Permeabilization of yeast for in situ determination of alpha-glucosidase

Valorization of winery waste vs. the costs of not recycling

Wine production generates huge amounts of waste. Before the 1990s, the most economical option for waste removal was the payment of a disposal fee usually being of around 3000 Euros. However, in recent years the disposal fee and fines for unauthorized discharges have increased considerably, often reaching 30,000-40,000 Euros, and a prison sentence is sometimes also imposed. Some environmental friendly technologies have been proposed for the valorization of winery waste products. Fermentation of grape marc, trimming vine shoot or vinification lees has been reported to produce lactic acid, biosurfactants, xylitol, ethanol and other compounds. Furthermore, grape marc and seeds are rich in phenolic compounds, which have antioxidants properties, and vinasse contains tartaric acid that can be extracted and commercialized. Companies must therefore invest in new technologies to decrease the impact of agro-industrial residues on the environment and to establish new processes that will provide additional sources of income.

Optimization of accessible catalase activity in polyacrylamide gel-immobilized Saccharomyces cerevisiae

The permeabilization of Saccharomyces cerevisiae (baker's yeast), either before or after immobilization in polyacrylamide gel (PAG), has been examined as a means to increase the catalase activity of PAG-immobilized yeast cells. Prior permeabilization of the cells resulted in large losses of catalase activity during immobilization, but permeabilization after immobilization produced increases in the catalase activity of yeast/PAG particles. A dependence of the accessible catalase activity on the concentration of polyacrylamide in permeabilized yeast/PAG particles, and on the method of permeabilization of the immobilized cells, was observed. Optimal levels of stable catalase activity (1000-2000 IU/g PAG particles; ca. 5%-10% of total available activity) were obtained by immobilizing yeast cells (0.5 g wet cells/mL gel) in 10% (w/v) PAG, followed by permeabilization of the entrapped cells with either cetyltrimethylammonium bromide, Triton X-100 and one freeze-thaw, or five freeze-thaw cycles.

Permeabilization of baker's yeast with N-lauroyl sarcosine

N-Lauroyl sarcosine (LS), a cationic, non-toxic and biodegradable detergent readily permeabilized whole cells of baker's yeast (Saccharomyces cerevisiae). Permeabilization was carried out to increase assayable cellular catalase activity, an enzyme of great physiological and industrial importance, and to release 5'-nucleotides which find food/nutritional applications. The event of permeabilization was concentration, time and temperature dependent. Maximum permeabilization of yeast cells were observed when 1 g wet weight (0.2 g dry wt) of cells were permeabilized with 1.0 ml of 2% LS at 45 degrees C for 15 min. LS-permeabilized cells showed 350-fold increase in catalase activity and the supernatant obtained after permeabilization was rich in 5'-nucleotides. LS-permeabilized baker's yeast cells can be used as a source of biocatalyst and to isolate valuable by-products.

Cloning and overexpression of a maltase gene from Schizosaccharomyces pombe in Escherichia coli and characterization of the recombinant maltase

The Schizosaccharomyces pombe maltase structural gene (SPMAL1(+)) was amplified from genomic DNA of S. pombe by PCR. An open reading frame of 1740bp, encoding a putative 579 amino-acid protein with a calculated molecular mass of 67.7kDa was characterized in the genomic DNA insert of plasmid pQE30. The specific maltase activity in the induced transformants was 21 times higher than that in wild-type. However, the estimated molecular mass of the purified recombinant maltase was 44.3kDa by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The optimal temperature and pH of the purified recombinant maltase were 40 degrees C and 6, respectively. The recombinant maltase was weakly activated by Mg(2+), Ca(2+), Na(+), and Ba(2+), but was strongly inhibited by Hg(2+), Ag(+) and Cu(2+), EDTA, and PMSF. The purified maltase could actively hydrolyse rho-nitrophenyl glucoside (PNPG), maltose, dextrin, and soluble starch. The results demonstrate that maltase from S. pombe was different from that from other yeasts, and might be usefully exploited in the future by the biotechnology industry or lead to the development of new molecular genetic tools.

