CAS Concentration Research Articles

Effect of microencapsulation on the bio-preservative and probiotic properties of Enterococcus durans F21

This study aimed to assess the probiotic potential of Enterococcus durans F21 and its microencapsulation. Two microencapsulation methods, spray-drying (SD) and freeze-drying (FD), were employed using sodium caseinate (Cas) as a cell protectant at concentrations of 0.035% and 1% and at two pHs, 3 and 7. Maltodextrins (MD) served as wall material (10%). Microcapsules were analysed for cell viability and membrane damage after drying, survival under simulated gastro-intestinal conditions, antimicrobial activity, stability during storage, and physicochemical characterization. Results showed that E. durans F21 exhibited promising probiotic properties, including moderate auto-aggregation, high co-aggregation with pathogens, moderate biofilm formation, and resistance to simulated gastrointestinal conditions. The encapsulation pH showed to be a crucial factor affecting the viability of microencapsulated cells. Microencapsulation at pH 3 adversely affected cell viability during drying. However, microencapsulation at pH 7 using Cas (at 0.035 and 1%) was found to be most effective in maintaining higher cell viability under similar conditions. No significant difference was detected between both Cas formulations, suggesting that 0.035% Cas concentration might be sufficient for the microencapsulation process at pH 7. Moreover, FD proved to be the most effective method to produce E. durans F21 microcapsules with high viability (cell viability of 93%) and stability during storage (cell viability of 99%). Conclusively, microencapsulation of E. durans F21 using Cas, at pH 7, and employing FD method could be a promising strategy for producing highly viable microcapsules containing E. durans F21 cells with high probiotic and bio-preservative potentials in foods.

Nutritional Performance of Five Citrus Rootstocks under Different Fe Levels.

Iron is an essential micronutrient for citrus, playing an important role in photosynthesis and yield. The aim of this paper was to evaluate the tolerance to Fe deficiency of five citrus rootstocks: sour orange (S), Carrizo citrange (C), Citrus macrophylla (M), Troyer citrange (T), and Volkamer lemon (V). Plants were grown for 5 weeks in nutrient solution that contained the following Fe concentrations (in µM): 0, 5, 10, 15, and 20. At the end of the experiment, biomass (dry weight-DW), leaf area, total leaf chlorophyll (CHL), and the activity of root chelate reductase (FCR) were recorded. Additionally, the mineral composition of roots (R) and shoots (S) was evaluated. Principal component analysis was used to study the relationships between all parameters and, subsequently, the relations between rootstocks. In the first component, N-S, P-S, Ca-S, Cu-S, Zn-S, Mn-S, Zn-R, and Mn-R concentrations were related to leaf CHL and FCR. Increases in leaf CHL, Mg-R, and DW (shoots and roots) were inversely related to Cu-R, which was shown in the second component. The values obtained were consistent for V10, C15, and C20, but in contrast for S0 and S5. In conclusion, micronutrient homeostasis in roots and shoots of all rootstocks were affected by Fe stress conditions. The Fe/Cu ratio was significantly related to CHL, which may be used to assist rootstock performance.

Inorganic sulfate–based signatures of chemosymbiosis in modern infaunal lucinids

Abstract Bivalves that host sulfur-oxidizing bacterial gill-hosted endosymbionts can inhabit low-diversity, sulfidic environmental niches. However, understanding the history of this life strategy is limited by the lack of a robust method that can be applied to fossils. Measurements of carbonate-associated sulfate S isotope ratios (CAS-δ34S) in carbonate fossils could fill this void by fingerprinting symbiont-driven oxidation of environmental sulfide. We begin to evaluate this prediction using modern lucinid bivalves, a useful test case because: (1) all modern genera host symbionts and live in sulfidic sediments, and (2) morphological evidence suggests that this has been true since the earliest ancestral lucinids. We measured S speciation, abundance, and CAS-δ34S values in the shells of a suite of modern infaunal lucinids, in addition to epifaunal bivalves with and without S-oxidizing symbionts as controls. For infaunal lucinids, CAS concentrations were at most one-third of those of non-symbiotic epifaunal bivalves, and CAS-δ34S values were lower (9.2‰–18.5‰) than in modern seawater (21‰) or epifaunal bivalves (20.8‰–21‰). These observations indicate that lucinids with symbionts incorporate sulfide-derived sulfate into their shells as a direct consequence of their chemosymbiosis. We argue that both the concentration and the magnitude of 34S depletion in infaunal lucinid CAS reflect environmental sulfide concentrations and could viably reveal chemosymbiosis in fossils.

