Comparison of carbon storage under aerobic and anoxic conditions

1998 ◽  
Vol 38 (8-9) ◽  
pp. 77-84 ◽  
Author(s):  
M. Majone ◽  
P. Massanisso ◽  
R. Ramadori
Keyword(s):  
Mixed Culture ◽  
External Source ◽  
Hydrolysis Rate ◽  
Minor Effect ◽  
Aerobic Conditions ◽  
Anoxic Conditions ◽  
Rate Limiting Step ◽  
A Minor ◽  
Rate Limiting

In various activated sludge systems, the biomass grows under transient (unbalanced) conditions and the storage response (formation of internal polymers as the fastest adaptation to the changing environment) becomes important. Till now the role of storage on population dynamics has been deeply investigated under anaerobic (EBPR processes) or aerobic (bulking control) conditions. Little attention has been given to processes including anoxic conditions even though in many of them storage phenomena are likely to occur (anoxic selectors, nitrogen removal processes with addition of an external source of readily biodegradable COD or with aerobic contact/anoxic stabilization). For these reasons, the aim of the present work was to investigate storage and succeeding use of stored products under anoxic and mixed (anoxic/aerobic) conditions. Batch experiments have shown that a mixed culture selected under aerobic conditions and intermittent feed (acetate-limited medium), was also able to take up acetate (90–100 mgCOD/gCOD h) and store it as PHB (35–40 mgCOD/gCOD h) under anoxic conditions. After acetate depletion, the stored PHB was used for growth and maintenance. The NUR on acetate in the presence of storage was 20 mgN/gVSS h (which corresponded to a COD removal of 6.9 mgCOD/mgN) while it dropped to 10–3 mgN/gVSS h in the “endogenous phase” when denitrification was on the stored PHB. The presence of aerobic conditions instead of anoxic ones had a major positive effect on the rate and yield of PHB storage while it had only a minor effect on the rate of PHB consumption. The latter observation can be explained by assuming that the hydrolysis of the stored product is the rate limiting step of the “endogenous” metabolism and that the hydrolysis rate is not highly dependent on aerobic-anoxic conditions. Cross-comparison of PHB storage and consumption under aerobic/anoxic conditions made it possible to determine that, in the particular mixed culture under investigation, all aerobic heterotrophs able to store were also able to denitrify.

Anaerobic digestion of solid animal waste in an accumulation system at mesophilic and thermophilic conditions, start up

2003 ◽  
Vol 48 (4) ◽  
pp. 217-220 ◽  
Author(s):  
H.M. El-mashad ◽  
G. Zeeman ◽  
W.K.P. van Loon ◽  
G.P.A. Bot ◽  
G. Lettinga
Keyword(s):  
Anaerobic Digestion ◽  
Minor Effect ◽  
Mixing Conditions ◽  
Rate Limiting Step ◽  
Start Up ◽  
Accumulation System ◽  
Filling Time ◽  
Thermophilic Conditions ◽  
A Minor ◽  
Rate Limiting

The anaerobic digestion of solid animal wastes has been studied in an accumulation system (AC) at a filling time of 60 days followed by about 50 days batch digestion at 40 and 50°C. Poor mixing conditions during anaerobic digestion of solid wastes promote stratification of the substrate and intermediate products along the reactor height. The effect of layers stratification has also been followed in the AC system. The results showed a pronounced stratification of both CODdis and VFA concentrations along the AC system height. The temperature had a minor effect on the methane yield. The results also showed that methanogenesis was rate limiting in the AC system while the hydrolysis was the rate-limiting step during batch digestion.

scholarly journals Removal of Paracetamol from Wastewater by Calcined Gypsum: Adsorption and Kinetics Study

2020 ◽  
Vol 3 (1) ◽  
pp. 11-18
Author(s):  
Hossam Al-Itawi
Keyword(s):  
Aqueous Solutions ◽  
Minor Effect ◽  
Recrystallization Process ◽  
Rate Limiting Step ◽  
Pseudo Second Order ◽  
Calcined Gypsum ◽  
A Minor ◽  
Two Stages ◽  
Rate Limiting ◽  
Best Fit

It has been established that the presence of paracetamol in wastewaters can cause a potential risk to the environment. This work examined the possibility of using calcined gypsum in removing paracetamol from aqueous solutions. At neutral pH conditions, calcined gypsum was successful in removing paracetamol via adsorption, from aqueous solutions with a removal efficiency that ranged between 56.8 to 65.3 % of an initial concentration of 600 ppm. Increased temperature (from 20 to 500C) had a minor effect on the removal % of paracetamol while increasing the initial calcined gypsum dose (from 0.5 gm to 3 gm) and contact time (up to 15 min) increased by the removal % of paracetamol. Thermodynamically, the adsorption of paracetamol by calcined gypsum process was found to be spontaneous and endothermic, and more likely a physical process, while kinetically; the Pseudo-Second order model was found to be the best fit compared to the Elovich model. The removal process mainly consists of two stages, and it could be deduced from the kinetic behavior of paracetamol adsorption that the recrystallization process can be another rate-limiting step in the process.

