insensitive carboxyl proteinases (from Pseudomonas sp. 101 (pseudomonapepsin; PCP) and Xanthomonas sp. T-22 (xanthomonapepsin; XCP)). The specificity constant [kcat/Km(app)] of PCP and XCP for a synthetic peptide substrate showed only a slight decrease with increasing pressure, whereas pepsin and proteinase A showed substantial disactivation at higher pressures. The calculated apparent activation volume (,Vkcat/Km) was about 1, 3, 13, and 14 mL·mol,1 for PCP, XCP, pepsin, and proteinase A, respectively. The hydrolysis of acid-denatured myoglobin by the four carboxyl proteinases was only slightly affected by high pressure (except for proteinase A at 400 MPa), in contrast to the results for the peptide hydrolysis. In fact, PCP, XCP, and proteinase A actually showed slightly higher degradations of acid-denatured myoglobin at higher pressures. The residual activities of these enzymes after the incubation at high pressures implied a pressure-induced stabilization towards autolysis. The changes in the fourth derivative near-UV absorbance spectrum of the four enzymes in aqueous solution were measured at various pressures from 0.1 to 400 MPa. Upon an increase in pressure, the peaks from PCP and XCP red-shifted slightly, whereas pepsin and proteinase A blue-shifted substantially, thus indicating a more polar environment. The intrinsic fluorescence also decreased upon increasing pressure. However, the change for XCP was rather small, but the change for the other three was very large. The changes in the peak wavelength for pepsin and proteinase A were characteristic, and also indicated a more polar environment under high pressure. An analysis by the center of spectra mass (CSM) gave the ,G and ,V of transition as 9.8 kJ·mol,1 and ,24 mL·mol,1 (pepsin) and 11.7 kJ·mol,1 and ,43 mL·mol,1 (proteinase A), respectively, by assuming a simple two-state transition. The circular dichroism (CD) showed relatively small changes after 1-h incubations at 400 MPa, indicating that the secondary structures were largely maintained. [source] Freeze tolerance of the yeast Torulaspora delbrueckii: cellular and biochemical basisFEMS MICROBIOLOGY LETTERS, Issue 1 2004Cecília Alves-Araújo Abstract The freeze stress responses to prolonged storage at ,20 °C in Torulaspora delbrueckii PYCC5323 were investigated. In this yeast, no loss of cell viability was observed for at least 120 days during freezing at ,20 °C, whereas a loss of 80% was observed in a commercial baker's yeast after 15 days. In the former strain, freeze resistance was dependent on an adaptation process. The primary cell target of freeze stress was the plasma membrane, preservation of its integrity being related with a lower increase of lipid peroxidation and with a higher resistance to H2O2, but not with the intracellular trehalose concentration. [source] Enantioselective reduction of 2-keto-3-haloalkane phosphonates by baker's yeastHETEROATOM CHEMISTRY, Issue 6 2001Cheng-ye Yuan Bioreduction of 3-substituted-2-oxoal-kanephosphonates by baker's yeast afforded 3-substituted-2-hydroxy-alkanephosphonates in moderate to good yields and ee value. These compounds could serve as useful chirons for the stereoselective synthesis of phosphorus analogs of biologically active molecules including R-(,)-3-trimethylammonium-2-hydroxypropanoic acid and R-(,)-3- trimethylammonium-2-hydroxypropanoic acid. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:551,556, 2001 [source] Enantioselective Synthesis of 4-(Dimethylamino)pyridines through a Chemical Oxidation-Enzymatic Reduction Sequence.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2006Application in Asymmetric Catalysis Abstract Enantiomerically pure 4-(dimethylamino)-3-(1-hydroxyalkyl)pyridines and 4-(dimethylamino)-3-[hydroxy(phenyl)methyl]pyridine have been prepared through efficient chemoenzymatic routes. For this purpose different lipases and oxidoreductases have been tested in the preparation of optically active 4-chloro derivatives and baker's yeast was found to be an excellent catalyst for the bioreductions of the corresponding ketones. Their applications as enantioselective nucleophilic catalysts have been studied, important catalytic properties were observed in the stereoselective