Biological fermentation of syngas

Este resumo faz parte de: Book of abstracts of the Meeting of the Institute for Biotechnology and Bioengineering, 2, Braga, Portugal, 2010. A versão completa do livro de atas está disponível em: http://hdl.handle.net/1822/1096

Microbial syngas conversion by mesophilic and thermophilic anaerobic mixed-cultures

Synthesis gas (or syngas) can be produced from the gasification of a variety of recalcitrant or biodegradable wastes. Syngas is a mixture composed of mainly H2, CO and CO2 that can be used in a biological process for the production of fuels or usable chemicals. The main goal of this work was to study the physiology and microbial composition of anaerobic cultures able to utilize syngas. The results indicated that the thermophilic sludge inoculum presents a promising carboxydotrophic potential comparing to the mesophilic sludge inoculum. Monitoring of microbial structure of thermophilic enriched cultures by using PCR-DGGE and cloning techniques showed that bacterial community profiles clustered in three different groups

Precession and Nutation in the eta Carinae binary system: Evidences from the X-ray light curve

It is believed that eta Carinae is actually a massive binary system, with the wind-wind interaction responsible for the strong X-ray emission. Although the overall shape of the X-ray light curve can be explained by the high eccentricity of the binary orbit, other features like the asymmetry near periastron passage and the short quasi-periodic oscillations seen at those epochs, have not yet been accounted for. In this paper we explain these features assuming that the rotation axis of eta Carinae is not perpendicular to the orbital plane of the binary system. As a consequence, the companion star will face eta Carinae on the orbital plane at different latitudes for different orbital phases and, since both the mass loss rate and the wind velocity are latitude dependent, they would produce the observed asymmetries in the X-ray flux. We were able to reproduce the main features of the X-ray light curve assuming that the rotation axis of eta Carinae forms an angle of 29 degrees with the axis of the binary orbit. We also explained the short quasi-periodic oscillations by assuming nutation of the rotation axis, with amplitude of about 5 degrees and period of about 22 days. The nutation parameters, as well as the precession of the apsis, with a period of about 274 years, are consistent with what is expected from the torques induced by the companion star.Comment: 9 pages, 8 figures, MNRAS accepte

Microbial communities shifts in dark fermentative H2 production at mesophilic, thermophylic and hyperthermophylic conditions

Hydrogen is foreseen as a viable CO2-neutral alternative to fossil fuels for generation of energy. Production of H2 from wastes/wastewaters is possible as this is one of the main products resulting from anaerobic fermentation of organic compounds. If hydrogenotrophic methanogens are suppressed, H2-rich biogas can be recovered from anaerobic reactors. In order to optimize and improve H2 production, it is essential to get more insight into the composition and structure of the microbial communities involved in the process. In this study microbial community shifts in expanded granular sludge blanket (EGSB) reactors producing H2 at different temperatures and organic loading rates (OLR) were studied using PCRDGGE fingerprinting analysis. The aim was to get more insight into the microbiology of dark fermentative hydrogen production at mesophilic, thermophilic and hyperthermophilic temperatures. Three EGSB reactors were inoculated with granular biomass previously treated with heat to suppress methanogens. Reactors were operated at 37, 55 and 70 ºC with 5gCOD L-1of a mixture containing glucose and L-arabinose (1:1); pH was kept at 5.5. OLR applied varied from 5 to 16. PCR amplification of the 16S rRNA gene and subsequent DGGE analysis of sludge samples collected from the reactors at different operational times showed different profiling, mainly correlated with differences in temperature. Bacterial diversity (measured as the number of bands) in sludge samples from reactors operating at 55 ºC and 70ºC was remarkably lower than in sludges growing at 37ºC. No significant changes on DGGE profiles diversity were observed with the increase of OLR over time

Exact Renormalization of Massless QED2

We perform the exact renormalization of two-dimensional massless gauge theories. Using these exact results we discuss the cluster property and confinement in both the anomalous and chiral Schwinger models.Comment: 14 pages, no figures, introduction and conclusions modifie

Modelling spectral line profiles of wind-wind shock emissions from massive binary systems

