Mol Min Research Articles

Optimization and Kinetic Studies on Biodiesel Production from Kusum (Schleichera triguga) Oil Using Response Surface Methodology.

In the present study, the low-cost non-edible kusum (Schleichera triguga) oil with a substantial amount of free fatty acid (FFA) was utilized for biodiesel synthesis. In pretreatment step, FFA was reduced by the acid catalyzed esterification method. Then, response surface method (RSM) in conjunction with centre composite design (CCD) containing 30 experimental runs were statistically employed for process optimization and kinetic study for the base catalyzed transesterification process. A statistical model predicted highest fatty acid methyl ester (FAME) yield of 97.37% at the optimal values of process parameters as follows: sodium methoxide concentration 0.9 wt% of oil, Methanol to oil molar ratio 9:1, temperature 58.9 ℃ and reaction time 58.5 min. Using these optimal parameters under experimental conditions in three independent replicates an actual FAME content of 98.14% was obtained which was in reasonable agreement with predicted one. The developed kinetic model suggested a 1.8(th) order reaction with activation energy of 31.42 kcal mol(-1) and frequency factor of 5.53×10(19) L mol(-1)min(-1). Furthermore, Important fuel properties of kusum oil biodiesel (KOB) was compared with ASTM 6751 and DIN EN 14214. The viscosity was found to be 5.34 Cst at 40 °C and the flash point was 152°C.

Synthesis of C1 symmetrical ansa-cyclopentadienylamidotitanium complexes and their application for living polymerization of propylene

Optically active C1 symmetrical [(R)-NCHMe(Naphthyl)SiMe2Flu]TiMe2 (1) and [(R)-NCHMe(Naphthyl)SiMe2(C5Me4)]TiMe2 (2) were synthesized and characterized by elemental analysis, 1H NMR and single crystal X-ray analysis. These complexes were applied for propylene polymerization using dried modified methyaluminoxane (dMMAO) as a cocatalyst at 0 °C in toluene, heptane and chlorobenzene, respectively. All the systems showed steady polymerization rate and gave high molecular weight polypropylene with narrow molecular weight distribution, and the toluene system showed higher activity than the heptane system. The postpolymerization testified that each catalytic system conducted the propylene polymerization in a living manner. The 2-chlorobenzene system showed fastest propagation rate of 437 mol min−1. The polymers produced with the 1-heptane and -toluene systems or 2-heptane system were statistically atactic, while the polymers produced with the 2-toluene system were isotactic-rich PP with isotactic triad (mm) of 0.61.

Role of graphene in MnO2/graphene composite for catalytic ozonation of gaseous toluene

Abstract The degradation of gaseous toluene is of great significance to protect human health. In this work, a facile and environmentally friendly route for synthesis of different MnO2 loadings (14.2–94.8 wt.%) on graphene composites was developed through the direct redox reaction between graphene oxide and potassium permanganate at 160 °C for 12 h under hydrothermal condition. The elemental composition, crystal structure, and material properties of the MnO2/graphene samples were characterized using ICP-AES, XRD, TEM, FTIR spectroscopy, Raman spectroscopy, N2 physisorption technique, and TG/DTA. The results show that the hydrothermal method is an effective way to prepare tightly anchored birnessite-type MnO2 on graphene. MnO2 nanoparticles were uniformly distributed throughout the surface of graphene nanosheets at 64.6 wt.% MnO2 loading, whereas aggregation or erosion of graphene sheets occurred at low or high loading of MnO2. The activities of graphene, MnO2, and the MnO2/graphene samples in catalytic ozonation of gaseous toluene were determined at 22 °C. The amount of MnO2 loaded on graphene showed a significant influence on the BET surface area, and the catalytic activity of the MnO2/graphene samples. The highest toluene degradation rate (7.89 × 10−6 mol min−1 g−1) over the 64.6 wt.% MnO2/graphene sample was attributed to the synergetic effect of graphene and MnO2 which was attributed to the tight connection between the active sites on graphene for adsorption of toluene and decomposition of ozone, and the MnO2 on graphene for decomposition of ozone to form atomic oxygen species.