construction of quaternary centers. [source] Alternative technologies for biotechnological fuel ethanol manufacturingJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2007Alain A Vertès Abstract The challenges of implementing biorefineries on a global scale include socioeconomic, financial, and technological constraints. In particular, the development of biorefineries is tightly linked to the continued availability of fermentation raw materials. These constraints can be relaxed by the use of diverse raw materials, while advances that confer higher flexibility would enable biotechnological plant managers to swiftly react to volatile markets. In conventional processes, Saccharomyces cerevisiae grows on a relatively limited range of substrates, and produces only a single product,ethanol. Given the observed maturity of the S. cerevisiae fermentation technology, alternatives to baker's yeast may be needed to tip the economic balance in favour of biotechnological ethanol. These alternative fermentation technologies may allow a greater diversity of substrates to be used to produce an individually tailored mix of ethanol and other chemicals. Copyright © 2007 Society of Chemical Industry [source] Pretreatment of barley husk for bioethanol productionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2005Beatriz Palmarola-Adrados Abstract This paper reports on the optimization of steam pretreatment of barley husk for high pentose and hexose recovery in the subsequent enzymatic hydrolysis step, as well as high ethanol yield, following simultaneous saccharification and fermentation. The parameters optimized in the steam pretreatment step were residence time (5,15 min), temperature (190,215 °C), and concentration of the acid catalyst (0 or 0.5% H2SO4). A microwave oven was employed for screening of the optimal conditions to obtain the highest sugar yield following combined pretreatment and enzymatic hydrolysis. The final optimization of the pretreatment prior to enzymatic hydrolysis was performed on a larger scale, in a steam pretreatment unit. Simultaneous saccharification and fermentation was carried out following steam pretreatment on 5 and 10% dry matter steam-pretreated slurries. Fermentability tests were performed to determine the effect of by-products (ie furfural and 5-hydroxymethyl furfural) in the bioconversion of glucose to ethanol by baker's yeast. The maximum glucose yield, 88% of the theoretical, was obtained following steam pretreatment with 0.5% H2SO4 at 200 °C for 10 min. Under these conditions, a sugar to ethanol conversion of 81% was attained in simultaneous saccharification and fermentation. Copyright © 2004 Society of Chemical Industry [source] PARTIAL PURIFICATION AND CHARACTERIZATION OF NEUTRAL TREHALASE FROM COMMERCIAL BAKER'S YEAST, SACCHAROMYCES CEREVISIAEJOURNAL OF FOOD BIOCHEMISTRY, Issue 6 2000SANIYE YARAR ABSTRACT The neutral trehalase of a commercial baker's yeast (S. cerevisiae) strain has been partially purified using ammonium sidfate fractionation and DEAE-cellulose column chromatography techniques. Trehalase was precipitated between 35,50% ammonium sulfate saturation and approximately 5,8 fold purification was achieved. The yeast cAMP-dependent protein kinase was also precipitated in the same fraction and these two proteins were separated by DEAE-cellulose column chromatography. Trehalase became totally inactive after ion exchange chromatography, "cryptic trehalase" (tre-c), but was later activated with the addition of partially purified protem kinase together with cAMP and ATP. A 215 fold purification was obtained after DEAE-ceUulose column chromatography. One mM EDTA caused complete inhibition of the enzyme in crude extract, however the inhibition levels in ammonium sulfate and DEAE-cellulose fractions were 73.5% and 50%, respectively. Optimal pH range and temperature of the enzyme were determined as pH 6,6.8 and 30C, respectively. The kinetic parameters, Km and Vmax, were estimated as 11.78 mM trehalose and 12.47 ,mole glucose/min-mg protein, respectively. [source] APPLICATION OF DISCRETE MODELING APPROACH TO FLUIDIZED BED YEAST DRYINGJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2010F. DEBASTE ABSTRACT Yeast drying is widely