A study of the influence of yeast cell debris on protein and α-glucosidase adsorption at various zones within the expanded bed usingIn-Bed sampling

Expanded bed adsorption chromatography is used to capture products directly from unclarified feedstocks, thus combining solid-liquid separation, product concentration and preliminary purification into a single step. However, when non-specific ion-exchangers are used as the adsorbent in the expanded bed, there is the possibility that electrostatic interactions of cells or cell debris with the adsorbent may interfere with the adsorption of soluble products. These interactions depend on the particle size of the cell debris and its surface charge, which in turn depend on the extent of disruption used to release the intracellular products. The interactions occurring during expanded bed adsorption between the anionic ion-exchanger STREAMLINE DEAE and particulate yeast homogenates obtained by high pressure homogenisation at different intensities of disruption achieved by operating at different pressures were studied, while maintaining all other parameters constant. In-bed sampling from the expanded bed using ports fitted up the height of expanded bed was used to study the retention of yeast cells and cell debris within the bed and its influence on the adsorption of total soluble protein and alpha-glucosidase within various zones of the expanded bed. The retention of the biomass present in the homogenate obtained at a lower intensity of disruption was found to be high at the lower end of the column (17% from 13.8 MPa sample compared to 1% from 41.4 MPa sample). This interaction of the particulate material with the adsorbent was found to reduce the dynamic binding capacity of the adsorbent for total soluble protein from 3.6 mg/mL adsorbent for 41.4 MPa sample to 3.0 mg/mL adsorbent for 13.8 MPa sample. The adsorption of alpha-glucosidase was found to increase with an increase in the concentration of the enzyme in the feed, which increased with the intensity of disruption. Selective adsorption of 6,732 U alpha-glucosidase per mg of total protein bound, was noticed for the feedstock prepared at a higher disruption intensity at 41.4 MPa compared to adsorption of 1,262 U/mg of total protein bound for that prepared at 13.8 MPa. The selective adsorption of alpha-glucosidase due to its high concentration together with simultaneous high specific activity of the enzyme in the feed indicated the significance of selective release of enzymes during microbial cell disruption for efficient expanded bed adsorption processes.

Disruption of Brewers' yeast by hydrodynamic cavitation: Process variables and their influence on selective release

Intracellular products, not secreted from the microbial cell, are released by breaking the cell envelope consisting of cytoplasmic membrane and an outer cell wall. Hydrodynamic cavitation has been reported to cause microbial cell disruption. By manipulating the operating variables involved, a wide range of intensity of cavitation can be achieved resulting in a varying extent of disruption. The effect of the process variables including cavitation number, initial cell concentration of the suspension and the number of passes across the cavitation zone on the release of enzymes from various locations of the Brewers' yeast was studied. The release profile of the enzymes studied include alpha-glucosidase (periplasmic), invertase (cell wall bound), alcohol dehydrogenase (ADH; cytoplasmic) and glucose-6-phosphate dehydrogenase (G6PDH; cytoplasmic). An optimum cavitation number Cv of 0.13 for maximum disruption was observed across the range Cv 0.09-0.99. The optimum cell concentration was found to be 0.5% (w/v, wet wt) when varying over the range 0.1%-5%. The sustained effect of cavitation on the yeast cell wall when re-circulating the suspension across the cavitation zone was found to release the cell wall bound enzyme invertase (86%) to a greater extent than the enzymes from other locations of the cell (e.g. periplasmic alpha-glucosidase at 17%). Localised damage to the cell wall could be observed using transmission electron microscopy (TEM) of cells subjected to less intense cavitation conditions. Absence of the release of cytoplasmic enzymes to a significant extent, absence of micronisation as observed by TEM and presence of a lower number of proteins bands in the culture supernatant on SDS-PAGE analysis following hydrodynamic cavitation compared to disruption by high-pressure homogenisation confirmed the selective release offered by hydrodynamic cavitation.

