Changes in tissue adenylates and water content of bluegill, Lepomis macrochirus, exposed to copper

Bluegill were exposed to copper (2–0 mg/1⁻¹ unfiltered) for 24, 48, 72 or 96 h at 24° C. This concentration approximated the 96 h LC20. Water content of liver increased 4–8% after 24 h exposure and muscle 4–6% by 48 h. These changes persisted throughout the 96 h experiments. Copper exposed fish exhibited decreases in muscle ATP, ADP, total adenylates, and energy charge by 48 h. There was a trend toward recovery of ATP with further exposure. Liver ATP of exposed fish was lower than controls at all intervals with the greatest difference evident at 48 h. No significant changes in brain adenylates were observed. Muscle and liver lactic acid was unchanged at 48 h exposure, therefore tissue hypoxia was not the cause of the adenylate changes. It was concluded that copper causes decreases in muscle and liver ATP several days before probable death of copper exposed fish and the changes seen are the result of dilution by increased tissue water, and the copper acting on certain cellular enzymes involved in detoxification and energy metabolism.     

Changes in the adenine nucleotide content of cysts of Globodera rostochiensis associated with the hatching of juveniles

The content of AMP, ADP and ATP within single cysts of Globodera rostochiensis (60–80 fig dry weight) was determined as ATP to an accuracy of ± 10^-11 mol by a bioluminescent technique, after microenzymic methods had been used to phosphorylate AMP and ADP to ATP. Results for a total of 120 cysts showed that a change occurs in the adenylate energy charge of their contents after they have been exposed to potato root diffusate. Cysts in water had a mean adenylate energy charge of 0–63 (s.E. ± 0–04), but a randomly selected group of cysts after 24 h treatment with potato root diffusate had a significantly lower mean of 0–49±0–04. In a second, similar experiment, cysts in diffusate for only 8 h had an energy charge of 0*55 ± 0–03, but this value was not significantly less than the corresponding mean of o-6i ±0–03 of cysts that remained in water. The results indicate an effect on the metabolism of the unhatched juveniles that occurs too soon after the addition of diffusate to be directly due to any increase in locomotor activity. Apparently, the primary action of the hatching factor had affected many juveniles within 24 h of the addition of potato root diffusate to the cyst.     

Effect of culture media on protease and oxytetracycline production with mycelium and protoplasts of Streptomyces rimosus

For the simultaneous production of protease and oxytetracycline, mycelium and protoplasts of Streptomyces rimosus TM-55 were cultivated in basal medium containing soluble starch, corn steep liquid, ammonium sulphate, calcium carbonate, sodium chloride and soybean oil. Protease and oxytetracycline production increased with decreasing in ratio of culture broth to vessel volume from 1:2 to 1:5. Each ml of broth with 0.286 mg fresh mycelia yielded 168–204 units of protease and 785–972 g of oxytetracycline after replacement of corn steep liquor, sodium chloride and soybean oil with beef extract and sunflower oil, while each ml of broth with 7.5 × 10⁷ protoplasts produced 141–153 units of protease and 504–615 g of oxytetracycline. Protease and oxytetracycline production were low when the pH was 5.1 or 9.0. Soluble starch and ammonium sulphate were the best carbon and nitrogen sources, respectively. Supplementation with calcium carbonate enhanced protease and oxytetracycline production. The productivity of protoplasts decreased sharply when the incubation temperature increased from 28 to 34 °C, while the productivity of mycelium was almost unchanged.     