Size‐Controlled Synthesis of Tetrametallic Ag@CoNiFe Core–Shell Nanoparticles Supported on Graphene: A Highly Efficient Catalyst for the Hydrolytic Dehydrogenation of Amine Boranes

AbstractTetrametallic core–shell Ag@CoNiFe nanoparticles (NPs) supported on graphene have been synthesized by a facile one‐step in situ procedure for the first time. We tuned the reducing ability of the reductants to control the structure and particle size of the as‐synthesized NPs. The use of weaker reducing agents, such as ammonia borane (AB) and methylamine borane (MeAB), result in the core–shell structure, whereas the stronger reducing agent NaBH4 results in alloy NPs. The as‐synthesized core–shell NPs reduced by MeAB possess a smaller particle size and exhibit a superior catalytic activity compared to the core–shell NPs reduced by AB and alloy NPs reduced by NaBH4 for the hydrolytic dehydrogenation of AB. Moreover, the turnover frequency of the as‐synthesized tetrametallic core–shell NPs is 118.5 mol min−1 molAg−1, which is higher than that of Ag‐based trimetallic, bimetallic core–shell, and alloy counterparts and even higher than that of most reported noble‐metal‐based NPs. Kinetic studies indicate that the catalytic hydrolysis of AB and MeAB by the Ag@CoNiFe/graphene NPs is a first‐order reaction. Furthermore, the as‐prepared NPs exert good catalytic activities and recycle stabilities towards the hydrolysis of AB. Additionally, the as‐prepared NPs display magnetic recyclability, which makes the practical recycling of the NPs more convenient.

English

This work describes the larvicidal activity of the ethanolic crude extract (EEB) as well as the hexanic (FH), chloroform (FCL), ethyl acetate (FAE) and remaining (FR) fractions obtained from Byrsonima intermedia leaves and bark against Aedes aegypti. Hexanic and remaining fractions from the leaves demonstrated larvicide activity against A. aegypti larvae on the 3rd stage, with LC50 values of 250 and 125 μg/ml-1, respectively, with less mortality as compared to the other fractions. Hexanic and remaining fraction from the leaves demonstrated larvicide acitivity against A. aegypti larvae on the 3rd stage, with LC50 values of 250 and 125 μg/ml-1, respectively, with less mortality as compared to the other fractions. Trypsin activities from gut of larvae treated with the extract or the fractions were significant (p < 0.05), and the major effects occurred with hexanic fraction (0.06 μmol min-1) and remaining fraction (0.09 μmol min-1) in the 1000 μg/ml-1 concentration, respectively. The same fractions inhibited chymotrypsin activity in 0.06 μmol/ml-1 (hexanic fraction) and 0.13 μmol/ml-1 (remaining fraction) at 1000 μg/ml-1. The inhibition was dose-dependent. The results show the inhibitory effects of the hexanic and remaining fractions from the leaves of B. intermedia on trypsin and chymotrypsin activity, which may be responsible for the deleterious effects on larvae mortality. The crude ethanolic extract and fractions of the bark does not inhibit the synthesis of trypsin compared to control. The results show the inhibitory effects of the hexanic and remaining fraction from the leaves of B. intermedia on trypsin and chymotrypsin activity, which may be responsible for the deleterious effects on larvae mortality.   Key words: Digestive system, dengue fever, larvicidal activity, natural products.

Lipase production from a novel thermo-tolerant and extreme acidophile Bacillus pumilus using palm oil as the substrate and treatment of palm oil-containing wastewater

The thermo-tolerant and extreme acidophilic microorganism Bacillus pumilus was isolated from the soil collected from a commercial edible-oil extraction industry. Optimisation of conditions for the lipase production was conducted using response surface methodology. The optimum conditions for obtaining the maximum activity (1,100 U/mL) of extremely acidic thermostable lipase were fermentation time, 96 h; pH, 1; temperature, 50 °C; and concentration of palm oil, 50 g/L. After purification, a 7.1-fold purity of lipase with specific activity of 5,173 U/mg protein was obtained. The molecular weight of the thermo-tolerant acidophilic lipase (TAL) was 55 kDa. The predominant amino acid in the TAL was glycine. The functional groups of lipase were determined by Fourier transform infrared spectroscopy. TAL exhibited enhanced activity (114 %) with dimethyl sulphoxide (20 %, v/v), and it showed a moderate activity with methanol, hexane and benzene. The optimum conditions for the treatment of palm oil in wastewater using the TAL were found to be time, 3 h; pH, 1; temperature, 50 °C with pseudo second-order kinetic constant of 1.88 × 10(-3) L mol(-1) min(-1). The Michaelis-Menten enzyme kinetic model and the nonlinear kinetic model were evaluated for the TAL. TAL established hydrolysis efficiency of 96 % for palm oil in wastewater at 50 °C.

