35 research outputs found
Involvement of carbon dioxide in the aerobic biodegradation of ethylene oxide, ethene, and vinyl chloride
The involvement of a carboxylase in metabolism of C-2 alkenes by Ochrobactrum sp. strain TD and Pseudomonas putida strain AJ was examined. With resting cells of strain TD grown on vinyl chloride, ethene, and ethylene oxide, the maximum specific rate of ethylene oxide consumption decreased significantly in the absence of external CO2 in comparison to cells provided with room air or added CO2. The amount of 14CO2 incorporated into biomass by resting cells of strain TD grown on ethylene oxide increased more than 13-fold when the assay substrate was ethylene oxide versus acetate. These results indicate that strain TD uses a carboxylase. Similar experiments were performed with strain AJ with the results suggesting that a carboxylase is not involved. In this regard, strain AJ is more similar to various Mycobacterium isolates that also do not appear to use a carboxylase during metabolism of vinyl chloride and ethene.Department of Biomedical and Biomolecular
Sciences, Sheffield Hallam University
Effect of temperature and hydraulic retention time on hydrogen producing granules : homoacetogenesis and morphological characteristics
The effect of temperature and hydraulic retention time (HRT) on the
homoacetogenesis and on .the morphological characteristics of hydrogen
producing granules was investigated. Hydrogen was produced using an
expanded granular sludge blanket (EGSB) reactor, fed with glucose and Larabinose,
under mesophilic (37ºC), thermophilic (55ºC), and hyperthermophilic
(70ºC) conditions. Apparent homoacetogenesis was observed only at
mesophilic conditions. Glucose was utilized preferentially over L-arabinose at
thermophilic and hyper-thermophilic conditions. Higher yields of hydrogen
production were linked to the decrease of lactic acid and the increase of nbutyrate,
in all temperatures tested. Under mesophilic conditions with an
organic loading rate (OLR) of 5KgCOD/m3/d the total filaments length per VSS
(TL/VSS) increased and the apparent granules density (VSS/TA) dropped off.
With the application of OLR 10 and 16KgCOD/m3/d, TL/VSS decreased and the
VSS/TA augmented suggesting an increase of granules density. Under
thermophilic conditions the enhance of TL/VSS and the diminish of VSS/TA only
occurred with the application of OLR16KgCOD/m3/d, while under
hyperthermophilic conditions it happened since the beginning of operation with
the application of OLR10KgCOD/m3/d. Granules size was not affected by
temperature but the application of higher OLR promote a decline on the
percentage of projected area of aggregates with equivalent diameter (Deq)
larger than 1 mm.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/29823/2006, SFRH/BPD/24221/2005,
projecto POCTI/ENR/57786/200
Bio-hydrogen production in an EGSB reactor under mesophilic, thermophilic and hyperthermophilic conditions
Mesophilic, thermophilic and hyperthermophilic bio-hydrogen production with an expanded
granular sludge blanket (EGSB) fed with glucose and arabinose, without methane production, was
demonstrated. Homoacetogenesis was observed on reactor when operated under mesophilic (37ºC)
conditions but not under thermophilic (55ºC) and hyper-thermophilic conditions (70ºC). It was
also found that under thermophilic and hyper-thermophilic conditions glucose is preferentially
consumed than arabinose.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/29823/2006, SFRH/BPD/24221/2005, POCI/ENR/57786/2004
Effect of arabinose concentration on dark fermentation hydrogen production using different mixed cultures
Dark fermentation hydrogen production from arabinose at concentrations ranging
between 0 and 100 g/L was examined in batch assays for three different mixed anaerobic
cultures, two suspended sludges (S1, S2) obtained from two different sludge digesters
and one granular sludge (G) obtained from a brewery wastewater treatment plant. After
elimination of the methanogenic activity by heat treatment, all mixed cultures produced
hydrogen, and optimal hydrogen rates and yields were generally observed for concentrations
between 10 and 40 g/L of substrate. Higher concentrations of arabinose up to 100 g/L
inhibited hydrogen production, although the effect was different from inoculum to inoculum.
It was evident that the granular biomass was less affected by increased initial arabinose
concentrations when calculating the rate of decrease in hydrogen yields versus
arabinose concentrations, compared against the two suspended sludges.
The largest amount of soluble microbial product produced for all three inocula was for
n-butyrate. Also, valeric acid production was observed in some samples.Fundação para a Ciência e a Tecnologia (FCT
Effect of methanogenic inhibitors, inocula type, and temperature on biohydrogen production from food components
Dark fermentation hydrogen production from a mixture of food components using two different methods of methanogenic
inhibition (autoclaving and BES) and three different temperatures (37, 60, and 70 ºC) was examined in batch assays for two
different mixed anaerobic cultures - one suspended sludge (S) obtained from an anaerobic digester and one granular sludge (G)
obtained from a brewery wastewater treatment plant. In general, BES-inhibition of sludge was more robust when compared
against heat-treated inoculum. Also, hydrogen, VFA, and sCOD production were affected by increases in temperature although
the effects were less severe for G than for S. In addition, differences in individual VFAs were observed between the two inocula.
S produced more acetate as a percentage of VFATOTAL compared to G. Conversely, G produced more butyrate compared to S.