Adenylate nucleotide levels and energy charge in Arthrobacter crystallopoietes during growth and starvation

The adenylate nucleotide concentrations, based on internal water space, were determined in cells of Arthrobacter crystallopoietes during growth and starvation and the energy charge of the cells was calculated. The energy charge of spherical cells rose during the first 10 h of growth, then remained nearly constant for as long as 20 h into the stationary phase. The energy charge of rod-shaped cells rose during the first 4 h of growth, then remained constant during subsequent growth and decreased in the stationary growth phase. Both spherical and rod-shaped cells excreted adenosine monophosphate but not adenosine triphosphate or adenosine diphosphate during starvation. The intracellular energy charge of spherical cells declined during the initial 10 h and then remained constant for 1 week of starvation at a value of 0.78. The intracellular energy charge of rod-shaped cells declined during the first 24 h of starvation, remained constant for the next 80 h, then decreased to a value of 0.73 after a total of 168 h starvation. Both cell forms remained more than 90% viable during this time. Addition of a carbon and energy source to starving cells resulted in an increase in the ATP concentration and as a result the energy charge increased to the same levels as found during growth.Nonstandard Abbreviations cGMP 3,5 guanosine monophosphate - ppGpp guanosine tetraphosphate - MS mineral salts - HC casein hydrolysate - TEA triethanolamine buffer - Pi inorganic phosphate     

不同温度下黄曲霉菌菌丝超微形态的比较研究

为探究黄曲霉菌的毒素合成是否影响菌丝超微形态,本研究结合扫描和透射电镜技术比较观察产毒(28℃和30℃)和不产毒(37℃和40℃)温度下培养的不同发育阶段的黄曲霉菌菌丝形态和超微结构.扫描电镜结果显示:28℃下,在24h和44h菌丝体表面有丝状粘性分泌物附着,48-72h之间菌丝体逐渐出现皱缩、塌陷和扭曲现象,而37℃...     

Response Surface Analysis of Solid State Growth of <Emphasis Type="Italic">Pleurotus ostreatus</Emphasis> Mycelia utilizing Whey Permeate

A novel approach to utilizing whey permeate, the cultivation of mycelia of the edible mushroom Pleurotus ostreatus, is introduced. Response surface analysis (RSA) was successfully applied to determine the combination of substrate concentration, temperature and pH that would result in a maximal mycelial extension rate under solid state cultivation. The conditions to maximize the mycelial extension rate were predicted to be 44 g lactose l⁻¹, pH 6.0 and 24.2 °C. Subsequent verification of these levels agreed with model predictions.     

Body temperature and seawater adaptation in farmed Atlantic salmon and rainbow trout during prolonged chilling

The core temperature of the rainbow trout Oncorhynchus mykiss (3·5 kg) dropped to 1·0° C during the first 6 h of chilling at 0·5° C, remained stable until 24 h, and dropped significantly to 0·7° C after 39 h. Blood plasma osmolality increased and muscle moisture content decreased gradually with increasing chilling time. After 39 h of chilling, the rainbow trout experienced 40 mosmol l^-1 higher blood plasma osmolality and 2·8% less muscle moisture content compared with initial values. In the Atlantic salmon Salmo salar (5·3 kg), core temperature dropped to 1·3° C and blood plasma osmolality increased significantly during the first 6 h of chilling at 0·5° C, but remained relatively stable throughout the rest of the experimental period. After 39 h of chilling, the salmon experienced 20 mosmol l^-1 higher blood plasma osmolality and 0·5% less muscle moisture content compared with initial values. In rainbow trout muscle moisture content was inversely related to blood plasma osmolality indicating reduced seawater adaptation with increasing hours of chilling. No such relationship was observed in the Atlantic salmon. Hence, changes in plasma osmolality and muscle moisture in the Atlantic salmon do not indicate osmoregulatory failure since the new levels, once established, were maintained throughout the chilling time.     

Relationship between ATP and energy charge during lethal metabolic stress of the marine isopod Cirolana borealis

The relationship between ATP and energy charge was studied in individuals of Cirolana borealis under heavy metabolic stress caused by anoxia or exposure to toluene. Prolonged anoxia led to a lowering of the ATP content to about 10% after 4 days, with a simultaneous decrease in energy charge to about 0.25. A lowering of the total adenylate pool reduced the fall in energy charge somewhat, but this effect was marked only in late anoxia when the individuals had become inactive. Exposure to 0.14 mM toluene for 8 days led to a similar decrease in ATP and energy charge. Exposure to 1.4 mM toluene for 24 h led to only slight changes in the adenine nucleotide pool, although the individuals became narcotized within a few hours. The energy charge associated with moribund individuals thus varied much. The mechanism of energy charge stabilization through reduction of the adenine nucleotide pool as ATP declined seemed to be of little significance for the survival of the individuals.     

