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  • 1
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-0832
    Keywords: Trichothecenes ; zearalenone ; α-zearalenol ; β-zearalenol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A total of 44, 40, 47, 51, and 58 barley samples for feed use were collected randomly after the 1987, 1989, 1990, 1991, and 1992 crops, respectively, from farms located in an area of southwest Germany. The sum of precipitation from May to September was high in 1987 and markedly lower in 1989–1992. Deoxynivalenol, 3-. and 15-acetyldeoxynivalenol, nivalenol, fusarenon-X, T-2 toxin, HT-2 toxin and diacetxyscirpenol were determined by gas chromatography with mass selective detection (GC-MS), zearalenone,α- and β-zearalenol by GC-MS or by HPLC. Deoxynivalenol was the major toxin with incidences at 71–98% and mean contents at 42–400 µg/kg. In contrast, incidences of zearalenone, 3-acetyldeoxynivalenol, nivalenol, HT-2 toxin, and T-2 toxin were at 7–68, 7–48, 11–41, 0–9, and 2–29%, respectively; with mean contents at 3–146 µg/kg. α- and β-zearalenol and diacetoxyscirpenol were not detected in any sample. 15-acetyldeoxynivalenol and fusarenon-X were assayed in samples from 1987, 1991 and 1992. 15-acetyldeoxynivalenol was detected in 30, 0 and 2% of samples, respectively, with an average content of positive samples at 8 and 4 µg/kg, fusarenon-X was not detected. Over the years, incidences and levels of toxins remained constant, decreased or increased. The correlation between the occurrence of toxins and level of precipitation is discussed.
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  • 3
    ISSN: 1573-0832
    Keywords: Bread ; conventional production ; deoxynivalenol ; infant food ; organic production ; trichothecenes ; zearalenone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A total of 237 commercially available samples of cereal-based foods including bread and related products, noodles, breakfast cereals, baby and infant foods, rice and other foods were randomly collected in southwest Germany during the first six months of 1998. The trichothecenes deoxynivalenol (DON), 3-and 15-acetyl-deoxynivalenol (3-,15-ADON), nivalenol (NIV), fusarenon-X (FUS-X), T-2 toxin (T-2) and HT-2 toxin (HT-2) were determined by gaschromatography/mass spectrometry following clean-up by a two stage solid-phase extraction. Detection limits ranged between 2 and 12 μg/kg. Based on all samples, the incidence of DON, HT-2, T-2, 3-ADON,15-ADON, and NIV was at 71, 18, 4, 4, 4 and 2%, respectively; the average contents in positive samples were at 103, 16, 14, 17, 24 and 109 μg/kg,respectively. Fus-X was not detected in any sample. A lower (P 〈 0.05) DON content was found in baby and infant foods as well as in cookies and cakes compared to bread. Overall, based on the incidence and level of all six toxins, the degree of contamination was lowest in baby and infant foods. Foods produced from either white or whole grain flour did not differ (P 〉 0.05) with regard to the incidence and level of DON. In foods produced from cereals of organic production both the incidence and median content of DON was lower compared to conventional production. Zearalenone, α- and β-zearalenol were determined by high performance liquid chromatography in 20 selected samples, mostly baby and infant foods. These toxins were not present in excess of the detection limit in any sample.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 53 (1966), S. 77-91 
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary 1. Aspergillus niger has been grown from conidia at 30° C on a medium containing KNO3 as a single source of nitrogen. Influence of KNO3 concentration (i.e. C/N-relation) in the original medium on time course and yields of gluconic, citric, and oxalic acid accumulation has been investigated. KNO3 concentrations were between 1,0 and 0,01%. As the medium has been buffered by addition of CaCO3 and NaOH there was no influence of KNO3 concentration on pH. 2. Time course of accumulation of the three acids principally was the same with all concentrations: Related to flask yields of gluconic and citric acid decrease after some time, yields of oxalic acid remain constant after having reached a maximum value. 3. There has been an influence of KNO3 concentration in the original medium on velocity of accumulation and/or consumption of the three acids and on time and value of maximum yields related to flask and to glucose consumed. 4. Maximum yields related to flask and to glucose consumed reached a maximum value at 0.03–0.01% KNO3 with gluconic acid and at 0.125% KNO3 with citric acid. During the time glucose is not used up yields of oxalic acid have been highest at 1.0% KNO3. After this time yields have been highest at 0.125% KNO3.