Studies on inositol-mediated expression of MAL gene encoding maltase and phospholipid biosynthesis in Schizosaccharomyces pombe

In this study, the effects of inositol addition on expression of the MAL gene encoding maltase and phosphatidylinositol (PI) biosynthesis in Schizosaccharomyces pombe (a naturally inositol-requiring strain) were examined. We found that specific maltase activity was at its maximum when the concentration of added inositol reached 6 microg ml(-1) in a synthetic medium containing 2.0% (w/v) glucose. When the concentration of added inositol was 1 microg ml(-1) in the medium, repression of MAL gene expression occurred at glucose concentration higher than 0.2% (w/v). However, when S. pombe was cultured in the synthetic medium containing 6 microg ml(-1), repression of maltase gene expression occurred only at initial glucose concentration above 1.0% (w/v). More mRNA encoding maltase was detected in the cells grown in the medium with 6 microg ml(-1) inositol than in those grown in the same medium with 1 microg ml(-1) inositol. These results demonstrate that higher inositol concentrations in the synthetic medium could derepress MAL gene expression in S. pombe. PI content of the yeast cells grown in the synthetic medium with 6 microg ml(-1) of inositol was higher than that of the yeast cells grown in the same medium with 1 microg ml(-1) of inositol. This means that PI may be involved in the derepression of MAL gene expression in S. pombe.

In situ study of K+ transport into the vacuole of Saccharomyces cerevisiae

Permeable spheroplasts were prepared from two strains of Saccharomyces cerevisiae by incubating with zymolyase without a permeabilizing agent. The loss of the plasma membrane barrier was confirmed by the nucleotide release, the activity of glucose 6-phosphate dehydrogenase with external substrates and by the effects on respiration of mitochondrial substrates and ADP. Mitochondrial integrity was maintained, as shown by respiration with lactate, pyruvate, glucose and ethanol, and its acceleration by ADP showed a coupled respiration. Potassium uptake into the vacuole was measured with a selective electrode and found to be taken up effectively by spheroplasts only in the presence of Mg-ATP; it was reverted by CCCP and PCP and inhibited by bafilomycin A1, but not by sodium vanadate or sodium azide. Potassium ions did not alter DeltaPsi of the vacuole, followed with oxonol V, but caused vacuolar alkalinization, as followed with pyranine. The increase of vacuolar pH was non-selective and observed at 50-200 mM of several monovalent cations. Isolated vacuoles with pyranine inside showed similar changes of the internal pH in the presence of KCl. Results indicate that some strains do not require a permeabilizing agent to directly access the vacuole in spheroplasts prepared with zymolyase. The hypothesis about the existence of a K+/H+ antiporter in the vacuolar membrane of S. cerevisiae is discussed.

Evaluation of vinification lees as a general medium for lactobacillus strains

Lactobacillus species present high nutritional requirements, so it is necessary to find new low-cost nutrient components for fermentation media. This work compares the utilization of vinification lees (an important residue of wineries) from red and white winemaking technology, distilled or not. An amount of 20 g of lees/L was used as the unique nutrient to obtain lactic acid from glucose using Lactobacillus strains with different properties: L. plantarum CECT-221, L. pentosus CECT-4023, L. casei CECT-5275, and L. coryniformis subsp. torquens CECT-25600. Only L. casei using distilled lees showed values (Pmax = 92.1 g/L and Y(P/S) = 1.05 g/g) similar to those obtained with the MRS broth. The UV spectra of white and red lees, distilled or not, allowed an interpretation of the different phenolic compounds present and their influence on the fermentation. Their detoxification by extraction with organic compounds and fermentation with L. pentosus was also considered. Time courses of glucose and lactic acid were modeled according to reported models to obtain more information about the process.

Inactivation of maltose permease and maltase in sporulating Saccharomyces cerevisiae

Maltose transport and maltase activities were inactivated during sporulation of a MAL constitutive yeast strain harboring different MAL loci. Both activities were reduced to almost zero after 5 h of incubation in sporulation medium. The inactivation of maltase and maltose permease seems to be related to optimal sporulation conditions such as a suitable supply of oxygen and cell concentration in the sporulating cultures, and occurs in the fully derepressed conditions of incubation in the sporulation acetate medium. The inactivation of maltase and maltose permease under sporulation conditions in MAL constitutive strains suggests an alternative mechanism for the regulation of the MAL gene expression during the sporulation process.

