Long-term stability of hydrogen and organic acids production in an anaerobic fluidized-bed reactor using heat treated anaerobic sludge inoculum

This study evaluates the stability of hydrogen and organic acids production in an anaerobic fluidized-bed reactor (AFBR) that contains expanded clay (2.8-3.35 mm in diameter) as a support medium and is operated on a long-term basis. The reactor was inoculated with thermally pre-treated anaerobic sludge and operated with decreasing hydraulic retention time (HRT), from 8 h to 1 h, at a controlled temperature of 30 degrees C and a pH of about 3.8. Glucose (2000 mg L(-1)) was used as the substrate, generating conversion rates of 92-98%. Decreasing the HRT from 8 h to 1 h led to an increase in average hydrogen-production rates, with a maximum value of 1.28 L h(-1) L(-1) for an HRT of 1 h. In general, hydrogen yield production increased as HRT decreased, reaching 2.29 mol of H(2)/mol glucose at an HRT of 2 h and yielding a maximum hydrogen content of 37% in the biogas. No methane was detected in the biogas throughout the period of operation. The main soluble metabolites (SMP) were acetic acid (46.94-53.84% of SMP) and butyric acid (34.51-42.16% of SMP), with less than 15.49% ethanol. The steady performance of the AFBR may be attributed to adequate thermal treatment of the inoculum, the selection of a suitable support medium for microbial adhesion, and the choice of satisfactory environmental conditions imposed on the system. The results show that stable hydrogen production and organic acids production were maintained in the AFBR over a period of 178 days. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Application of molecular techniques to evaluate the methanogenic archaea and anaerobic bacteria in the presence of oxygen with different COD : sulfate ratios in a UASB reactor

In this paper, the microbial characteristics of the granular sludge in the presence of oxygen (3.0 +/- 0.7 mg O-2 1(-1)) were analyzed using molecular biology techniques. The granules were provided by an upflow anaerobic sludge blanket (UASB) operated over 469 days and fed with synthetic substrate. Ethanol and sulfate were added to obtain different COD/SO42- ratios (3.0, 2.0, and 1.6). The results of fluorescent in situ hybridization (FISH) analyses showed that archaeal cells, detected by the ARC915 probe, accounted for 77%, 84%, and 75% in the COD/SO42- ratios (3.0, 2.0, and 1.6, respectively). Methanosaeta sp. was the predominant acetoclastic archaea observed by optical microscopy and FISH analyses, and confirmed by sequencing of the excised bands of the DGGE gel with a similarity of 96%. The sulfate-reducing bacterium Desulfovibrio vulgaris subsp. vulgaris (similarity of 99%) was verified by sequencing of the DGGE band. Others identified microorganism were similar to Shewanella sp. and Desulfitobacterium hafniense, with similarities of 95% and 99%, respectively. These results confirmed that the presence of oxygen did not severely affect the metabolism of microorganisms that are commonly considered strictly anaerobic. We obtained mean efficiencies of organic matter conversion and sulfate reducing higher than 74%. (C) 2008 Elsevier Ltd. All rights reserved.

Catalytic conversion of wastes from the bioethanol production into carbon nanomaterials

This work addressed the production of carbon nanomaterials (CNMs) by catalytic conversion of wastes from the bioethanol industry, in the form of either sugarcane bagasse or corn-derived distillers dried grains with solubles (DDGS). Both bagasse and DDGS were pyrolysed at temperatures in the range of 600-1000 degrees C. The pyrolyzate gases were then used as CNM growth agents by chemical vapor deposition on stainless steel meshes, serving as both catalysts and substrates. CNM synthesis temperatures of 750-1000 degrees C were explored, and it was determined that their growth was most pronounced at 1000 degrees C. The nanomaterials produced from pyrolysis of bagasse were in the form of long, straight, multi-wall nanotubes with smooth walls and axially uniform diameters. Typical lengths were circa 50 mu m and diameters were in the range of 20-80 nm. The nanomaterials produced from pyrolysis of DDGS were in the form of long, entangled, rope-like structures with rugged walls, and axially non-uniform diameters. Typical diameters were in the range of 100-300 nm and their lengths were in the tens of microns. This process also produces a bio-syngas byproduct that is enriched in hydrogen. (C) 2011 Elsevier B.V. All rights reserved.

