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PubMed2002

Removal of natural organic matter by ion exchange.

Ion exchange is an effective method for removing humic substances from drinking water supplies. We have explored a range of anion exchangers for removal of natural organic matter (NOM), both as isolated from surface waters and after fractionation into four fractions based on hydrophobic and hydrophilic properties. Resins of open structure and high water content are confirmed as the better performers, being very efficient at removal of any charged material, especially that of smaller molecular size. Quaternary ammonium resins containing polar groups are especially effective. The presence of a neighbouring OH group close to the quaternary nitrogen, heteroatoms in the bridge between the exchange site and the polymer backbone, a secondary amino group as the exchange site, or a low ratio of carbon to quaternary nitrogen is beneficial. A suitable balance of polar and non-polar regions in the resin structure appears to be required. Weakly basic amino groups may have a greater affinity for hydrophilic counter ions than quaternary ammonium groups, but generally there are fewer charged sites in the resin at neutral pH. Nevertheless, weak base resins have NOM uptakes nearly as high as strong base resins of similar water content. Water content was found to be the most important parameter, though the effect was less pronounced for strong base resins. For weak base resins of low charge density a non-electrostatic mechanism involving hydrogen bonding of the undissociated acidic species in the NOM to the unprotonated amino groups on the resins is proposed.

Hydrogen-Ion Concentration↗

PubMed2004

Biomass production of yeast isolate from salad oil manufacturing wastewater.

Conversion of oil-rich salad oil manufacturing wastewater (SOMW) into protein source for animal feed through biomass production of yeast isolate was investigated in this study. Five species of yeasts, including Rhodotorula rubra, Candida tropicalis, C. utilis, C. boidinii, Trichosporon cutaneum, were isolated from SOMW following enrichment culture. Of them, C. utilis was chosen as the sole biomass producer in the study due to its greatest oil uptake rate, 0.96 kg oil kg(-1) biomass d(-1), and highest specific growth rate, 0.25 h(-1). The cells of C. utilis contained 26% protein, 9% crude lipid, 55% carbohydrate and balanced amino acid compositions. The initial N:C ratio in SOMW drastically influenced oil reduction efficiency, biomass production and protein content of C. utilis, and therefore a range between 1:6 and 1:8 was recommended in consideration of these three factors simultaneously.

Amino Acids↗

PubMed2002

Removal of N, P, BOD5, and coliform in pilot-scale constructed wetland systems.

Pilot-scale surface-flow (SF), subsurface-flow (SSF), and floating aquatic plant (FAP) constructed wetland system designs were installed and evaluated to determine the effectiveness of constructed wetlands to treat tertiary effluent wastewater in a Midwestern U.S. climate (central Illinois). Average ammonia-nitrogen (N) concentrations decreased approximately 50% in the SSF system design, suggesting that this design had the highest nitrification rate. Nitrate-N concentrations decreased by over 60% in the FAP system design, possibly due to dissimilatory reduction or plant uptake. Total phosphorus (P) concentration reductions of 25 to 40% were observed in all three system designs. Five-day biochemical oxygen demand (BOD5) and dissolved oxygen (DO) results suggested that biodegradation was highest in the SSF system design and lowest in the FAP system design. Greater than 90% concentration reductions of total coliform and E. coli recovered were also observed following treatment in all three system designs. The FAP system design appeared to yield the highest concentration reduction efficiency for E. coli, possibly due to increased sunlight and related bacteriocidal ultraviolet light exposure. Ongoing experiments will test regularly for a variety of vegetative, water quality, and biological conditions for longer time periods in order to gain a better understanding of the pilot constructed wetland system design kinetics.

Evaluation Study↗

PubMed1998

Effects of concentrations of peptides on microbial metabolism in continuous culture.

