Sandrine Bayle

Biofiltration of volatile organic compounds

The removal of volatile organic compounds (VOCs) from contaminated airstreams has become a major air pollution concern. Improvement of the biofiltration process commonly used for the removal of odorous compounds has led to a better control of key parameters, enabling the application of biofiltration to be extended also to the removal of VOCs. Moreover, biofiltration, which is based on the ability of micro-organisms to degrade a large variety of compounds, proves to be economical and environmentally viable. In a biofilter, the waste gas is forced to rise through a layer of packed porous material. Thus, pollutants contained in the gaseous effluent are oxidised or converted into biomass by the action of microorganisms previously fixed on the packing material. The biofiltration process is then based on two principal phenomena: (1) transfer of contaminants from the air to the water phase or support medium, (2) bioconversion of pollutants to biomass, metabolic end-products, or carbon dioxide and water. The diversity of biofiltration mechanisms and their interaction with the microflora mean that the biofilter is defined as a complex and structured ecosystem. As a result, in addition to operating conditions, research into the microbial ecology of biofilters is required in order better to optimise the management of such biological treatment systems.

Silver/chitosan/cellulose fibers foam composites: From synthesis to antibacterial properties

Chitosan, associated with cellulose fibers, can be used for elaborating sponge-like structures (membranes, foams) for the binding of silver ions. The composite material has very promising antibacterial properties versus Pseudomonas aeruginosa (Gram(-))≫Escherichia coli (Gram(-))>Staphylococcus hominis (Gram(+))≫Staphylococcus aureus (Gram(+)). The amount of silver required for bactericidal effect is quite low (below 0.1 mg per disk, this means less than 6 mg Ag g(-1)) in antibiogram-type test but also for the treatment of water suspensions (in dynamic mode with water recycling). The presence of cellulose fibers improves the efficiency of metal binding, due to chitosan dispersion and enhancement of the availability and accessibility of amine groups. Silver nanoparticles (about 100 nm) were observed by scanning electron microscopy. The photo-reduction (exposure to sun light or UV lamp) leaded to the partial aggregation of silver nanoparticles: metal ions that were released tended to aggregate at the surface of the material.

Endocrine Disrupting Chemicals and Human Health Risk Assessment: A Critical Review

Concerns over the threats posed by a large number of molecules, collectively termed as endocrine disrupting compounds (EDCs) and generally known to alter and disrupt hormone systems and physiological functions, have often been expressed in academic and scholarly debates. From the perspective of classical toxicology, EDCs have genomic mechanisms of actions and exert agonistic or antagonistic effects on steroid receptors. They are also able to alter reproductive function by binding to estrogen or androgen receptors, and the neuroendocrine system by binding to the thyroid receptor. Recently, EDCs have been shown to have equally complex nongenomic mechanisms, altering steroid synthesis or steroid metabolism. As environmental contaminants, these molecules proved disruptively harmful for many wildlife species, particularly those from or depending on the aquatic ecosystem. An increasingly growing body of research has voiced further concerns that human populations are not immune from the dangers of EDCs. Studies from this line of research caution that EDCs can alter hormonal balance and that a whole range of breast and prostate cancers, endometriosis, cryptorchidism, and hypospadias have been linked to exposure to EDCs. This particular area has raised a lot of controversy and the literature on this subject often presents opposing, and sometimes conflicting, perceptions and perspectives. Accordingly, the authors aimed to contribute to the committed academic search for better appreciation of the topic. They first discuss the major natural and synthetic chemicals with endocrine disrupting properties to which humans and wildlife may be exposed. They then describe the key endocrine mechanisms of action and conclude by addressing the main observed effects in human and wildlife populations.

Structural and functional responses of sewage microbial communities used for the treatment of a complex mixture of volatile organic compounds (VOCs)

Aims:  The aim of this work was to assess the impact of the applied mass loading on the selection of an efficient microbial community able to degrade a complex mixture of volatile organic compounds (VOCs).

One-stage biotrickling filter for the removal of a mixture of volatile pollutants from air: Performance and microbial community analysis

The biodegradation of gas-phase mixtures of methanol, α-pinene and H2S was examined in a biotrickling filter (BTF), inoculated with a microbial consortium composed of an autotrophic H2S-degrading culture, and pure strains of Candida boidinii, Rhodococcus erythropolis, and Ophiostoma stenoceras. The inlet concentrations of methanol, α-pinene and H2S varied from 0.05 to 3.3 gm(-3), 0.05 to 2.7 gm(-3), and 0.01 to 1.4 gm(-3), respectively, at empty bed residence times (EBRT) of either 38 or 26s. The maximum elimination capacities (ECmax) of the BTF were 302, 175, and 191 gm(-3)h(-1), with 100%, 67%, and >99% removal of methanol, α-pinene and H2S, respectively. The presence of methanol showed an antagonistic removal pattern for α-pinene, but the opposite did not occur. For α-pinene, inlet loading rates (ILRs) >150 gα-pinenem(-3)h(-1) affected its own removal in the BTF. The presence of H2S did not show any declining effect on the removal of both methanol and α-pinene.

