PubMed Health⌕ Search

Biomedical subjects

C Augur

Publications and source records attributed to C Augur.

9 recordsLinked to original sources
PubMed2004

Effect of the nitrogen source on caffeine degradation by Aspergillus tamarii.

AIMS: To evaluate caffeine degradation and nitrogen requirements during Aspergillus tamarii growth in submerged culture. METHODS AND RESULTS: Aspergillus tamarii spores produced on a coffee infusion agar medium added with sucrose were used. Several caffeine and ammonium sulphate concentrations (0-1 and 0-1.36 g l-1, respectively) were tested simultaneously on fungal biomass production and caffeine degradation. An additional caffeine pulse (4 g l-1) was added for all experiments after 48 h of fermentation. Results revealed that when using 0.90 g l-1 of caffeine and 0.14 g l-1 of ammonium sulphate, biomass production and caffeine degradation were enhanced. Highest biomass production (Xmax = 9.87 g l-1) with a specific growth rate (micro) of 0.073 h-1 and caffeine degradation rate of 0.033 g l-1 h-1, was observed under these conditions. CONCLUSIONS: Caffeine degradation as well as biomass production were characterized. SIGNIFICANCE AND IMPACT OF THE STUDY: These studies set the stage for future characterization studies of intracellular enzymes involved in caffeine degradation. Moreover, results observed may help in the biotreatment of residues from the coffee agroindustry.

Ammonium Sulfate↗
PubMed2001

Exopectinases produced by Aspergillus niger in solid-state and submerged fermentation: a comparative study.

Exopectinase production by Aspergillus niger was compared in submerged fermentation (SmF) and solid-state fermentation (SSF). SSF was carried out using polyurethane foam (PUF) as the solid support. The purpose was to study the effect of sucrose addition (0 or 40 g/l) and water activity level (A(w)=0.99 or 0.96) on the level of enzyme activity induced by 15 g/l of pectin. Mycelial growth, as well as extracellular protease production, was also monitored. Sucrose addition in SmF resulted in catabolite repression of exopectinase activity. However, in SSF, an enhancement of enzyme activity was observed. Protease levels were minimal in SSF experiments with sucrose and maximal in SmF without sucrose. Exopectinase yields (IU/g X) were negligible in SmF with sucrose. The high levels of exopectinase with sucrose and high A(w) in SSF can be explained by a much higher level of biomass production without catabolite repression and with lower protease contamination.

Aspergillus niger↗
PubMed2001

Production of tannase by Aspergillus niger Aa-20 in submerged and solid-state fermentation: influence of glucose and tannic acid.

Tannase production by Aspergillus niger Aa-20 was studied in submerged (SmF) and solid-state (SSF) fermentation systems with different tannic acid and glucose concentrations. Tannase activity and productivity were at least 2.5 times higher in SSF than in SmF. Addition of high tannic acid concentrations increased total tannase activity in SSF, while in SmF it was decreased. In SmF, total tannase activity increased from 0.57 to 1.03 IU/mL, when the initial glucose concentration increased from 6.25 to 25 g/L, but a strong catabolite repression of tannase synthesis was observed in SmF when an initial glucose concentration of 50 g/L was used. In SSF, maximal values of total tannase activity decreased from 7.79 to 2.51 IU when the initial glucose concentration was increased from 6.25 to 200 g/L. Kinetic results on tannase production indicate that low tannase activity titers in SmF could be associated to an enzyme degradation process which is not present in SSF. Tannase titers produced by A. niger Aa-20 are fermentation system-dependent, favoring SSF over SmF.

Aspergillus niger↗
PubMed1999

Cometabolic biodegradation of methyl t-butyl ether by Pseudomonas aeruginosa grown on pentane.

A bacterial strain identified as Pseudomonas aeruginosa was isolated from a soil consortium able to mineralize pentane. P. aeruginosa could metabolize methyl t-butyl ether (MTBE) in the presence of pentane as the sole carbon and energy source. The carbon balance for this strain, grown on pentane, was established in order to determine the fate of pentane and the growth yield (0.9 g biomass/g pentane). An inhibition model for P. aeruginosa grown on pentane was proposed. Pentane had an inhibitory effect on growth of P. aeruginosa, even at a concentration as low as 85 micrograms/l. This resulted in the calculation of the following kinetic parameters (mumax = 0.19 h-1, Ks = 2.9 micrograms/l, Ki = 3.5 mg/l). Finally a simple model of MTBE degradation was derived in order to predict the quantity of MTBE able to be degraded in batch culture in the presence of pentane. This model depends only on two parameters: the concentrations of pentane and MTBE.