used to ease transport and conservation. In this work, baker's yeast drying in fluidized bed is modeled using a pore network model. Classical balanced equations at the reactor scale are coupled with the pore network for the grain, which takes into account diffusion in the gas phase, transport by liquid film in partially saturated region and pressure gradient effects in the liquid phase. The porous structure to be applied in the model is obtained using environmental scanning electron microscopy. Simulations are validated on a thermogravimetric analysis experiment. The model is then applied to fluidized bed drying for which experimental results obtained on a laboratory pilot are available. Finally, the model results are compared to those of a simplified receding front model. PRACTICAL APPLICATIONS The presented model allows simulation of Saccharomyces cerevisiae fluidized bed drying. Taking into account transport phenomena in the grain offers the opportunity to predict drying rate without the use of a desorption isotherm. Moreover, the model predicts roughly the critical humidity. Therefore, the model can be used for scale-up, design and optimization of dryer including the effect of changes in yeast granulation. [source] SEQUENCE ANALYSIS AND TRANSCRIPTIONAL REGULATION OF IRON ACQUISITION GENES IN TWO MARINE DIATOMS,JOURNAL OF PHYCOLOGY, Issue 4 2007Adam B. Kustka The centric diatom Thalassiosira pseudonana Hasle et Heimdal and the pennate diatom Phaeodactylum tricornutum Bohlin possess genes with translated sequences homologous to high-affinity ferric reductases present in model organisms. Thalassiosira pseudonana also possesses putative genes for membrane-bound ferroxidase (TpFET3) and two highly similar iron (Fe) permeases (TpFTR1 and TpFTR2), as well as a divalent metal (M2+) transporter belonging to the NRAMP superfamily (TpNRAMP). In baker's yeast, the ferroxidase,permease complex transports Fe(II) produced by reductases. We investigated transcript abundances of these genes as a function of Fe quota (QFe). Ferric reductase transcripts are abundant in both species (15%,60% of actin) under low QFe and are down-regulated by 5- to 35-fold at high QFe, suggesting Fe(III) reduction is a common, inducible strategy for Fe acquisition in marine diatoms. Permease transcript abundance was regulated by Fe status in T. pseudonana, but we did not detect significant differences in expression of the copper (Cu)-containing ferroxidase. TpNRAMP showed the most dramatic regulation by QFe, suggesting a role in cellular Fe transport in either cell-surface uptake or vacuolar mobilization. We could not identify ferroxidase or permease homologues in the P. tricornutum genome. The up-regulation of genes in T. pseudonana that appear to be missing altogether from P. tricornutum as well as the finding that P. tricornutum seems to have an efficient system to acquire Fe,, suggest that diverse (and uncharacterized) Fe-uptake systems may be at play within diatom assemblages. Different uptake systems among diatoms may provide a mechanistic basis for niche differentiation with respect to Fe availability in the ocean. [source] Influence of carboxypeptidases on free amino acid, peptide and methylpyrazine contents of under-fermented cocoa beansJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2002I Yusep Abstract A study of the action of two carboxypeptidases on free amino acids, peptides and methylpyrazines in under-fermented cocoa beans was carried out. Carboxypeptidase B from porcine pancreas and carboxypeptidase Y from baker's yeast were used separately for digestion. Hydrophobic free amino acids (alanine, valine, isoleucine, leucine, phenylalanine and tyrosine) were predominantly produced in samples digested with both carboxypeptidase B and Y. The peptide patterns of samples digested with both carboxypeptidases were similar to that of the control. The concentration of 2,3,5,6-tetramethylpyrazine in samples with carboxypeptidase B addition was significantly higher than those of 2,5-dimethyl- and 2,3,5-trimethylpyrazine; the concentration of 2,3,5-trimethylpyrazine was highest (1727.86,µg per 100,g) in the sample with carboxypeptidase B addition that had been incubated for 24,h. These