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Comparison of operating strategies for increased biogas production from thin stillage.
Moestedt, J, Nordell, E, Schnürer, A
Journal of biotechnology. 2014;:22-30
Abstract
The effect of increasing organic loading rate (OLR) and simultaneously decreasing hydraulic retention time (HRT) during anaerobic digestion of sulphur- and nitrogen-rich thin stillage was investigated during operation of continuously stirred tank laboratory reactors at two different temperatures. The operating strategies and substrate were set in order to mimic an existing full-scale commercial biogas plant in Sweden. The reactors were operated for 554-570 days with a substrate mixture of thin stillage and milled grain, resulting in high ammonium concentrations (>4.5gL(-1)). Initially, one reactor was operated at 38°C, as in the full-scale plant, while in the experimental reactor the temperature was raised to 44°C. Both reactors were then subjected to increasing OLR (from 3.2 to 6.0gVSL(-1)d(-1)) and simultaneously decreasing HRT (from 45 to 24 days) to evaluate the effects of these operational strategies on process stability, hydrogen sulphide levels and microbial composition. The results showed that operation at 44°C was the most successful strategy, resulting in up to 22% higher methane yield compared with the mesophilic reactor, despite higher free ammonia concentration. Furthermore, kinetic studies revealed higher biogas production rate at 44°C compared with 38°C, while the level of hydrogen sulphide was not affected. Quantitative PCR analysis of the microbiological population showed that methanogenic archaea and syntrophic acetate-oxidising bacteria had responded to the new process temperature while sulphate-reducing bacteria were only marginally affected by the temperature-change.
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Ammonia control in children ages 2 months through 5 years with urea cycle disorders: comparison of sodium phenylbutyrate and glycerol phenylbutyrate.
Smith, W, Diaz, GA, Lichter-Konecki, U, Berry, SA, Harding, CO, McCandless, SE, LeMons, C, Mauney, J, Dickinson, K, Coakley, DF, et al
The Journal of pediatrics. 2013;(6):1228-34, 1234.e1
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Abstract
OBJECTIVES To examine ammonia levels, pharmacokinetics, and safety of glycerol phenylbutyrate (GPB; also referred to as HPN-100) and sodium phenylbutyrate (NaPBA) in young children with urea cycle disorders (UCDs). STUDY DESIGN This open label switch-over study enrolled patients ages 29 days to under 6 years taking NaPBA. Patients underwent 24-hour blood and urine sampling on NaPBA and again on a phenylbutyric acid-equimolar dose of GPB and completed questionnaires regarding signs and symptoms associated with NaPBA and/or their UCD. RESULTS Fifteen patients (8 argininosuccinate lyase deficiency, 3 argininosuccinic acid synthetase deficiency, 3 ornithine transcarbamylase deficiency, 1 arginase deficiency) ages 2 months through 5 years enrolled in and completed the study. Daily ammonia exposure (24-hour area under the curve) was lower on GPB and met predefined noninferiority criteria (ratio of means 0.79; 95% CI 0.593-1.055; P=.03 Wilcoxon; 0.07 t test). Six patients experienced mild adverse events on GPB; there were no serious adverse events or significant laboratory changes. Liver tests and argininosuccinic acid levels among patients with argininosuccinate lyase deficiency were unchanged or improved on GPB. Eleven of 15 patients reported 35 symptoms on day 1; 23 of these 35 symptoms improved or resolved on GPB. Mean systemic exposure to phenylbutyric acid, phenylacetic acid, and phenylacetylglutamine (PAGN) were similar and phenylacetic acid exposure tended to be higher in the youngest children on both drugs. Urinary PAGN concentration was greater on morning voids and varied less over 24 hours on GPB versus NaPBA. CONCLUSIONS GPB results in more evenly distributed urinary output of PAGN over 24 hours were associated with fewer symptoms and offers ammonia control comparable with that observed with NaPBA in young children with UCDs.
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The ammonia transport, retention and futile cycling problem in cyanobacteria.