Effects of peptide concentrations on microbial metabolism were investigated using a basal diet in which peptides replaced urea as a N source at levels of 0, 10, 20, and 30% of total N. The basal diet contained 17.8% CP and 46% nonstructural carbohydrates. Each diet was provided to continuous cultures of rumen contents operating at liquid and solids flow rates of 12 and 4.5%/h, respectively. Production of microbial CP and digestion of DM and protein were affected quadratically by peptide addition, with the highest values for each variable on the diet containing 10% peptides. Fiber digestion decreased linearly with peptide addition. The depressed fiber digestion and microbial CP production at peptide concentrations > 10% seemed related to a linear decrease in ammonia concentration in the fermenters as peptide levels increased. Peptide-amino acid N recovered in the supernatant fluid did not increase with increasing peptides, because peptide uptake by the microbes increased as peptide concentrations increased. Even though the efficiency of conversion of peptide N to microbial CP increased with increasing peptides, there was no change in grams of microbial N produced per kilogram of OMD. We suggest that in diets high in nonstructural carbohydrates, excessive peptides can depress protein digestion and ammonia concentrations, resulting in decreased OMD, fiber digestion, and total microbial CP production.

Amino Acids↗

PubMed2004

The davDT operon of Pseudomonas putida, involved in lysine catabolism, is induced in response to the pathway intermediate delta-aminovaleric acid.

Pseudomonas putida KT2440 is a soil microorganism that attaches to seeds and efficiently colonizes the plant's rhizosphere. Lysine is one of the major compounds in root exudates, and P. putida KT2440 uses this amino acid as a source of carbon, nitrogen, and energy. Lysine is channeled to delta-aminovaleric acid and then further degraded to glutaric acid via the action of the davDT gene products. We show that the davDT genes form an operon transcribed from a single sigma70-dependent promoter. The relatively high level of basal expression from the davD promoter increased about fourfold in response to the addition of exogenous lysine to the culture medium. However, the true inducer of this operon seems to be delta-aminovaleric acid because in a mutant unable to metabolize lysine to delta-aminovaleric acid, this compound, but not lysine, acted as an effector. Effective induction of the P. putida P(davD) promoter by exogenously added lysine requires efficient uptake of this amino acid, which seems to proceed by at least two uptake systems for basic amino acids that belong to the superfamily of ABC transporters. Mutants in these ABC uptake systems retained basal expression from the davD promoter but exhibited lower induction levels in response to exogenous lysine than the wild-type strain.

Amino Acids, Neutral↗

PubMed1976

[Studies on methionine metabolism. 1. Studies on general metabolism and body composition].

19-day trials were carried out with diets containing varying amounts of methionine (0.3%), 0.8%, 1.3%, 2.0%, 2.8%, 5.3%). Diets containing 0.8% methionine were found to have the most favourable effect. Increasing methionine supplementation gradually decreased the food consumption, the daily weight gains and the efficiency of food utilization of the animals. Data on weight gains and food utilization in the "pair-fed" groups were more favourable. A stepwise decline was observed with regard to the absolute quantity of nitrogen retained (mg) as well as with regard to the quotient (%) of the amount of N retained to the amount of N utilized. Studies on the body composition of the animals showed that all those animals consuming large quantities of methionine did not synthesize protein while the process of protein synthesis in "pair fed" animals was found to be reduced, but still positive. These results suggest the occurrence of disorders in the protein metabolism arising in the organism of the animals in response to the uptake of large amounts of methionine. The relatively low fat content of the bodies of animals receiving excessive amounts of methionine, the increasing losses of fat during the trial as well as decreases in the RQ values indicated an increased rate of fat utilization in these animals. The relative water content of the body of animals receiving excessive quantities of methionine was higher, but, nevertheless, the massive weight decreases were, in the first instance, due to losses of water. Loss of water and fat as well as relative hydratation are characteristic symptoms of malnutrition. These were, to some extent, also observed in "pair fed" animals.

Animal Nutritional Physiological Phenomena↗

PubMed2004

[Effect of reduced N application on N utilization and balance in winter wheat-summer maize cropping system].