Microbial Metabolic Potential Affected by Surplus Wastewater Irrigation in Tropical Soil Cultivated with Tifton 85 Bermuda Grass (Cynodon dactylon Pers. X C. niemfuensis Vanderyst)

Agricultural reuse of treated sewage effluent (TSE) is an environmental and economic practice; however, little is known about its effects on the characteristics and microbial function in tropical soils. The effect of surplus irrigation of a pasture with TSE, in a period of 18 months, was investigated, considering the effect of 0% surplus irrigation with TSE as a control. In addition, the experiment consisted of three surplus treatments (25%, 50%, and 100% excess) and a nonirrigated pasture area (SE) to compare the soil microbial community level physiological profiles, using the Biolog method. The TSE application increased the average substrate consumption of the soil microbial community, based on the kinetic parameters of the average well color development curve fitting. There were no significant differences between the levels of surplus irrigation treatments. Surplus TSE pasture irrigation caused minor increases in the physiological status of the soil microbial community but no detectable damage to the pasture or soil.

Changes in the genetic structure of Bacteria and microbial activity in an agricultural soil amended with tannery sludge

The application of tannery sludge to soils is a form of recycling; however, few studies have examined the impacts of this practice on soil microbial properties. We studied effects of two applications (2006 and 2007) of tannery sludge (with a low chromium content) on the structure of the bacterial community and on the microbial activity of soils. We fertilized an agricultural area in Rolandia, Parana state, Brazil with different doses of sludge based on total N content, which ranged from 0 to 1200 kg N ha(-1). Sludge remained on the soil surface for three months before being plowed. Soils were sampled seven times during the experiment. Bacterial community structure, assessed by denaturing gradient gel electrophoresis (DGGE), was modified by the application of tannery sludge. Soon after the first application, there was clear separation between the bacterial communities in different treatments, such that each dose of sludge was associated with a specific community. These differences remained until 300 days after application and also after the second sludge application, but 666 days after the beginning of the experiment no differences were found in the bacterial communities of the lowest doses and the control. The principal response curve (PRC) analysis showed that the first sludge application strongly stimulated biological activity even 300 days after application. The second application also stimulated activity, but at a lower magnitude and for a shorter time, given that 260 days after the second application there was no difference in biological activity among treatments. PRC also showed that the properties most influenced by the application of tannery sludge were enzymatic activities related to N cycling (asparaginase and urease). The redundancy analysis (RDA) showed that tannery sludge`s influence on microbial activity is mainly related to increases in inorganic N and soil pH. Results showed that changes in the structure of the bacterial community in the studied soils were directly related to changes of their biological activity. (C) 2010 Elsevier Ltd. All rights reserved.

Microbial activity and community composition in saline and non-saline soils exposed to multiple drying and rewetting events

The effects of drying and rewetting (DRW) have been studied extensively in non-saline soils, but little is known about the impact of DRW in saline soils. An incubation experiment was conducted to determine the impact of 1-3 drying and re-wetting events on soil microbial activity and community composition at different levels of electrical conductivity in the saturated soil extract (ECe) (ECe 0.7, 9.3, 17.6 dS m(-1)). A non-saline sandy loam was amended with NaCl to achieve the three EC levels 21 days prior to the first DRW; wheat straw was added 7 days prior to the first DRW. Each DRW event consisted of 1 week drying and 1 week moist (50% of water holding capacity, WHC). After the last DRW, the soils were maintained moist until the end of the incubation period (63 days after addition of the wheat straw). A control was kept moist (50% of WHC) throughout the incubation period. Respiration rates on the day after rewetting were similar after the first and the second DRW, but significantly lower after the third DRW. After the first and second DRW, respiration rates were lower at EC17.6 compared to the lower EC levels, whereas salinity had little effect on respiration rates after the third DRW or at the end of the experiment when respiration rates were low. Compared to the continuously moist treatment, respiration rates were about 50% higher on day 15 (d15) and d29. On d44, respiration rates were about 50% higher at EC9.7 than at the other two EC levels. Cumulative respiration was increased by DRW only in the treatment with one DRW and only at the two lower EC levels. Salinity affected microbial biomass and community composition in the moist soils but not in the DRW treatments. At all EC levels and all sampling dates, the community composition in the continuously moist treatment differed from that in the DRW treatments, but there were no differences among the DRW treatments. Microbes in moderately saline soils may be able to utilise substrates released after multiple DRW events better than microbes in non-saline soil. However, at high EC (EC17.6), the low osmotic potential reduced microbial activity to such an extent that the microbes were not able to utilise substrate released after rewetting of dry soil.