Kinetic features of the adsorption of sodium oleate on talc

Kinetic features of the adsorption of sodium oleate on dispersed talc samples of Onotskoe deposit are studied. It is shown that adsorption proceeds in two steps with different rate constants of adsorption ka and desorption kd. It is found that at the first step, lasting for nearly one hour under experimental conditions, the process is characterized by high ka and kd values (1.23 × 10−2 m2/(mol min) and 1.06 × 10−5 m2/(L min), respectively). It is concluded that the final stage associated with the rearrangement of molecules on a talc surface lasts for a long time with ka = 2.12 × 10−3 m2/(mol min) and kd = 1.82 × 10−6 m2/(L min).

Preparation and reaction dynamics on biodiesel made from Zanthoxylum bungeanum seed oil and methanol

Zanthoxylum bungeanum seed oil (ZSO) was the by-product of the zanthoxylum industry, and was a kind of cheap and abundant source in China; it can be of great potential to use as a feedstock for biodiesel production in terms of reducing the producing cost. Biodiesel preparation of ZSO methyl ester by transesterification using potassium hydroxide (KOH) as an alkaline catalyst was studied in this paper. First, the single-factor experiment was practiced, the influence on conversion rate of different factor was studied, such as methanol-to-oil molar ratio, content of catalyst, reaction temperature, and reaction time, etc. Second, the response surface methodology was used to optimize the conditions for ZSO biodiesel production using KOH as a catalyst. A quadratic polynomial equation was obtained for biodiesel conversion by multiple regression analysis and verification experiments confirmed the validity of the predicted model. The optimum combination for transesterification was methanol-to-oil molar ratio 8.5:1, catalyst amount 1.0%, reaction temperature 56 °C, and reaction time 67 min. At this optimum condition, the conversion to biodiesel reached above 98.4%. The relevant error was less than 5% between measurement value of the conversion to biodiesel and expected value. Finally, the reaction kinetics of transesterification was studied. The “Iodine Clock Reaction” principle was used for establishing dynamic model, and corresponding kinetic equation was established. The results showed that the progression of transesterification was grade 1.5, the reaction activation energy was 20.0434 kJ·mol−1, and the pre-exponential factor was 7.8963 dm3/(mol min).

Kinetics of Homogeneous and Surface-Catalyzed Mercury(II) Reduction by Iron(II)

Production of elemental mercury, Hg(0), via Hg(II) reduction is an important pathway that should be considered when studying Hg fate in environment. We conducted a kinetic study of abiotic homogeneous and surface-catalyzed Hg(0) production by Fe(II) under dark anoxic conditions. Hg(0) production rate, from initial 50 pM Hg(II) concentration, increased with increasing pH (5.5-8.1) and aqueous Fe(II) concentration (0.1-1 mM). The homogeneous rate was best described by the expression, r(hom) = k(hom) [FeOH(+)] [Hg(OH)2]; k(hom) = 7.19 × 10(+3) L (mol min)(-1). Compared to the homogeneous case, goethite (α-FeOOH) and hematite (α-Fe2O3) increased and γ-alumina (γ-Al2O3) decreased the Hg(0) production rate. Heterogeneous Hg(0) production rates were well described by a model incorporating equilibrium Fe(II) adsorption, rate-limited Hg(II) reduction by dissolved and adsorbed Fe(II), and rate-limited Hg(II) adsorption. Equilibrium Fe(II) adsorption was described using a surface complexation model calibrated with previously published experimental data. The Hg(0) production rate was well described by the expression r(het) = k(het) [>SOFe((II))] [Hg(OH)2], where >SOFe((II)) is the total adsorbed Fe(II) concentration; k(het) values were 5.36 × 10(+3), 4.69 × 10(+3), and 1.08 × 10(+2) L (mol min)(-1) for hematite, goethite, and γ-alumina, respectively. Hg(0) production coupled to reduction by Fe(II) may be an important process to consider in ecosystem Hg studies.