In vitro adenine nucleotide catabolism in African catfish spermatozoa

It has been shown recently that African catfish (Clarias gariepinus) spermatozoa possess relatively low ATP content and low adenylate energy charge (AEC). One of the possible explanations for this phenomenon is that the spermatozoa actively catabolize adenine nucleotides. A relatively high rate of such catabolism could then contribute to the low ATP concentration and low adenylate energy charge observed in the spermatozoa in vitro. To check this hypothesis, we investigated ATP content and adenine nucleotide catabolism in African catfish spermatozoa stored at 4 °C in the presence of glycine as an energetic substrate. Our results indicate that the storage of African catfish sperm at 4 °C in the presence of glycine causes time-dependent ATP depletion. In contrast to ATP, the AMP content increases significantly during the same period of sperm storage, while the ADP increases only slightly. Moreover, a significant increase of inosine and hypoxanthine content was also found. Hypoxanthine was accumulated in the storage medium, but xanthine was found neither in spermatozoa nor in the storage medium. It indicates that hypoxanthine is not converted to xanthine, probably due to lack of xanthine oxidase activity in catfish spermatozoa. Present results suggest that adenine nucleotides may be converted to hypoxanthine according to the following pathway: ATP→ADP→AMP (adenosine/IMP)→inosine→hypoxanthine. Moreover, hypoxanthine seems to be the end product of adenine nucleotide catabolism in African catfish spermatozoa. In conclusion, our results suggest that a relatively high rate of adenine nucleotide catabolism contributes to the low ATP concentration and low adenylate energy charge observed in African catfish spermatozoa in vitro.     

Factors affecting the survival of Salmonella and Escherichia coli in anaerobically fermented pig waste

The survival of Salmonella typhimurium was investigated in acidogenic, anaerobically fermented pig wastes and in synthetic media, each containing volatile fatty acids (VFA). Salm. typhimurium survived at pH 6·8, but not at pH 4·0, when incubated at 37°C for 24 h in either fermented or synthetic medium containing VFA. The minimum inhibiting concentration of VFA for Salm. typhimurium after 48 h incubation at 30°C at pH 4·0 was 0·03 mol/l and for Escherichia coli it was 0·09 mol/l. Fermented pig wastes in a digester, maintained at pH 5·9, were inoculated with Salm. typhimurium and then incubated at 37°C for 24 h. The pH was adjusted to either 4·0 or 5·0 and after a further 48 h at 30°C, Salm. typhimurium survived at pH 5·0 but not at pH 4·0. It was concluded that pH is critical in determining the survival of this organism in acidogenic anaerobically fermented pig waste.     

Autotriploid tench Tinca tinca (L.) larvae obtained by fertilization of eggs previously subjected to postovulatory ageing in vitro and in vivo

Eggs of diploid tench Tinca tinca were half-stripped out and stored for 0 (control batch), 1, 3 and 5 h at mean ± s . d . 17·0 ± 0·4 and 21·9 ± 0·5° C or for 0, 1, 2, 3, 4 and 5 h at 24·0 ± 0·0° C in vitro prior to fertilization. The eggs remaining in vivo in the fish kept at 17·0 ± 0·4 and 21·9 ± 0·5° C were collected and fertilized in the same time intervals. Fertilization rate and larval yield mostly decreased after 3–5 h storage of eggs both in vitro and in vivo and only the diploid larvae were found in all control batches. Triploid larval yields increased to a maximum 5·26% after 5 h in vitro storage at 24·0° C and 1·07 and 1·60% after 3 h in vitro storage at 21·9 and 17·0° C, respectively. Triploid larval yield during in vivo storage at 21·9° C reached a maximum 0·91% after 5 h. As the spontaneous autotriploid larvae arose solely from fertilized eggs previously subjected to postovulatory egg ageing by means of prolongated storage, the autotriploidy was probably caused by failure of extrusion of the second polar body.     

