Einfluß des Sauerstoffpartialdrucks auf die Citronensäuresynthese durch Saccharomycopsis lipolytica aus n-Paraffinen

The dependence of growth formation of citric acids (citrate: isocitrate = 1:1) on oxygen partial pressure of an alkane utilising yeast Saccharomycopsis lipolytica was investigated. During growth oxygen corresponds to a MICHAELIS-MENTEN-kinetics (K_s = 2.0 · 10^?6 m). The respiration quotient RQ for a dissolved oxygen concentration in the range of 10–100% (air saturation) is 0.46 ± ± 0.04 The phase of product formation is characterized by 3 sections. Immediately after N-exhaustion the cell activities are the highest. They decline during the first 30 hours of production. Besides the production of reserve material in this first section the highest production rate for citrate and isocitrate is observed. The rate of citric acid production depends on the oxygen partial pressure and is governed by MICHAELIS-MENTEN-kinetics. The specific production rate and the rate of oxygen consumption correspond to K_s-values of 4.0 · 10^?5 and 3.3 · 10^?5 M, respectively The RQ-value declines to a constant value of 0.23 ± 0.02 and is not influenced by oxygen partial pressures in the range of 10–100% (related to air saturation) During the second section cell activities remain nearly constant for about 100 h. Due to this constancy the following equation could be derived: 14 O₂ + C₁₅H₃₂ 2 C₆H₈O₇ + 3 CO₂ - ₈ H₂O. In the third section the cell activities decline again.     

Zur Kinetik der Citronensäurebildung bei Candida lipolytica

The kinetics of citrate and isocitrate accumulation by Candida lipolytica has been studied, with special emphasis of the carbon sources glucose and n-alkanes and the shifts from one carbon source to the other. The accumulation of the citric acids starts with the beginning of ideophase. Trophophase and ideophase behaviour is in parts different. Ideophase behaviour may be influenced by exogenic factors during growth. From the course of the curves for the citric acids two phases can be distinguished: The specific production rate of the first phase is higher than in the second phase (π₁ ? 0.19 h^?1; π² ? 0.14 h^?1). The influence of the carbon source on the course of the curves and the numeric value for the specific production rate is negligible. Alcane grown cells accumulate citric acids from added glucose and left-over n-alcanes simultaneously. When both substrates are added from the beginning only glucose is taken up for growth, for citric acid production both substances are utilized simultaneously. Glucose grown cells do not utilize alcanes for production of citric acids. Citric acids are accumulated only as long as glucose is available. Alcane uptake starts after addition of a nitrogen source.     

Nutzung von Paraffinen und anderen Nichtkohlenhydrat-Kohlenstoffquellen zur mikrobiellen Citronensäuresynthese

This article reviews the developments achieved in citrate and isocitrate accumulation with non-carbohydrate substrates by microorganisms presented as well in academic publications as in patents. The efficiency of citrate and isocitrate overproducing microorganisms and of mutants obtained thereof with respect to different carbon sources (n-alkanes, triglycerides, organic acids, etc.) is discussed. The influence of environmental conditions (media, pH etc.) and biochemical mechanisms which lead to metabolic overflow are emphasized. The kinetics of fermentation processes are discribed, calculations concerning carbon balances are involved. The production of by-products and the conversion of isocitrate to citrate is considered. The production of citric acid by yeasts which utilize different carbon sources may be economically feasible and an accession to the practized molasse-Aspergillus-process.     

Verbesserung der Y-Werte bei Wachstum von Hansenula polymorpha auf Methanol durch simultane Verwertung von Glucose

The simultaneous utilization of methanol and glucose by Hansenula polymorpha MH20 was investigated in chemostat (C-limited) cultivation. The mixed-substrate utilization results in biomass yields which are greater up to 20 to 25% as expected assuming an additive growth on both substrates. This is referred to as an auxiliary-substrate effect. Additionally, methanol can be utilized at higher growth rates in the presence of glucose compared to those obtained on this substrate alone. The extend of the auxiliary-substrate effect and the optimum ratio of substrates to reach this effect depend on dilution rate. The greatest stimulation in yield is obtained at D ～ 0.1 h^?1, after raising the dilution rate this effect diminishes. At a rate of 0.1 h^?1 the optimum mixed-substrate ratio of methanol: glucose is 7: 1(g). By increasing the growth rate the ratio changes toward glucose and reached a value of 1:1 (g) at D = 0.3 h^?1. This change in the optimum ratio correlates with diminution in yield coefficient of methanolp accomanying an increase in growth rate > 0.15 h^?1. Energy balances of the utilization of the single substrates are used for interpretation of these results. From this it is evident that methanol does not play the role of an energy-rich substrate in the metabolism of yeast. Rather glucose is the energy-providing substrate in this combination.     

