Optimal Nitrogen Concentration Research Articles

Response-surface methodology for optimizing citric acid fermentation by Aspergillus foetidus

Response-surface experiments with the Box-Behnken design were conducted on Aspergillus foetidus CCRC 30206 to determine the optimal concentrations of carbon, nitrogen and phosphorus for citric acid production. Results of six-day fermentations at 30°C showed that the minimal contours of citric acid production under various sucrose concentrations (60–180 g/litre) overlapped at a region where the concentrations of ammonium chloride and potassium dihydrogen phosphate were in the range of 1.5–2.0 and 0.6–1.0 g/litre respectively. Accumulation of citric acid occurred when growth was limited by the supply of either nitrogen or phosphorus. Nitrogen exerted a stronger catabolite repression on citric acid production than phosphorous. The maximal citric acid concentration and specific production rate appeared at the region where the respective concentrations of carbon, nitrogen and phosphorus sources were around 48, 0.50 and 0.35 g/litre. The optimal levels of carbon, nitrogen and phosphorus sources for a 15-day fermentation differed from those of a six-day fermentation.

Controlled mycelial growth for kojic acid production using Ca-alginate-immobilized fungal cells.

Conidia of Aspergillus oryzae were immobilized in Ca-alginate beads and then incubated in a nutrient medium to yield an immobilized biocatalyst producing kojic acid. The immobilized cell cultures produced kojic acid linearly during cultivation. Regardless of the size of the immobilized particles, there existed an optimal nitrogen concentration for the maximum production rate of kojic acid, at which smaller bead sizes resulted in a higher production rate. When the growth of mycelia were confined within the bead surface and segregated from each other by gel material, they produced kojic acid with maximal catalytic activity and exhibited the highest conversion yield of glucose. The extent of mycelial segregation was especially higher in cultures of smaller bead particles, and the depth of mycelial growth was 150 to 250 microns from the gel bead surface in all cultures of different nitrogen concentrations and bead sizes. Therefore, for the maximum expression of catalytic activities of immobilized mycelial cultures, it was found very critical to optimally control the mycelial distribution in gel beads by the culture conditions affecting mycelial growth.

Nutritional requirements and growth characteristics of a biosurfactant-producingRhodococcus bacterium

The nutritional requirements and growth characteristics of a biosurfactant-producingRhodococcus bacterium isolated from Kuwaiti soil were determined. Maximum cell yields (6.6 g/l) and biosurfactant production were achieved with a medium containing 2% (v/v)n-paraffin as a carbon and energy source, 0.2% lactose broth, optimal concentrations of nitrogen (nitrate), phosphorus, iron, magnesium and sodium sources, and minimal concentrations of potassium and trace element sources. The optimal pH was 6.8 for surfactant production and optimal temperature was 37°C. The biosurfactant produced after 16 to 33 h growth in a 7 I fermenter decreased both surface tension and interfacial tension of culture broth to below 27 and 1.8 mN/m, respectively, and was effective at critical micelle dilutions of 10(-3). Data on biosurfactant biosynthesis suggest that the product is produced as a primary metabolite and, therefore, could be produced effectively under continuous fermentation conditions.

Results of a ground-water level and nitrogen fertilizer field experiment with apple trees on a marine clay soil

This paper summarizes and reviews some of the results of a 12-year experiment which was carried out in order to examine drainage requirements of apple trees on a newly reclaimed soil. The experiment involved production of Cox's Orange Pippin and Golden Delicious apples, grafted on M9 rootstock, that were planted on 11 different ground-water regime plots which were split into three nitrogen treatment sub-plots. It was found that there was a distinct variation in amounts of shoot growth, apple production nitrogen mineralization, and fruit quality on account of variations in the ground-water regime. No optimum ground-water regime could be established. This optimum may be quantified by using the capital budgeting decision procedure. The optimum nitrogen concentration in mid-shoot leaves, however, was found to be 2.3 and 2.4 percent of dry matter for Golden Delicious and Cox's Orange Pippin respectively.

Optimum foliar nitrogen concentration in pine and its change with stand age

Levels of nitrogen in foliage associated with optimum growth of pine were determined in two hydroponic experiments in the glasshouse and two forest fertilizer experiments each designed to cover the full response range for Pinusnigra var. maritima (Ait.) Melv. During the years prior to canopy closure optimum nitrogen concentrations declined with the logarithm of tree weight, falling from 3.3% in very young seedlings to 1.5% in forest trees of 2.0–2.5 m in height. After canopy closure the level increased to about 2.0%. At all stages the concentrations associated with maximum height growth were less than those for maximum volume, weight, or diameter increment. The relationships in the forest experiments, which are on sand dunes in the north of Scotland, could be improved by including factors of rainfall during the previous August and September and of temperature in June of the same year, but this did not alter the optima. It is concluded that for diagnostic purposes critical foliar nitrogen levels must be qualified by the age or developmental stage of the trees.

Culture conditions for nicotine production in tobacco tissue culture.