Microbial Decontamination Study of Medicinal Plants by Plasma Treatment

In the present work the microbial decontamination of some medicinal plants by plasma treatment using oxygen gas or a mixture of oxygen and hydrogen peroxide was investigated. The efficiency of the decontamination process was analyzed by the count of heterotropic microorganisms and pathogenic research. The results showed a reduction in the microorganism number such as 3 and 4 logarithmic cycles for ginkgo and artichoke, while it was not efficient for samples containing hard and thick cells, and mucilage, such as guarana and chamomile.

Electron beam irradiation of Matricaria chamomilla L. for microbial decontamination

Wild chamomile (Matricaria chamomilla L.) is one of the most popular herbal materials with both internal and external use to cure different health disturbances. As a consequence of its origin, chamomile could carry various microbial contaminants which offer different hazards to the final consumer. Reduction of the microbial load to the in force regulation limits represents an important phase in the technological process of vegetal materials, and the electron beam treatment might be an efficient alternative to the classical methods of hygienic quality assurance. The purpose of the study was to analyze the potential application of the electron beam treatment in order to assure the microbial safety of the wild chamomile. Samples of chamomile dry inflorescences were treated in electron beam (e-beam) of 6 MeV mean energy, at room temperature and ambient pressure. Some loss of the chemical compounds with bioactive role could be noticed, but the number of microorganisms decreased as a function on the absorbed dose. Consequently, the microbial quality of studied vegetal material inflorescences was improved by e-beam. irradiation. (C) 2008 Elsevier B.V. All rights reserved.

One-step biomimetic conversion of a furanoheliangolide into an eremantholide using Stryker`s reagent

The conversion of a furanoheliangolide structure (15-deoxygoyazensolide) into an eremantholide one (eremantholide C) was achieved by tandem hydride conjugate addition-intramolecular carbanion addition using Stryker`s reagent. (c) 2008 Elsevier Ltd. All rights reserved.

Acid-mediated conversion of methylene-interrupted bisepoxides to tetrahydrofurans: A biomimetic transformation

The acid-mediated transformation of syn and anti methylene interrupted cis,cis and cis,trans bisepoxides to tetrahydrofurans is high yielding, and demonstrates both regioselectivity and stereoselectivity. Trans,trans methylene interrupted bisepoxides do not yield tetrahydrofurans under the same conditions.

On the mechanism of microbial cell disruption in high-pressure homogenisation

The tensions produced in the wall of a rigid, thin-walled, liquid-filled sphere as it moves with an axisymmetric straining flow are examined. This problem has not been previously addressed. A generalised correlation for the maximum wall tension, expressed in dimensionless form as a Weber number (We), is developed in terms of the acceleration number (Ac) and Reynolds number (Re) of the straining flow. At low Reynolds number We is dominated by viscous forces, while inertial forces due to internal pressure gradients caused by sphere acceleration dominate at higher Re. The generalised correlation has been used to examine the case of a typical yeast cell (a thin-walled, liquid-filled sphere) passing through a typical high-pressure homogeniser (a straining-flow device). At 56 MPa homogenising pressure, a 6 mu m yeast cell experiences tensions in the inertially dominated regime (Re = 100). The correlation gives We = 0.206, corresponding to a maximum wall tension of 8 Nm(-1). This is equivalent to an applied compressive force of 150 mu N and compares favourably with the force required to break yeast cells under compressive micromanipulation (40-90 mu N). Inertial forces may therefore be an important and previously unrecognised. mechanism of microbial cell disruption during high-pressure homogenisation. Further work is required to examine the likelihood of cell deformation in the high-strain-rate short-residence-time environment of the homogeniser, and the effect that such deformation may have on the contribution of inertial forces to disruption. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.

