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