Co-production of hydrogen and electricity from macroalgae by simultaneous dark fermentation and microbial fuel cell

In this study, a hybrid process of dark fermentation (DF) and microbial fuel cell (MFC), sDFMFC, was investigated for simultaneous H2 and electricity production from Saccharina japonica in a single reactor. The sDFMFC exhibited a considerably enhanced energy recovery owing to simultaneous H2/carboxylic acids (CAs) production by DF and electricity production by MFC consuming CAs. The co-production of H2 and electricity was confirmed by a time course of CAs concentration in sDFMFC. An excellent energy recovery of 17.3% was obtained from S. japonica with H2 yield of 110 mL/g-VS and maximum power density of 1.82 W/m2. The sDFMFC showed a diverse microbial community for a desirable microbial conversion of organic substrates. The results indicate that sDFMFC can be a promising single reactor process to produce H2 and electricity from various biomass feedstock with considerable cost savings while ensuring the strength of the individual DF and MFC process.

Enhanced oral absorption and anti-inflammatory activity of ellagic acid via a novel type of case in nanosheets constructed by simple coacervation

As a nature component, ellagic acid (EA) shows a broad array of pharmacological activities but is lost in clinical translation partly due to poor aqueous solubility. In an effort to enhance its oral absorption, novel EA-loaded casein nanosheets (EA@CAS-NSs) was constructed by simple coacervation and investigated for in vitro characterization and in vivo evaluation. The influences of factors including pH, EA concentration, and mass ratio of CAS and EA on properties of EA@CAS-NSs were also studied. The low pH value and high matrix and drug ratio were harmful to small particle size of EA@CAS-NSs. Meanwhile, the low and high concentration of EA went against the 8 h short-term stability of EA@CAS-NSs. Interestingly, EA@CAS-NSs showed a typical disk-like structure with a diameter of 100–400 nm and good long-term storage stability for 24 months. The molecular structure of EA in NSs remained unchanged, but the EA in NSs had lower crystallinity and better thermal stability than in raw state. No chemical interaction occurred between CAS and EA, although the intermolecular distance of them was less than 10 nm. In simulated intestinal fluid, the solubility of EA in NSs was nearly three times that of raw EA, and the dissolution of EA@CAS-NSs was 12 folds of raw EA at 120 min. With oral administration, EA@CAS-NSs demonstrated an improved oral absorption in rats, as evidenced by an AUC0-24 value 2.34 times higher than raw EA. Also, the EA@CAS-NSs showed a better anti-inflammatory activity than EA. Generally, EA@CAS-NSs could be a potential strategy for the further clinic use of EA.

Detection of a multi‐disease biomarker in saliva with graphene field effect transistors

AbstractHuman carbonic anhydrase 1 (CA1) has been suggested as a biomarker for identification of several diseases including cancers, pancreatitis, diabetes and Sjogren's syndrome. However, the lack of a rapid, cheap, accurate and easy‐to‐use quantification technique has prevented widespread utilization of CA1 for practical clinical applications. To this end, we present a label‐free electronic biosensor for detection of CA1 utilizing highly sensitive graphene field effect transistors (G‐FETs) as a transducer and specific RNA aptamers as a probe. The binding of CA1 with aptamers resulted in a positive shift in Dirac voltage VD of the G‐FETs, the magnitude of which depended on target concentration. These aptameric G‐FET biosensors showed the binding affinity (KD) of ~2.3 ng/ml (70 pM), which is four orders lower than that reported using a gel shift assay. This lower value of KD enabled us to achieve a detection range (10 pg/ml –100 ng/ml) which is well in line with the clinically relevant range. These highly sensitive devices allowed us to further prove their clinical relevance by successfully detecting the presence of CA1 in human saliva samples. Utilization of this label‐free biosensor could facilitate the early‐stage identification of various diseases associated with changes in concentration of CAs.