Kinetics of the oxidation of hexacyanoferrate(III) with pyrolusite

It is established that the oxidation of potassium ferricyanide at pH 7–11 proceeds as a pseudo-second-order reaction with rate constants of 2.93, 4.19, 6.16, 8.66, and 9.22 L/(mol min) at 313, 323, 333, 343, and 353 K, respectively. The activation energy of the reaction is found to be 27.82 kJ/mol. The second order of the reaction, as along with the non-dependence of the rate constant on the liquid-phase volume: solidphase weight ratio, and on the rotation speed of the mixer, allow us to assume that the reaction proceeds in the kinetic region with a transition to the diffusion-kinetic mode at 353 K.

Sacrificial Hydrogen Generation from Formaldehyde with Pt/TiO2 Photocatalyst in Solar Radiation

In this work, solar TiO2 photocatalysis was used for sacrificial hydrogen generation from formaldehyde. Platinum was loaded onto a TiO2 photocatalyst by a solar photodeposition method to suppress the electron/hole recombination process. The photocatalyst inside the reactor was irradiated from the top with a solar simulator. Photocatalytic hydrogen generation from formaldehyde was influenced by the solution pH, platinum loading (wt %) on TiO2, catalyst concentration, light intensity, and initial formaldehyde concentration. A Langmuir-type model fitted well with the experimental data, and the values of surface reaction rate constant, k, and the adsorption equilibrium constant, K, are 2.3598 × 10–6 mol min–1 and 17.73 M–1, respectively. Apparent quantum yield (QY) was higher for the UV light-driven hydrogen generation (10.91%) compared to the solar light-driven hydrogen generation (1.24%).

Comparative analysis of heterologous expression, biochemical characterization optimal production of an alkaline α‐amylase from alkaliphilic Alkalimonas amylolytica in Escherichia coli and Pichia pastoris

An alkaline α-amylase gene from alkaliphilic Alkalimonas amylolytica was synthesized based on the preferred codon usage of Escherichia coli and Pichia pastoris, respectively, and then was expressed in the according heterologous host, E. coli BL21 (DE3) and P. pastoris GS115. The alkaline α-amylase expressed in E. coli was designated AmyA, whereas that produced by P. pastoris was designated AmyB. The specific activity of AmyA and AmyB was 16.0 and 16.6 U/mg at pH 9.5 and 50°C, respectively. The optimal pH and pH stability of AmyA and AmyB were similar, whereas the optimum temperature and thermal stability of AmyB were slightly enhanced compared with those of AmyA. The AmyA and AmyB had a similar melting temperature of 64°C and the same catalytic efficiency (k(cat) /K(m) ) of 2.0 × 10(6) L/(mol min). AmyA and AmyB were slightly activated by 1 mM Co(2+) , Ca(2+) , or Na(+) , but inhibited by all other metal ions (K(+) , Mg(2+) , Fe(3+) , Fe(2+) , Zn(2+) , Mn(2+) , and Cu(2+) ). Tween 80 or Tween 60 (10% (w/v)) had little influence on the stability of AmyA and AmyB, while the 10% (w/v) sodium dodecyl sulfate caused the complete loss of AmyA and AmyB activities. The AmyA and AmyB were stable in the presence of solid detergents (washing powder), while were less stable in liquid detergents. Under the optimal conditions in 3-L bioreactor, the extracellular AmyB activity reached 600 U/mL, which was about 10 times as that of AmyA. These results indicated that P. pastoris was a preferable host for alkaline α-amylase expression and the produced alkaline α-amylase had a certain application potential in solid detergents.