    Notes: Zusammenfassung 1. Aspergillus niger wurde, ausgehend von Conidien, bei 30° C auf einer Nährlösung mit KNO3 als alleiniger Stickstoffquelle kultiviert. Es wurde untersucht, wie sich die KNO3-Konzentration und damit das C/N-Verhältnis in der Ausgangs-Nährlösung auf den zeitlichen Verlauf und die Stärke der Glucon-, Citronen- und Oxalsäureanhäufung auswirkt. Die KNO3-Konzentration wurde dabei zwischen 1,0 und 0,01% variiert. Ein Einfluß des KNO3-Angebotes auf den pH-Wert wurde durch Zusatz von CaCO3 und NaOH zur Kulturflüssigkeit verhindert. 2. Die Anhäufung der drei Säuren folgt bei allen KNO3-Ausgangskonzentrationen demselben Prinzip. Dieses besteht darin, daß der absolute Gehalt der Kulturen an Glucon- und Citronensäure nach Erreichen eines maximalen Wertes wieder abnimmt, der absolute Gehalt an Oxalsäure dagegen konstant bleibt. 3. Die KNO3-Ausgangskonzentration hat einen Einfluß darauf, mit welcher Geschwindigkeit die Säuren angehäuft werden bzw. wieder verschwinden, zu welchem Zeitpunkt ihr Gehalt absolut und auf den Glucoseverbrauch bezogenseinen maximalen Wert erreicht und wie hoch dieser ist. 4. Gemessen an den Maximalwerten des absoluten und des auf den Glucoseverbrauch bezogenen Säuregehaltes ist die Gluconsäureanhäufung am stärksten bei einer sehr niedrigen (0,03–0,01%) und die Citronensäureanhäufung bei einer mittleren (0,25–0,125%) KNO3-Ausgangskonzentration. Die Oxalsäureanhäufung hat ihr Optimum in der Zeit vor dem fast völligen Glucoseverbrauch bei 1,0%, danach bei 0,125% KNO3.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 55 (1966), S. 81-90 
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary Aspergillus niger has been grown from conidia at 43, 30 or 10° C on a medium containing glucose (5%) as a source of carbon and KNO3 (1%) as a source of nitrogen. Gluconic and citric acid have been added before and after glucose in the medium has been used up almost completely. By addition of each of the acids yield of oxalic acid related to flask could be increased. Yield of oxalic acid related to flask and to citric acid consumed depends on temperature and on time of addition. Incorporation of C14 from gluconate-C14 (U) and citric acid-1,5-C14 into oxalic acid has been demonstrated at 43° C for cultures having used up glucose almost completely. By this it is proofed that under these conditions gluconic and citric acid can be used as a source of carbon for accumulation of oxalic acid. It is suggested that increase of oxalic acid yield caused by addition of gluconic or citric acid is due to conversion of the two acids into oxalic acid (among other products) under all conditions investigated.
    Notes: Zusammenfassung Entwickelt sich das Mycel von Aspergillus niger ausgehend von Conidien bei 43, 30 bzw. 10° C auf einer Nährlösung mit Glucose (5%) als C-Quelle und KNO3 (1%) als N-Quelle, so kann durch Zusatz von Glucon- bzw. Citronensäure vor und nach dem Zeitpunkt des fast völligen Glucoseverbrauches eine Mehranhäufung von Oxalsäure erzielt werden. Die auf die Kultur und auf den Verbrauch an Citronensäure bezogene Ausbeute ist von der Temperatur und dem Zeitpunkt des Zusatzes abhängig. Bei 43° C wurde für die Zeit nach dem fast völligen Glucoseverbrauch ein Einbau von C14 aus Gluconsäure-C14 (U) und Citronensäure-1,5-C14 in die Oxalsäure nachgewiesen. Unter diesen Bedingungen können also beide Säuren als C-Quelle für die Oxalsäureanhäufung dienen. Es wird vermutet, daß die Mehranhäufung von Oxalsäure durchweg mit einem Umsatz von Glucon- und Citronensäure u. a. in Oxalsäure verknüpft ist.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 103 (1975), S. 185-189 
    ISSN: 1432-072X