Prediction on the spatial distribution of the composition of inclusions in a heavy rail steel continuous casting bloom

Industrial trials were performed to investigate the evolution of inclusions in the molten steel of the continuous casing tundish and the bloom of a heavy rail steel, and the spatial distribution of inclusion composition along the bloom thickness was studied. An integrated model was established to predict the spatial distribution of the inclusion composition on the entire cross-section of a heavy rail steel continuous casting, which coupled the heat transfer and solidification of steel during continuous casting, the thermodynamic transformation of inclusions with temperature and the kinetic diffusion of dissolved elements in the steel. Both industrial trials and model predictions achieved similar conclusions.Inclusions within the 30mm subsurface layer had a similar composition and size to those of the molten steel and were more than other locations of the bloom and at 1/4 thickness of the bloom inclusions were larger and contained the biggest concentration of CaS. Along the thickness of the bloom, an opposite fluctuation of CaO to that of CaS in inclusions existed so that the main reaction between the inclusion and the steel matrix was (CaO)+[S]=(CaS)+[O]. When the cooling rate was larger than 150K/s, the newly precipitated CaO–Al2O3–MgO–SiO2–(<5 pct CaS) inclusions averaged <1.5μm in diameter. If the cooling rate was smaller than 150K/s, inclusions were transformed to larger CaO–Al2O3–MgO–SiO2–(>10 pct CaS) ones. In order to achieve an optimized composition of inclusions, the total oxygen and aluminum in the steel should be <10ppm and <40ppm.

Dynamic carbon and sulfur cycling in the aftermath of the Lomagundi-Jatuli Event: Evidence from the Paleoproterozoic Hutuo Supergroup, North China Craton

The unprecedented positive δ13C excursion in carbonates deposited between 2.2 and 2.0 Ga, known as the Lomagundi-Jatuli Event (LJE), has been documented globally and linked to the rise of atmospheric oxygen. Increasing oxidation inevitably changed the atmosphere-hydrosphere system, but few chemostratigraphic or quantitative constraints for the aftermath of this event exists. Here, we describe a ~200 m-thick carbonate succession in the Huaiyincun Formation, Hutuo Supergroup, ~2.0–1.9 Ga, from the North China Craton. There is a lithological transition from pink-purple dolostones to grey dolostones at ca. 91.6 m above the base of the Huaiyincun Formation. The former are more enriched in hematite and detrital minerals, whereas the latter contain more organic matter but almost no detrital phases. Meanwhile, the frequent occurrence of tempesite structures, along with the abrupt decline of stromatolites in the upper Huaiyincun Formation, suggest a storm-dominated environment. These distinct features within the Huaiyincun Formation reveal increased water depth during a transgression event. Two types of Raman spectra of organic matter were found in the lower and upper Huaiyincun Formation, respectively, which is proposed to be the result of variable oxidation.At 65.6 m, 26 m below the lithological transition (~91.6 m), remarkable decreases in both δ13Ccarb and δ34SCAS are observed. This discordance between C-S isotopic excursions and sedimentological and mineralogical variations argues against a seawater depth gradient effect of the δ13Ccarb and δ34SCAS curves. Instead, the decline of δ13Ccarb rather correlates with the negative δ13Ccarb excursions in ca. 2.0 Ga carbonates from Gabon and Russia, known as the Shunga-Francevillian Event (SFE). The result of the quantitatively constrained paleo-seawater [SO42−]sw suggests a crash of the seawater sulfate reservoir compared with that during the preceding LJE. However, the decreased δ34SCAS and increased CAS concentration towards the top of the study unit represent the recovery of seawater sulfate reservoir. The coordinated decline in δ34SCAS and δ13Ccarb values is likely related to enhanced oxidation of continental pyrite and organic matter in the aftermath of the LJE. The Huaiyincun Formation therefore represents a critical interval that recorded dynamic carbon and sulfur cycles after the LJE.

