Production of Bioethanol from Olive Solid Waste "JEFT"

Abstract

Olive solid residue (JEFT) is the solid waste generated during olive oil production process in three-phase olive mills. It consists of the remaining pulp of olive processing after the extraction of oil, as well as the cracked seeds of the olive fruits. As a lignocellulosic material, the hemicellulose, cellulose and lignin are the main components of olive stone. The present study standardized production of ethanol from olive solid wastes using Saccharomyces cerevisiae isolates. S. cerevisiae isolated from yogurt, grape and sugarcane. These isolates were identified according to morphological and biochemical characterization tests. The alcohol tolerance test indicated that S. cerevisiae tolerated up to 10% of ethanol in the medium. Optimization of culture conditions such as pH and temperature of yeast isolates was did. 10g JEFT subjected to hydrolysis to sugar by different concentrations of diluted sulfuric and hydrochloric acids. Among acid treatment, the maximum amount of reducing sugar was 312 mg/dl obtained by 5% HCl. Using combined microwave-acid treatment with 5% HCl followed by incubation at 90°C in shaker water path for 3 hours resulted in higher amount of reducing sugars reached up to 389 mg/dl. pH 4.5 and 30°C temperature for 72 hours were the optimum fermentation conditions. The maximum observed amount of ethanol production by using JEFT hydrolysate was (9.3 g/l). When compared with hydrolysis with conventional heating by dilute 5% HCl, the microwave assisted 5% HCl process improved the yield of ethanol by 33.3%.