A field trial on a calcareous soil was carried out at an experimental station of China Agricultural University with the objective of assessing the effect of reduced nitrogen application on N utilization and N balance in a winter wheat-summer maize cropping system. Before this study, the trial has been conducted for one rotation cycle of wheat and maize with four-fixed N rates of 0, 120, 240 and 360 N kg.hm-2 per crop. In this study, each plot was divided into two sub-plots for two N application rates: normal N application(original rate) and reduced N application(reduced rate). The results showed that the grain yields of wheat and maize reached the platform at N rate of 120 kg.hm-2(N120), and then almost kept the same level regardless of the further increase of N rate(N240 and N360). The N uptake by wheat and maize followed the similar tendency like their yield. The grain yield and N uptake of wheat were not significantly declined with the half reduction of original N rate except the treatment N120. However, the same items in maize significantly declined with the further reduction of N fertilizer to zero. The residual NO3-N(main source of mineral N) in reduced N sub-plots was significantly lower in 0-1 m soil layer, but not different in 1-2 m soil layer compared with those receiving original N rate, indicating that 1-2 m soil NO3-N could hardly be utilized by crops. N balance calculation further showed that the N recovery by crops could be largely raised by the reduction of N fertilizer, while the apparent N loss rate decreased in wheat-maize rotation, respectively. Thus, the reduction of fertilizer N under high N rate can significantly increase N use efficiency and reduce NO3-N accumulation and apparent N loss.

Crops, Agricultural↗

PubMed2001

State of the art for animal wastewater treatment in constructed wetlands.

Although confined animal production generates enormous per-unit-area quantities of waste, wastewater from dairy and swine operations has been successfully treated in constructed wetlands. However, solids removal prior to wetland treatment is essential for long-term functionality. Plants are an integral part of wetlands; cattails and bulrushes are commonly used in constructed wetlands for nutrient uptake, surface area, and oxygen transport to sediment. Improved oxidation and nitrification may also be obtained by the use of the open water of marsh-pond-marsh designed wetlands. Wetlands normally have sufficient denitrifying population to produce enzymes, carbon to provide microbial energy, and anaerobic conditions to promote denitrification. However, the anaerobic conditions of wetland sediments limit the rate of nitrification. Thus, denitrification of animal wastewaters in wetlands is generally nitrate-limited. Wetlands are also helpful in reducing pathogen microorganisms. On the other hand, phosphorus removal is somewhat limited by the anaerobic conditions of wetlands. Therefore, when very high mass removals of nitrogen and phosphorus are required, pre- or in-wetland procedures that promote oxidation are needed to increase treatment efficiency. Such procedures offer potential for enhanced constructed wetland treatment of animal wastewater.

Animals↗

PubMed1994

Proton-Peptide Co-Transport in Broad Bean Leaf Tissues.

The transport of [14C]glycyl-glycine (Gly-Gly) has been characterized in leaf discs from mature exporting leaves of broad bean (Vicia faba L.). In terms of glycine (Gly) equivalents, the rate of transport of Gly-Gly was similar to that of Gly uptake. Uptake of Gly-Gly was localized mainly in the mesophyll cells, with little accumulation in the veins. It was optimal at pH 6.0, sensitive to thiol reagents and metabolic inhibitors, and exhibited a single saturable phase with an apparent Michaelis constant of 16 mM. Gly-Gly did not inhibit the uptake of labeled Gly. Addition of Gly-Gly induced a concentration-dependent pH rise in the medium, showing that peptide uptake is mediated with proton co-transport. Gly-Gly also induced a concentration-dependent transmembrane depolarization of mesophyll cells with an apparent Michaelis constant of 15 mM. This depolarization was followed by a transient hyperpolarization. When present at a 10-fold excess, various peptides and tripeptides were able to inhibit Gly-Gly uptake with the following decreasing order of efficiency: Gly-Gly-Gly = leucine-Gly > Gly-tyrosine > Gly-glutamine = Gly-glutamic acid > Gly-phenylalanine > Gly-threonine > Gly-aspartic acid = Gly-asparagine = aspartic acid-Gly. Gly inhibited the uptake of Gly-Gly only slightly, whereas tetraGly and the tripeptide glutathione were not inhibitory. The dipeptides inhibiting Gly-Gly uptake also induced changes in the transmembrane potential difference of mesophyll cells and were able to affect in a complex way the response normally induced by Gly-Gly. Altogether, the data demonstrate the existence of a low-affinity, broad-specificity H+/peptide co-transporter at the plasma membrane of mesophyll cells. The physiological importance of this transporter for the exchange of nitrogenous compounds in mature leaves remains to be determined, as do the details of the electrophysiological events induced by the dipeptides.

Journal Article↗

PubMed1991

Pollution by animal production in The Netherlands: solutions.