Role of Ca2+-NFAT Signaling Pathway in Ph+ ALL Drug-resistance Mediated by Bone Marrow Stromal Cells

To explore the role of Ca2+-NFAT signaling pathway in Ph+-ALL drug resistance mediated by bone marrow stromal cells. The transcription level of NFAT mRNA in Sup-B15 cells and Ph+ ALL primary cells was detected by polymerase chain reaction. The expression of P-glycoprotein in Sup-B15 cells was detected by flow cytometry. The change of NFAT protein in Sup-B15 cells was detected by Western blot. AnnexinV/7-AAD was used to label cells. Flow cytometry was used to detect cell apoptosis; Fluo 3-AM dye was used to label cells, and flow cytometry used to detect changes of Ca2+ concentration in leukemia cells. NFAT expression could be detected in both Sup-B15 and Ph+ ALL primary cells; P-glycoprotein could not be detected by flow cytometry; CAS could significantly inhibit NFAT protein expression in clinically applied drug concentrations (2.5, 5 μmol/L); Clinically applied concentration of CAS (2.5, 5 μmol / L) has no significant effect on the apoptosis of Sup-B15 cells, while higher concentration of CAS (10 μmol / L) could induce apoptosis of Sup-B15 cells. Bone marrow stromal cells OP9 could, decrease the sensitivity of Sup-B15 cells and Ph+ ALL primary cells to imatinib (IM); After co-culture with bone were marrow stromal cells, the Ca2+ concentration in Sup-B15 cells was enhanced, the levels of NFAT protein and nullear protein in sup-B15 cells also were enhanced. The addition of CAS in co-culture system could inlibit the Ca2+-NFAT signaling pathway, reduce the protective effect of OP9 on Sup-B15 cells.Conclution:The Ca2+-NFAT sigualing pathway, contributes to the survival of Ph+ ALL cells. Bone marrow stromal cells can mediate the resistance of Ph+ ALL cells to IM by activating Ca2+-NFAT signaling pathway.

Numerical Simulation of Inclusion Modification During Calcium Treatment Process in Ladle

In order to investigate the inclusion modification process and predict final inclusions after the injection of calcium, based on actual data of injection of calcium and inclusion thermodynamic calculation, a three-dimensional model for calcium treatment in LF refining furnace for pipeline steel was established. The evolution of concentrations and distribution of the modification inclusions in the liquid steel during the injection of calcium were investigated. The results showed that when the length of feeding calcium was 600 m, after about 1000 s, the average calcium equilibrium concentration was 1.86 × 10−5 and the recovery of calcium was 23.2%. The average equilibrium concentration of C3A, C12A7, CA(C stands for CaO and A stands for Al2O3) and CaS, respectively, was 0, 25.7 × 10−6, 3.04 × 10−6 and 13.7 × 10−6. The final modified inclusion was related to the amount of feeding calcium. The equilibrium value of C12A7 and CaS increased with the increase of feeding amount; however for CA, the regularity was opposite.

Study of interactions between anionic exopolysaccharides produced by newly isolated probiotic bacteria and sodium caseinate.

The present study aims to evaluate the interactions between four exopolysaccharides (EPS) produced by probiotic bacteria and sodium caseinate (Cas) in order to simulate their behavior in dairy products. Complexation between the produced EPS samples and Cas was investigated as a function of polysaccharide to protein ratio. The highest turbidity and average size of complexes were formed at an EPS/Cas ratio of 3 (corresponding to 1 g/L of EPS and 0.33 g/L of Cas) as a result of the combination of individual complexes to form aggregates. Zeta potential measurements and Cas surface hydrophobicity results suggested that complex formation occurred essentially through electrostatic attractions with a possible contribution of hydrophobic interaction for EPS-GM which was produced by Bacillus tequilensis-GM. Afterwards, the effect of pH on the complexation between biopolymers was studied when EPS and Cas concentrations were maintained constant at 1 and 0.33 g/L, respectively. pH was adjusted to 3.0 and 3.5, respectively. Results showed that the highest amount and sizes of EPS/Cas complexes were formed at pH 3.5 and that EPS-GM enabled to obtain the biggest and highest amount of aggregates. Therefore, the obtained results support the fact that the simultaneous presence of EPS and Cas in dairy products results in complexes formation via electrostatic interactions depending on EPS/Cas ratio and pH of the medium.