One of the most intriguing spectral features of WR binary stars is the presence of time-dependent line profiles. Long term observations of several systems revealed the periodicity of this variability, synchronized with the orbital movement. Several partially successful models have been proposed to reproduce the observed data. The most promising assume that the origin of the emission is the wind-wind interaction zone. In this scenario, two high velocity and dense winds produce a strong shock layer, responsible for most of the X-rays observed from these systems. As the secondary star moves along its orbital path, the shock region of conical shape, changes its position with relation to the line of sight. As a consequence, the stream measured Doppler shift presents time variations resulting in position changes of the spectral line. In our work, we present an alternative model, introducing turbulence in the shock layer to account for the line broadening and opacity effects for the asymmetry in the line profiles. We showed that the gas turbulence avoids the need of an unnaturally large contact layer thickness to reproduce line broadening. Also, we demonstrated that if the emission from the opposing cone surface is absorbed, the result is a single peaked profile. This result fully satisfies the recent data obtained from massive binary systems, and can help on the determination of both winds and orbital parameters. We successfully applied this model to the Br22 system and determined its orbital parameters.Comment: To appear in the MNRA

Comparative analysis of carbon monoxide tolerance among Thermoanaerobacter species

An anaerobic thermophilic strain (strain PCO) was isolated from a syngas-converting enrichment culture. Syngas components cannot be used by strain PCO, but the new strain is very tolerant to carbon monoxide (pCO = 1.7 × 105 Pa, 100% CO). 16S rRNA gene analysis and DNA-DNA hybridization revealed that strain PCO is a strain of Thermoanaerobacter thermohydrosulfuricus. The physiology of strain PCO and other Thermoanaerobacter species was compared, focusing on their tolerance to carbon monoxide. T. thermohydrosulfuricus, T. brockii subsp. finnii, T. pseudethanolicus, and T. wiegelii were exposed to increased CO concentrations in the headspace, while growth, glucose consumption and product formation were monitored. Remarkably, glucose conversion rates by Thermoanaerobacter species were not affected by CO. All the tested strains fermented glucose to mainly lactate, ethanol, acetate, and hydrogen, but final product concentrations differed. In the presence of CO, ethanol production was generally less affected, but H2 production decreased with increasing CO partial pressure. This study highlights the CO resistance of Thermoanaerobacter species.Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684)FCT and European Social Fund (POPH-QREN) through postdoc grant SFRH/BPD/104837/2014ERC grant (project 323009) and a Gravitation grant (project 024.002.002) of the Netherlands Ministry of Education, Culture and Science and the Netherlands Science Foundation (NWO

Rugged Metropolis Sampling with Simultaneous Updating of Two Dynamical Variables

The Rugged Metropolis (RM) algorithm is a biased updating scheme, which aims at directly hitting the most likely configurations in a rugged free energy landscape. Details of the one-variable (RM$_1$) implementation of this algorithm are presented. This is followed by an extension to simultaneous updating of two dynamical variables (RM$_2$). In a test with Met-Enkephalin in vacuum RM$_2$ improves conventional Metropolis simulations by a factor of about four. Correlations between three or more dihedral angles appear to prevent larger improvements at low temperatures. We also investigate a multi-hit Metropolis scheme, which spends more CPU time on variables with large autocorrelation times.Comment: 8 pages, 5 figures. Revisions after referee reports. Additional simulations for temperatures down to 220

Induction of hydrogen production affects micro and macro structure of granular sludge

Mixed-culture dark fermentation is an environmentally friendly bio-hydrogen production process. In this work we study the potential for directing microbial anaerobic mixed communities towards improved hydrogen production. Strategies applied for promoting the selection of hydrogen-producing bacteria in anaerobic granules consisted of Heat treatment and chemical treatment with 2-bromo-ethane sulfonate (BES) and with BES+Chloroform. Three EGSB reactors, RHeat, RBES and RBES+Chlo, where inoculated with each treated granules and fed with synthetic sugar-based wastewater. Hydrogen production was monitored. Morphological integrity and microbial diversity of the granules were studied using image analysis technique and 16S rRNA gene based techniques, respectively. Hydrogen production in RHeat was below 300 mLH2L-1d-1, with the exception of a single transient production of 1000 mLH2L-1d-1, after decrease the HRT. In RBES+Chlo hydrogen production rate never exceeded 300 mLH2L-1d-1. In this sludge, a physical deterioration of the granules was observed along with a decrease of their density and microbial diversity. In RBES, a transient period of unstable H2 production was observed but an additional pulse of BES triggered hydrogen production rate to an average value of 700 ± 200 mLH2L-1d-1, which was kept for 30 days. This strategy did not affect significantly granules structure. Dominant bacterial ribotypes found in RBES were closely related to Clostridium species and to uncultured microorganisms belonging to Clostridiaceae and Ruminococcaceae. This work demonstrates that different methods applied for directing granular sludge for hydrogen production can cause changes in the macro- and microstructure of granular sludge, which can be incompatible with the long-term operation of high-rate reactors