Kinetic analysis of constructed systems for the recovery of contaminated areas by acid mine drainage

Flowing of the acid mine drainage may contaminate the adjacent water bodies causing substantial changes in the aquatic ecosystem. This aspect is the most relevant problem in the southern of Santa Catarina once the contaminated areas are inserted in the watershed of the Araranguá, Urussanga, and Tubarão rivers, increasing the need for recovery studies. These areas are between Criciúma, Içara, Urussanga, Siderópolis, Lauro Müller, Orleans, and Alfredo Wagner towns where a conservation unit exist called the Environmental Preservation Area of Baleia Franca. Aiming to compare the kinetics of the ash derived from burning coal and to neutralize acid mine drainage, different neutralizer, limestone, fly, and bottom ash, was mounted on a pilot scale experiment. The transport parameters showed the same order of infiltration and dispersion: fly ash < bottom ash < limestone. The order of measured alkalinity was: limestone < fly ash < bottom ash, with pH values of 9.34, 12.07, and 12.25, respectively. The limestone kinetics of acidic drainage neutralization was first order with reaction rate constant k = 0.0963 min(-1), bottom ash was 3/4 with k = 0.0723 mol(1/4) L(-1/4) min(-1), and the fly ash had higher order kinetics, 4/3, with reaction rate constant k = 27.122 L(1/3) mol(-1/3) min(-1). However, by mathematical modeling, it was found that due to a combination of transport and kinetics, only limestone treatment reached a pH above 6 within 5 years, corresponding to the ideal as planned.

A novel polyol method to synthesize colloidal silver nanoparticles by ultrasonic irradiation

A polyol synthesis of silver nanoparticles in the presence of ultrasonic irradiation was compared with other configurations (at ambient temperature, 120 °C, and 120 °C with injected solutions) in the absence of ultrasonic irradiation in order to obtain systematic results for morphology and size distribution. For applying ultrasonic irradiation, rather fine and uniform spherical silver particles (21 ± 3.7 nm) were obtained in a simple (at ambient temperature without mechanical stirring) and fast (within 4 min, 3.61 × 10 −3 mol min −1) manner than other cases (at ambient temperature (for 8 h, 0.03 × 10 −3 mol min −1): 86 ± 16.8 nm, 120 °C (for 12 min, 1.16 × 10 −3 mol min −1): 64 ± 14.9 nm, and 120 °C with injected solutions (during 12 min): 35 ± 6.8 nm; all other cases contained anisotropic shaped particles). Even though the temperature of polyol reaction reached only at 80 °C (<120 °C) in the presence of ultrasonic irradiation, a uniform mixing (i.e. enhanced collision between silver particle and surrounding components) by ultrasonic irradiation might induce a better formation kinetics and morphological uniformity.

Improvement in Insulin Sensitivity and Β-Cell Function Following Ileal Interposition with Sleeve Gastrectomy in Type 2 Diabetic Patients: Potential Mechanisms

IntroductionBariatric surgery in morbidly obese type 2 diabetic (T2DM) patients is associated with high rates of diabetes remission. We investigated the mechanisms of the anti-diabetic effect of the laparoscopic ileal interposition with sleeve gastrectomy (LII-SG) in normal weight (NW), overweight (OW) and obese (OB) T2DM patients. MethodsNinety-four patients (aged 54 ± 8 years) with long-standing (median 10 years), treated diabetes (median HbA1c = 8.6%), who were NW (15), OW (64) or OB (15) based on BMI, underwent LII-SG. Insulin sensitivity and parameters of ß-cell function were measured from an Oral Glycaemic Tolerance Test pre- and post-operatively. ResultsAt a median of 13.4 months post-operatively, weight loss averaged 9.4 ± 1.3, 16.8±0.8 and 23.2±1.7 kg in NW, OW and OB subjects, respectively (p < 0.0001). Insulin sensitivity was fully restored (395 [108] vs 208 [99] ml min−1 m−2), fasting insulin secretion rate decreased (68 [52] vs 146 [120] pmol min−1 m−2) and total insulin output increased (52 [26] vs 39 [28] nmol m−2, all p ≤ 0.001). ß-cell glucose sensitivity doubled (37 [33] vs 18 [24] mol min−1 m−2 mM−1, p < 0.0001). The only parameter predicting remission of diabetes was a lower baseline insulin sensitivity (p = 0.005). ConclusionsLII-SG induced changes on T2DM by mechanisms in part distinct from weight loss, principally involving restoration of insulin sensitivity and improvement of ß-cell function.