findings indicate that carboxypeptidase B from porcine pancreas was more prominent in the formation of cocoa-specific aroma. © 2002 Society of Chemical Industry [source] Adaptive evolution of baker's yeast in a dough-like environment enhances freeze and salinity toleranceMICROBIAL BIOTECHNOLOGY, Issue 2 2010Jaime Aguilera Summary We used adaptive evolution to improve freeze tolerance of industrial baker's yeast. Our hypothesis was that adaptation to low temperature is accompanied by enhanced resistance of yeast to freezing. Based on this hypothesis, yeast was propagated in a flour-free liquid dough model system, which contained sorbitol and NaCl, by successive batch refreshments maintained constantly at 12°C over at least 200 generations. Relative to the parental population, the maximal growth rate (µmax) under the restrictive conditions, increased gradually over the time course of the experiment. This increase was accompanied by enhanced freeze tolerance. However, these changes were not the consequence of genetic adaptation to low temperature, a fact that was confirmed by prolonged selection of yeast cells in YPD at 12°C. Instead, the experimental populations showed a progressive increase in NaCl tolerance. This phenotype was likely achieved at the expense of others traits, since evolved cells showed a ploidy reduction, a defect in the glucose derepression mechanism and a loss in their ability to utilize gluconeogenic carbon sources. We discuss the genetic flexibility of S. cerevisiae in terms of adaptation to the multiple constraints of the experimental design applied to drive adaptive evolution and the technologically advantageous phenotype of the evolved population. [source] Protein phosphatase 2A on track for nutrient-induced signalling in yeastMOLECULAR MICROBIOLOGY, Issue 4 2002Piotr Zabrocki Summary Early studies identified two bona fide protein phosphatase 2A (PP2A)-encoding genes in Saccharo-myces cerevisiae, designated PPH21 and PPH22. In addition, three PP2A-related phosphatases, encoded by PPH3, SIT4 and PPG1, have been identified. All share as much as 86% sequence similarity at the amino acid level. This review will focus primarily on Pph21 and Pph22, but some aspects of Sit4 regulation will also be discussed. Whereas a role for PP2A in yeast morphology and cell cycle has been readily recognized, uncovering its function in yeast signal transduction is a more recent breakthrough. Via their interaction with phosphorylated Tap42, PP2A and Sit4 play a pivotal role in target of rapamycin (TOR) signalling. PPH22 overexpression mimics overactive cAMP,PKA (protein kinase A) signalling and PP2A and Sit4 might represent ceramide signalling targets. The methylation of its catalytic subunit stabilizes the heterotrimeric form of PP2A and might counteract TOR signalling. We will show how these new elements could lead us to understand the role and regulation of PP2A in nutrient-induced signalling in baker's yeast. [source] Activity, molecular mass and hydrolysis on baker's yeast protein of extracellular proteases from the putative probiotic bacteria Microbacterium sp. strain 8L and Exiguobacterium mexicanum strain 8NAQUACULTURE RESEARCH, Issue 1 2009César Orozco-Medina Abstract The bacteria Microbacterium sp. 8L and Exiguobacterium mexicanum 8N are known to improve the culture of Artemia franciscana using baker's yeast as food. Using spectrophotometry, sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), substrate-SDS-PAGE and pH-stat in vitro -digestibility assays, the activity, molecular mass and hydrolysis on baker's yeast protein of proteases from extracellular polymeric substances (EPS) of the strains 8L and 8N along with the pathogenic strains Microbacterium sp. 8R and Vibrio parahaemolyticus 588 CECT (Vp) were studied. The EPSs of 8L and 8R showed one activity band, on which the serine inhibitor phenylmethylsulphonyl fluoride (PMSF) had no effect. The EPSs of 8N showed four bands; two were unaffected by PMSF, whereas one was affected, and the other was partially affected. The EPSs of Vp showed two bands, one partially inhibited by PMSF. No inhibitory effects from 1-chloro-3-tosylamido-7-amino-2-heptanone (trypsin inhibitor) were observed in the protease