Ritchie, RJ
Microbial ecology. 2013;(1):180-96
Abstract
Ammonia is the preferred nitrogen source for many algae including the cyanobacterium Synechococcus elongatis (Synechococcus R-2; PCC 7942). Modelling ammonia uptake by cells is not straightforward because it exists in solution as NH(3) and NH (4) (+) . NH(3) is readily diffusible not only via the lipid bilayer but also through aquaporins and other more specific porins. On the other hand, NH (4) (+) requires cationic transporters to cross a membrane. Significant intracellular ammonia pools (≈1-10 mol m(-3)) are essential for the synthesis of amino acids from ammonia. The most common model envisaged for how cells take up ammonia and use it as a nitrogen source is the "pump-leak model" where uptake occurs through a simple diffusion of NH(3) or through an energy-driven NH (4) (+) pump balancing a leak of NH(3) out of the cell. The flaw in such models is that cells maintain intracellular pools of ammonia much higher than predicted by such models. With caution, [(14)C]-methylamine can be used as an analogue tracer for ammonia and has been used to test various models of ammonia transport and metabolism. In this study, simple "proton trapping" accumulation by the diffusion of uncharged CH(3)NH(2) has been compared to systems where CH(3)NH (3) (+) is taken up through channels, driven by the membrane potential (ΔU (i,o)) or the electrochemical potential for Na(+) (ΔμNa (i,o) (+) ). No model can be reconciled with experimental data unless the permeability of CH(3)NH(2) across the cell membrane is asymmetric: permeability into the cell is very high through gated porins, whereas permeability out of the cell is very low (≈40 nm s(-1)) and independent of the extracellular pH. The best model is a Na (in) (+) /CH(3)NH (3) (+) (in) co-porter driven by ΔμNa (i,o) (+) balancing synthesis of methylglutamine and a slow leak governed by Ficks law, and so there is significant futile cycling of methylamine across the cell membrane to maintain intracellular methylamine pools high enough for fixation by glutamine synthetase. The modified pump-leak model with asymmetric permeability of the uncharged form is a viable model for understanding ammonia uptake and retention in plants, free-living microbes and organisms in symbiotic relationships.
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Experimental evaluation of the nitrite sensitivity coefficient in granular anammox biomass.
Rosenthal, A, Ramalingam, K, Beckmann, K, Deur, A, Fillos, J
Water science and technology : a journal of the International Association on Water Pollution Research. 2013;(9):2103-10
Abstract
Nitrite is widely reported to inhibit anammox activity and growth. One modeling approach for nitrite impairment of anammox growth is the use of a nitrite sensitivity coefficient which increases the endogenous decay coefficient of anammox bacteria proportionally to nitrite concentration. The objective of this study was to measure nitrite concentration profiles within active anammox granules incubated at fixed bulk nitrite concentrations and to compare these with nitrite concentration profiles predicted by a biofilm model that incorporates the nitrite sensitivity coefficient. We developed an apparatus for the repeated measurement of nitrite concentration profiles along the radius of granular anammox biomass over a period of 6 days at fixed bulk nitrite concentrations. Granular anammox biomass was obtained from a two-stage bench-scale partial nitritation/anammox reactor system. There was no apparent effect of nitrite concentration on nitrite utilization kinetics after 6 days at exposures up to 90 mg NO(2)(-)-N/L. These findings suggest that anammox bacteria tolerate extended exposures to elevated nitrite concentrations, and in its present form, the nitrite sensitivity coefficient is not applicable for anammox growth modeling.
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Ammonia control in children with urea cycle disorders (UCDs); phase 2 comparison of sodium phenylbutyrate and glycerol phenylbutyrate.
Lichter-Konecki, U, Diaz, GA, Merritt, JL, Feigenbaum, A, Jomphe, C, Marier, JF, Beliveau, M, Mauney, J, Dickinson, K, Martinez, A, et al
Molecular genetics and metabolism. 2011;(4):323-9
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Abstract
UNLABELLED Twenty four hour ammonia profiles and correlates of drug effect were examined in a phase 2 comparison of sodium phenylbutyrate (NaPBA) and glycerol phenylbutyrate (GPB or HPN-100), an investigational drug being developed for urea cycle disorders (UCDs). STUDY DESIGN Protocol HPN-100-005 involved open label fixed-sequence switch-over from the prescribed NaPBA dose to a PBA-equimolar GPB dose with controlled diet. After 7 days on NaPBA or GPB, subjects underwent 24-hour blood sampling for ammonia and drug metabolite levels as well as measurement of 24-hour urinary phenyacetylglutamine (PAGN). Adverse events (AEs), safety labs and triplicate ECGs were monitored. RESULTS Eleven subjects (9 OTC, 1 ASS, 1 ASL) enrolled and completed the switch-over from NaPBA (mean dose=12.4 g/d or 322 mg/kg/d; range=198-476 mg/kg/d) to GPB (mean dose=10.8 mL or 0.284 mL/kg/d or 313 mg/kg/d; range=192-449 mg/kg/d). Possibly-related AEs were reported in 2 subjects on NaPBA and 4 subjects on GPB. All were mild, except for one moderate AE of vomiting on GPB related to an intercurrent illness. No clinically significant laboratory or ECG changes were observed. Ammonia was lowest after overnight fast, peaked postprandially in the afternoon to early evening and varied widely over 24h with occasional values >100 μmol/L without symptoms. Ammonia values were ~25% lower on GPB vs. NaPBA (p≥0.1 for ITT and p<0.05 for per protocol population). The upper 95% confidence interval for the difference between ammonia on GPB vs. NaPBA in the ITT population (95% CI 0.575, 1.061; p=0.102) was less than the predefined non-inferiority margin of 1.25 and less than 1.0 in the pre-defined per-protocol population (95% CI 0.516, 0.958; p<0.05). No statistically significant differences were observed in plasma phenylacetic acid and PAGN exposure during dosing with GPB vs. NaPBA, and the percentage of orally administered PBA excreted as PAGN (66% for GPB vs. 69% for NaPBA) was very similar. GPB and NaPBA dose correlated best with urinary-PAGN. CONCLUSIONS These findings suggest that GPB is at least equivalent to NaPBA in terms of ammonia control, has potential utility in pediatric UCD patients and that U-PAGN is a clinically useful biomarker for dose selection and monitoring.