Impact of biochemical design on estrogen receptor/estrogen response element interaction by surface plasmon resonance technology

The estrogen receptor (ER) is a transcription factor that binds under 17-β-estradiol (E2) stimulation as homodimer to a short DNA consensus sequence named estrogen response element (ERE). The ER/ERE interaction has been assessed by several research groups through different methodologies notably by surface plasmon resonance (SPR) techniques. The biochemical parameters and conditions (solvent, ER concentration, salt, time and temperature) used to prepare samples before analysis were very different from one study to another. But no studies have aimed to compare the effect of these modifications on ER/ERE interaction. Therefore the main objective of the present paper was to assess the influence of biochemical parameters onto the ER/ERE interaction with the final aim to improve the comprehension of this interaction. Our results highlighted that parameters like solvent, ER concentration, salt and surfactant concentration, temperature and time deeply modify ER/ERE interaction. Nevertheless, the dimer formation under E2 stimulation occurred with all tested conditions. Altogether, incubation parameters of ER with E2, deeply modify its binding level onto ERE. These data constitute an important key point to consider for the improvement of ER/ERE detection method depending upon the aim of the study (interaction measurement, environmental detection, development of new technologies or devices).

Estrogen receptor preparation effects on the receptor–DNA interaction by surface plasmon resonance

Up to now, several studies have investigated estrogen receptor (ER)–estrogen response element (ERE) interaction using biosensors such as surface plasmon resonance. These strategies have aimed to understand the molecular mechanism of such interaction as well as the effect of the ligand on this interaction. These approaches start to be used to determine the mechanisms of protein/DNA interaction, in particular in the context of drug discovery or environmental applications. However, some physical and biochemical parameters (incubation time, temperature, protease inhibitor cocktail, and bovine serum albumin (BSA)) are not completely described in the literature and could deeply modify the obtained results. This paper aims to focus not only on the preliminary steps of sample preparation such as protein thawing and incubation conditions (time and temperature) but also on the evaluation of protease inhibitor cocktail and BSA effect on the measurement of ER–ERE interactions.

Investigation of Removal Capacities of Biofilters for Airborne Viable Micro-Organisms

New emerging issues appears regarding the possible aerosolization of micro-organisms from biofilters to the ambient air. Traditional bioaerosol sampling and cultural methods used in literature offer relative efficiencies. In this study, a new method revolving around a particle counter capable of detecting total and viable particles in real time was used. This counter (BioTrak 9510-BD) uses laser-induced fluorescence (LIF) technology to determine the biological nature of the particle. The concentration of viable particles was measured on two semi-industrial pilot scale biofilters in order to estimate the Removal Efficiency in viable particles (REvp) in stable conditions and to examine the influence of pollutant feeding and relative humidification of the gaseous effluent on the REvp. The REvp of biofilters reached near 80% and highlighted both the stability of that removal and the statistical equivalence between two identical biofilters. Pollutant deprivation periods of 12 h, 48 h and 30 days were shown to have no influence on the biofilters’ removal capacity, demonstrating the robustness and adaptation capacities of the flora. In contrast, a 90-day famine period turned the biofilters into emitters of viable particles. Finally, the humidification of the effluent was shown to negatively influence the removal capacity for viable particles, as drying off the air was shown to increase the REvp from 60 to 85%.

Investigation of the acclimatization period: example of the microbial aerobic degradation of volatile organic compounds (VOCs).

The aim of this study is to better evaluate the occurrence of an acclimatization-enrichment period, defined as a selection period of consortia having the capability to biodegrade pollutants. In order to perform this evaluation, two experimental strategies were carried out and the results were studied carefully. Two laboratory-scale reactors were inoculated with activated sludge from an urban treatment plant. During the experiment, these reactors were supplied with a gaseous effluent containing VOCs. For both reactors, the composition is different. Three parameters were monitored to characterize the microflora: bacterial activities, bacterial densities, and the genetic structure of Bacteria and Eukarya domains (Single Strand Conformation Polymorphism fingerprint). The obtained results showed that the resultant biodegradation functions were equivalent. The bacterial community structure differs even if six co-migrated peaks were observed. These data suggest that the microbial communities in both reactors were altered differently in response to the treatment but developed a similar capacity to remove VOCs at the issue of this period. Furthermore, it is suggested that the experimental strategies developed in this work lead to an enrichment in terms of functionality and microbial diversity almost equivalent.