Energy requirement for the mobilization of vacuolar arginine in Neurospora crassa

The bulk of the intracellular arginine pool in exponentially growing mycelia of Neurospora crassa is sequestered in the vacuoles. Vacuolar arginine effluxes from the vacuoles into the cytosol and is catabolized to ornithine and urea upon nitrogen starvation. The energy requirement for mobilization has been studied by treating nitrogen-starved mycelia with inhibitors or respiration or glycolysis or an uncoupler of respiration. Mobilization was inhibited by the inhibitors or the uncoupler of respiration, but not by the inhibitors of glycolysis. The inhibitors and the uncoupler of respiration reduced the ATP pool and the energy charge of the treated mycelia. The inhibitors of glycolysis reduced the ATP pool but had no effect on the energy charge. The results indicate that mobilization of arginine from the vacuoles requires metabolic energy. The forms of this energy and the mode of its association with the mobilization process are discussed.     

Sclerotial Formation of Polyporus umbellatus by Low Temperature Treatment under Artificial Conditions

Background

Polyporus umbellatus sclerotia have been used as a diuretic agent in China for over two thousand years. A shortage of the natural P. umbellatus has prompted researchers to induce sclerotial formation in the laboratory.

Methodology/Principal Finding

P. umbellatus cultivation in a sawdust-based substrate was investigated to evaluate the effect of low temperature conditions on sclerotial formation. A phenol-sulfuric acid method was employed to determine the polysaccharide content of wild P. umbellatus sclerotia and mycelia and sclerotia grown in low-temperature treatments. In addition, reactive oxygen species (ROS) content, expressed as the fluorescence intensity of mycelia during sclerotial differentiation was determined. Analysis of ROS generation and sclerotial formation in mycelia after treatment with the antioxidants such as diphenyleneiodonium chloride (DPI), apocynin (Apo), or vitamin C were studied. Furthermore, macroscopic and microscopic characteristics of sclerotial differentiation were observed. Sclerotia were not induced by continuous cultivation at 25°C. The polysaccharide content of the artificial sclerotia is 78% of that of wild sclerotia. In the low-temperature treatment group, the fluorescent intensity of ROS was higher than that of the room temperature (25°C) group which did not induce sclerotial formation all through the cultivation. The antioxidants DPI and Apo reduced ROS levels and did not induce sclerotial formation. Although the concentration-dependent effects of vitamin C (5–15 mg mL⁻¹) also reduced ROS generation and inhibited sclerotial formation, using a low concentration of vitamin C (1 mg mL⁻¹) successfully induced sclerotial differentiation and increased ROS production.

Conclusions/Significance

Exposure to low temperatures induced P. umbellatus sclerotial morphogenesis during cultivation. Low temperature treatment enhanced ROS in mycelia, which may be important in triggering sclerotial differentiation in P. umbellatus. Moreover, the application of antioxidants impaired ROS generation and inhibited sclerotial formation. Our findings may help to provide new insights into the biological mechanisms underlying sclerotial morphogenesis in P. umbellatus.     

The linamarase of Mucor circinelloides LU M40 and its detoxifying activity on cassava

Mucor circinelloides LU M40 produced 12·2 mU ml⁻¹ of linamarase activity when grown in a 3 l fermenter in the following optimized medium (g l⁻¹ deionized water): pectin, 10·0; (NH₄)₂SO₄,
1·0; KH₂PO₄, 2·0; Na₂HPO₄, 0·7; MgSO₄.7H₂O, 0·5; yeast extract, 1·0; Tween-80,
1·0, added after 48 h of fermentation. The purified linamarase was a dimeric protein with a molecular mass of 210 kDa; the enzyme showed optimum catalytic activity at pH 5·5 and 40 °C and had a wide range (3·0–7·0) of pH stability. The enzyme substrate specificity on plant cyanogenic glycosides was wide; the K_m value for linamarin was 2·93 mmol l⁻¹. The addition, before processing, of the fungal crude enzyme to cassava roots facilitated and shortened detoxification; after 24 h of fermentation, all cyanogenic glycosides were hydrolysed.     