Population Pharmacokinetics of Escalating Doses of Caspofungin in a Phase II Study of Patients with Invasive Aspergillosis

Caspofungin (CAS) is approved for second-line management of proven or probable invasive aspergillosis at a dose of 50 mg once daily (QD). Preclinical and limited clinical data support the concept of the dose-dependent antifungal efficacy of CAS with preservation of its favorable safety profile. Little is known, however, about the pharmacokinetics (PKs) of higher doses of CAS in patients. In a formal multicenter phase II dose-escalation study, CAS was administered as a 2-h infusion at doses ranging from 70 to 200 mg QD. CAS PK sampling (n = 468 samples) was performed on day 1 and at peak and trough time points on days 4, 7, 14, and 28 (70 mg, n = 9 patients; 100 mg, n = 8 patients; 150 mg, n = 9 patients; 200 mg, n = 20 patients; total, n = 46 patients). Drug concentrations in plasma were measured by liquid chromatography tandem mass spectroscopy. Population pharmacokinetic analysis (PopPK) was performed using NONMEM (version 7) software. Model evaluation was performed using bootstrap analysis, prediction-corrected visual predictive check (pcVPC), as well as standardized visual predictive check (SVPC). The four investigated dose levels showed no difference in log-transformed dose-normalized trough levels of CAS (analysis of variance). CAS concentration data fitted best to a two-compartment model with a proportional-error model, interindividual variability (IIV) fitted best on clearance (CL), central and peripheral volume of distribution (V(1) and V(2), respectively) covariance fitted best on CL and V(1), interoccasion variability (IOV) fitted best on CL, and body weight fitted best as a covariate on CL and V(1) (CL, 0.411 liters/h ± 29% IIV; IOV on CL, 16%; V(1), 5.785 liters ± 29% IIV; intercompartmental clearance, 0.843 liters/h; V2, 6.53 liters ± 67% IIV). None of the other examined covariates (dose level, gender, age, serum bilirubin concentration, creatinine clearance) improved the model further. Bootstrap results showed the robustness of the final PopPK model. pcVPC and SVPC showed the predictability of the model and further confirmed the linear PKs of CAS over the dosage range of 70 to 200 mg QD. On the basis of the final model, geometric mean simulated peak plasma levels at steady state ranged from 13.8 to 39.4 mg/liter (geometric coefficient of variation, 31%), geometric mean trough levels ranged from 4.2 to 12.0 mg/liter (49%), and geometric mean areas under the concentration-time curves ranged from 170 to 487 mg · h/liter (34%) for the dosage range of 70 to 200 mg QD. CAS showed linear PKs across the investigated dosage range of 70 to 200 mg QD. Drug exposure in the present study population was comparable to that in other populations. (This study has been registered with the European Union Drug Regulating Authorities Clinical Trials website under registration no. 2006-001936-30 and at ClinicalTrials.gov under registration no. NCT00404092.).

Dissolution Modeling and Experimental Measurement of CaS‐H2O Binary System

AbstractCaS formed during the retorting process of oil shale has a hazardous influence on surface water quality. Interaction of retorted oil shale with water generates highly alkaline leachate with a high content of sulfur due to the CaS component. A theoretical model describing the behavior of solid calcium sulfide in contact with water was developed. The model was consistent with the measurements showing change in dissolution behavior when solid CaS remained in the solution. Experimental measurements of pH and concentrations of ions were carried out in oxygen‐free water at 25°C using CaS concentrations from 24.2–131.5 mg·L−1 (0.335–1.823 mmol/L). Analysis of pH and concentrations of ions in the solution and calculations by the developed model showed that the solubility of CaS was estimated as 125.0 mg·L−1 (1.733 mmol/L), and therefore the solubility product of CaS is 3.41×10−10 (mo·L−1)2 at a temperature of 25°C.

Reaction mechanism and influence factors analysis for calcium sulfide generation in the process of phosphogypsum decomposition

FactSage6.1 software simulation and experiments had been used to analysis the reaction mechanism and influence factors for CaS generation during the process of phosphogypsum decomposition. Thermodynamic calculation showed that the reaction for CaS generation was very complex and CaS was generated mainly through solid–solid reaction and gas–solid reaction. The proper CO and CO 2 have benefit for improving the decomposition effects of phosphogypsum and reducing the generation of CaS at 1100 °C. Using high sulfur concentration coal as reducer, the proper reaction conditions to control the generation of CaS were: the coal particle size was between 60 mesh and 100 mesh, reaction temperature was above 1100 °C and the heating rate was 5 °C/min. Experimental and theoretical calculation indicated that the concentration of CaS was only ten percents in the solid product at 1100 °C, which is favorable for the further cement producing using solid production.

