Biological nitrification–denitrification with alternating oxic and anoxic operations using aerobic granules

Efficient nitrification and denitrification of wastewater containing 1,700 mgl⁻¹ of ammonium-nitrogen was achieved using aerobic granular sludge cultivated at medium-to-high organic loading rates. The cultivated granules were tested in a sequencing batch reactor (SBR) fed with 6.4 or 10.2 kg NH₄⁺-N m⁻³ day⁻¹, a loading significantly higher than that reported in literature. With alternating 2 h oxic and 2 h anoxic operation (OA) modes, removal rate was 45.5 mg NH₄⁺-N g⁻¹ volatile suspended solids⁻¹ h⁻¹ at 6.4 kg NH₄⁺-N m⁻³ day⁻¹ loading and 41.3 ± 2.0 at 10.2 kg NH₄⁺-N m⁻³ day⁻¹ loading. Following the 60 days SBR test, granules were intact. The fluorescence in situ hybridization and confocal laser scanning microscopy results indicate that the SBR-OA granules have a distribution with nitrifers outside and heterotrophs outside that can effectively expose functional strains to surrounding substrates at high concentrations with minimal mass transfer limit. This microbial alignment combined with the smooth granule surface achieved nitrification–denitrification of wastewaters containing high-strength ammonium using aerobic granules. Conversely, the SBR continuous aeration mode yielded a distribution with nitrifers outside and heterotrophs inside with an unsatisfactory denitrification rate and floating granules as gas likely accumulated deep in the granules.     

Expression of NAD<Superscript>+</Superscript>-dependent formate dehydrogenase in <Emphasis Type="Italic">Enterobacter aerogenes</Emphasis> and its involvement in anaerobic metabolism and H<Subscript>2</Subscript> production

An expression system for NAD⁺-dependent formate dehydrogenase gene (fdh1), from Candida boidinii, was constructed and cloned into Enterobacter aerogenes IAM1183. With the fdh1 expression, the total H₂ yield was attributed to a decrease in activity of the lactate pathway and an increase of the formate pathway flux due to the NADH regeneration. Analysis of the redox state balance and ethanol-to-acetate ratio in the fdhl-expressed strain showed that increased reducing power arose from the reconstruction of NADH regeneration pathway from formate thereby contributing to the improved H₂ production.     

Ca regulation of connexin 43 hemichannels in C6 glioma and glial cells

Connexin hemichannels have a low open probability under normal conditions but open in response to various stimuli, forming a release pathway for small paracrine messengers. We investigated hemichannel-mediated ATP responses triggered by changes of intracellular Ca²⁺ ([Ca²⁺]_i) in Cx43 expressing glioma cells and primary glial cells. The involvement of hemichannels was confirmed with gja1 gene-silencing and exclusion of other release mechanisms. Hemichannel responses were triggered when [Ca²⁺]_i was in the 500 nM range but the responses disappeared with larger [Ca²⁺]_i transients. Ca²⁺-triggered responses induced by A23187 and glutamate activated a signaling cascade that involved calmodulin (CaM), CaM-dependent kinase II, p38 mitogen activated kinase, phospholipase A2, arachidonic acid (AA), lipoxygenases, cyclo-oxygenases, reactive oxygen species, nitric oxide and depolarization. Hemichannel responses were also triggered by activation of CaM with a Ca²⁺-like peptide or exogenous application of AA, and the cascade was furthermore operational in primary glial cells isolated from rat cortex. In addition, several positive feed-back loops contributed to amplify the responses. We conclude that an elevation of [Ca²⁺]_i triggers hemichannel opening, not by a direct action of Ca²⁺ on hemichannels but via multiple intermediate signaling steps that are adjoined by distinct signaling mechanisms activated by high [Ca²⁺]_i and acting to restrain cellular ATP loss.     