Body composition and energy allocation in life-history stages of brown trout

Energy contents of immature parr and smolts, and mature resident and anadromous brown trout Salmo trutta sampled from a small stream in southern Norway were estimated from lipid, protein and carbohydrate concentrations. In immatures the lipid concentrations were highest in parr in the autumn. Mean lipid concentrations increased significantly with age in parr sampled in autumn (1·3% in age 0+ to 3·4% in age 3+), whereas they did not in smolts. The lipid concentrations of parr in spring were not significantly different from those of similarly aged smolts. By contrast, the relative water content (%) decreased with age in parr in the autumn and increased with age in smolts, mean values being slightly higher in smolts (78%) than in parr (77%). Protein and carbohydrate concentrations did not vary with age in the immature fish, mean protein concentrations being 18·0, 17·5 and 16·8% in parr in the autumn and spring, and in smolts, respectively. In residents, the concentrations of lipids were lower and of water higher, in age group 1 than in older fish, whereas there was no significant variation with age amongst anadromous trout. The energy concentration of 2+ smolts (349 kJ 100 g^-1) was similar to that of 0+ parr in the autumn. Mean somatic energy density in autumn was 1·1 times higher in freshwater residents than in parr at age 1+ (407 and 387 kJ 100 g^-1) and marginally different at age 2+ (462 and 426 kJ 100 g^-1, respectively). The energy contents per unit mass of residents were 1·3–1·6 times that of similar aged smolts. Mean somatic energy density of anadromous trout (504 kJ 100 g^-1) was higher than that of residents (455 kJ 100 g^-1). Somatic energy, lipid and protein concentrations were correlated highly with water contents of all life stages, age and sex groups.     

Adenine nucleotides and the xanthophyll cycle in leaves

The relationships among the leaf adenylate energy charge, the xanthophyll-cycle components, and photosystem II (PSII) fluorescence quenching were determined in leaves of cotton (Gossypium hirsutum L. cv. Acala) under different leaf temperatures and different intercellular CO₂ concentrations (C_i). Attenuating the rate of photosynthesis by lowering the C_i at a given temperature and photon flux density increased the concentration of high-energy adenylate phosphate bonds (adenylate energy charge) in the cell by restricting ATP consumption (A.M. Gilmore, O. Björkman 1994, Planta 192, 526–536). In this study we show that decreases in photosynthesis and increases in the adenylate energy charge at steady state were both correlated with decreases in PSII photo-chemical efficiency as determined by chlorophyll fluorescence analysis. Attenuating photosynthesis by decreasing C_i also stimulated violaxanthin-de-epoxidation-dependent nonradiative dissipation (NRD) of excess energy in PSII, measured by nonphotochemical fluorescence quenching. However, high NRD levels, which indicate a large trans-thylakoid proton gradient, were not dependent on a high adenylate energy charge, especially at low temperatures. Moreover, dithiothreitol at concentrations sufficient to fully inhibit violaxanthin de-epoxidation and strongly inhibit NRD, affected neither the increased adenylate energy charge nor the decreased PSII photo-chemical efficiency that result from inhibiting photosynthesis. The build-up of a high adenylate energy charge in the light that took place at low C_i and low temperatures was accompanied by a slowing of the relaxation of non-photochemical fluorescence quenching after darkening. This slowly relaxing component of nonphotochemical quenching was also correlated with a sustained high adenylate energy charge in the dark. These results indicate that hydrolysis of ATP that accumulated in the light may acidify the lumen and thus sustain the level of NRD for extended periods after darkening the leaf. Hence, sustained nonphotochemical quenching often observed in leaves subjected to stress, rather than being indicative of photoinhibitory damage, apparently reflects the continued operation of NRD, a photoprotective process.Abbreviations A antheraxanthin - adenylate kinase (myokinase), ATP:AMPphosphotransferase - C_i intercellular CO₂ concentration - DPS de-epoxidation state of violaxanthin, ([Z+A]/[V+A+Z]) - DTT dithiothreitol - pH trans-thylakoid proton gradient - [2ATP+ADP] - F steady-state fluorescence in the presence of NRD - F_M maximal fluorescence in the absence of NRD - F_M maximal fluorescence in the presence of NRD - NRD nonradiative energy dissipation - PET photosynthetic electron transport rate - PFD photon flux density - _PSII photon yield of PSII photochemistry at the actual reduction state in the light or dark - Q_A the primary electron acceptor of PSII - [ATP+ADP+AMP] - SV_N Stern-Volmer nonphotochemical quenching - V violaxanthin - Z zeaxanthin We thank Connie Shih for skillful assistance in growing plants and for conducting HPLC analyses. A Carnegie Institution Fellowship to A.G. is also gratefully acknowledged.     