The Change in Composition of Inclusions in Molten Steel during Simultaneous Addition of Ca alloy and CaO–Al2O3 flux

In order to examine the effects of calcium addition method on inclusion composition, the variations of the inclusion composition were measured during simultaneous addition of calcium alloy and CaO–Al2O3 flux to the molten steel by 180 kg scale experiments. Fifty four grams CaSi alloy mixed with 13.5 g CaO–Al2O3 flux was added 10 times at the interval of 1 min and the samples of molten steel were sampled during the experiments. The composition of the molten steel and the composition of the inclusions were analyzed. From the experiments and chemical reaction kinetic calculation, the effects of CaO–Al2O3 composition in flux on the changes in the inclusion composition were examined. The results obtained are summarized as follows;(1) Calcium concentration in molten steel increased with increasing CaO concentration in CaO–Al2O3 flux.(2) The CaO concentration in inclusion at which CaS concentration began to increase was changed by the composition of CaO–Al2O3 flux.The results of the reaction rate calculation considering the reaction of calcium in molten steel and flux showed a good agreement with the experimental results.(3) The reaction path of the variation of inclusion concentration was changed as a result of the reaction among calcium in molten steel, inclusion and flux.(4) It was suggested that an inclusion composition could be optionally controlled by adding CaSi alloy and CaO–Al2O3 flux at the same time.

Colloidal Stability of Bovine Calcium Caseinate Suspensions. Effect of Protein Concentration and the Presence of Sucrose and Lactose

Sodium caseinate suspensions (Cas) are stabilized as submicelles in a dynamic system consisting of caseins α, β, and κ. Their use in the food industry is quite widespread because of their functional properties and nutritional value. In the presence of calcium ions, Cas are able to form colloidal stable aggregates in suspension (CCA) at certain Ca2+ and Cas concentration ratios (Ca:Cas). The aim of this work was to study the effect of the protein concentration on the CCA solubility and viscosity at different Ca:Cas and to relate those two functional properties to protein composition and conformational changes. The stability of CCA was also evaluated in the presence of lactose and sucrose. The apparent solubility of the CCA was determined by applying a spectrophotometric method, and the stability test parameters were obtained using a model based on thermodynamic linked functions. The protein conformational changes were followed by using fluorescence techniques and were related to the partial specific volume...

Oxidation of the sulphurised dolomite produced in the desulphurisation of the gasification gases

Dolomite reacts with H2S to produce calcium sulphide and has been broadly investigated as a desulphurisation agent due to its low-cost and favourable properties.Because CaS reacts with water or water vapour in the environment to regenerate hydrogen sulphide and, therefore, disposal is problematic and the chemical cannot be uses as a landfill material. One of the methods used to make this material inert is oxidation to convert calcium sulphide into calcium sulphate or calcium oxide.In our study, tests were carried out using dolomite from Granada, Spain, that was previously calcined and sulphurised at high temperature with a gas similar to that produced in gasification facilities. To approximate real-scale results, a relatively large amount of substance was used for each sample (100–150g) and the samples were used in a fixed-bed position.The influence of different conditions, such as grain size, composition of the oxidation gas, gas velocity, bed length and temperature, was them investigated. The final solid products were characterised by X-ray diffraction and chemical analysis and the CO2, SO2, H2S and COS concentrations in the gases produced during oxidation were analysed by gas chromatography.The results showed that the most influential factor was grain size and that the best oxidant was O2 mixed with nitrogen.The presence of water vapour increases the residual concentration of CaS in the end product, but increased the CaO contentThe higher the oxygen concentration and the higher the gas velocity, the lower the residual content of CaS. CO2 used alone oxidises CaS to produce SO2 and COS, but at very low rates. It also produces some CS2. Water vapour used alone can also oxidise the CaS to produce H2S and SO2 but also at very low velocity.At higher oxidation temperature, between 700°C and 850°C, lesser residual CaS is obtained in the oxidised product.