The effects of tunicamycin, mevinolin and mevalonic acid on HMG-CoA reductase activity and nuclear division in the myxomycete Physarum polycephalum

1989 ◽  
Vol 92 (3) ◽  
pp. 341-344
Author(s):  
W. Engstrom ◽  
O. Larsson ◽  
W. Sachsenmaier
Keyword(s):  
Physarum Polycephalum ◽  
Nuclear Division ◽  
Reductase Activity ◽  
Mevalonic Acid ◽  
Minor Effect ◽  
Hmg Coa Reductase ◽  
Rate Limiting Step ◽  
Coa Reductase ◽  
A Minor ◽  
Rate Limiting

The effects of two inhibitors of 3-hydroxy 3-methyl glutaryl-coenzyme A reductase (tunicamycin and mevinolin) on nuclear division in the myxomycete Physarum polycephalum were examined. Tunicamycin exerted a minor effect on division in synchronized cultures, whereas mevinolin delayed the second, third and fourth nuclear divisions with increasing efficiency. Mevinolin also appeared to be the more potent inhibitor of HMG-CoA reductase, which catalyses the rate-limiting step in the biosynthesis of cholesterol and other isoprene derivatives. These effects of mevinolin could be partially reversed by the addition of mevalonate, suggesting that mevinolin exerts its inhibitory effects on Physarum nuclear division by decreasing the activity of HMG-CoA reductase.

scholarly journals Folding initiation sites and protein folding.

1999 ◽  
Vol 46 (3) ◽  
pp. 487-508 ◽  
Author(s):  
M Dadlez
Keyword(s):  
Protein Folding ◽  
Protein Fragments ◽  
Denatured State ◽  
Local Structures ◽  
Rate Limiting Step ◽  
Structural Preferences ◽  
Low Levels ◽  
Rate Limiting ◽  
Transition State Barrier

The paper discusses the role of local structural preferences of protein segments in the folding of proteins. First a short overview of the local, secondary structures detected in peptides, protein fragments, denatured proteins and early folding intermediates is given. Next the discussion of their role in protein folding is presented based on recent literature and data obtained in our laboratory. In conclusion it is pointed out that, during folding, local structures populated at low levels in denatured state may facilitate the crossing of the folding transition state barrier, and consequently accelerate the rate limiting step in folding. However, the data show that this effect does not follow simple rules.

Role of mature leaves in inhibition of root bud growth inEuphorbia esulaL.

Weed Science ◽  
1999 ◽  
Vol 47 (5) ◽  
pp. 544-550 ◽  
Author(s):  
David P. Horvath
Keyword(s):  
Lateral Roots ◽  
Axillary Buds ◽  
Minor Effect ◽  
Correlative Inhibition ◽  
Auxin Transport Inhibitor ◽  
Naphthylphthalamic Acid ◽  
Bud Growth ◽  
A Minor ◽  
Root Buds

Earlier studies on the source of signals controlling correlative inhibition of root buds (underground adventitious buds located on the lateral roots) inEuphorbia esulaindicated that either growing meristems (apical or axillary buds) or fully expanded leaves could prevent root buds from breaking quiescence. An investigation of the production and transport requirements of the leaf-derived signal is described. As few as three leaves remaining on budless stems greatly reduced the growth of (but not the number of growing) root buds. Also, light and CO2fixation were necessary for the leaf effects on root bud growth, but not necessary for correlative inhibition imposed by growing axillary buds. Treatment of plants with Ametryn induced root bud growth on budless plants but not on plants with intact axillary buds. The polar auxin transport inhibitor N-1-naphthylphthalamic acid prevented transmission or the signal from growing axillary buds, but it had only a minor effect on the transmission of the leaf-derived signal. Treatment of plants with gibberellic acid (GA) induced growth of root buds under otherwise noninducing conditions to some extent in all plants. However, the greatest effects of GA were on plants with intact leaves (meristemless/budless and meristemless). GA had no significant effect on root bud quiescence under conditions that induced root bud growth.

Adenoviral expression of 15-lipoxygenase-1 in rabbit aortic endothelium: role in arachidonic acid-induced relaxation

2007 ◽  
Vol 292 (2) ◽  
pp. H1033-H1041 ◽  
Author(s):  
Nitin T. Aggarwal ◽  
Blythe B. Holmes ◽  
Lijie Cui ◽  
Helena Viita ◽  
Seppo Yla-Herttuala ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Arachidonic Acid ◽  
Rabbit Aorta ◽  
Epoxyeicosatrienoic Acid ◽  
Aortic Endothelial Cells ◽  
Aortic Endothelium ◽  
Rate Limiting Step ◽  
Immunohistochemical Studies ◽  
Rate Limiting