Differences in the microbial communities were likely responsible for the diverse behaviour of the two inocula.Fundação para a Ciência e a Tecnologia (FCT
Impact of magnetite nanoparticles on the syntrophic dechlorination of 1,2-dichloroethane
In anaerobic environments microorganisms exchange electrons with community members and with soil and groundwater compounds. Interspecies electron transfer (IET) occurs by several mechanisms: diffusion of redox compounds or direct contact between cells. This latter mechanism may be facilitated by the presence of conductive nanoparticles (NP), possibly serving as electron conduits among microorganisms. Our study examined the effect of magnetite (Fe3O4) NP on the dechlorination of 1,2-dichloroethane (1,2-DCA) by a mixed-culture. The addition of NP (170 mg L− 1 total Fe) enhanced the acetate-driven reductive dechlorination of 1,2-DCA to harmless ethene (via reductive dihaloelimination) up to 3.3-times (2.3 μeq L− 1 d− 1 vs. 0.7 μeq L− 1 d− 1), while decreasing the lag time by 0.8 times (23 days) when compared to unamended (magnetite-free) microcosms. Dechlorination activity was correlated with the abundance of Dehalococcoides mccartyi, which accounted up to 50% of total bacteria as quantified by CARD-FISH analysis, pointing to a key role of this microorganism in the process. Given the widespread abundance of conductive minerals in the environment, the results of this study may provide new insights into the fate of 1,2-DCA and suggest new tools for its remediation by linking biogeochemical mechanisms.The authors would like to thank FCT (Portuguese Foundation for Science and Technology) for the financial support of Patrícia Leitão through the PhD grant SFRH/BD/87312/2012 and to CEMUP - Centro de Materiais da Universidade do Porto for expert assistance and helpful discussions about SEM measurements.info:eu-repo/semantics/publishedVersio
Fermentative bio-hydrogen production from organic wastes and sugars
Utilization of renewable energy has been identified as a priority within the “European Energy Policy”
which stresses the need to develop new sources of green energy. A follow-up of the programme
“Intelligent Energy – Europe” (Decision No. 1230/2003/EC of the European Parliament and of the
Council of 26 June 2003) is projected for the 7th Framework Programme (2007-2013). The main focus
of the programme is the production of electricity from renewable sources of energy, as described in
Directive 2001/77/EC of the European Parliament and of the Council of 27 September 2001. According
to this document, Portugal has committed to raise the national electricity production exclusively from
renewable sources to 39% by 2010. In addition, it constitutes an essential part of the package of
measures necessary to comply with the commitments made by the EU under the 1997 Kyoto Protocol
on the reduction of greenhouse gas emissions.
Hydrogen is a CO2-neutral energy source with a very promising future as an alternative to fossil fuels
for energy production. The treatment and disposal of wastes by conventional methods poses many
problems throughout the world and may result in the consumption of energy. In addition, costs to
dispose and treat wastes are escalating. Hydrogen can be produced, from undesirable waste products
by bacterial fermentation, to generate electricity.
The Centre for Biological Engineering at the University of Minho is studying bio-hydrogen production
from organic wastes and sugars. The specific tasks of the project (FCT/POCI/ENR/57786/2004)
include the utilization of different waste compositions from a real kitchen waste and sugars to produce
and optimize H2 yields, methanogenesis inhibition strategies, design, construction and operation of
batch and continuous lab scale reactors for mesophilic (37 °C), thermophilic (55 °C), and
hyperthermophilic (70 °C) conditions. In addition, molecular ecology techniques are being used to
study bacterial community dynamics in the different bioreactors, comparing the microbial communities
developed at different temperatures and different OLR. One objective is to determine the optimal
conditions to select the most important microorganisms involved in H2 production
Effect of pH on fermentative hydrogen production from L-arabinose using mixed cultures
Hydrogen is now considered one of the alternatives to fossil fuels. It is preferred to biogas or methane
because hydrogen is not chemically bound to carbon and therefore, combustion does not contribute to
green house gases or acid rain [1]. One alternative to sustainable H2 energy production from
renewable energy sources is through microbiological fermentation. There have been many studies
examining the effect of pH in fermentative hydrogen production from glucose and sucrose using mixed
microflora [2,3,4,5,6]. However, fermentative hydrogen production from arabinose, one of the most
common pentoses and a component of various biopolymers such as hemicellulose and plant
polysaccharides using mixed microflora has not been previously examined. Understanding the
influence of pH on biohydrogen production is necessary to develop arabinose-based hydrogen
fermentation applications, such as the use of agricultural wastes.
Biohydrogen production from arabinose was examined using three different anaerobic sludges with
different pHs ranging from 4.5 to 8.0. Arabinose (30 g/L) was used as the substrate for all experiments.
Individual cumulative hydrogen production data were used to estimate the three parameters of the
modified Gompertz equation. This model has been used for describing the progress of cumulative gas
production obtained from the batch experiments. Higher hydrogen production potentials (more than 35
mL) were observed with pH values greater than 6.0 for Unicer (granular sludge) and Choupal (disperse
anaerobic digester sludge supplemented with fat) and greater than 6.5 for Freixo (disperse anaerobic
digester sludge). Choupal biomass had the largest hydrogen production rate (4.8±1.4 mL/h) at pH 7.5,
compared with the other two sludges. Unicer biomass had the shortest lag time (10.6±2.4 h) at pH 8.0.
The highest hydrogen yield was observed with Choupal biomass (2.5 mol H2/mol arabinose
consumed), with pH 6.0. The granular biomass showed different behaviour than the suspended
biomasses. The differences may be explained by smaller lag phases, the percentage of acetate
produced, the higher percentage of ethanol produced, and the amount of arabinose consumed. The
percentage of n-butyrate was highly correlated with the percentage of acetate (R2 = 0.980) in Freixo
biomass. A high correlation (R2 = 0.973) was observed between the percentage of n-butyrate and the
percentage of ethanol in Unicer biomass, suggesting that the fermentation is following the
butyrate/ethanol pathways which correspond to the lower yields of hydrogen obtained