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The effect of pre- and probiotics on the colonic ammonia metabolism in humans as measured by lactose-[¹⁵N₂]ureide.
Wutzke, KD, Lotz, M, Zipprich, C
European journal of clinical nutrition. 2010;(10):1215-21
Abstract
BACKGROUND The evaluation of ammonia detoxification by pre- and probiotics by means of colonic lactose-[(15)N(2)]ureide ((15)N-LU) degradation is of great interest both scientifically and in terms of nutrition physiology. OBJECTIVE Pre- and probiotics were supplemented in healthy adults to evaluate the effect of the ammonia metabolism in the human colon by means of (15)N-LU. METHODS A total of 14 participants aged 20-28 years daily received a regular diet either without (no treatment) or with supplementation of 30 g fibre of potatoes (FPs), 30 g wrinkle pea starch (WPS, resistant starch content: 12 and 70%, respectively) and 375 g Lactobacillus acidophilus (LC1) yoghurt, over a 10-day period in a randomised order. After 1 week, 5.7 mg/kg body weight (15)N-LU was administered together with breakfast. A venous blood sample was taken after 6 h. Urine and faeces were collected over a period of 48 and 72 h, respectively. The (15)N abundances were measured by isotope ratio mass spectrometry. RESULTS The mean renal (15)N-excretion differed significantly between the supplementation of FP and no treatment (32.5 versus 46.3%, P=0.034), FP and LC1 (32.5 versus 51.6%, P=0.001), and WPS and LC1 (38.5 versus 51.6%, P=0.048). The mean faecal (15)N-excretion amounted to 42.7% (no treatment), 59.7% (FP), 41.8% (WPS) and 44.0% (LC1). In comparison with no treatment, the urinary (15)NH(3)-enrichment was significantly decreased at 16 h after FP supplementation. CONCLUSION The prebiotic intake of FP and WPS lowered the colonic generation and the renal excretion of toxic (15)NH(3), respectively, when using (15)N-LU as a xenobiotic marker.
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Phase 2 comparison of a novel ammonia scavenging agent with sodium phenylbutyrate in patients with urea cycle disorders: safety, pharmacokinetics and ammonia control.
Lee, B, Rhead, W, Diaz, GA, Scharschmidt, BF, Mian, A, Shchelochkov, O, Marier, JF, Beliveau, M, Mauney, J, Dickinson, K, et al
Molecular genetics and metabolism. 2010;(3):221-8
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UNLABELLED Glycerol phenylbutyrate (glyceryl tri (4-phenylbutyrate)) (GPB) is being studied as an alternative to sodium phenylbutyrate (NaPBA) for the treatment of urea cycle disorders (UCDs). This phase 2 study explored the hypothesis that GPB offers similar safety and ammonia control as NaPBA, which is currently approved as adjunctive therapy in the chronic management of UCDs, and examined correlates of 24-h blood ammonia. METHODS An open-label, fixed sequence switch-over study was conducted in adult UCD patients taking maintenance NaPBA. Blood ammonia and blood and urine metabolites were compared after 7 days (steady state) of TID dosing on either drug, both dosed to deliver the same amount of phenylbutyric acid (PBA). RESULTS Ten subjects completed the study. Adverse events were comparable for the two drugs; 2 subjects experienced hyperammonemic events on NaPBA while none occurred on GPB. Ammonia values on GPB were approximately 30% lower than on NaPBA (time-normalized AUC=26.2 vs. 38.4 micromol/L; Cmax=56.3 vs. 79.1 micromol/L; not statistically significant), and GPB achieved non-inferiority to NaPBA with respect to ammonia (time-normalized AUC) by post hoc analysis. Systemic exposure (AUC(0-24)) to PBA on GPB was 27% lower than on NaPBA (540 vs. 739 microgh/mL), whereas exposure to phenylacetic acid (PAA) (575 vs. 596 microg h/mL) and phenylacetylglutamine (PAGN) (1098 vs. 1133 microg h/mL) were similar. Urinary PAGN excretion accounted for approximately 54% of PBA administered for both NaPBA and GPB; other metabolites accounted for <1%. Intact GPB was generally undetectable in blood and urine. Blood ammonia correlated strongly and inversely with urinary PAGN (r=-0.82; p<0.0001) but weakly or not at all with blood metabolite levels. CONCLUSIONS Safety and ammonia control with GPB appear at least equal to NaPBA. Urinary PAGN, which is stoichiometrically related to nitrogen scavenging, may be a useful biomarker for both dose selection and adjustment for optimal control of venous ammonia.
