Genotoxic effect induced by hydrogen peroxide in human hepatoma cells using comet assay

Background: Hydrogen peroxide is a common reactive oxygen intermediate generated by variousforms of oxidative stress. Aims: The aim of this study was to investigate the DNA damage capacity ofH2O2 in HepG2 cells. Methods: Cells were treated with H2O2 at concentrations of 25 μM or 50 μM for5 min, 30 min, 40 min, 1 h or 24 h in parallel. The extent of DNA damage was assessed by the cometassay. Results: Compared to the control, DNA damage by 25 μM and 50 μM H2O2 increasedsignificantly with increasing incubation time up to 1 h, but it was not increased at 24 h. Conclusions:Our Findings confirm that H2O2 is a typical DNA damage inducing agent and thus is a good modelsystem to study the effects of oxidative stress. DNA damage in HepG2 cells increased significantlywith H2O2 concentration and time of incubation but later decreased likely due to DNA repairmechanisms and antioxidant enzyme

Direct fermentation of fodder maize, chicory fructans and perennial ryegrass to hydrogen using mixed microflora

This study examined the feasibility of producing hydrogen by direct fermentation of fodder maize, chicory fructooligosaccharides and perennial ryegrass (Lolium perenne) in batch culture (pH 5.2–5.3, 35 °C, heat-treated anaerobically digested sludge inoculum). Gas was produced from each substrate and contained up to 50–80% hydrogen during the peak periods of gas production with the remainder carbon dioxide. Hydrogen yields obtained were 62.4 ± 6.1 mL/g dry matter added for fodder maize, 218 ± 28 mL/g chicory fructooligosaccharides added, 75.6 ± 8.8 mL H2/g dry matter added for wilted perennial ryegrass and 21.8 ± 8 mL H2/g dry matter added for fresh perennial ryegrass. Butyrate, acetate and ethanol were the main soluble fermentation products. Hydrogen yields of 392–501 m3/hectare of perennial ryegrass per year and 1060–1309 m3/hectare of fodder maize per year can be obtained based on the UK annual yield per hectare of these crops. These results significantly extend the range of substrates that can be used for hydrogen production without pre-treatment

ADM1 can be applied to continuous bio-hydrogen production using a variable stoichiometry approach

The IWA Anaerobic Digestion Model No.1 (ADM1) has been extensively used in recent years. However, its application to non-methanogenic systems is limited by the use of constant-stoichiometry to describe product formation from carbohydrate fermentation. This study presents a modification of the ADM1 using a variable stoichiometry approach, derived from experimental information. The biomass and product yields from glucose degradation are assumed to be dynamically depending on the total concentration of undissociated acids in the reactor. Experimental data from an 11 L mesophilic continuous bio-hydrogen reactor fed with 20, 40, 50 and 10 g/L of sucrose, were used to validate the approach. The modified model achieved good predictions of the experimental data, using the standard ADM1 parameter values, without any parameter fitting beyond the implementation of the variable stoichiometry. The modification approach proposed extends the applicability of the ADM1 to non-methanogenic fermentative systems and in particular to continuous bio-hydrogen production

Influence of catholyte pH and temperature on hydrogen production from acetate using a two chamber concentric tubular microbial electrolysis cell

Microbial electrolysis cells (MECs) could be integrated with dark fermentative hydrogen production to increase the overall system yield of hydrogen. The influence of catholyte pH on hydrogen production from MECs and associated parameters such as electrode potentials (vs Ag/AgCl), COD reduction, current density and quantity of acid needed to control pH in the cathode of an MEC were investigated. Acetate (10 mM, HRT 9 h, 24 °C, pH 7) was used as the substrate in a two chamber MEC operated at 600 mV and 850 mV applied voltage. The effect of catholyte pH on current density was more significant at an applied voltage of 600 mV than at 850 mV. The highest hydrogen production rate was obtained at 850 mV, pH 5 amounting to 200 cm3stp/lanode/day (coulombic efficiency 60%, cathodic hydrogen recovery 45%, H2 yield 1.1 mol/mol acetate converted and a COD reduction of 30.5%). Within the range (18.5–49.4 °C) of temperatures tested, 30 °C was found to be optimal for hydrogen production in the system tested, with the performance of the reactor being reduced at higher temperatures. These results show that an optimum temperature (approximately 30 °C) exists for MEC and that lower pH in the cathode chamber improves hydrogen production and may be needed if potentials applied to MECs are to be minimised

The potential for hydrogen-enriched biogas production from crops: scenarios in the UK

There is increasing international interest in developing low carbon technologies to provide hydrogen renewably. Hydrogen can be produced through dark anaerobic fermentation using carbohydrate-rich substrates, and methane can be produced in a methanogenic second stage. The suitability of a range of crops for hydrogen and methane production in the UK is examined, using selection criteria including yield, harvest window and composition of the crops. The annual potential for hydrogen and methane production is calculated using the selected crops, taking into account the energy required to grow and harvest the biomass and run the process. The fermentable energy crops fodder beet, forage maize, sugar beet and rye grass were identified as the most suitable substrates for this farm-scale process. A conservative estimate of the amount of agricultural land in the UK excluding permanent grassland not already used for food production or energy crops (currently unused "set-aside" land) has been made (294,960 ha). If this was used to grow a rotation of the selected crops, 9.6 TW h net energy could be produced per year. This equates to electrical power for 2.2 million homes in the UK annually and a reduction of CO2 emissions by over 2.3 million tones per annum in the UK

Defining the biomethane potential (BMP) of solid organicwastes and energy crops: a proposed protocol for batchassays

The application of anaerobic digestion technology is growing worldwide because of its economic and environmental benefits. As a consequence, a number of studies and research activities dealing with the determination of the biogas potential of solid organic substrates have been carrying out in the recent years. Therefore, it is of particular importance to define a protocol for the determination of the ultimate methane potential for a given solid substrates. In fact, this parameter determines, to a certain extent, both design and economic details of a biogas plant. Furthermore, the definition of common units to be used in anaerobic assays is increasingly requested from the scientific and engineering community. This paper presents some guidelines for biomethane potential assays prepared by the Task Group for the Anaerobic Biodegradation, Activity and Inhibition Assays of the Anaerobic Digestion Specialist Group of the International Water Association. This is the first step for the definition of a standard protoco

Integration of biohydrogen, biomethane and bioelectrochemical systems

Anaerobic bioprocesses such as Anaerobic digestion (AD), fermentative biohydrogen (BioH2), and Bioelectrochemical system (BES), converting municipal, agro-industrial wastes and crops to energy have attracted accelerating interest. Anaerobic digestion (AD) however, still requires optimisation of conversion efficiency from biomass to methane. Augmenting methane energy production with simultaneous BioH2 and bioelectrochemical stage(s) would increase process efficiencies while meeting post treatment effluent quality. Pre-treatment of feedstock increase bacterial accessibility to biomass, thus increasing the conversion yield to target product, but an alternative is separating the acidogenic/hydrolytic processes of AD from methanogenesis. Acidogenesis can be combined with BioH2 production, prior to methanogenesis. Depending on operating conditions and without further treatment after digestion, the methanogenic stage may discharge a digestate with significant organic strength including volatile fatty acids (VFAs). To meet wastewater discharge consents; adequate use of digestates on land; to minimise environmental impact and; enhance recovery of energy, VFAs should be low. Concatenating bioelectrochemical systems (BES) producing hydrogen and/or electricity can facilitate effluent polishing and improved energy efficiency. Various configurations of the BioH2, methanogenesis and BES are plausible, and should improve the conversion of wet biomass to energy