Intravascular glucose/lactate sensors prepared with nitric oxide releasing poly(lactide- co-glycolide)-based coatings for enhanced biocompatibility

Intravenous amperometric needle-type enzymatic glucose/lactate sensors intended for continuous monitoring are prepared with a novel nitric oxide (NO) releasing layer to improve device hemocompatibility. To create an underlying NO release coating, the sensors with immobilized enzymes (either glucose oxidase or lactate oxidase) are prepared with a thin layer of poly(lactide- co-glycolide) (PLGA) loaded with lipophilic diazeniumdiolate species that slowly release NO via a proton driven reaction. An outer thin layer (ca. 30 μm) of PurSil (polyurethane/dimethylsiloxane copolymer) limits the flux of glucose and lactate to the inner layer of enzyme, to provide the desired linear amperometric response. A 30 μm coating of PLGA containing 33 wt% of the appropriate NO donor ( N-diazeniumdiolated dibutylhexanediamine, DBHD/N 2O 2) can release NO at a physiologically relevant rate >1 × 10 −10 mol min −1 cm −2 for at least 7 days without influencing the analytical performance of the glucose/lactate sensors. In vitro, the sensors exhibit relatively stable amperometric response over a one-week period with high selectivity over interferences (e.g., ascorbic acid) required for blood monitoring applications. Glucose sensors implanted in the veins of rabbits for 8 h exhibit significantly enhanced hemocompatibility for the NO release sensors vs. corresponding controls (without NO release in same animals), with greatly reduced thrombus formation on their surfaces. Further, the analytical performance of the NO release glucose sensors are superior to controls placed in the veins of the same animals, with a greater accuracy in measuring blood glucose levels as evaluated using a Clarke error grid type analysis.

Antidiuretic action of angiotensin II in the river lamprey Lampetra fluviatilis: evidence for endocrine control of kidney function in cyclostomes

Intravenous infusion of angiotensin II ([Asn¹ Val⁵]-Ang II) at 10⁻⁹ mol min⁻¹ kg⁻¹ body mass produced a significant antidiuresis in river lamprey Lampetra fluviatilis, captured during upstream migration and maintained in fresh water. Although the renin-angiotensin hormonal system (RAS) is now recognized in jawless fishes, until this study, the role of homologous Ang II in L. fluviatilis kidney function had not been examined. This study provides the first evidence for an antidiuretic action of Ang II in cyclostomes and, in evolutionary terms, suggests a renal function for the RAS in early vertebrates.

Gas emission into the atmosphere from controlled landfills: an example from Legoli landfill (Tuscany, Italy)

Landfill gas (LFG) tends to escape from the landfill surface even when LFG collecting systems are installed. Since LFG leaks are generally a noticeable percentage of the total production of LFG, the optimisation of the collection system is a fundamental step for both energy recovery and environmental impact mitigation. In this work, we suggest to take into account the results of direct measurements of gas fluxes at the air-cover interface to achieve this goal. During the last 5 years (2004-2009), 11 soil gas emission surveys have been carried out at the Municipal Solid Waste landfill of Legoli (Peccioli municipality, Pisa Province, Italy) by means of the accumulation chamber method. Direct and simultaneous measurements of CH(4) and CO(2) fluxes from the landfill cover (about 140,000 m(2)) have been performed to estimate the total output of both gases discharged into the atmosphere. Three different data processing have been applied and compared: Arithmetic mean of raw data (AMRD), sequential Gaussian conditional simulations (SGCS) and turning bands conditional simulations (TBCS). The total amount of LFG (captured and not captured) obtained from processing of direct measurements has been compared with the corresponding outcomes of three different numerical models (LandGEM, IPCC waste model and GasSim). Measured fluxes vary from undetectable values (<0.05 mol m(-2) day(-1) for CH(4) and <0.02 mol m(-2) day(-1) for CO(2)) to 246 mol m(-2) day(-1) for CH(4) and 275 mol m(-2) day(-1) for CO(2). The specific CH(4) and CO(2) fluxes (flux per surface unit) vary from 1.8 to 7.9 mol m(-2) day(-1) and from 2.4 to 7.8 mol m(-2) day(-1), respectively. The three different estimation methodologies (AMRD, SGCS and TBCS) used to evaluate the total output of diffused CO(2) and CH(4) fluxes from soil provide similar estimations, whereas there are some mismatches between these results and those of numerical LFG production models. Isoflux maps show a non-uniform spatial distribution, with high-flux zones not always corresponding with high-temperature areas shown by thermographic images. The average value estimated over the 5-year period for the Legoli landfill is 245 mol min(-1) for CH(4) and 379 mol min(-1) for CO(2), whereas the volume percentage of CH(4) in the total gas discharged into the atmosphere varies from 29% to 51%, with a mean value of 39%. The estimated yearly emissions from the landfill cover is about 1.29 x 10(8) mol annum(-1) (2,100 t year(-1)) of CH(4) and 1.99 x 10(8) mol annum(-1) (8,800 t year(-1)) of CO(2). Considering that the CH(4) global warming potential is 63 times greater than that of CO(2) (20 a time horizon, Lashof and Ahuja 1990), the emission of methane corresponds to 130,000 t annum(-1) of CO(2). The importance of these studies is to provide data for the worldwide inventory of CH(4) and CO(2) emissions from landfills, with the ultimate aim of determining the contribution of waste disposal to global warming. This kind of studies could be extended to other gas species, like the volatile organic compounds.

