Differentiation Between Amino Acids Used as Carbon and Energy Sources During Growth of Geotrichum candidum Geo17

Geotrichum candidum Geo17 was cultivated on peptones as carbon and nitrogen source, and in the presence of lactate as the second carbon source. From the analysis of the initial and final culture medium after total hydrolysis, the yield of consumption was determined for each amino acid. Amino acids have been considered a convenient carbon source for biosynthesis, while the rest of the amino acids were assumed to be used only as a nitrogen source, with the corresponding carbon released as CO2 resulting from energy supply. Carbon mass balances confirmed this assumption. A clear differentiation between the amino acids assimilated as carbon sources and those assimilated as energy sources was therefore highlighted

Differentiation Between Amino Acids Used as Carbon and Energy Sources During Growth of Geotrichum candidum Geo17

Geotrichum candidum Geo17 was cultivated on peptones as carbon and nitrogen source, and in the presence of lactate as the second carbon source. From the analysis of the initial and final culture medium after total hydrolysis, the yield of consumption was determined for each amino acid. Amino acids have been considered a convenient carbon source for biosynthesis, while the rest of the amino acids were assumed to be used only as a nitrogen source, with the corresponding carbon released as CO2 resulting from energy supply. Carbon mass balances confirmed this assumption. A clear differentiation between the amino acids assimilated as carbon sources and those assimilated as energy sources was therefore highlighted

Removal of Hydrophobic Volatile Organic Compounds in an Integrated Process Coupling Absorption and Biodegradation -- Selection of an Organic Liquid Phase

International audienceSince usual processes involve water as ab- sorbent, they appear not always really efficient for the treatment of hydrophobic volatile organic compound (VOC). Recently, absorption and biodegradation cou- pling in a two-phase partitioning bioreactor (TPPB) proved to be a promising technology for hydrophobic compound treatment. The choice of the organic phase, the non-aqueous phase liquid (NAPL) is based on various parameters involved in both steps of the pro- cess, hydrophobic VOC absorption in a gas - liquid contactor, and biodegradation in the TPPB. VOC sol- ubility and diffusivity in the selected NAPL, as well as NAPL viscosity, seems to be the main parameters during the absorption step, while biocompatibility, namely the absence of toxic effect of the NAPL to- wards microorganisms, non-biodegradability and VOC partition coefficient between NAPL and water were revealed as the key factors during the biodegra- dation step. The screening of the various NAPL avail- able in the literature highlighted two families of compounds matching the required conditions for the proposed integrated process, silicone oils and ionic liquids

Equivalent Absorption Capacity (EAC) concept applied to the absorption of hydrophobic VOCs in a water/PDMS mixture

International audienceAbsorption of hydrophobic Volatile Organic Compounds (VOCs) in multiphase system gas water PolyDiMethylSiloxane (PDMS, i.e. silicone oils) was considered. Absorption experiments were carried out in a countercurrent gas-liquid absorber filled with Raschig rings as packing. Three absorbing liquids, water, PDMS and a mixture of water/PDMS (90/10 v/v) were used to transfer toluene and dimethyl disulfide (DMDS) selected as VOC targets. Moreover, the Equivalent Absorption Capacity (EAC) concept previously developed to characterize the mixtures of water/PDMS was applied to the experimental data obtained at three different gas flow rates (18, 25 and 32 m3 h-1). Experimental measurements showed that absorption efficiencies (E) were low for water (around 2-8% for toluene and around 12-25% for DMDS) and higher for PDMS (from 88% to 98% according to the operating conditions). For the water/PDMS mixture, it was shown that the PDMS addition increased significantly the absorption of pollutants (E values in the range 25 to 65% according to the operating conditions). Besides, it was emphasized that the EAC concept describes satisfactorily the absorption behavior of the water/PDMS mixture. Finally, results confirmed that pure PDMS has to be used rather than a (90/10 v/v) water/PDMS mixture for hydrophobic VOC absorption. Using pure PDMS as absorbing liquid (dynamic viscosity of 5 mPa s), high absorption efficiencies (up to 98%) were obtained for L’/G’ value around 5 (L’/G’ corresponding to the ratio between the specific flow of the liquid and the specific flow of the gas). Under such conditions, pressure drops (ΔP) in the packed column and overall mass transfer coefficients (KLa) were around 1000 Pa m-1 (G’ = 1.06 kg m-2 h-1) and 5 10-3 s-1, respectively

Impact of nutrients supply and pH changes on the elimination of hydrogen sulfide, dimethyl disulfide and ethanethiol by biofiltration.

International audienc

Characterization of gaseous odorous emissions from a rendering plant by GC/MS and treatment by biofiltration.

