Inorganic N-source Research Articles

Differential Utilization of Dissolved Organic and Inorganic Nitrogen by Wheat (Triticum Aestivum L.)

A study was conducted under greenhouse conditions on wheat to investigate the utilization of dissolved organic nitrogen (N) in comparison with conventionally applied inorganic N sources (INS). Nitrogen was applied at a rate of 90 kg N ha−1 in an inorganic form, an organic high molecular weight (MW) form (casein, haemoglobin, albumin), and an organic low MW amino acid form (glycine, alanine, valine). Inorganic N sources recorded the maximum response (126% to 150%) in total dry matter (DM) production while dissolved organic nitrogen (DON) sources showed 61% to 116% increase in comparison to the control treatment. Glycine gave the maximum DM production, which was comparable with both INS treatments. In hydroponics, greater utilization occurred and the shoots had a higher N content in comparison to those grown in soil. The concentration of DON and NO3− in soil after wheat harvest was similar in all the treatments.

The lack of a nitrogen source and/or the C/N ratio affects the molecular weight of alginate and its productivity in submerged cultures of Azotobacter vinelandii

The effect of a nitrogen (N) source on growth of the N-fixing bacteria Azotobacter vinelandii was evaluated in terms of the production of alginate and its macromolecular characteristics [mean molecular weight (MMW) and viscosity] in the presence of an organic or inorganic N-source or under N-fixing conditions, in submerged shake flask cultures. The effect of the C/N ratio was also investigated in the best alginate-producing nitrogen sources. The best N-sources were peptone, tryptone, and yeast extract, yielding a maximal final alginate concentration of 4.0 ± 0.4 g/L. Under N-fixing conditions, only 1.7 ± 0.2 g/L alginate was obtained. The highest MMW was obtained in cultures grown with peptone (1,520 ± 110 kDa), and cultures grown with yeast extract, tryptone, ammonium acetate, and ammonium sulfate were not significantly different, showing values between 1,400 and 1,100 kDa. On the other hand, a lower MMW was obtained under N-fixing conditions (625 ± 110 kDa). Higher alginate productivity was obtained using a C/N ratio of 14:1 for the best inorganic N-source, but when using the best organic N-source, no significant differences were observed by increasing the amount of nitrogen at a C/N ratio of 29:1. The lower alginate production under N-fixing conditions, along with the lower MMW, led us to propose that A. vinelandii sacrifices production of the biopolymer by establishing other mechanisms that can protect the polymerase complex—findings that are consistent with the current existing literature.

Oxygen stress in Salvinia natans: Interactive effects of oxygen availability and nitrogen source

The ability of Salvinia natans (L.) All. to tolerate growth in oxic, hypoxic and anoxic nutrient solutions when supplied with either NH 4 + or NO 3 − were studied in the laboratory to test the hypothesis that inorganic N-source affects the response of the plants to O 2 deprivation. The relative growth rate (RGR) was significantly reduced in the anoxic treatment, but in the hypoxic treatment RGR was only slightly affected. The NH 4 + fed plants generally had a higher shoot to root ratio than the NO 3 − fed plants, and highest in the anoxic treatment. Plants had more roots and larger leaves when supplied with NH 4 + as compared with NO 3 −, particularly in the oxic treatment, and root length was most affected by O 2 deprivation for NO 3 − fed plants. Cell walls in the endodermis, the bundle sheath and the cortex adjacent to endodermis developed thickened sclerenchymatous walls when deprived of O 2, and more so in plants supplied with NO 3 −. Plants lost chlorophylls, had lower rates of photosynthetic electron transport (ETR max) and lower quantum yields (Fv/Fm ratios) when grown in anoxic solutions, and the negative effects were mildest for NO 3 − fed plants suggesting that NO 3 − may be used as an alternative e −-acceptor in non-cyclic electron transport in the chloroplasts. Overall S. natans grew best on NH 4 +, but it also grew well on NO 3 −, and the O 2 stress symptoms differed somewhat between NH 4 + fed and NO 3 − fed plants. However, because N-form itself significantly influenced morphology and cell metabolism, it was impossible to conclusively identify the role of N-form for the O 2 stress reactions. S. natans is not well-adapted to grow in O 2 deficient waters and will not tolerate completely anoxic conditions as will prevail in waters receiving high loadings of organic pollutants such as livestock wastewater.

Improvement of erythromycin production by Saccharopolyspora erythraea in molasses based medium through cultivation medium optimization

In the present work, erythromycin production was carried out in submerged culture using Saccharopolyspora erythraea. Different experiments were conducted to optimize the cultivation medium through the change of carbon and nitrogen sources to cheaper one in order to reduce the cost of medium and to utilize sugar cane molasses as one of major sugar industry by-products in Egypt. It was found that the addition of sugar cane molasses a sole carbon source at a concentration of 60 g/l accompanied by corn steep liquor (as organic N-source) in combination with ammonium sulphate (as inorganic N-source) gave the maximal erythromycin production. The antibiotic production in this medium reached about 600 mg/l which is about 33% higher than the value obtained in glucose based medium. On the other hand, the addition of n-propanol in concentration of 1% (v/v) increased the antibiotic production reaching about 720 mg/l after 144 h. Concluding, the new medium formulation based on cheap carbon source, sugar cane molasses, was a good alternative solution for the production of erythromycin economically.