Provided that the application rates of manure do not exceed the crop uptake of nutrients, pollution by animal production is mainly caused by nitrogenous substances. Applying manure outside the growing season causes pollution of groundwater and surface water due to leaching and runoff. In regions with a high livestock density, the evaporation of ammonia has a serious impact on the environment. It contributes to acidification and causes a nutrient imbalance in natural vegetation. The prevention of nutrient losses from manure is unprofitable. The environmental impact is not caused by the individual farmer but is a result of the sum of activities in a region. This means that legislation is necessary to impose limits in order to arrive at production without pollution. Within this framework, the farmer should optimise the utilisation of minerals from manure by more efficient animal nutrition and better handling of the manure. One of the most difficult problems is the prevention of ammonia evaporation. A reduction of these losses generally also has a favourable effect on odour emissions. A new development is the processing of manure surpluses into a dried manure of sufficient quality to compete on the fertiliser market. As is usually the case with pollution control, these measures raise the costs of livestock production.

Air Pollution↗

PubMed2004

99mTc-Tetraethylenepentamine-Folate--a new 99mTc-based folate derivative for the detection of folate receptor positive tumors: synthesis and biological evaluation.

A new radiopharmaceutical, 99mTc-Tetraethylenepentamine(TEPA)-Folate has been synthesized introducing TEPA to the gamma-carboxyl group of folic acid. This binds with 99mTc high efficiency at ambient temperature. The resulting 99mTc-N5-Folate is stable under physiological conditions at least for 24 h after radiocomplexation. TEPA is a known open chain pentamine (N5) chelator, its four-nitrogen act as the binding site for 99mTc. The folate membrane receptor binding of the 99mTc-TEPA-Folate by established human tumor cell lines (KB, U-87MG and MDA-MB-468) showed Kd in microM range in normal DMEM (10% serum, 10 microM folic acid). The blood kinetic studies showed more than 70% clearance within five minutes from the circulation. The KB cell line tumors in mice were readily identifiable in the gamma images and revealed major accumulation of radiotracer in liver, kidneys and intestines. High tumor uptake was shown in the tumor bearing nude mice; tumorto-blood ratios reached 2.68 +/- 0.52 and 5.5 +/- 1.47 at 1 and 4 h after post injection respectively. Surviving fractions as obtained in clonogenic assay were 1.02 +/- 0.07 and 1.03 +/- 0.05 in U-87MG and MDA-MB-468 cell lines respectively. The 99mTc-N5-Folate conjugate have promising utility as a receptor specific radiopharmaceutical for imaging neoplastic tissues known to over express folate-binding protein.

Animals↗

PubMed1993

Microscale characterization of dissolved organic matter production and uptake in marine microbial mat communities.

Intertidal marine microbial mats exhibited biologically mediated uptake of low molecular weight dissolved organic matter (DOM), including D-glucose, acetate, and an L-amino acid mixture at trace concentrations. Uptake of all compounds occurred in darkness, but was frequently enhanced under natural illumination. The photosystem 2 inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) generally failed to inhibit light-stimulated DOM uptake. Occasionally, light plus DCMU-amended treatments led to uptake rates higher than light-incubated samples, possibly due to phototrophic bacteria present in subsurface anoxic layers. Uptake was similar with either 3H- or 14C-labeled substrates, indicating that recycling of labeled CO2 via photosynthetic fixation was not interfering with measurements of light-stimulated DOM uptake. Microautoradiographs showed a variety of pigmented and nonpigmented bacteria and, to a lesser extent, cyanobacteria and eucaryotic microalgae involved in light-mediated DOM uptake. Light-stimulated DOM uptake was often observed in bacteria associated with sheaths and mucilage surrounding filamentous cyanobacteria, revealing a close association of organisms taking up DOM with photoautotrophic members of the mat community. The capacity for dark- and light-mediated heterotrophy, coupled to efficient retention of fixed carbon in the mat community, may help optimize net production and accretion of mats, even in oligotrophic waters.

Amino Acids↗

PubMed2006

A family of oligopeptide transporters is required for growth of Candida albicans on proteins.