International audienceThis research focuses on the identification and quantification of odorous components in rendering plant emissions by GC/MS and other analytical methods, as well as the description of phenomena occurring in biofilter in order to improve the removal efficiency of industrial biofilters. Among the 36 compounds quantified in the process air stream, methanethiol, isopentanal and hydrogen sulfide, presented the major odorous contributions according to their high concentrations, generally higher than 10 mg m(-3), and their low odorous detection thresholds. The elimination of such component mixtures by biofiltration (Peat packing material, EBRT: 113 s) was investigated and revealed that more than 83% of hydrogen sulfide and isopentanal were removed by biofilter. Nevertheless, the incomplete degradation of such easily degradable pollutants suggested inappropriate conditions as lack of nutrients and acidic pH. These inadequate conditions could explain the lack of performance, especially observed on methanethiol (53% of RE) and the production of oxygenated and sulfur by-products by the biofilter itself

Volumetric mass transfer coefficients characterising VOC absorption in water/silicone oil mixtures

International audienceThe physical absorption of three Volatile Organic Compounds (dimethyldisulphide (DMDS), dimethylsulphide (DMS) and toluene) in "water/silicone oil" systems at a constant flow rate for mixtures of different compositions (f = 0, 5, 10, 15, 20 and 100%) was investigated using a dynamic absorption method. The results indicate that silicone oil addition leads to a dramatic decrease in KLa which can be related to the change in the partition coefficient (Hmix). They confirm the results obtained for styrene absorption using another measurement technique [15]. The interpretation of the results using dimensionless ratios KLa(f)/KLa(f=0%) and KLa(f)/KLa(f=100%) versus f also confirms the importance of the partition coefficient ratio mR = Hwater/Hoil in the KLa change. Moreover, the results obtained for toluene absorption in "air/water/silicone oil" systems (f = 10, 15 and 20%) suggest that the mass transfer pathway is in the order gas→water→oil for these operating conditions

Proposed mechanisms of toluene removal by vermicompost and earthworms Eisenia fetida

International audienceFor potential use in air treatment by biofiltration, a new material composed of vermicompost and earthworms () was tested for the removal of a volatile organic compound (VOC), toluene. The removal rate of toluene was measured during batch experiments in presence of vermicompost only, earthworms only and a mixture of both. In the chosen experimental conditions, no mortality of earthworms was recorded and the results showed that the presence of earthworms allowed an increase in toluene removal rate (0.213 mg h) compared to vermicompost only (0.084 mg h) and earthworms only (0.136 mg h). From the experimental data, mechanisms of toluene transfer and adsorption/biodegradation by microorganisms from vermicompost and/or earthworms were proposed

Integrated process for hydrophobic VOC treatment--solvent choice

International audienceA process coupling absorption of a gaseous pollutant in an organic phase and biodegradation was considered to treat hydrophobic volatile organic compounds (VOC). The purpose of this work was to choose the best solvent for the absorption of some VOC (dimethylsulfide, dimethyldisulfide, and toluene) and to examine solvent biodegradability as well as VOC biodegradation by activated sludge. Some experiments were carried out on some selected solvents leading to select di-2-ethylhexyl-adipate (DEHA) and poly-di-methyl-siloxane (PDMS) for their high absorption capacity. Biodegradation experiments showed that toluene and DMDS can be removed in solvent on water emulsions, while DMS removal by biodegradation remains to confirm owing to its high volatility. However, experiments showed DEHA biodegradation, contrarily to PDMS which was therefore selected for subsequent experiments

Biological waste gas treatments

International audienceProfit and protection are two fundamental reasons to clean up waste gas streams. According to the nature of the contaminants and/or the complex mixture of pollutants in the gaseous phase, their concentrations and the flow to be cleaned, removing non-particulate pollutants from a gas stream is achieved by different processes classified into three categories: (i) thermal and/or catalytic oxidation, biological transformation; (ii) transfer into a liquid phase (absorption) or onto a solid phase (adsorption); and (iii) phase change (condensation). Bioprocesses, a relatively recent technology, appear to be a competitive way to treat the waste gas stream before its discharge to the atmosphere. The optimal range of pollutant concentration goes from a very diluted pollutant present in the gas stream (from some μg to mg m−3) to above 1 g m−3. The installation designs cater for an air flow from a few m3 h−1 to more than 100 000 m3 h−1. This chapter describes general approaches for bioreactors used in waste gas stream treatment and more specifically the different biosystems such as biofilters, biological trickling beds and bioscrubbers. The general presentation, operating conditions, yields and industrial applications of these bioprocesses are discussed