bands of the studied bacteria. The EPSs of 8L and 8N showed a similar degree of hydrolysis (pH-stat). The EPSs of 8L had the lowest Dice index of similarity of yeast protein profiles at 1 h of reaction. We conclude that the strain 8L could benefit A. franciscana by providing bacterial proteases for digestion of baker's yeast. [source] Potential of agroindustrial waste from olive oil industry for fuel ethanol productionBIOTECHNOLOGY JOURNAL, Issue 12 2007Tania I. Georgieva Abstract Olive pulp (OP) is a highly polluting semi-solid residue generated from the two-stage extraction processing of olives and is a major environmental issue in Southern Europe, where 80% of the world olive oil is produced. At present, OP is either discarded to the environment or combusted with low calorific value. In this work, utilization of OP as a potential substrate for production of bioethanol was studied. Enzymatic hydrolysis and subsequent glucose fermentation by baker's yeast were evaluated for OP from 10% to 30% dry matter (i.e., undiluted). Enzymatic hydrolysis resulted in an increase in glucose concentration by 75%, giving final glucose yields near 70%. Fermentation of undiluted OP hydrolysate (OPH) resulted in the maximum ethanol produced (11.2 g/L) with productivity of 2.1 g/L/h. Ethanol yields were similar for all tested OPH concentrations and were in the range of 0.49-0.51 g/g. Results showed that yeast could effectively ferment OPH even without nutrient addition, revealing the tolerance of yeast to OP toxicity. Because of low xylan (12.4%) and glucan (16%) content in OP, this specific type of OP is not a suitable material for producing only ethanol and thus, bioethanol production should be integrated with production of other value-added products. [source] In situ extraction of polar product of whole cell microbial transformation with polyethylene glycol-induced cloud point systemBIOTECHNOLOGY PROGRESS, Issue 5 2008Zhilong Wang Abstract A novel polyethylene glycol-induced cloud point system (PEG-CPS) was developed for in situ extraction of moderate polar product by setting a microbial transformation of benzaldehyde into L -phenylacetylcarbinol (L -PAC) with Saccharomyces cerevisiae (baker's yeast) as a model reaction. The biocompatibility of the microorganism in PEG-CPS was comparatively studied with a series of water-organic solvent two-phase partitioning systems. The tolerance of microorganism to the toxic substrate benzaldehyde was increased and the moderate polar product L -PAC was extracted into the surfactant-rich phase in the PEG-CPS. The novel PEG-CPS fills the gap of in situ extraction of polar product in microbial transformation left by water-organic solvent two-phase partitioning system. At the same time, the application of PEG-CPS in a microbial transformation also avoids expensive solvent when compared with that of aqueous two-phase system or CPS. [source] Design of the pH Profile for Asymmetric Bioreduction of Ethyl 4-Chloro-3-oxobutyrate on the Basis of a Data-Driven MethodBIOTECHNOLOGY PROGRESS, Issue 6 2002Junghui Chen The goal of this paper was to design the optimal time-varying operating pH profile in the asymmetric reduction of ethyl 4-chloro-3-oxobutyrate by baker's yeast. Ethyl ( S)-4-chloro-3-hydroxybutyrate was produced to reach two important quality indices: reaction yield and product optical purity. The method integrated an orthogonal function approximation and an orthogonal array. The technique used a set of orthonormal functions as the basis for representing the possible profile. The optimal profile could be obtained if the orthogonal coefficients were properly adjusted. The orthogonal array was used to design and analyze the effect of each orthogonal coefficient in order to reach the optimal objective (quality) function. The performance based on the proposed strategy was significantly improved by over 10% compared with the traditional fixed pH or uncontrolled pH values during the reaction. The proposed method can be applied to the required dynamic profile in the bioreactor process to effectively improve the product quality, given good design directions and the advantage of the traditional statistical approach. [source] Glass Transition Temperatures