Showing papers on "Arabitol published in 2003"

Glycerol dehydrogenase, encoded by gldB is essential for osmotolerance in Aspergillus nidulans.

Abstract: Summary We have characterized the Aspergillus nidulans gldB gene encoding a NADP + -dependent glycerol dehydro- genase. A basal expression level was observed for gldB , which increased significantly under conditions of hyper-osmotic shock (1 M NaCl). Growth of strains in which gldB was disrupted was severely reduced on plates containing 1% glucose and 1 M NaCl, but these strains were able to grow on plates containing 1 M NaCl and 1% glycerol, arabitol, mannitol or erythritol. Uptake of these polyols compensated for the inability of the gldB disruptants to produce glycerol. Presence of 1% glucose in these plates prevented growth res- toration by all the polyols tested with the exemption of glycerol, indicating that uptake of mannitol, arabitol and erythritol is subject to glucose repression, whereas uptake of glycerol is significantly less or not repressed. No intracellular glycerol dehydrogenase activity could be detected in the gldB disruption strains. Intracellular glycerol levels in these strains were strongly decreased compared to wild type, whereas intracellular mannitol, erythritol and arabitol levels were increased. Conidia of the gldB disruption strain did not accumulate glycerol upon germination in glucose media with or without 1 M NaCl and germ tube emergence was significantly delayed in this strain in the presence of 1 M NaCl in comparison to the wild type. These data indicate that gldB is essen- tial for osmotolerance in A. nidulans and that the pathways for glycerol biosynthesis under osmotic stress differ between yeast and filamentous fungi.

Carbon material and bioenergetic balances of xylitol production from corncobs by Debaryomyces hansenii.

Abstract: The effect of oxygenation on xylitol production by the yeast Debaryomyces hansenii has been investigated in this work using the liquors from corncob hydrolysis as the fermentation medium. The concentrations of consumed substrates (glucose, xylose, arabinose, acetate and oxygen) and formed products (xylitol, arabitol, ethanol, biomass and carbon dioxide) have been used, together with those previously obtained varying the hydrolysis technique, the level of adaptation of the microorganism, the sterilization procedure and the initial substrate and biomass concentrations, in carbon material balances to evaluate the percentages of xylose consumed by the yeast for the reduction to xylitol, alcohol fermentation, respiration and cell growth. The highest xylitol concentration (71 g/L) and volumetric productivity (1.5 g/L.h) were obtained semiaerobically using detoxified hydrolyzate produced by autohydrolysis-posthydrolysis, at starting levels of xylose (S(0)) and biomass (X(0)) of about 100 g/L and 12 g(DM)/L, respectively. No less than 80% xylose was addressed to xylitol production under these conditions. The experimental data collected in this work at variable oxygen levels allowed estimating a P/O ratio of 1.16 mol(ATP)/mol(O). The overall ATP requirements for biomass production and maintenance demonstrated to remarkably increase with X(0) and for S(0) >or= 130 g/L and to reach minimum values (1.9-2.1 mol(ATP)/C-mol(DM)) just under semiaerobic conditions favoring xylitol accumulation.

Water availability affects the growth, accumulation of compatible solutes and the viability of the biocontrol agent Epicoccum nigrum.

Abstract: Growth of the biocontrol fungus Epicoccum nigrum was more sensitive to ionic solute water stress (NaCl) than non-ionic (glycerol) on potato dextrose-based media at −0.5, −3.0 and −5.5 MPa water potentials. Subsequent physiological manipulation of growth of E. nigrum in glycerol-modified media to −3.0 MPa water potential resulted in a significant increase in the accumulation of compatible solutes in both mycelial liquid cultures and spores, but no enhanced accumulation of the desiccation protectant trehalose, when compared to unmodified media (−0.5MPa). The main solute accumulated was glycerol, followed by arabitol. In temporal studies over 20 days maximum accumulation of glycerol occurred in 5-d old cultures with water stressed cultures having 250× greater amounts than those from unmodified medium. The arabitol content was also higher in mycelium and spores produced under water stress. The difference was maximum after 15 days growth. Glucose content decreased over time in mycelial colonies but increased in spores. The germination of conidia from the two treatments was similar, regardless of compatible solute content, even at −9.25 MPa water potential stress. However, germ tube extension was significantly increased at this water potential level. The production of E. nigrum spores at −3.0 MPa water potential resulted in improved survival when stored fresh at 4 and 25 °C. However, freeze-drying severely affected the viability of spores produced on both media (−0.5 or 3.0 MPa). Accumulation of compatible solutes may assist the fungus in better ecological competence and establishment in the phyllosphere, where water availability is often limited.