5-Cyanovaleramide production using immobilized Pseudomonas chlororaphis B23

A biocatalytic process for the hydration of adiponitrile to 5-cyanovaleramide has been developed which can be run to higher conversion, produces more product per weight of catalyst, and generates significantly less waste products than alternate chemical processes. The biocatalyst consists of Pseudomonas chlororaphis B23 microbial cells immobilized in calcium alginate beads. The cells contain a nitrile hydratase (EC 4.2.1.84) which catalyzes the hydration of adiponitrile to 5-cyanovaleramide with high regioselectivity, and with less than 5% selectivity to byproduct adipamide. Fifty-eight consecutive batch reactions with biocatalyst recycle were run to convert a total of 12.7 metric tons of adiponitrile to 5-cyanovaleramide. At 97% adiponitrile conversion, the yield of 5-cyanovaleramide was 13.6 metric tons (93% yield, 96% selectivity), and the total weight of 5-cyanovaleramide produced per weight of catalyst was 3150 kg/kg (dry cell weight).

Trehalose accumulation in mutants of Saccharomyces cerevisiae deleted in the UDPG-dependent trehalose synthase-phosphatase complex

In Saccharomyces cerevisiae, trehalose-6-phosphate synthase converts uridine-5'-diphosphoglucose and glucose 6-phosphate to trehalose 6-phosphate which is dephosphorylated by trehalose 6-phosphatase to trehalose. These two steps take place within a complex consisting of three proteins: trehalose-6-phosphate synthase encoded by the GGS1/TPS1 (= FDP1, = BYP1, = CIF1) gene, trehalose 6-phosphatase encoded by the TPS2 gene and by a third protein encoded by both the TSL1 and TPS3 genes. Using three different methods for trehalose determination, we observed trehalose accumulation in ggs1/tps1delta, tps2delta and tsl1delta mutants, and in the double mutants ggs1/tps1delta/tps2delta and also in ggs1/tps1delta deleted mutants suppressed for growth on glucose. All these mutants harbor MAL genes. Trehalose synthesis in these mutants is probably performed by the adenosine-5'-diphosphoglucose-dependent trehalose synthase, (ADPG-dependent trehalose synthase) which was detected in all strains tested. It is noteworthy that trehalose accumulation in these mutants was detected only in cells grown on weakly repressive carbon sources such as maltose and galactose or during the transition phase from fermentable to non-fermentable growth on glucose. alpha-Glucosidase activity was always present in high amounts. We also describe an adenosine-diphosphoglucosepyrophosphorylase (ADPG-pyrophosphorylase) activity in Saccharomyces cerevisiae which increased concomitantly with the accumulation of trehalose during the transition phase from fermentable to non-fermentable growth in MAL-constitutive (MAL2-8c) strains. The same was observed when MAL-induced (MAL1) strains were compared during growth on glucose and maltose. These results led us to conclude that maltose-induced trehalose accumulation is independent of the UDPG-dependent trehalose-6-phosphate synthase/phosphatase complex; that the ADPG-dependent trehalose synthase is responsible for maltose-induced trehalose accumulation probably by forming a complex with a specific trehalose-6-phosphatase activity and that ADPG synthesis is activated during trehalose accumulation under these conditions.

Identification of an ADPG-dependent trehalose synthase in Saccharomyces

Uridine diphosphoglucose is not the sole donor for trehalose synthesis in yeast cells: an ADPG-dependent trehalose synthase, has been identified in mutant strains with undetectable UDPG-dependent trehalose-6-P synthase activity. Genetic and chromatographic studies indicate that the two activities correspond to different proteins. The apparent Km for the nucleotide is similar for both enzymes, and Mg2+ is also required for both activities; however, a striking difference was observed with respect to ATP.Mg activation. This newly determined enzymatic activity in Saccharomyces clarifies previous contradictory results with mutant strains that are able to accumulate trehalose during growth yet whose UDPG-dependent trehalose synthase activity is undetectable in vitro.