and Fermentative Activity of Heat-Treated Commercial Active Dry YeastsBIOTECHNOLOGY PROGRESS, Issue 2 2000Carolina Schebor Differential scanning calorimetry thermograms of various samples of commercial instant active dry yeasts revealed a clear glass transition typical of amorphous carbohydrates and sugars. The resulting glass transition temperatures were found to decrease with increasing moisture content. The observed glass curve was similar to that of pure trehalose, which is known to accumulate in large amounts in baker's yeast. The effect of heat treatment at various temperatures on the fermentative activity (as measured by the metabolic production of CO2) of dry yeast was studied. First-order plots were obtained representing the loss of fermentative activity as a function of heating time at the various temperatures assayed. Significant losses of fermentative activity were observed in vitrified yeast samples. The dependence of rate constants with temperature was found to follow Arrhenius behavior. The relationship between the loss of fermentative activity and glass transition was not verified, and the glass transition was not reflected on the temperature dependence of fermentative activity loss. [source] Regio- and Stereo-selective Bioreduction of Diketo- n -butylphosphonate by Baker's YeastCHINESE JOURNAL OF CHEMISTRY, Issue 11 2002Ke Wang Abstract A regio- and stereo-selective reduction of diketo-n-butylphosphonates by baker's yeast was reported. The chemical yield and ee value of these reactions are highly dependent on the structure of substrates. The resulting optical active hydroxyalkanephosphonates can be used as chirons for the synthesis of polyfunctional organophosphorus compounds. As useful building block, a series of ,, ,-unsaturated ketones bearing chiral hydroxy group in addition to trifluoromethyl moiety was prepared via the Homer-Wadsworth-Emmons (HWE) reaction of the biotransformation products. [source] Determination of the absolute configuration of bicyclo[3.3.1]nonane-2,7-dione by circular dichroism spectroscopy and chemical correlationCHIRALITY, Issue 10 2001Eugenius Butkus Abstract A study of the enantiomers of bicyclo[3.3.1]nonane-2,7-dione, a chiral molecule containing two carbonyl chromophores, was performed. Enantiomers of this structure were obtained by HPLC resolution and the (+)-(1R,5S)-enantiomer by enantiospecific synthesis from(+)-(1S,5S)-bicyclo[3.3.1]nonane-2,6-dione. The title structure is an interesting molecule to demonstrate the validity of the octant rule. The location of the major chair,chair conformer into octants placing each chromophore into the origin of the octants led to the opposite configuration assignments. In order to prove unequivocally absolute configuration, enantiospecific synthesis of the title compound was carried out. The kinetic resolution of racemic bicyclo[3.3.1]nonane-2,6-dione using baker's yeast afforded (+)-(1S,5S)-2,6-dione. Employing a reaction sequence analogous to one developed earlier by us with racemic substrates led to carbonyl group shift giving enantiomerically pure (+)-(1R,5S)-bicyclo[3.3.1]nonane-2,7-dione. The absolute configuration of the investigated compound was established by combined use of the octant rule and chemical correlation. Chirality 13:694,698, 2001. © 2001 Wiley-Liss, Inc. [source] Yeast species composition differs between artisan bakery and spontaneous laboratory sourdoughsFEMS YEAST RESEARCH, Issue 4 2010Gino Vrancken Abstract Sourdough fermentations are characterized by the combined activity of lactic acid bacteria and yeasts. An investigation of the microbial composition of 21 artisan sourdoughs from 11 different Belgian bakeries yielded 127 yeast isolates. Also, 12 spontaneous 10-day laboratory sourdough fermentations with daily backslopping were performed with rye, wheat, and spelt flour, resulting in the isolation of 217 yeast colonies. The isolates were grouped according to PCR-fingerprints obtained with the primer M13. Representative isolates of each M13 fingerprint group were identified using the D1/D2 region of the large subunit rRNA gene, internal transcribed spacer sequences, and partial actin gene sequences, leading to the detection of six species. The dominant