Coincident negative shifts in sulfur and carbon isotope compositions prior to the end-Permian mass extinction at Shangsi Section of Guangyuan, South China

Sulfur isotope composition of carbonate-associated sulfate (δ34SCAS) and carbon isotope composition of carbonate (δ13Ccarb) were jointly investigated on the Late Permian rocks at Shangsi Section, Guanyuan, Northeast Sichuan, South China. Both δ34SCAS and δ13Ccarb show gradual decline trends in Late Permian strata, inferring the occurrence of the long-term variation of marine environmental conditions. Associated with the long-term variation are the two coincident negative shifts in δ34SCAS and δ13Ccarb, with one occurring at the boundary between Middle Permian Maokou Formation and Late Permian Wujiaping Formation and another at Middle Dalong Formation. Of significance is the second shift which clearly predates the regression and the biotic crisis at the end of Permian at Shangsi Section, providing evidence that a catastrophic event occurred prior to the biotic crisis. The frequent volcanisms indicated by the volcanic rocks or fragments, and the upwelling are proposed to cause the second negative excursion. An abrupt extreme negative δ34SCAS (ca. −20‰) associated with a low relative concentration of CAS and total organic carbon without large change in δ13Ccarb is found at the end of the second shift, which might arise from the short-term oxygenation of bottom waters and sediments that resulted from the abrupt sea level drop.

Hierarchical amino acid utilization and its influence on fermentation dynamics: rifamycin B fermentation using Amycolatopsis mediterraneiS699, a case study

BackgroundIndustrial fermentation typically uses complex nitrogen substrates which consist of mixture of amino acids. The uptake of amino acids is known to be mediated by several amino acid transporters with certain preferences. However, models to predict this preferential uptake are not available. We present the stoichiometry for the utilization of amino acids as a sole carbon and nitrogen substrate or along with glucose as an additional carbon source. In the former case, the excess nitrogen provided by the amino acids is excreted by the organism in the form of ammonia. We have developed a cybernetic model to predict the sequence and kinetics of uptake of amino acids. The model is based on the assumption that the growth on a specific substrate is dependent on key enzyme(s) responsible for the uptake and assimilation of the substrates. These enzymes may be regulated by mechanisms of nitrogen catabolite repression. The model hypothesizes that the organism is an optimal strategist and invests resources for the uptake of a substrate that are proportional to the returns.ResultsStoichiometric coefficients and kinetic parameters of the model were estimated experimentally for Amycolatopsis mediterranei S699, a rifamycin B overproducer. The model was then used to predict the uptake kinetics in a medium containing cas amino acids. In contrast to the other amino acids, the uptake of proline was not affected by the carbon or nitrogen catabolite repression in this strain. The model accurately predicted simultaneous uptake of amino acids at low cas concentrations and sequential uptake at high cas concentrations. The simulated profile of the key enzymes implies the presence of specific transporters for small groups of amino acids.ConclusionThe work demonstrates utility of the cybernetic model in predicting the sequence and kinetics of amino acid uptake in a case study involving Amycolatopsis mediterranei, an industrially important organism. This work also throws some light on amino acid transporters and their regulation in A. mediterranei .Further, cybernetic model based experimental strategy unravels formation and utilization of ammonia as well as its inhibitory role during amino acid uptake. Our results have implications for model based optimization and monitoring of other industrial fermentation processes involving complex nitrogen substrate.

Calcium sulphide in FBC boilers and its fate using liquid water reactivation

Abstract CaSO 4 and CaS are the only sulphur compounds found in solid residues from the sulphation process in FBC boilers. Early results indicated very high levels of CaS in ashes from small-scale FBC pilot plant combustors. However, these results were due to the presence of high levels of char carbon in standpipes and cyclones. In commercial-scale FBC boilers, CaS concentrations are normally less than 0.1% although levels of up to 0.6% are seen in some ashes. Sometimes elevated CaS concentrations are found in deposits in CFBC boilers firing high levels of petroleum coke (although this is unusual), and in ashes from stripper coolers. In both cases, this can be minimized by proper design. CaS can also be deliberately introduced into FBC boilers with the char from a topping cycle gasifier. Test work using hydration in a similar manner to a reactivation strategy has been shown to be ineffective for sulphide destruction when used directly with char from a topping cycle gasifier. Instead it is recommended that reactivation be used on ashes from the CFBC boiler receiving the sulphided char residues. This guarantees overall high sorbent utilization and the effective elimination of sulphides in the ashes finally discharged from the CFBC boiler.