Membrane-bounded nucleoids in microbial symbionts of marine sponges

In thin sections of resin-embedded samples of glutaraldehyde- and osmium tetroxide-fixed tissue from five genera of marine sponges, Stromatospongia, Astrosclera, Jaspis, Pseudoceratina and Axinyssa, cells of a bacteria-like symbiont microorganism which exhibit a membrane-bounded nuclear region encompassing the fibrillar nucleoid have been observed within the sponge mesohyl. The nuclear region in these cells is bounded by a single bilayer membrane, so that the cell cytoplasm is divided into two distinct regions. The cell wall consists of subunits analogous to those in walls of some Archaea. Cells of the sponge symbionts observed here are similar to those of the archaeal sponge symbiont Cenarchaeum symbiosum. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

A comparative study of N2O conversion to N-2 over Co/AC and Cu/AC catalysts

Catalytic conversion of N2O to N-2 over Cu- and Co-impregnated activated carbon catalysts (Cu/AC and Co/AC) was investigated. Catalytic activity measurements were carried out in a fixed-bed flow reactor at atmospheric pressure. The catalysts were characterized by N-2 adsorption, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). This study aimed to provide insights into the following aspects: the metal dispersion, changes in pore structure, influence of catalyst loading on reaction, and reaction mechanism. Increasing loading of Co or Cu led to decreasing dispersion, but 20 wt % loading was an upper limit for optimal activities in both cases, with too high loading causing sintering of metal. Co exhibited a relatively better dispersion than Cu. Impregnation of metal led to a large decrease in surface area and pore volume, especially for 30 wt % of loading. 20 wt % of loading has proved to be the optimum for both Cu and Co, which shows the highest activity. Both N2O-Co/AC and -Cu/AC reactions are based upon a redox mechanism, but the former is limited by the oxygen transfer from catalysts to carbon, while N2O chemisorption on the surface of Cu catalyst controls the latter. The removal of oxygen from cobalt promotes the activity of Co/AC, but it is beneficial for Cu/AC to keep plenty of oxygen to maintain the intermediate oxidation of copper-Cu1+. The different nature of the two catalysts and their catalytic reaction mechanisms are closely related to their different electronegativities.

Catalytic conversion to N2O to N2 over potassium catalyst supported on activated carbon

Catalytic conversion of N2O to N-2 With potassium catalysts supported on activated carbon (K/AC) was investigated. Potassium proves to be much more active and stable than either copper or cobalt because potassium possesses strong abilities both for N2O chemisorption and oxygen transfer. Potassium redispersion is found to play a critical role in influencing the catalyst stability. A detailed study of the reaction mechanism was conducted based upon three different catalyst loadings. It was found that during temperature-programmed reaction (TPR), the negative oxygen balance at low temperatures (< 50 degrees C) is due to the oxidation of the external surface of potassium oxide particles, while the bulk oxidation accounts for the oxygen accumulation at higher temperatures (below ca. 270 degrees C). N2O is beneficial for the removal of carbon-oxygen complexes because of the formation of CO2 instead of CO and because of its role in making the chemisorption of produced CO2 on potassium oxide particles less stable. A conceptual three-zone model was proposed to clarify the reaction mechanism over K/AC catalysts. CO2 chemisorption at 250 degrees C proves to be an effective measurement of potassium dispersion. (C) 1999 Academic Press.