species in the bakery sourdoughs were Saccharomyces cerevisiae and Wickerhamomyces anomalus (formerly Pichia anomala), while the dominant species in the laboratory sourdough fermentations were W. anomalus and Candida glabrata. The presence of S. cerevisiae in the bakery sourdoughs might be due to contamination of the bakery environment with commercial bakers yeast, while the yeasts in the laboratory sourdoughs, which were carried out under aseptic conditions with flour as the only nonsterile component, could only have come from the flour used. [source] Glucose-induced and nitrogen-starvation-induced peroxisome degradation are distinct processes in Hansenula polymorpha that involve both common and unique genesFEMS YEAST RESEARCH, Issue 1 2001Anna Rita Bellu Abstract In the methylotrophic yeast Hansenula polymorpha non-selective autophagy, induced by nitrogen starvation, results in the turnover of cytoplasmic components, including peroxisomes. We show that the uptake of these components occurs by invagination of the vacuolar membrane without their prior sequestration and thus differs from the mechanism described for bakers yeast. A selective mode of autophagy in H. polymorpha, namely glucose-induced peroxisome degradation, involves sequestration of individual peroxisomes tagged for degradation by membrane layers that subsequently fuse with the vacuole where the organelle is digested. H. polymorpha pdd mutants are blocked in selective peroxisome degradation. We observed that pdd1-201 is also impaired in non-selective autophagy, whereas this process still normally functions in pdd2-4. These findings suggest that mechanistically distinct processes as selective and non-selective autophagy involve common but also unique genes. [source] Dynamics of cell wall structure in Saccharomyces cerevisiaeFEMS MICROBIOLOGY REVIEWS, Issue 3 2002Frans M Klis Abstract The cell wall of Saccharomyces cerevisiae is an elastic structure that provides osmotic and physical protection and determines the shape of the cell. The inner layer of the wall is largely responsible for the mechanical strength of the wall and also provides the attachment sites for the proteins that form the outer layer of the wall. Here we find among others the sexual agglutinins and the flocculins. The outer protein layer also limits the permeability of the cell wall, thus shielding the plasma membrane from attack by foreign enzymes and membrane-perturbing compounds. The main features of the molecular organization of the yeast cell wall are now known. Importantly, the molecular composition and organization of the cell wall may vary considerably. For example, the incorporation of many cell wall proteins is temporally and spatially controlled and depends strongly on environmental conditions. Similarly, the formation of specific cell wall protein,polysaccharide complexes is strongly affected by external conditions. This points to a tight regulation of cell wall construction. Indeed, all five mitogen-activated protein kinase pathways in bakers' yeast affect the cell wall, and additional cell wall-related signaling routes have been identified. Finally, some potential targets for new antifungal compounds related to cell wall construction are discussed. [source] The Absolute Configuration of (+)-Ethyl cis -1-Benzyl-3-hydroxypiperidine-4-carboxylate and (+)-4-Ethyl 1-Methyl cis -3-Hydroxypiperidine-1,4-dicarboxylate; a RevisionHELVETICA CHIMICA ACTA, Issue 12 2006Piergiorgio Abstract Discrepancies between chiroptical data from the literature and our determination of the structure of the title compounds (+)- 5 and (+)- 9a were resolved by an unambiguous assignment of their absolute configuration. Accordingly, the dextrorotatory cis -3-hydroxy esters have (3R,4R)- and the laevorotatory enantiomers (3S,4S)-configuration. The final evidences were demonstrated on both enantiomers (+)- and (,)- 5 by biological reduction of 4 by bakers' yeast and stereoselective [RuII(binap)]-catalyzed hydrogenations of 4 (Scheme,2), by the application of the NMR Mosher method on (+)- and (,)- 5 (Scheme,3), as well as by the transformation of (+)- 5 into a common derivative and chiroptical correlation (Scheme,4). [source] | |||||||||||||||||||||||||