Winter behaviour of juvenile Atlantic salmon Salmo salar L. in experimental stream channels: effect of substratum size and full ice cover on spatial distribution and activity pattern

Activity and choice of areas offering different cover (substratum or surface ice) for juvenile Atlantic salmon Salmo salar were studied in experimental stream channels during winter. Channels were completely ice covered between December and March. During this period, the ice thickness increased from 50 to 300 mm after which 50% of the ice was experimentally removed and followed by c. 2·5-fold increase in discharge to simulate the effects of spring flood. Large substrata provided preferred habitats but areas with small substratum sizes were also used when full surface ice provided above-stream cover and the stream discharge was relatively low. The fish remained nocturnal throughout the study but the level of day activity significantly increased as the surface ice became thicker. Maximum movement distance during a 24 h period and homing-at-dawn behaviour remained at a constant level throughout the main winter, but significantly changed during the simulated spring flood (mean ± s . e . maximum extent of movements within 24 h increased from 1·1 ± 0·1 to 3·0 ± 0·5 m; homing behaviour decreased from the highest level of 89·3 to 34·6% during spring flood). Overwinter survival was high (92·9%). Relative mass increase during the study ranged from –8·3 to 28·5%, and 84% of the juvenile Atlantic salmon gained mass. The highest rates of mass increase were associated with frequent movements between areas of different substratum size. The results indicate that during winter: (1) Atlantic salmon parr preferred large substratum cover compared with surface ice cover at the fish densities studied here, (2) juvenile Atlantic salmon were predominantly nocturnal but diurnal activity increased as surface ice became thicker and (3) increase in water discharge during spring altered the behaviour of juvenile Atlantic salmon and may have caused additional habitat shifts.     

Liver metabolism in cold hypoxia: a comparison of energy metabolism and glycolysis in cold-sensitive and cold-resistant mammals

