Bioethanol Production from Olive Solid Residues by Using Rhodotorula Minuta

Abstract

Bioethanol is an attractive fuel with higher potential for energy security and environmental safety. Olive solid residues were used as a raw material for the production of bioethanol through the use of different preliminary treatments. Separate treatments with cellulose, hydrochloric acid (HCl 5%), sulfuric acid (H2SO4 2%), and liquid ammonia NH4OH (20%) were used to convert cellulose and hemicellulose into monosaccharaides. The production of ethanol was observed during the fermentation process using R. minuta under anaerobic conditions. After 3 days of fermentation, lowest concentrations of ethanol of 0.233, 0.249, 0.261, and 0.275 g/ l were produced from olive waste powder sample as a result of separate pretreatment with cellulase, hydrochloric acid (HCl 5%), sulfuric acid (H2SO4 2%), and liquid ammonia NH4OH (20%), respectively, whereas the untreated sample showed ethanol yield of 0.264 g/ l. The highest ethanol concentrations for the same samples were 0.510, 0.564, 0.737, and 0.696 g/ l, respectively, whereas that for the untreated samples was 0.445 g/ l. The highest concentration of ethanol produced (0.737 g/ l) was achieved after 3 days of fermentation of olive solid waste pretreated with H2SO4 2% at 30 oC and pH 5. The average yield of ethanol resulted from these saccharification and fermentation processes following the pretreatment of olive solid waste was 0.59 g/10 g dry olive solid residues.