Biodegradation, Environmental↗
PubMed1995

Molecular cloning and pattern of expression of an alpha-L-fucosidase gene from pea seedlings.

alpha-L-Fucosidase is a cell wall protein purified from pea (Pisum sativum) epicotyls. The alpha-L-fucosidase hydrolyzes terminal fucosyl residues from oligosaccharides of plant cell wall xyloglucan. alpha-L-Fucosidase may be an important factor in plant growth regulation, as it inactivates fucose-containing xyloglucan oligosaccharides that inhibit growth of pea stem segments. The amino acid sequences of the NH2-terminal region and one internal peptide were used to design redundant oligonucleotides that were utilized as primers in a polymerase chain reaction (PCR) with cDNA, generated from pea mRNA, as the template. A specific PCR amplification product containing 357 base pairs was isolated, cloned, and sequenced. The deduced amino acid sequence included the two peptides used to design the primers for PCR plus two other peptides obtained by proteinase digestion of alpha-L-fucosidase. No sequence homology to other alpha-L-fucosidases was apparent, although the NH2-terminal region is strongly homologous to Kunitz-type trypsin inhibitors. cDNA and genomic copies were isolated and sequenced. In pea, the gene is present in two or three copies. Its mRNA is present in roots, leaves, and elongating shoots. The spatial pattern of expression of the alpha-L-fucosidase was determined by in situ hybridization.

Amino Acid Sequence↗
PubMed1993

Purification, characterization, and cell wall localization of an alpha-fucosidase that inactivates a xyloglucan oligosaccharin.

An alpha-fucosidase that releases fucosyl residues from oligosaccharide fragments of xyloglucan, a plant cell wall hemicellulosic polysaccharide, was purified to homogeneity from pea (Pisum sativum) epicotyls using a combination of cation exchange chromatography and isoelectric focusing. The alpha-fucosidase has a molecular mass of 20 kDa according to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The alpha-fucosidase has an isoelectric point of 5.5. The substrate specificity of the alpha-fucosidase was determined by high performance anion exchange chromatographic analysis of oligosaccharide substrates and products. The enzyme hydrolyzes the terminal alpha-1,2-fucosidic linkage of oligosaccharides and does not cleave p-nitrophenyl-alpha-L-fucoside. The enzyme does not release measurable amounts of fucosyl residues from large polysaccharides. The subcellular localization of alpha-fucosidase in pea stems and leaves has been studied by immunogold cytochemistry. The alpha-fucosidase accumulates in primary cell walls and is not detectable in the middle lamella or in the cytoplasm of 8-day-old stem tissue and 14-day-old leaf tissue. alpha-Fucosidase activity was readily detected in extracts of 8-day-old stem tissue. No significant alpha-fucosidase activity or immunogold labeling of the alpha-fucosidase was detected in 2- and 4-day-old stem tissue indicating that production of alpha-fucosidase is developmentally regulated.

Antibody Specificity↗
PubMed1992

Further studies of the ability of xyloglucan oligosaccharides to inhibit auxin-stimulated growth.

The structural features required for xyloglucan oligosaccharides to inhibit 2,4-dichlorophenoxyacetic acid-stimulated elongation of pea stem segments have been investigated. A nonasaccharide (XG9) containing one fucosyl-galactosyl side chain and an undecasaccharide (XG11) containing two fucosyl-galactosyl side chains were purified from endo-beta-1,4-glucanase-treated xyloglucan, which had been isolated from soluble extracellular polysaccharides of suspension-cultured sycamore (Acerpseudoplatanus) cells and tested in the pea stem bioassay. A novel octasaccharide (XG8') was prepared by treatment of XG9 with a xyloglucan oligosaccharide-specific alpha-xylosidase from pea seedlings. XG8' was characterized and tested for its ability to inhibit auxin-induced growth. All three oligosaccharides, at a concentration of 0.1 microgram per milliliter, inhibited 2,4-dichlorophenoxyacetic acid-stimulated growth of pea stem segments. XG11 inhibited the growth to a greater extent than did XG9. Chemically synthesized nona- and pentasaccharides (XG9, XG5) inhibited 2,4-dichlorophenoxyacetic acid-stimulated elongation of pea stems to the same extent as the same oligosaccharides isolated from xyloglucan. A chemically synthesized structurally related heptasaccharide that lacked a fucosyl-galactosyl side chain did not, unlike the identical heptasaccharide isolated from xyloglucan, significantly inhibit 2,4-dichlorophenoxyacetic acid-stimulated growth.

Journal Article↗
PubMed1990

Cytokinins and Differentiation Processes in Mercurialis annua: Genetic Regulation, Relations with Auxins, Indoleacetic Acid Oxidases, and Sexual Expression Patterns.

Cytokinins in apices of eight isogenic lines of Mercurialis annua were compared (high performance liquid chromatography-gas chromatography mass spectroscopy-computer system). These apices develop normal staminate or pistillate differentiation processes (sex series lines) or empty (sterile), semiempty (semisterile), and full anthers (restored fertile male) in the sterility series in which a pistillate line was constructed. Both series developed two different cytokinin pathways: trans-cytokinins characterized the sex series, whereas the cis pathway characterized the sterility series. Drastic changes in the trans pathway (0/250 nanograms trans-zeatin and 166/0 nanograms zeatin nucleotide) induced staminate/pistillate differentiations. Less drastic quantitative changes in the cis pathway induced sterility or restored fertility compared to normal fertile anthers (192 or 669 nanograms/traces). The action of the complete cis-pathway was morphologically effective in the sterility series when the ratio of cis to trans pathways was 1:2 or 1:1 instead of 1:3. A final diagram shows the action of each sex or sterility allele on the enzymes controlling specific metabolites in both pathways. The discussion provides insights on the regulation of cytokinin-auxin balances specific for each kind of reproductive differentiation.

Journal Article↗