Stratigraphy and palaeoenvironmental implications of Pleistocene and Holocene aeolian sediments in the Lhasa area,southern Tibet (China)

Along the middle and lower reaches of the Kyichu River and its tributaries (Lhasa area, southern Tibet), a multidisciplinary study was carried out in order to investigate the areal distribution, sedimentological properties, ages and palaeoenvironmental implications of aeolian deposits including intercalated palaeosols. This research was initiated to investigate to what extent southern Tibet is influenced by past human activity, as even recent evaluations perceive the present treeless desertic environment as natural. Fifteen profiles were recorded at an altitude of 3540–4580 m a.s.l. with subsequent sedimentological, geochronological (OSL, AMS ¹⁴C) and palaeobotanical (charcoal) analyses. Sediment properties of both loesses and aeolian sands reveal an origin from aeolian sorting of nearby fluvial deposits. The calculated ages are the oldest obtained thus far on aeolian sediments from southern and interior Tibet, revealing natural aeolian sedimentation before and around the Last Glacial Maximum (c. 20 ka). However, a distinct portion of Late Holocene sandy aeolian sediments also occurs. Both the evidence for the aeolian dynamics (widespread Pleistocene loess and aeolian sand deposition, local Late Holocene aeolian sand deposition, modern reactivation of widespread Pleistocene aeolian sands) and the palaeobotanical findings (Late Holocene vegetation change from a tree-bearing to a widely treeless landscape) provide evidence that the Lhasa area was strongly influenced by human activity since at least the Late Neolithic (c. 4200 cal yrs BP). Thus the present-day desertic environment might not primarily be a result of the semiarid climate or the high-altitude conditions, but rather of activities of the humans and their collateral effects. However, once established, this semi-natural ecosystem persisted, controlled by strong grazing, firewood extraction, erosion and harsh edaphic conditions, preventing the recovery of trees.     

Baicalein induces proliferation inhibition in B16F10 melanoma cells by generating reactive oxygen species via 12-lipoxygenase

In a previous study, we demonstrated that baicalein induces hydroxyl radical formation in human platelets but the mechanisms are unclear. Herein, we show, using an electron spin resonance technique, that baicalein also induces hydroxyl radical formation in B16F10 melanoma cells in a dose-dependent manner. Baicalein produced superoxide anions in the presence of an iron chelator and superoxide dismutase (SOD) inhibitor. We suggest that superoxide anions produced by baicalein were promptly converted to hydroxyl radicals through SOD and the Fenton reaction in B16F10 melanoma cells. According to Western blotting results, the 12-LOX protein was expressed in B16F10 melanoma cells, but baicalein had no effect on 12-LOX expression. Decreases in 12-LOX protein expression and hydroxyl radical signals occurred in a 12-LOX small interfering RNA knockdown protein group compared with the baicalein control. In the MTT assay, we also found that baicalein caused a reduction in cellular viability, which was reversed by the addition of ROS scavengers. On the basis of these data, we conclude that ROS formation catalyzed by 12-LOX is one possible mechanism of growth inhibition by baicalein in B16F10 melanoma cells.     

Epitope mapping of a chimeric CD137 mAb: a necessary step for assessing the biologic relevance of non‐human primate models

Antibody based manipulation of the CD137 (4‐1BB) co‐signaling pathway is an attractive option for the treatment of cancer and autoimmune disease. We developed a chimeric anti‐human CD137 monoclonal antibody (GG) and characterized its function. As a component of planned preclinical studies, we evaluated the binding of GG to activated peripheral blood mononuclear cells (PBMCs) from cynomolgus macaque and baboon against human. Interestingly, GG only recognized human CD137, while a commercial anti‐CD137 mAb (4B4‐1), recognized activated PBMCs from both human and non‐human primates (NHP). Subsequent analysis revealed that the amino acid sequence of CD137 is largely conserved between primate species (～95% identical), with the extracellular domain differing by only 9–10 amino acids. Based on these data, we generated mutant constructs in the extracellular domain, replacing NHP with human CD137 sequences, and identified 3 amino acids critical for GG binding. These residues are likely part of a conformational epitope, as a peptide spanning this region is unable to block mAb binding. These data demonstrate that subtle sequence variations of defined co‐stimulatory molecules amongst primate species can be employed as a strategy for mapping residues necessary for antibody binding to conformational epitopes. Copyright © 2009 John Wiley & Sons, Ltd.     