Endothelium-dependent vasorelaxation of the rabbit aorta is mediated by either nitric oxide (NO) or arachidonic acid (AA) metabolites from cyclooxygenase (COX) and 15-lipoxygenase (15-LO) pathways. 15-LO-1 metabolites of AA, 11,12,15-trihydroxyeicosatrienoic acid (THETA), and 15-hydroxy-11,12-epoxyeicosatrienoic acid (HEETA) cause concentration-dependent relaxation. We tested the hypothesis that in the 15-LO pathway of AA metabolism, 15-LO-1 is sufficient and is the rate-limiting step in inducing relaxations in rabbit aorta. Aorta and rabbit aortic endothelial cells were treated with adenoviruses containing human 15-LO-1 cDNA (Ad-15-LO-1) or β-galactosidase (Ad-β-Gal). Ad-15-LO-1-transduction increased the expression of a 75-kDa protein corresponding to 15-LO-1, detected by immunoblotting with an anti-human15-LO-1 antibody, and increased the production of HEETA and THETA from [14C]AA. Immunohistochemical studies on Ad-15-LO-1-transduced rabbit aorta showed the presence of 15-LO-1 in endothelial cells. Ad-15-LO-1-treated aortic rings showed enhanced relaxation to AA (max 31.7 ± 3.2%) compared with Ad-β-Gal-treated (max 12.7 ± 3.2%) or control nontreated rings (max 13.1 ± 1.6%) ( P < 0.01). The relaxations in Ad-15-LO-1-treated aorta were blocked by the 15-LO inhibitor cinnamyl-3,4-dihydroxy-a-cyanocinnamate. Overexpression of 15-LO-1 in the rabbit aortic endothelium is sufficient to increase the production of the vasodilatory HEETA and THETA and enhance the relaxations to AA. This confirms the role of HEETA and THETA as endothelium-derived relaxing factors.

Daily prolactin pulse inhibits the corpus luteum during lactational quiescence in the marsupial, Macropus eugenii

2013 ◽  
Vol 25 (2) ◽  
pp. 456 ◽  
Author(s):  
L. A. Hinds ◽  
C. H. Tyndale-Biscoe
Keyword(s):  
Corpus Luteum ◽  
Tammar Wallaby ◽  
Marked Contrast ◽  
Previous Conclusion ◽  
Macropus Eugenii ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Progesterone Synthesis ◽  
Rate Limiting

The corpus luteum (CL) of the tammar wallaby is inhibited by prolactin during lactation and seasonal quiescence. In seasonal quiescence a daily transient pulse of prolactin (PRL) of less than 2 h duration is sufficient to maintain inhibition. We investigated whether the same inhibition applies in lactation and, if so, how. Our results show that inhibition of the CL during lactation is maintained by a transient pulse of prolactin once a day. They also show that the minimum time without a PRL pulse for the CL to escape inhibition is more than 48 h and less than 72 h. Nevertheless, some animals had a longer refractory period than 72 h, which was reflected in a longer interval to the progesterone peak and birth. These results support the previous conclusion that PRL exercises its effect on a rate-limiting step in progesterone synthesis and secretion rate from the CL, which precedes any increase in its mass. Therefore, we conclude that the role of PRL is to act as a luteostatic agent, an effect that is in marked contrast to its luteotrophic effect in many eutherian species, including rodents.

scholarly journals Syntaxin-6 SNARE Involvement in Secretory and Endocytic Pathways of Cultured Pancreatic β-Cells

2004 ◽  
Vol 15 (4) ◽  
pp. 1690-1701 ◽  
Author(s):  
Regina Kuliawat ◽  
Elena Kalinina ◽  
Jason Bock ◽  
Lloyd Fricker ◽  
Timothy E. McGraw ◽  
...  
Keyword(s):  
Secretory Granules ◽  
Expression System ◽  
Secretory Cells ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Rate Limiting Step ◽  
Protein Receptor ◽  
Golgi Network ◽  
Rate Limiting

In pancreatic β-cells, the syntaxin 6 (Syn6) soluble N-ethylmaleimide-sensitive factor attachment protein receptor is distributed in the trans-Golgi network (TGN) (with spillover into immature secretory granules) and endosomes. A possible Syn6 requirement has been suggested in secretory granule biogenesis, but the role of Syn6 in live regulated secretory cells remains unexplored. We have created an ecdysone-inducible gene expression system in the INS-1 β-cell line and find that induced expression of a membrane-anchorless, cytosolic Syn6 (called Syn6t), but not full-length Syn6, causes a prominent defect in endosomal delivery to lysosomes, and the TGN, in these cells. The defect occurs downstream of the endosomal branchpoint involved in transferrin recycling, and upstream of the steady-state distribution of mannose 6-phosphate receptors. By contrast, neither acquisition of stimulus competence nor the ultimate size of β-granules is affected. Biosynthetic effects of dominant-interfering Syn6 seem limited to slowed intragranular processing to insulin (achieving normal levels within 2 h) and minor perturbation of sorting of newly synthesized lysosomal proenzymes. We conclude that expression of the Syn6t mutant slows a rate-limiting step in endosomal maturation but provides only modest and potentially indirect interference with regulated and constitutive secretory pathways, and in TGN sorting of lysosomal enzymes.

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