Effect of the dissolved oxygen on the bioproduction of glycerol and ethanol by Hansenula anomala growing under salt stress conditions

International audienceThe effect of the dissolved oxygen on glycerol and ethanol productions by an osmotolerant yeast Hansenula anomala was examined during growth in media at low water activity resulting from the addition of 2M NaCl in the culture medium. High stirring rate, high culture medium aeration, as well as high mass transfer surface inhibited both glycerol and ethanol biosynthesis. In absence of oxygen, yeast used acetaldehyde as a hydrogen acceptor, leading to the stimulation of ethanol biosynthesis and accounting for the low biomass and glycerol production; the experimental ratio ethanol on glycerol produced was 5.1 when the available oxygen was lowered (low stirring rate, 500rpm) and increased to 10.2 in absence of aeration. Extracellular glycerol production was therefore optimal for a moderate stirring (1000rpm) and aeration (1.4vvm) rates. These optimal conditions resulted in an experimental ratio ethanol on glycerol produced of 4.1, namely close to the theoretical value of 4, illustrating the osmodependent channelling of carbon towards polyols productio

Experimental study on the valorization of poplar by-products in cement-based materials

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Photocatalytic Reactors Dedicated to the Degradation of Hazardous Organic Pollutants: Kinetics, Mechanistic Aspects, and Design – A Review

International audienceIn recent years, heterogeneous photocatalysis has emerged as a new effective, powerful, clean, and safe decontamination technology for the treatment of organic pollutants and the transformation of hazardous chemicals into different forms. This review focuses on the recent development of various conventional technologies of reactors designated for the photodegradation of hazardous organic pollutants with their limitations. This phenomenon is strongly influenced by reaction conditions such as temperature of reaction, pH, light intensity and wavelength, pollutant concentration, photocatalyst quantity, relative humidity (RH), and other parameters. The catalyst photoactivity depends on the structural characteristics of the semiconductor, its morphology, and its particles size. This paper presents the progression of photocatalytic reactors for synthetic dyes degradation with special consideration to the use of supported photocatalyst and nanostructured titanium supported over volcanic ashes, owing to the major advantage of an easy separation of the catalyst when compared to homogenous system, namely suspended catalyst. In addition, special attention was paid to the literature dealing with the promotion of light efficiency by testing various light sources. © 2016, Copyright © Taylor & Francis Group, LLC

Une revue compréhensive du biochar dans l'élimination des polluants organiques des eaux usées : caractérisation, toxicité, activation/fonctionnalisation et influence des facteurs de traitement

International audienceThe current climate and environmental challenges demand novel and cost-effective sustainable materials with a high efficacy and eco-friendly properties. Biochar (BC) has gathered a great interest in the last years across different research fields, thanks to its special physicochemical characteristics such as high specific surface area, high porosity, ion exchange capacity and because of scientific evidence in removing various contaminants from soil, water, and air. This review aims to give the state of the art on the removal of toxic organic pollutants from wastewater using biochar, activated biochar, functionalized biochar and metal oxide or clay base biochar composites, commenting on the substrates' physiochemical properties, the role of the most used characterization techniques toxicity, activation/functionalization and influencing treatment factors in organic pollutant removal from wastewater.The effect of different operating parameters of the water treatment process is summarized and thoroughly discussed. The toxicity of biochar components such as heavy metals, dioxins and polycyclic aromatic hydrocarbons (PAHs) is addressed. The various application processes of biochar in water treatment at both laboratory and pilot scale is also reviewed. The activation techniques, functionalization pathways and biochar basednanocomposite synthesis methods for enhancing the pollutant elimination efficiency are also extensively discussed. Finally, the paper suggests research directions in the field of biochar application in wastewater treatment

Photocatalytic performance of TiO2 impregnated polyester for the degradation of Reactive Green 12: Implications of the surface pretreatment and the microstructure

International audienceIn the present work, we investigate the degradation of recalcitrant industrial textile dye (Reactive green 12) in aqueous solution by TiO2 impregnated polyester at room temperature. The TiO2 loading on polyester was optimized using different polyester pretreatments (plasma surface activation and UV-C photons). The applied surface pretreatments led to slightly different microstructure, crystalline sizes and photocatalytic activities. Both catalyst tests showed no photocatalytic activity for Radio-Frequency plasma (from now as “RF-plasma”) pretreated polyester under visible light and a lower activity compared to UVC-pretreated-impregnated-fabrics under UV light. This was attributed to the TiO2 aggregation on the surface of RF-plasma activated polyester. However, the photocatalytic performance of UV-C activated catalyst was investigated studying the optimal reaction conditions such as pollutant initial concentration, applied light (UV or Visible), catalyst loading and the presence of hydrogen peroxide at different concentrations. Under optimized operating conditions, namely catalyst dose of 5.18 g/L and an initial dye concentration of 2 mg/L, the removal of Reactive green 12 reached 100% under UV light and 87.14% under visible light within 120 min. Moreover, the presence of hydrogen peroxide showed a positive impact on the degradation, since the time needed for total dye decreased to 80 min under UV light irradiation for a [H2O2] to [RG 12]0 ratio in the range 20–30. The kinetic results showed that the removal of this recalcitrant dye nearly followed a Langmuir-Hinshelwood (L-H) model with a regression coefficient (R2) value of 0.926. The catalyst activity was found to be stable for more than five reuse cycles. © 2017 Elsevier B.V

By-products of dates: Optimization of the extraction of juice using response surface methodology and ethanol production

International audienceThe optimal extraction conditions were determined for by-product of date fruit by using the response surface design method. The obtained juice was used for the production of ethanol by fermentation of free cells of Saccharomyces cerevisiae. Optimal conditions for date juice extraction were found to be 80°C, 60 min, 1:2 dilution (fruit on water ratio) according to the result of response surface analysis (Equivalents glucose: 219 g.L-1). Saccharomyces cerevisiae showed a preference for glucose over fructose and among the tested total sugar concentrations, namely 50, 100, 174 and 358 g.L-1, 174 g.L-1 appeared to be the optimal amount, leading to 70 g.L-1 ethanol concentration after 66 h of fermentation,; while an inhibitory effect of a high sugar content, 358 g.L-1 of total sugars, namely about 2 mol/L of monosaccharide like glucose or fructose was also shown. Overall, this study suggested that date juice can be utilized for ethanol production

Effect of Alfa fibers on the mechanical and thermal properties of compacted earth bricks

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Kinetic of sugar consumption and ethanol production on very high gravity fermentation from syrup of dates by- products (Phoenix dactylifera L.) by using Saccharomyces cerevisiae, Candida pelliculosa and Zygosaccharomyces rouxii

International audienceThree yeasts, Saccharomyces cerevisiae, Zygosaccharomyces rouxii and Candida pelliculosa, were tested for ethanol production on dates'syrup. In batch fermentation, the ethanol concentration depended on the initial sugar concentration and the yeast strain. For an initial sugar concentration of 17.4°Brix, maximum ethanol concentration was 63 g/L during S. cerevisiae growth, higher than the amounts achieved during Z. rouxii and C. pelliculosa growth, 33 g/L and 41 g/L respectively. On 35.8°Brix initial sugar amount, only Z. rouxii was able to grow, resulting in 50 g/L ethanol production, showing an inhibitory effect on S.cerevisae and C. Pelliculosa due to the osmotic stress resulting from the high sugar concentration