A new microdialysis-electrochemical device for in vivo simultaneous determination of acetylcholine and choline in rat brain treated with N-methyl-(R)-salsolinol

Acetylcholine (ACh) and choline (Ch) play a critical role in cholinergic neurotransmission and the abnormalities in their concentrations are related to several neural diseases. Therefore, the in vivo determination of ACh and Ch is important to the research on neurodegenerative disorders. In this work, electrochemical biosensors based on poly(m-(1,3)-phenylenediamine) (pmPD) and polytyramine (PTy) modified enzyme electrodes were fabricated. The electropolymerized pmPD polymer was used to exclude interfering substances and the PTy layer facilitated the immobilization of acetylcholinesterase (AChE) and choline oxidase (ChOx). Then, ACh/Ch sensor and Ch sensor were coupled with microdialysis to produce a novel device, which provides a sensitive and selective method for simultaneous determination of ACh and Ch. This method has detection limits of 63.0 ± 3.4 nM for ACh and 25.0 ± 1.2 nM for Ch. The integrated device was successfully applied to assessing the impact of endogenous neurotoxin N-methyl-(R)-salsolinol [1(R),2-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, (R)-NMSal] on ACh and Ch concentration, which is of great benefit to understand the pathogenesis of Parkinson's disease.     

Innovative treatment system for digester liquor using anammox process

This study demonstrated that partial nitritation using nitrifying activated sludge entrapped in a polyethylene glycol (PEG) gel carrier, as a pretreatment to anammox process, could be successfully applied to digester liquor of biogas plant at a nitrogen loading rate of 3.0 kg-N/m³/d. The nitritation process produced an effluent with a NO₂–N/NH₄–N ratio between 1.0 and 1.4, which was found to be suitable for the subsequent anammox process. A high SS concentration (2000–3000 mg/l) in the digester liquor did not affect partial nitritation treatment performances. Effluent from this partial nitritation reactor was successfully treated in the anammox reactor using anammox sludge entrapped in the PEG gel carrier with T-N removal rates of greater than 4.0 kg-N/m³/d. Influent BOD and SS contents did not inhibit anammox activity of the anammox gel carrier. The combination of partial nitritation and anammox reactors using PEG entrapped nitrifying and anammox bacteria was shown to be effective for the removal of high concentration ammonium in the digester liquor of a biogas plant.     

Carbon balance of anaerobic granulation process: carbon credit

The concept of carbon credit arose out of increasing awareness of the need to reduce emissions of greenhouse gases to combat global warming which was formalized in the Kyoto protocol. In addition to contribution to sustainable development with energy recovery in the form of methane, carbon credits can be claimed by application of advanced anaerobic processes in wastewater treatment for reducing emissions of greenhouse gases. As anaerobic granular systems are capable of handling high organic loadings concomitant with high strength wastewater and short hydraulic retention time, they could render much more carbon credits than other conventional anaerobic systems. This study investigated the potential carbon credit derived from laboratory-scale upflow anaerobic sludge blanket (UASB) reactors based on a carbon balance analysis. Methane emission reduction could be calculated by calculating the difference of UASB reactors and open lagoon treatment systems. Based on the 2.5l bench-scale reactor, the total CH(4) emissions reduction was calculated as 29 kg CO(2)/year. On scaling up to a typical full-scale anaerobic digester, the total CH(4) emissions reduction could achieve 46,420 tons CO(2) reduction/year. The estimated carbon credits would amount to 278,500 US$ per year by assuming a carbon price of 6 US$ per metric ton CO(2) reduction. The analysis postulated that it is financially viable to invest in advanced anaerobic granular treatment system from the revenue generated from carbon credits.