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Frequent intravenous pulses of growth hormone together with glutamine supplementation in prolonged critical illness after multiple trauma: effects on nitrogen balance, insulin resistance, and substrate oxidation.
Duska, F, Fric, M, Waldauf, P, Pazout, J, Andel, M, Mokrejs, P, Tůma, P, Pachl, J
Critical care medicine. 2008;(6):1707-13
Abstract
OBJECTIVES To estimate the efficacy and metabolic effects of growth hormone substitution as intravenous pulses together with alanyl-glutamine supplementation and tight blood glucose control in prolonged critical illness. DESIGN Prospective double-blind, randomized trial with open-label control arm. SETTING Intensive care unit of tertiary level hospital. PATIENTS Thirty multiple trauma patients (median Injury Severity Score 34). INTERVENTIONS Patients were randomized, at day 4 after trauma, to receive intravenous alanyl-glutamine supplementation (0.3 g/kg x day(-1) from day 4 until day 17) and intravenous growth hormone (administered days 7-17, full dose 50 microg/kg x day(-1) from day 10 onward) (group 1, n = 10) or alanyl-glutamine and placebo (group 2, n = 10). Group 3 (n = 10) received isocaloric isonitrogenous nutrition (proteins 1.5 g/kg x day(-1)) without alanyl-glutamine. MEASUREMENTS AND MAIN RESULTS Cumulative nitrogen balance for the whole study period was -97 +/- 38 g of nitrogen for group 1, -193 +/- 50 g of nitrogen for group 2, and -198 +/- 77 g of nitrogen for group 3 (p < .001). This represents a daily saving of 300 g of lean body mass in group 1. Insulin-mediated glucose disposal, during euglycemic clamp, as a measure of insulin sensitivity, significantly worsened between days 4 and 17 in group 1 but improved in groups 2 and 3. Group 1 required significantly more insulin to control blood glucose, resulting in higher insulinemia (approximately 70 mIU in group 1 vs. approximately 25 mIU in groups 2 and 3). Despite this, growth hormone treatment caused an increase in plasma nonesterified fatty acid (approximately 0.5-0.6 mM in group 1 in comparison with approximately 0.2-0.3 mM in groups 2 and 3) but did not influence lipid oxidation. There were no differences in morbidity, mortality, or 6-month outcome among the groups. CONCLUSIONS Treatment with frequent intravenous pulses of low-dose growth hormone together with alanyl-glutamine supplementation improves nitrogen economy in patients with prolonged critical illness after multiple trauma but worsens insulin sensitivity. Tight blood glucose control is possible but requires higher doses of insulin.
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Further studies related to the scale-up of high cell density Escherichia coli fed-batch fermentations: the additional effect of a changing microenvironment when using aqueous ammonia to control pH.
Onyeaka, H, Nienow, AW, Hewitt, CJ
Biotechnology and bioengineering. 2003;(4):474-84
Abstract
In this work, we report on the further development of the scale-down, two-compartment (STR + PFR) experimental simulation model. For the first time, the effect on high cell density Escherichia coli fed-batch fermentations of a changing microenvironment with respect to all three of the major spatial heterogeneities that may be associated with large-scale processing (pH, glucose, and dissolved oxygen concentration) were studied simultaneously. To achieve this, we used traditional microbiological analyses as well as multiparameter flow cytometry to monitor cell physiological response at the individual cell level. It was demonstrated that for E. coli W3110 under such conditions in a 20 m(3) industrial fed-batch fermentation, the biomass yield is lower and final cell viability is higher than those found in the equivalent well-mixed, 5L laboratory scale case. However, by using a combination of the well-mixed 5L stirred tank reactor (STR) with a suitable plug flow reactor (PFR) to mimic the changing microenvironment at the large scale, very similar results to those in the 20 m(3) reactor may be obtained. The similarity is greatest when the PFR is operated with a mean residence time of 50 sec with a low level of dO(2) and a high glucose concentration with either a pH of 7 throughout the two reactors or with pH controlled at 7 in the STR by addition into the PFR where the pH is > 7.