Carbohydrate metabolism of Penicillium chrysogenum

Metabolic flux distributions in Penicillium chrysogenum during fed-batch cultivations

Based on a review of the Penicillium chrysogenum biochemistry a stoichiometric model has been set up. The model considers 61 internal fluxes and there are 49 intracellular metabolites which are assumed to be in pseudo-steady state. In addition to the intracellular fluxes the model considers the uptake of 21 amino acids. From the stoichiometric model the maximum theoretical yield of penicillin V is calculated to 0.43 mol/mol glucose. If biosynthesis of cysteine is by direct sulfhydrylation rather than by transsulfuration, the maximum theoretical yield is about 20% higher, i.e., 0.50 mol/mol glucose. The theoretical yield decreases substantially if alpha-aminoadipate is converted to 6-oxo-piperidine-2-carboxylic acid (OPC). If only 40% of the alpha-aminoadipate is recycled, the maximum theoretical yield is 0.31 mol/mol glucose. The uptake rates of glucose, lactate, gamma-aminobutyrate, and 21 amino acids were measured during fed-batch cultivations. The rates of formation of penicillin V, delta-(L-alpha)-aminoadipyl-L-cysteinyl-D-valine (ACV), OPC, and the pool of isopenicillin N, 6-APA, and 8-HPA were also measured. Finally the synthesis rates of the biomass constituents RNA/DNA, protein, lipid, carbohydrate, and amino carbohydrate were measured. From these measured rates and the stoichiometric model the metabolic fluxes through the different intracellular pathways are calculated. The calculations show that penicillin formation is accompanied by a large flux through the pentose phosphate (PP) pathway due to a large requirement for nicotinamide-adenine dinucleotide phosphate (NADPH) used in the biosynthesis of cysteine. If cysteine is added to the medium, the flux through the PP pathway decreases. From the stoichiometric model Y(xATP) is calculated to 87 mmol adenosine triphosphate (ATP)/g dry weight (DW), and from the flux calculations m(ATP) is found to 3 mmol ATP/g DW/h. (c) 1995 John Wiley & Sons, Inc.

Ballistic disruption of Penicillium chrysogenum cells

The use of glass beads in a high-speed mixing device to rupture organisms was applied to molds. The use of a mixer in which the propellor shaft enters from the top into a metal mixing chamber made it possible to immerse the whole device in a salt water and ice mixture so that the temperature of the glass-bead slurry could be kept below 5 C without difficulty. Mycelia, glass beads, and buffer in a 1:2:3 (w/w) ratio gave above 95% breakage in 15 min with Penicillium chrysogenum cells and in 4 min with Rhizopus nigricans. Some of the factors influencing breakage are discussed.

Catabolism of D-glucose by Pseudomonas putida U occurs via extracellular transformation into D-gluconic acid and induction of a specific gluconate transport system

Pseudomonas putida U does not degrade D-glucose through the glycolytic pathway but requires (i) its oxidation to D-gluconic acid by a peripherally located constitutive glucose dehydrogenase (insensitive to osmotic shock), (ii) accumulation of D-gluconic acid in the extracellular medium, and (iii) the induction of a specific energy-dependent transport system responsible for the uptake of D-gluconic acid. This uptake system showed maximal rates of transport at 30 degrees C in 50 mM potassium phosphate buffer, pH 7.0. Under these conditions the K(m) calculated for D-gluconic acid was 6.7 microM. Furthermore, a different transport system, specific for the uptake of glucose, was also identified. It is active and shows maximal uptake rates at 35 degrees C in 50 mM potassium phosphate buffer, pH 6.0, with a K(m) value of 8.3 microM.

Changes in fungi with age. II. Respiration and respiratory enzymes of Rhizoctonia solani and Sclerotium bataticola

Van Etten, James L. (University of Illinois, Urbana), H. Peter Molitoris, and David Gottlieb. Changes in fungi with age. II. Respiration and respiratory enzymes of Rhizoctonia solani and Sclerotium bataticola. J. Bacteriol. 91:169-175. 1966.-The rate of respiration of Rhizoctonia solani and Sclerotium bataticola decreased with age. This decrease in respiratory rate might be produced by a decrease in the specific activity of one or more enzymes involved in carbohydrate metabolism. Specific activities in cell-free extracts were measured for most of the enzymes in the hexose monophosphate shunt, Embden-Meyerhof-Parnas pathway, tricarboxylic acid cycle, and terminal electron-transport system. In addition, glucose oxidase, isocitritase, and malic enzyme were measured. In R. solani, increases in activity with age occurred for hexokinase, alpha-glycerolphosphate dehydrogenase, malic dehydrogenase, and cytochrome oxidase. Decreases occurred for phosphohexokinase, aconitase, nicotinamide adenine dinucleotide-specific isocitric dehydrogenase, reduced nicotinamide adenine dinucleotide oxidase, and at least one of the enzymes between 3-phosphoglycerate and pyruvate. In S. bataticola, increases in activity with age were observed for phosphohexokinase, pyruvic dehydrogenase, fumarase, malic dehydrogenase, and malic enzyme, whereas none of the enzymes decreased. The specific activities of the remaining enzymes did not change with age in either fungus.