Physiological role and redox properties of a small cytochrome c5, cytochrome c-552, from alkaliphile, Pseudomonas alcaliphila AL15-21T

Cytochrome c-552 from Pseudomonas alcaliphila AL15-21(T), which is a small cytochrome c(5) from Pseudomonas spp., was first purified and characterized in our previous study. Although it has been found that cytochrome c-552 is induced at a high pH under air-limited condition, the physiological role of this cytochrome c has not been clarified yet. Therefore, to understand its physiological role, further characterization of this cytochrome expressed in Escherichia coli was performed. The yield of the recombinant protein reached 2.8 mg/l of culture, which was 76.4-fold larger than that of native cells. Analytical data of the recombinant protein exactly agreed with that of native cytochrome c-552. The recombinant cytochrome c-552 was oxidized by partially purified cb-type cytochrome c oxidase from P. alcaliphila AL15-21(T) at a rate of 9.6 mu mol min(-1) mg oxidase(-1). Unlike reported cytochromes c from other Pseudomonas spp., the E degrees ' values between pHs 5.0 and 10.0 were nearly unchanged. Cytochrome c-552 oxidized very slowly at pHs 8.0 (6.1 x 10(-4) h(-1)), 9.0 (1.4 x 10(-3) h(-1)) and 10.0 (1.6 x 10(-3) h(-1)), whereas it oxidized more rapidly at pH 7.0 (2.5 x 10(-3) h(-1)). On the other hand, horse heart cytochrome c showed higher oxidation rates at pHs 6.0-10.0 than cytochrome c-552. It is considered that the high electron-retaining ability of cytochrome c-552 at high pHs is important for its physiological function in the environmental adaptation of this bacteria for superior growth at high pHs under air-limited conditions.

ICChI, a glycosylated chitinase from the latex of Ipomoea carnea

A multi-functional enzyme ICChI with chitinase/lysozyme/exochitinase activity from the latex of Ipomoea carnea subsp. fistulosa was purified to homogeneity using ammonium sulphate precipitation, hydrophobic interaction and size exclusion chromatography. The enzyme is glycosylated (14–15%), has a molecular mass of 34.94 kDa (MALDI–TOF) and an isoelectric point of pH 5.3. The enzyme is stable in pH range 5.0–9.0, 80 °C and the optimal activity is observed at pH 6.0 and 60 °C. Using p-nitrophenyl- N-acetyl-β- d-glucosaminide, the kinetic parameters K m, V max, K cat and specificity constant of the enzyme were calculated as 0.5 mM, 2.5 × 10 −8 mol min −1 μg enzyme −1, 29.0 s −1 and 58.0 mM −1 s −1 respectively. The extinction coefficient was estimated as 20.56 M −1 cm −1. The protein contains eight tryptophan, 20 tyrosine and six cysteine residues forming three disulfide bridges. The polyclonal antibodies raised and immunodiffusion suggests that the antigenic determinants of ICChI are unique. The first fifteen N-terminal residues G–E–I–A–I–Y–W–G–Q–N–G–G–E–G–S exhibited considerable similarity to other known chitinases. Owing to these unique properties the reported enzyme would find applications in agricultural, pharmaceutical, biomedical and biotechnological fields.