The human fungal pathogen Candida albicans can use proteins as the sole source of nitrogen for growth. The secretion of aspartic proteinases, which have been shown to contribute to virulence of C. albicans, allows the fungus to digest host proteins to produce peptides that must be taken up into the cell by specific transporters. To understand in more detail how C. albicans utilizes proteins as a nitrogen source, we undertook a comprehensive analysis of oligopeptide transporters encoded in the C. albicans genome. We identified eight OPT genes encoding putative oligopeptide transporters, almost all of which are represented by polymorphic alleles in strain SC5314. Expression of these genes was differentially induced when C. albicans was grown in YCB-BSA medium, which contains bovine serum albumin as the sole nitrogen source. Whereas deletion of single OPT genes in strain SC5314 did not affect its ability to utilize proteins as a nitrogen source, opt123delta triple mutants had a severe growth defect in YCB-BSA which was rescued by reintroduction of a single copy of OPT1, OPT2 or OPT3. In addition, forced expression of OPT4 or OPT5 under control of the ADH1 promoter also restored growth of an opt123delta mutant, demonstrating that at least OPT1-OPT5 encode functional peptide transporters. The various oligopeptide transporters differ in their substrate preferences, as shown by the ability of strains expressing specific OPT genes to grow on peptides of defined length and sequence. We present evidence that in addition to the known role of oligopeptide transporters in the uptake of tetra- and pentapeptides these proteins can also transport longer peptides up to at least eight amino acids in length, ensuring an efficient utilization of the various peptides produced via endoproteolytic digestion of proteins by the secreted aspartic proteinases. As even transporters encoded by polymorphic alleles of a single gene exhibited differences in their efficiency to take up specific peptides, the oligopeptide transporters represent an example for how the evolution of gene families containing differentially expressed and functionally optimized members increases the nutritional versatility and, presumably, the adaptation of C. albicans to different host niches.

Biological Transport↗

PubMed1995

Effects of resistance training and dietary protein intake on protein metabolism in older adults.

Nitrogen (N) balance, fed-state leucine kinetics, and urinary 3-methylhistidine (3-MeH) excretion were examined in 12 men and women, aged 56-80 yr, before and during 12 wk of resistance training (RT). Subjects were randomized to groups that consumed diets providing either 0.80 +/- 0.02 g protein.kg-1.day-1 (lower protein, LP) or 1.62 +/- 0.02 g protein.kg-1.day-1 (higher protein, HP). At baseline, mean N balance was negative for LP (-4.6 +/- 3.4 mg N.kg-1.day-1) and positive for HP (13.6 +/- 1.0 mg N.kg-1.day-1). N retention increased similarly in LP and HP at the 11th wk of RT by 12.8 and 12.7 mg N.kg-1.day-1, respectively. Thus LP had an increased efficiency of N retention. LP had decreased leucine flux (P < 0.001), oxidation (P < 0.001), and uptake for protein synthesis (P < 0.02), relative to HP, both at baseline and after RT. Leucine flux increased with RT in both diet groups (P < 0.05) and was associated mainly with an increase in protein synthesis in LP (91% of change in flux) and an increase in oxidation in HP (72% of change in flux; RT-diet interaction, P < 0.05). RT increased actomyosin protein breakdown (increased 3-MeH-to-creatinine ratio, P < 0.01). Diet-related differences in protein metabolism did not influence body composition changes with RT. These data show that the efficiency of N retention and protein utilization during RT is higher in older subjects who consume 0.8 vs. 1.6 g protein.kg-1.day-1 dietary protein.

Aged↗

PubMed1981

CO(2) Exchange and Dinitrogen Fixation of Subterranean Clover in Response to Light Level.

Small swards of nodulated subterranean clover plants were grown in pots to a common dry weight under controlled conditions. The rooting medium was a porous calcined clay. All mineral nutrients except nitrogen were supplied daily in solution. Pots then were placed in an assimilation chamber for 3 days for the measurement of net CO(2) exchange at light levels ranging from 0.1 to 2.0 millieinsteins per square meter per second. N(2)-fixation (acetylene reduction) of each pot was measured subsequently. H(2)-evolution and N(2)-fixation were measured for similar treatments in separate experiments using smaller pots.CO(2)-assimilation rate and N(2)-fixation rate responded similarly to increase in light level so that N(2)-fixation was found to be a linear function of both the daily (12-hour) net CO(2)-uptake and of the growth rate (24 hours) of the sward over a wide range. N-concentration of the plants was independent of the light level under which they were grown. The rate of N(2)-fixation per unit weight of nodule varied over a wide range depending on the number of nodules present and on the demand for nitrogen as determined by the growth rate of the sward. It is concluded that the amount of assimilate available to the whole plant is a major factor determining the rate of N(2)-fixation by the whole plant, although it may not be important in determining specific rates of nodule activity. N(2)-fixation per unit weight of nodule therefore is considered to have limited utility for comparative purposes.The relative efficiency of N(2)-fixation was found to be about 0.7 and independent of the level of the incident light after growth at two contrasting light levels, 0.4 and 1.0 millieinsteins per square meter per second.