Construction of a microbial consortium used for solid-state fermentation on rice chaff

Trichoderma reesei 3.3711 and Aspergillus niger 3.316 were co-cultured with Saccharomyces cerevisiaes AS2.399 in solid substrate fermentation on rice chaff for its intenerate. Pretreatment of rice chaff was supplemented with appropriate wheat bran, inorganic N-sources and some metal compounds, and fermented at 100% moisture content, pH 5.5 and 30 °C. Under the same fermentation conditions, mixed culture of three microorganisms had higher ratio of cellulose degradation (RCD) than mixed culture of T. reesei 3.3711 and A. niger 3.316, and mixed culture of two microorganisms had higher RCD than single microorganisms of T. reesei 3.3711 and A. niger 3.316, respectively. But the same law was not found in filter paper enzyme activity (FPA). It was found that mixed culture of three microorganisms had 4.82% higher RCD than two strains culture, and two strains culture had 12.68% higher than T. reesei 3.3711 which had 11.14% higher than A. niger 3.316. According to the microbial consortium this article constructed is invaluable for exploiting cellulose resources.

Modelling of environmental impact of different N-sources in soil/atmosphere system

Intensive application of N-fertilizer (inorganic and organic N-sources) may lead to water (nitrate leaching) and air (NO x , NH 3 emission) pollution. Estimation and prediction of environmental hazard connected by N-fertilization requires modelling of N-cycling in agroecosystems. A three-level experimental system was built up for modelling the N-transformation processes running in different spatial and time scale in the soil/plant(biota)/atmosphere system. In 10 years harmonized series of micro-cosmos, meso-cosmos and field experiments using the stable isotopic 15N-tracer technique a solid data basis was collected for mathematical modelling. The three-compartmental mathematical model was based on the principles of the non-equilibrium thermodynamics. The experimental system made possible the quantitative estimation of plant—uptake and NO x-gas losses on a yearly scale. The mobilization/immobilization and nitrification/denitrification processes were described on a shorter-term scale (hours, days). The 20–80% of inorganic N-sources was taken up yearly by plants and NO x -gas losses were in the range of 10–25% of the source-N. The inorganic N-sources were totally depleted from the soil during the 3 years.

Mixed culture solid substrate fermentation of Trichoderma reesei with Aspergillus niger on sugar cane bagasse

Trichoderma reesei LM-UC4, the parent strain, and its hypercellulolytic mutant LM-UC4E1 were co-cultured with Aspergillus niger ATCC 10864 in solid substrate fermentation on alkali-treated sugar cane for cellulolytic enzyme production. Bagasse was supplemented with either soymeal or with ammonium sulfate and urea, and fermented at 80% moisture content and 30°C. Mixed culturing produced better results with the inorganic supplement. The mutant strain was more responsive to mixed culturing than the parent strain when A. niger was the cooperating partner. In a mixed culture of the mutant with inorganic N-source, 10% more biomass, but 63% more cellulase, 85% more endoglucanase and 147% more β-glucosidase was produced than in single culture. Since co-culturing helped enzyme production more than growth, it appeared that synergistic interactions not directly related to growth were responsible for increased enzyme production. Although soymeal supplementation increased biomass production in the same mixed culture by 30%, it did not increase enzyme production. Mixed culturing is thus beneficial for the economic production of cellulases on nutritionally poor agricultural residues, without the need for supplementation with expensive organic supplements.

Nitrogen metabolism inErica and soybean, two species differing by their sensitivity to inorganic N source

Growth of soybean was not altered, whatever the inorganic N-source (NO3, NH4 or a NO3/NH4 mixture); conversely, growth of Erica x darleyensis plants in vitro decreased more in. NH4 medium than in a NO3 medium, compared to a NO3/NH4 medium. The GS/GOGAT pathway (in NH4 medium), the nitrate and nitrite reductase activities (in NO3 medium), as the contents in free nitrogenous forms and total nitrogen (in NO3 and NH4 media) were not more altered in Erica than in soybean, compared to a NO3/NH4 medium. PEPCase activity was the highest in soybean irrespective of the N-treatments; the involvement of PEPCase in N-metabolism could be explained by its function in ionic and osmotic balances rather than its function in supplying carboxylates as acceptors for NH4-assimilation.

Characteristics of pectate lyase formation by Hypomyces solani f. sp. cucurbitae.

Pectate lyase, produced by Hypomyces (Fusarium) solani f. sp. cucurbitae, is considered a normal extracellular enzyme in that most of the enzyme was found in the culture medium during early stages of enzyme production and before extensive lysis. This enzyme was produced during active growth in the presence of citrus pectate but not citrus pectin. Enzyme yield was highest when the initial pH of the medium was between 5.5 and 7.5 and the temperature was between 25 and 29 C. Production of the enzyme was reduced when individual amino acids or inorganic N-sources were substituted for casein hydrolyzates. Glucose repressed enzyme formation when it exceeded 0.025%, while arabinose and xylose had little effect or stimulated greater production at 0.1%. Pectate lyase yield varied considerably, depending on fungus strain and inoculum level used. A delay in enzyme formation was reduced substantially when small amounts of agar were present in the liquid medium or the medium was solidified with agar.