Optimisation de l’extraction des jus de sous-produits de dattes (Phoenix dactilyphera L.) et valorisation par production de bioéthanol

National audienceLa valorisation énergétique des sous-produits de l’industrie des dattes en biocarburant s’inscrit dans une démarche économique et environnementale. L’optimisation de l’extraction des sucres des sous-produits de dattes a été effectuée en utilisant la méthodologie de surface de réponses, ‘MSR’, par le plan d’expérience de Doehlert. Le facteur ratio pulpe/eau (X3), qui a influencé significativement la concentration des jus en sucres, a été modélisé et optimisé. Il a été possible d’avoir des jus avec des concentrations élevées en sucres (220 g.l-1). Les essais de fermentation alcoolique menés dans un milieu de culture à base de jus de dattes à 17.4 °Brix, conduisent à la production d’éthanol aux concentrations de 63 g.l-1, 41 g.l-1 et 33 g.l-1, respectivement pour les levures Saccharomyces cerevisiae, Candida Pelliculosa et Zygosaccharomyces rouxii. Les essais menés dans le milieu à 35.8 °Brix (milieu de culture se rapprochant le plus des sirops de dattes brutes) montrent que la croissance des levures Saccharomyces cerevisiae et Candida Pelliculosa est inhibée par la pression osmotique élevée causée par la haute concentration en sucres. Seule la levure xérotolérante Zygosaccharomyces rouxii s’est adaptée au milieu en produisant 55 g.l-1 de bioéthanol

Optimization of enzymatic hydrolysis and fermentation conditions for improved bioethanol production from potato peel residues

The aim of this work was the optimization of the enzyme hydrolysis of potato peel residues (PPR) for bioethanol production. The process included a pretreatment step followed by an enzyme hydrolysis using crude enzyme system composed of cellulase, amylase and hemicellulase, produced by a mixed culture of Aspergillus niger and Trichoderma reesei. Hydrothermal, alkali and acid pretreatments were considered with regards to the enhancement of enzyme hydrolysis of potato peel residues. The obtained results showed that hydrothermal pretreatment lead to a higher enzyme hydrolysis yield compared to both acid and alkali pretreatments. Enzyme hydrolysis was also optimized for parameters such as temperature, pH, substrate loading and surfactant loading using a response surface methodology. Under optimized conditions, 77 g L−1 of reducing sugars were obtained. Yeast fermentation of the released reducing sugars led to an ethanol titer of 30 g L−1 after supplementation of the culture medium with ammonium sulfate. Moreover, a comparative study between acid and enzyme hydrolysis of potato peel residues was investigated. Results showed that enzyme hydrolysis offers higher yield of bioethanol production than acid hydrolysis. These results highlight the potential of second generation bioethanol production from potato peel residues treated with onsite produced hydrolytic enzymes. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:397–406, 2017. © 2017 American Institute of Chemical Engineer

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

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

Selective <i>S</i>-methylation of highly fluorinated thiocarbamates

<p>A series of new <i>S</i>-methyl <i>O</i>-fluoroalkyl <i>N</i>-alkyl(aryl)imidothiocarbonates were prepared by <i>S</i>-methylation of various fluoroalkylated thiocarbamates with methyl iodide in the presence of cesium carbonate and tetrabutylammonium iodide (TBAI) in tetrahydrofuran (THF) at room temperature. As expected from the mostly soft electrophilic alkyl halide (MeI), no isomer products derived from <i>N</i>-methylation were detected. The products were characterized by spectroscopic (¹H, ¹³C and ¹⁹F) NMR, infrared, and high-resolution mass spectrometric techniques.</p