A tobacco callus strain, OMT-53, was selected from many cultures as a desirable strain having high nicotine producing capacity. Several culture conditions were examined, aiming to get higher nicotine production with the callus strain, OMT-53. It was revealed that the nicotine production was remarkably enhanced when the callus tissues were cultured at a limited concentration of α-NAA in culture medium. The optimal concentrations of sucrose and nitrogen in the culture medium were 3 % and 840 mg N/L respectively. Some precursors in nicotine biosynthesis were examined, and only ornithine gave a slightly positive effect at 2x10-4m concentration. Cultures at 25°C produced the highest yield for nicotine. Considerable amounts of nicotine (ca. 20% of total nicotine) were also recognized in the culture medium. Under the best culture condition mentioned above, nicotine production in tobacco callus tissues has been elevated to 2.14% on D.W, basis at 4 weeks’ culture. This value is near to that of the intact tobacco p...

Growth and properties of VPE GaP for green LEDs

The PH3-HCl-Ga-H2 technique for VPE growth of GaP is described. The influence of various growth parameters, including substrate temperature, orientation, and PH3 flow rate on morphology and growth rate are described. For both VPE and LPE nitrogen doping is known to be a major factor in obtaining high green luminescence efficiency. The major emphasis of this paper is an examination of the effect of nitrogen concentration in the range less than 1019 cm−3 (using the Lightowlers correction factor) on the growth process and materials properties, such as defect structure, photoluminescence spectra (at 300 and 77K) and photoluminescence intensity and lifetime. The LED device performance (B/J and efficiency) is used as the final test of material quality. Nitrogen is found to be incorporated far in excess of the solubility limit, and the solid gas distribution coefficient for nitrogen is found to increase rapidly with decreasing temperature below 840°C . The optimum nitrogen concentration for high diode efficacy, photoluminescence intensity, and lifetime is found to be approximately 5 × 1018 cm−3, where diodes fabricated by Zn diffusion into the VPE GaP have efficiencies at a current density of 10 A/cm2 of 0.1%, comparable to the state-of-the-art in the more widely used grown p-n junctions using LPE.

Factors affecting vegetative growth and the production of perithecia in culture by Ophiobolus graminis. I. Variations in media and age of mycelium

Perithecia were readily produced in culture on a suitable solid medium under certain conditions of light and temperature, once vegetative growth was established. Investigations into the carbon and nitrogen requirements for both vegetative growth and fruiting showed that, whereas vegetative growth increased with increasing carbon supplies up to10%, reproduction occurred only within a restricted range of carbon and nitrogen concentrations. No perithecia were produced on a starvation medium. Factors involved in fruiting included concentration of nutrients and the balance between them; both were important. A suitable fruiting medium required a minimum carbon concentration of 3000 p.p.m., supplied as 0.75 % glucose or fructose, and an optimum carbon concentration of 6000 p.p.m. supplied as 1.5 % glucose or fructose. The maximum number of perithecia was produced on a medium containing 1% glucose and 0.2 % asparagine (400 p.p.m. nitrogen), which had a carbonlnitrogen ratio of 11.8. A higher than optimum nitrogen concentration was partially offset by increasing the carbon concentration, that is by keeping the carbonlnitrogen ratio approximately constant. The actual concentrations inhibiting and promoting fruiting of the fungus were influenced by the balance between carbon and nitrogen supplies. High concentrations of carbon and nitrogen increased vegetative growth but decreased the number of perithecia. There was no sudden inhibition of perithecia with increased carbon concentrations, but at 10% glucose (40,000 p.p.m. carbon) vegetative growth and pigmentation were maximal but few or no perithecia developed. No evidence was obtained that perithecial production was influenced by ageing of the mycelium, the presence of staling factors, or exhaustion of food supplies.

Alloying of steels for nitrocementation

1. The principal alloying elements of steel for nitrocementation should be chromium, molybdenum, and boron (microalloying). 2. To increase the nitrocementation temperature without lowering the nitrogen content of the case it is possible to alloy the steel with 0.2% Al. 3. Since MS is lowered by nitrogen, the steel should not be alloyed with nickel, and the amount of manganese must be limited. 4. The carbon concentration of the case after nitrocementation should not exceed 0.8–0.95% (with the optimal nitrogen concentration of 0.2–0.3%), which ensures a negligible amount of residual austenite and high resistance of gear teeth to static bending.

NUTRITION OF THE GREEN ALGA GOLENKINIA

Defined media were established for four strains of Golenkinia. Strains 929 and 930 require thiamine and vitamin B12, strain 931 requires the latter and is stimulated by thiamine; only strain 320 and a mutant of strain 931 are capable of completely autotrophic growth. The optimal nitrogen concentration is 0.025 m except for strain 931 where it is 0.015 m and the requirement may be met by nitrate, ammonium, or urea. Optimal levels of the other components are: 0.0025 m KH2PO4, 0.0005 to 0.001 m MgSO4, and 50 ml of a stock trace‐element solution per liter. Only strain 931 required calcium; however, its addition stimulates the growth of strains 929 and 930. The optimal pH before autoclaving is 6.8. Maximal growth rates of two to three cell doublings per day and yields of 26 to 30 (log2) cells per ml were obtained. These growth data compare favorably with those for other unicellular green algae.