Trehalose and maltose metabolism in yeast transformed by a MAL4 regulatory gene cloned from a constitutive donor strain

A 6.8 kb fragment of DNA containing the regulatory sequence MAL4p has been cloned from a genomic library prepared from Saccharomyces cerevisiae strain 1403-7A which ferments maltose constitutively. The library was prepared by ligation of 5-20 kb Sau3AI restriction fragments of total yeast DNA into the BamH1 restriction site of shuttle vector YEp13. A restriction map of the cloned fragment indicates that it encompasses a 2.6 kb segment which closely resembles the regulatory MAL6 gene previously identified (Needleman et al. 1984). The hybrid plasmid, p(MAL4p)4, could transform maltose-nonfermenting strains which contain cryptic alpha-glucosidase and maltose permease genes (malp MALg), but could not transform strains containing a functional regulatory sequence and a defective maltase-permease region (MAlp malg). A correlated absence of maltase and permease DNA from the cloned fragment was indicated by the restriction map. Although the cloned DNA fragment was derived from a constitutive strain, maltose fermentation and alpha-glucosidase formation by yeast transformed with p(MAL4p)4 was largely inducible by maltose and sensitive to catabolite repression. Moreover, the active trehalose accumulation pattern (TAC(+) phenotype) linked to the complete MAL4 locus in strain 1403-7A and other constitutive MAL strains (Oliveira et al. 1981b) was not found in p(MAL4p)4 transformants. It may be concluded that constitutivity of maltose fermentation and the associated active trehalose accumulation are not merely consequences of a cis-dominant mutation causing constitutive formation of the MALp regulatory product. Moreover, constitutivity may not be caused solely by a mutation within the structural region of the MALp gene.

Further evidence for the alternative pathway of trehalose synthesis linked to maltose utilization in Saccharomyces

Yeast strains bearing a deficiency in trehalose-6-phosphate synthase activity are unable to accumulate trehalose on any carbon source unless they contain one of the MAL genes. If the gene is inducible then synthesis of trehalose occurs specifically during growth on maltose: when the MAL gene is constitutive then trehalose accumulation can also be seen when cells are grown on glucose. Different systems for trehalose synthesis were suggested: one of them would require the UDPG-linked trehalose synthase whereas the second would utilize an alternative pathway. We proposed a mechanism by which the gene-product of a MAL gene would serve as a common positive regulator for the expression of the genes coding for maltose permease, alpha-glucosidase and some component of the trehalose accumulation system. In order to elucidate this novel pathway a strain lacking UDPG-linked trehalose synthase activity and harboring a defect in maltose uptake was constructed. Excessive maltose uptake resulted in accumulation of intracellular maltose, and twice as much trehalose as in a control strain. Partial inhibition of hexokinase by xylose affected the ratio between internal maltose and trehalose and significantly reduced glycogen synthesis. Sodium fluoride also blocked glycogen synthesis but allowed for trehalose accumulation. Moreover, a mutant which lacks hexokinase I and II was unable to accumulate trehalose when grown on glucose in spite of the presence of a constitutive MAL2 gene. These results suggest that trehalose synthesis would require G-6-P formation derived from maltose. Such a deviation would allow for slowing down the glycolytic flux which, in turn, would favour efficient maltose utilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Deoxyribonucleotide biosynthesis in yeast: assay and properties of ribonucleotide reductase in permeabilized Saccharomyces cerevisiae cells

Yeast cells permeabilized by freeze-thaw cycles in a sorbitol-containing medium provide an experimentally favorable system for the study of ribonucleotide reduction in a small number of cells or in mutant strains. Ribonucleotide reductase activities determined in such cells are about twice those found in cell extracts but properties of the enzyme, except pH optimum, are closely comparable in both assay procedures. In contrast with other organisms, the activities measured in permeabilized cells from both diploid or haploid strains exceed the demand for deoxyribonucleotide formation during replication of the yeast genome. The method has been applied to yeast cultures growing in the presence of the ribonucleotide reductase inhibitor hydroxyurea and a twofold increase of enzyme activity has been established in such cells. On the other hand, analysis of a series of hus mutants, selected for hydroxyurea sensitivity in the laboratory of Singer and Johnston did not reveal obvious alterations of the enzyme vs the parental strains, suggesting that the hus phenotype may be due to lesions other than in ribonucleotide reductase.