Effect of culture conditions on the production of D-galactose oxidase by Dactylium dendroides

The effects on enzyme production of inoculum size and age, medium composition, and culture conditions were studied in shake flasks and in a pilot-plant fermentor. Using a medium consisting of glucose, yeast extract, and inorganic salts in deionized water, we found that the addition of Cu(++) was essential for the formation of active enzyme. Cultures grown in the absence of added copper produced an inactive enzyme protein which could be activated by 10(-3) M Cu(++). Thiamine fulfilled all requirements for exogenous vitamins for growth and enzyme production. Glucose concentrations higher than 1% markedly suppressed enzyme formation. The mycelium inactivated the enzyme on prolonged incubation of the culture. Mycelial autolysates and sonic extracts were found to contain a thermostable and slowly dialyzable galactose oxidase-inactivating factor. The experiments suggest that this factor operates as a chelating agent which forms complexes with the copper of the enzyme. Copper ions (10(-3) M) prevented enzyme inactivation and restored activity to samples previously inactivated by this factor.

PURIFICATION AND PROPERTIES OF PHOSPHOGLUCOSE ISOMERASE FROM ASPERGILLUS NIGER

Phosphoglucose isomerase from Aspergillus niger was purified about fiftyfold by ammonium sulphate fractionation and treatment with calcium phosphate gel. The properties and kinetics of the enzyme are described. The enzyme resembled the muscle phosphoglucose isomerase in not requiring metal ions for activation but differed in showing no inhibition with phosphate. The enzyme showed maximum activity between pH 7.8 to 8.0 as compared with the optimum pH 9.0 shown by the muscle enzyme.

PURIFICATION AND PROPERTIES OF PHOSPHOGLUCOSE ISOMERASE FROM ASPERGILLUS NIGER

Phosphoglucose isomerase from Aspergillus niger was purified about fiftyfold by ammonium sulphate fractionation and treatment with calcium phosphate gel. The properties and kinetics of the enzyme are described. The enzyme resembled the muscle phosphoglucose isomerase in not requiring metal ions for activation but differed in showing no inhibition with phosphate. The enzyme showed maximum activity between pH 7.8 to 8.0 as compared with the optimum pH 9.0 shown by the muscle enzyme.

THE HEXOSEMONOPHOSPHATE PATHWAY IN ASPERGILLUS NIGER

Enzymes of the hexosemonophosphate pathway were demonstrated in extracts obtained from Aspergillus niger grown in two types of media: a fermentation medium (molasses) and a rich growth medium (MYG). Preparations from cells grown in either medium contained a TPN-specific glucose-6-phosphate (G-6-P) dehydrogenase and a TPN-linked 6-phosphogluconate (6-P-G) dehydrogenase. The rate of pyridine nucleotide reduction by the latter was 20% of that by G-6-P dehydrogenase. For both enzymes the activity of the preparation from molasses cultures was twice that from MYG cultures. A DPN-linked 6-P-G dehydrogenase was demonstrated in molasses preparations though not in MYG preparations. On incubating extracts with R-5-P aerobically, total pentose decreased accompanied by a sequential increase and decrease in ketopentose. An increase in hexose was observed under anaerobic conditions but accounted for only one third of the pentose. Increases in heptulose and triose occurred only in the presence of hydrazine. The presence of phosphohexoisomerase, which is necessary to complete a "pentose cycle", was demonstrated.

Carbohydrate metabolism of Pullularia pullulans

Pullularia pullulans, ATCC No. 11942, has constitutive enzymes for the utilization of galactose, glucose, maltose, mannose, raffinose, sucrose, and trehalose, but not for lactose. The organism oxidized mannose more rapidly, and maltose and raffinose more slowly, than any of the other sugars. Moreover, it utilized galactose and glucose at approximately the same rate, but more rapidly than trehalose; the oxidation of sucrose, however, was very slow at first and then very rapid. When resting cells were incubated with glucose-1-C14, the carbon dioxide immediately produced was highly radioactive; when glucose-6-C14 was used, however, a considerable time elapsed before the production of noticeable amounts of radioactive carbon dioxide. The ratio of the activity of the carbon dioxide produced from glucose-1-C14 to that produced from glucose-6-C14 was greater in young cells than in old. The results indicated that resting cells catabolize glucose in such a manner that most of the carbon dioxide comes from carbon 1 of glucose. Extracts from cells were found to have an active phosphoglucomutase, glucose-6-phosphate dehydrogenase, 3-phosphoglyceraldehyde dehydrogenase, and fructose diphosphate aldolase. Both dehydrogenases were TPN-linked. The extracts also oxidized ribose-5-phosphate but not ribose. The organism has enzymes, therefore, to catabolize glucose by some of the reactions of the Embden–Meyerhof system as well as by those of the pentose phosphate cycle.