Biochemical and genetic characterization of a novel enzyme of pentitol metabolism: D-arabitol-phosphate dehydrogenase.

Abstract: An enzyme with a specificity that has not been described previously, D-arabitol-phosphate dehydrogenase (APDH), has been purified from cell lysate of Enterococcus avium. SDS/PAGE indicated that the enzyme had a molecular mass of 41+/-2 kDa, whereas a molecular mass of 160+/-5 kDa was observed under non-denaturing conditions, implying that the APDH may exist as a tetramer with identical subunits. Purified APDH was found to have a narrow substrate specificity, converting only D-arabitol 1-phosphate and D-arabitol 5-phosphate into xylulose 5-phosphate and ribulose 5-phosphate, respectively, in the oxidative reaction. Both NAD(+) and NADP(+) were accepted as cofactors. Based on the partial protein sequences, the APDH gene was cloned. Homology comparisons place APDH within the medium-range dehydrogenase family. Unlike most members of this family, APDH requires Mn(2+) but no Zn(2+) for enzymic activity. The DNA sequence surrounding the gene suggests that it belongs to an operon that also contains several components of phosphotransferase system. Both biochemical evidence and protein sequence homology comparisons indicate that similar enzymes are widespread among the Gram-positive bacteria. Their apparent biological role is to participate in arabitol catabolism via the 'arabitol phosphate route', similar to the ribitol and xylitol catabolic routes described previously.

Efficient desymmetrization of "pseudo"-C2-symmetric substrates: illustration in the synthesis of a disubstituted butenolide from arabitol.

Abstract: A short synthesis of the homochiral disubstituted butenolide 1 is described in four steps from arabitol. The key steps are the selective kinetic protection of arabitol and the cyclization of 11 to form the butenolide ring. This last transformation represents a rare example of a fully stereoselective cyclitive desymmetrization process of a “pseudo”-C2-symmetric substrate.

Short synthesis of enantiopure C2-symmetric 1,2:4,5-diepoxypentane and "pseudo"-C2-symmetric 3-azido-1,2:4,5-diepoxypentane from arabitol.

Abstract: On the basis of our previously described selective protection of arabitol as its 1,2:4,5-bis-pentylidene acetal 5, we report a straightforward synthesis of the novel “pseudo”-C2-symmetric 3-azido-1,2:4,5-diepoxypentane building block 4 in 6 steps from arabitol. Using a similar synthetic route, an improved synthesis of the C2-symmetrical 1,2:4,5-bis-epoxypentane building block 1 is described, also in 6 steps from arabitol. Both enantiomers of 1 and 4 are accessible, and all reactions involved are easily amenable for large-scale synthesis.

Requirements for vegetative growth of Tricholoma lobayensis (Heim), a Nigerian edible fungus

Abstract: The requirements for the vegetative growth of Tricholoma lobayensis (Heim), a Nigerian edible mushroom, were examined. Twenty carbon sources were tested and growth was best supported by mannitol, followed by fructose, glucose and dextrin (P <0.05), while sucrose, cellobiose and arabitol were the least stimulatory compounds. Among the twenty-one nitrogen sources tested, asparagine was the most utilizable. Tryptophan, methionine and ammonium nitrate also stimulated good growth rates, while the slowest growth was observed with sodium nitrate. The carbon/nitrogen ratios also affected growth and a ratio of 4:3 was the most stimulatory, while a ratio of 1:1 was the poorest. Mineral elements (K, Mg, Fe and Zn) significantly promoted the growth of this fungus, while the inclusion of Na and Cu noticeably reduced growth rate.

