Bioethanol from Jatropha Seed Cakes Produced by Acid Hydrolysis Followed by Fermentation with Baker’s Yeast
Ricardo Salviano dos Santos, Alice Lopes de Macedo, Lílian de Araujo Pantoja, Alexandre Soares dos Santos

Abstract
Jatropha curcas seed cake is produced annually as a co-product of the biodiesel production chain. A significant percentage of this solid waste is composed of polymeric carbohydrates. In this work, the residual polysaccharides present in Jatropha seed cake are converted to bioethanol by sequential hydrolytic and fermentative processes. Starch, hemicellulose and cellulose contents were quantified and presented 4.80, 10.41 and 16.88 grams of each polysaccharide per 100 grams of seed cake, respectively. The 3k-p fractional factorial design, whose factors were time, temperature and sulphuric acid concentration, resulted, under the best condition, in the conversion of 82% of the starch and hemicellulose present in the Jatropha seed cake to reducing sugars. Based on the results obtained in bench-scale alcoholic fermentation of the hydrolysate of Jatropha seed cake by Saccharomyces cerevisiae, the production of 88.5 litres of ethanol from the cake generated from the extraction of 1000 kg of oil can be predicted.

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