Journal Article↗

PubMed2002

Effluent polishing via pasture irrigation in Harare, Zimbabwe.

Harare, the capital city of Zimbabwe, is experiencing eutrophication-related problems in its downstream potable water supply source of Lake Chivero. This is due mainly to poorly treated sewage effluent encroachment into upstream rivers, especially Marimba River. Crowborough Pasture Irrigation farm is in the Marimba sub-catchment area and has 305 hectares of irrigated pastures. Studies started from July 2000 to August 2001 focusing on the pasture's management of nutrients (nitrogen and phosphorus) and their impact on Marimba River. Water and nutrient balances were developed. Reduction efficiencies for this pasture were found to be 84% for TN and 54% for TP. Both the Crowborough sewage treatment works and the pastures are overloaded. It was therefore concluded that the current system is no longer sustainable economically and environmentally. From the results of our study we recommend that additional treatment units be constructed at Crowborough sewage treatment works to meet current flows. Moreover, pasture management needs substantial improvement. Nutrient recovery should be enhanced by regular harvesting of pasture grass and converting cow dung into an economic commodity as manure for neighbouring residents. Maize cultivation is also recommended to replace pasture grass as it is a local staple crop and has high nutrient uptake rates.

Agriculture↗

PubMed1994

Rapid free radical reduction in the perfused rat liver.

The reduction of nitroxide free radicals was investigated in detail by Electron Paramagnetic Resonance (EPR) spectroscopy in perfused liver. The nitroxide free radical was rapidly reduced to the corresponding hydroxylamine more efficiently at the lower flow rate of 8 [ml/min], while at higher flow rates, the amount of reduced nitroxide showed a significant decrease. Oxidation of hydroxylamine using hydrogen peroxide provided dynamic information concerning the reduction of the free radical within the liver. In addition, liver homogenates were also investigated to determine the level of nitroxide uptake. The results suggested that a portion of the infused nitroxide was taken up by the liver and cleared from the circulation.

Animals↗

PubMed1990

Argon laser phototherapy of human malignancies using rhodamine-123 as a new laser dye: the intracellular role of oxygen.

Recent studies demonstrated that the cationic, mitochondrial-specific dye Rhodamine-123 (Rh-123), is an efficient tumor photosensitizer for Argon laser treatment of human cancer cells both in vitro and in tumors grown as xenografts in athymic mice. To demonstrate the photodynamic mechanism of action of this reaction, the intracellular role of oxygen and temperature changes in treated cells have to be defined. In the current study, a large panel of human tumor cell lines of diverse histologic origin were tested for in vitro sensitivity to Rh-123 and the Argon laser (514.5 nm) in oxygen, deuterium oxide (D2O), and nitrogen (N2) environment. Tumor cells in suspension were first sensitized to Rh-123 (1 or 20 micrograms/ml for 1 hour), cooled on ice to 4 degrees C, and then exposed to the Argon laser (delta T = 14 +/- 1 degree C). Cell proliferation measured by [3H]-thymidine uptake 24 hours after sensitization with Rh-123 and laser treatment was significantly decreased in tumor cells kept in oxygen and D2O atmospheres. No decrease in DNA synthesis was seen in Rh-123 and laser treated cells kept in an N2 environment. Control tumor cells treated with Rh-123 or the Argon laser separately did not show any decreased [3H]-thymidine uptake in oxygen, D2O or N2 environment. These results provide evidence of a photodynamic process since Rh-123 sensitization and Argon laser activation occur at nonthermal levels of energy and are oxygen dependent. The high effectiveness of this technique of photodynamic therapy with the Argon laser, and low toxicity of Rh-123 could make its clinical use very attractive for the treatment of superficial malignancies.

Deuterium↗