The effects of cold hypoxia were examined during a time-course at 2 °C on levels of glycolytic metabolites: glycogen, glucose, glucose-1-phosphate, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-bisphosphate, phosphoenolpyruvate, pyruvate, lactate and energetics (ATP, ADP, AMP) of livers from rats and columbian ground squirrels. Responses of adenylate pools reflected the energy imbalance created during cold hypoxia in both rat and ground squirrel liver within minutes of organ isolation. In rat, ATP levels and energy charge values for freshly isolated livers were 2.54 mol·g^-1 and 0.70, respectively. Within 5 min of cold hypoxia, ATP levels had dropped well below control values and by 8 h storage, ATP, AMP, and energy charge values were 0.21 mol·g^-1, 2.01 mol·g^-1, and 0.17, respectively. In columbian ground squirrels the patterns of rapid ATP depletion and AMP accumulation were similar to those found in rat. In rat liver, enzymatic regulatory control of glycolysis appeared to be extremely sensitive to the decline in cellular energy levels. After 8 h cold hypoxia levels of fructose-6-phosphate decreased and fructose-1,6-bisphosphate increased, thus reflecting an activation of glycolysis at the regulatory step catalysed by phospho-fructokinase fructose-1,6-bisphosphatase. Despite an initial increase in flux through glycolysis over the first 2 min (lactate levels increased 3.7 mol·g^-1), further flux through the pathway was not permitted even though glycolysis was activated at the phosphofructokinase/fructose-1,6-bisphosphatase locus at 8 h, since supplies of phosphorylated substrate glucose-1-phosphate or glucose-6-phosphate remained low throughout the duration of the 24-h period. Conversely, livers of Columbian ground squirrels exhibited no activation or inactivation of two key glycolytic regulatory loci, phosphofructokinase/fructose-1,6-bisphosphatase and pyruvate kinase/phosphoenolpyruvate carboxykinase and pyruvate carboxylase. Although previous studies have shown similar allosteric sensitivities to adenylates to rat liver phospho-fructokinase, there was no evidence of an activation of the pathway as a result of decreasing high energy adenylate, ATP or increasing AMP levels. The lack of any apparent regulatory control of glycosis during cold hypoxia may be related to hibernator-specific metabolic adaptations that are key to the survival of hypothermia during natural bouts of hibernation.Abbreviations DHAP dihydroxyacetonephosphate - EC energy charge - F1,6P₂ fructose-1,6-bisphosphate - F2,6P₂ fructose-2,6-bisphosphate - F6P fructose-6-phosphate - FBP fructose-1,6-bisphosphatase - G1P glucose-1-phosphate - G6P glucose-6-phosphate - GAP glyceraldehyde-3-phosphate - GAPDH glyceraldehyde-3-phosphate dehydrogenase - L/R lactobionate/raffinose-based solution - MR metabolic rate - PDH pyruvate dehydrogenase - PEP phosphoenolpyruvate - PEPCK & PC phosphoenolpyruvate carboxykinase and pyruvate carboxylase - PFK phosphofructokinase; PK, pyruvate kinase - Q ₁₀ the effect of a 10 °C drop in temperature on reaction rates (generally, Q ₁₀=2–3) - TA total adenylates - UW solution University of Wisconsin solution (L/R-based)     

Glucoamylase production in continuous cultures of Aspergillus niger with special emphasis on growth parameters

Maltose-limited continuous culture of Aspergillus niger was carried out with potassium nitrate to investigate growth and glucoamylase formation characteristics. Glucoamylase production was dependent on the specific growth rate. The maximal amount of glucoamylase (units/l and U/g dry weight) was obtained at =0.08h–1, and the maximum specific rate of production (units/g/dry weight per hour) was at =0.2h–1. The maintenance coefficients (ms and mATP) were higher than for some other fungi. Maximal growth yields on substrate, oxygen and ATP (Yxsm, YxO2m and Yxam) were very efficient (high) and the value of Yxam, which cannot exceed the theoretical maximal value, is obtained when a P/O ratio of 1:1 is assumed. This indicates that biomass formation is energetically inexpensive and most of the expended energy has to be invested in the process of glucoamylase excretion.     

The Production of a Yeast Killer Factor in the Chemostat and the Effects of Killer Yeasts in Mixed Continuous Culture with a Sensitive Strain

In batch culture in a complex medium the killer yeasts NCYC 738 and NCYC 235 gave maximal killer activity when grown in the pH ranges 4·2–4·4 and 4·6–4·8 respectively. Incubation of culture filtrates of NCYC 738 for 10 h at 25 °C or 2 h at 29 °C resulted in a 50% reduction in activity. The addition of bovine serum albumin or gelatine to a complex medium stabilized killer activity. In a defined medium the addition of yeast extract stimulated the production of killer activity. When killer yeast NCYC 738 was grown in a chemostat, killer activity was influenced by temperature, pH and the rate at which the culture was stirred. The production of killer activity was growth-linked and increased as dilution rate was raised to a maximum of 0·15 h"1. Steady state continuous cultures of the sensitive strain, NCYC 1006, were contaminated deliberately with either killer or killer-cured strains. During the first 30 h cultivation, the cell concentration of both strains increased. Subsequently the sensitive strain was displaced from the culture. When killer-cured NCYC 738 was added, the rate of displacement was proportional to the culture temperature. However, with killer NCYC 738 increase of temperature reduced the rate of displacement. When killer NCYC 235 was employed, a lowering of pH decreased the rate of displacement but had no effect when killer-cured NCYC 235 was used.