Mechanism of overproduction of secreted enzymes in the mycelial fungus Penicillium canescens

Abstract: The fungus Penicillium canescens strain F178 (VKPM) and its niaD- mutant exhibited an increased capability of synthesizing extracellular enzymes beta-galactosidase (70-80 U/ml) and xylanase (100 U/ml). The synthesis was induced by arabinose and its catabolite, arabitol. A deficiency in arabitol dehydrogenase, leading to arabitol accumulation in the cell, was detected in the chain of reactions of arabinose catabolism. The increased synthesis of beta-galactosidase and xylanase in P. canescens is accounted for by (1) cellular accumulation of the inducer (arabitol) at low concentrations of arabinose in the medium and (2) prevalence of induction over repression.

Mpg added to fermentation

Abstract: A method for fermenting a microorganism, producing a polypeptide of interest, in a culture medium of at least 50 litres, comprising:adding one or more compounds selected from the group consisting of monopropylene glycol, ethylene glycol, trehalose, xylitol, arabitol, dulcitol, mannitol, erythritol, cellobiose and sorbitol, to the culture medium before and/or during fermentation, wherein the compound is low metabolizable.

Induction of the Synthesis of Endo-1,4-β-xylanase and β-Galactosidase in Original and Recombinant Strains of the Fungus Penicillium canescens

Abstract: The induction of synthesis of the secreted enzymes endo-1,4-β-xylanase (EC 3.2.1.8) and β-galactosidase (EC 3.2.1.23) in original and recombinant Penicillium canescens strains has been studied. In all producer strains, the synthesis of these enzymes was induced by arabinose and its metabolite arabitol. The two enzymes differed in the concentration of arabinose required for induction: the synthesis of β-galactosidase was most pronounced at 1 mM, whereas maximum synthesis of endo-1,4-β-xylanase was observed at 5–10 mM. An increase in the number of endo-1,4-β-xylanase copies in the high-copy-number strain of the fungus suppressed the synthesis of β-galactosidase; the synthesis of endo-1,4-β-xylanase in the high-copy-number recombinant producing β-galactosidase was affected to a lesser extent. The amount of enzymes synthesized did not depend on the saccharide used as the sole source of carbon for growing the mycelium prior to its transfer to the inducer-containing medium.

[Induction of endo-1,4-beta-xylanase and beta-galactosidase in the original and recombinant strains of the fungus Penicillium canescens].

Abstract: The induction of the synthesis of secreted enzymes endo-1,4-beta-xylanase (EC 3.2.1.8) and beta-galactosidase (EC 3.2.1.23) in the original and recombinant Penicillium canescens strains has been studied. In all producer strains, the synthesis of these enzymes was induced by arabinose and its metabolite arabitol. The two enzymes differed in the concentration of arabinose required for the induction: the synthesis of beta-galactosidase was most pronounced at 1 mM, whereas maximum synthesis of endo-1,4-beta-xylanase was observed at 5 to 10 mM. An increase in the number of endo-1,4-beta-xylanase copies in the high-copy-number strain of the fungus suppressed the synthesis of beta-galactosidase; the synthesis of endo-1,4-beta-xylanase in the high-copy-number recombinant producing beta-galactosidase was affected to a lesser extent. The amount of the enzymes synthesized did not depend on the saccharide used as a sole source of carbon for growing the mycelium prior to its transfer to the inducer-containing medium.

1‐O‐p‐Toluene­sulfonyl‐2,3:4,5‐di‐O‐iso­propyl­idene‐l‐arabitol

Abstract: In the title compound, C18H26SO7, the absolute configuration was confirmed as S at all three chiral centres. Molecules are linked by three C—H⋯O contacts.

Monopropylene glycol added to fermentation

Abstract: A method for fermenting a microorganism, producing a polypeptide of interest, in a culture medium of at least 50 litres, comprising:adding one or more compounds selected from the group consisting of monopropylene glycol, ethylene glycol, trehalose, xylitol, arabitol, dulcitol, mannitol, erythritol, cellobiose and sorbitol, to the culture medium before and/or during fermentation, wherein the compound is low metabolizable.