Vergleich der Verwertung von Fructose und Glucose beim Menschen bei langdauernder parenteraler Zufuhr

Zusammenfassung 1. Bei langdauernder, konstanter, intravenöser Infusion von 0,5–1,5 g/kg/Std Glucose oder Fructose in 10% iger Lösung liegt die Verwertung zwischen 99 und 92%. Wesentliche Unterschiede zwischen den beiden Zuckern bestehen nicht. Bei niedriger Zufuhrrate wird Glucose, bei hoher Fructose etwas besser verwertet.2. Für die parenterale Ernährung sind beide Zucker gleich gut geeignet.3. Eine calorisch ausreichende parenterale Ernährung mit Glucose oder Fructose ist möglich.

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Summary 1. Clucose or fructose in a 10 per cent solution were administered intravenously by means of constant infusion at rates of 0.5–1.5 g/kg/h. Utilization was between 99 and 92 per cent, with no great differences between the hexoses. At low rates glucose is somewhat better utilized, at the higher rate fructose.2. For parenteral nutrition both sugars are equally well suited.3. A calorically sufficient parenteral nutrition with glucose or fructose is possible.

     

Untersuchungen zur Regulation der Enzyme des Glyoxylatzyklus bei Saccharomycopsis lipolytica I. Einfluß der C-Quelle auf die Aktivität von Isocitratlyase und Malatsynthase

Comperative studies on the activities of isocitrate lyase (ICL) and malate synthase (MS) were carried out with Saccharomycopsis lipolytica incubating the yeast on media with different carbon sources. When cells were incubated in minimal medium with glucose, the activities of both enzymes were very low. In contrast, in minimal medium with acetate enhanced enzyme activities could be demonstrated. It is probably that the synthesis of ICL is repressed in presence of glucose. Furthermore the activity of ICL was inhibited by tricarboxylic acid cycle intermediates like succinic acid and oxalacetic acid. It was concluded that the syntheses of enzymes are derepressed. When cells of Sm. lipolytica were incubated in minimal medium with acetate, a high enzyme activity is evident. Synthesis of ICL on acetate was inhibited by cycloheximid and actinomycin D. The results were discussed comparing them with data obtained from other organisms.     

Die Hemmung der Fettsäuresynthese bei in vitro-Versuchen durch Seren Gesunder und Kranker und durch Serumeiweißfraktionen

Ohne Zusammenfassung     

Kettenübertragung durch tetrabromkohlenstoff bei der polymerisation von styrol und von vinylacetat

The constant of chain transfer to carbon tetrabromide in the polymerization of styrene has been redetermined by directly measuring the consumption of the chain transfer agent using a GC-technique and simultaneously evaluating the conversion of monomer to polymer. Values of 250 (at 60°C) and 185 (at 95°C) have been obtained by this method. These values agree in order of magnitude with those recently obtained by Thomson and Walters from the determination of polymer molecular weights and, accordingly, exceed the values previously reported by approximately two powers of ten. An analysis of the limiting viscosity numbers of the polymers prepared in presence of carbon tetrabromide shows an excellent agreement with these new high values of the chain transfer constant of carbon tetrabromide. For the constant of chain transfer to carbon tetrabromide in the polymerization of vinyl acetate a value of 6·10³ has been obtained at 60°C, which again is two to three orders of magnitude higher than those values given previously.     

Die Verwertung von Kohlehydraten und ihre Unentbehrlichkeit bei Muskelarbeit

Ohne Zusammenfassung     

Verwertung von L-Aspartat,L-Malat und Fumarat durch Pasteurella multocida

Strains of Pasteurella multocida use L-aspartate, L-malate and furmarate, respectively, as substrates for production of succinic acid which accumulates in the medium. As was established by studies with ¹⁴C and ³H labelled substrates, the degradation of these substances proceeds analogous via the citric acid cycle.