    Keywords: Oxalate Accumulation ; Aspergillus ; Citrate Degradation ; Oxaloacetate Cleavage ; Glyoxylate Oxidation ; Enzyme Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Carbon-14 was incorporated from citrate-1,5-14C, glyoxylate-14C(U), or glyoxylate-1-14C into oxalate by cultures of Aspergillus niger pregrown on a medium with glucose as the sole source of carbon. Glyoxylate-14C(U) was superior to glyoxylate-1-14C and citrate-1,5-14C as a source of incorporation. By addition of a great amount of citrate the accumulation of oxalate was accelerated and its maximum yield increased. In a cell-free extract from mycelium forming oxalate from citrate the enzyme oxaloacetate hydrolase (EC 3.7.1.1) was identified. Its in vitro activity per flask exceeded the rate of in vivo accumulation of oxalate. Glyoxylate oxidizing enzymes (glycolate oxidase, EC 1.1.3.1; glyoxylate oxidase, EC 1.2.3.5; NAD(P)-dependent glyoxylate dehydrogenase; glyoxylate dehydrogenase, CoA-oxalylating, EC 1.2.1.17) could not be detected in cell-free extracts. It is concluded that in cultures accumulating oxalate from citrate after pregrowth on glucose, oxalate arises by hydrolytic cleavage of oxaloacetate but not by oxidation of glyoxylate.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 144 (1986), S. 151-157 
    ISSN: 1432-072X
    Keywords: Aspergillus niger ; Nitrogen limitation ; Gluconate accumulation ; Enzyme activities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Batch cultures of Aspergillus niger grown from conidia on a medium with high C/N ratio accumulated gluconate from glucose with a yield of 57%. During almost the whole time of accumulation there was no net synthesis of total protein in the mycelium but the activity per flask and the specific activity of glucose oxidase (EC 1.1.3.4) in mycelial extracts increased whereas both values decreased for glucose dehydrogenase (EC 1.1.99.10) ‘gluconate 6-phosphatase’ (cf. EC 3.1.3.1, 3.1.3.2), gluconokinase (EC 2.7.1.12), glucose 6-phosphate and phosphogluconate dehydrogenases (EC 1.1.1.49, EC 1.1.1.44), phosphoglucomutase (EC 2.7.5.1), and most enzymes of the Embden-Meyerhof pathway and the tricarboxylic acid cycle. Gluconate dehydratase (EC 4.2.1.39), gluconate dehydrogenase (EC 1.1.99.3) and enzymes of the Entner-Doudoroff pathway could not be detected. By cycloheximide the increase of glucose oxidase activity was inhibited. It is concluded that the high yield of gluconate was due mainly to the net (de novo) synthesis of glucose oxidase which occurred during protein turnover after the exhaustion of the nitrogen source, and which was not accompanied by a net synthesis of the other enzymes investigated. Some gluconate may also have been formed by hydrolytic cleavage of gluconate 6-phosphate.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 36 (1960), S. 350-359 
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Zusammenfassung Ein Stamm von Aspergillus niger häuft in einer physiologisch alkalischen Nährlösung bei 43° mehr Oxalsäure an als bei 30°. Dieser Unterschied beruht auf der verstärkten Anhäufung vor dem Zeitpunkt des völligen Glucoseverbrauches. Die autolytische Herkunft des größten Teils der nach diesem Zeitpunkt bei 30° und 43° noch hinzukommenden Oxalsäure wird nachgewiesen, ebenso die Intensivierung der Autolyse bei der hohen Temperatur. Dagegen, daß die Oxalsäure auch vor dem völligen Glucoseverbrauch autolytischen Ursprungs ist und bei 43° aus diesem Grunde in verstärktem Maße angehäuft wird, spricht der Befund, daß die Fraktion des NH4 +- und Amid-N vor diesem Zeitpunkt nur in sehr geringer Menge nachzuweisen ist. Es wird jedoch darauf hingewiesen, daß sie im Gegensatz zur Oxalsäure vielleicht wieder in das der Autolyse parallel laufende Wachstum mit einbezogen wird, solange noch Glucose vorhanden ist. Die Geschwindigkeit der Oxalsäurezersetzung ist bei 43° geringer als bei 30°. Eine Beteiligung dieses Temperatureffektes an der verstärkten Anhäufung bei 43° wird diskutiert, ebenso die Möglichkeit eines temperaturbedingten Shunt-Effektes.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 53 (1966), S. 277-287 
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 53 (1966), S. 303-316 
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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