Tuesday, May 3, 2011
Pruning is an essential operation for efficient olive oil production, which generates a huge amount of lignocellulose every year. On average, olive tree biomass contains 30% cellulose, 16.5% hemicelluloses, 19% lignin, 3.4% ashes, and 23% extractives that also include a significant amount of glucose. This work proposes a thermochemical pretreatment to obtain syrups with pentoses and hexoses, and a solid fraction with cellulose and lignin. Conversion of these sugars to ethanol will improve the overall economy of the olive oil farmers and also will help to disposal problems. Olive tree biomass was pretreated at 120ºC for 1 h, using 2% (w/w) sulphuric acid at 10% solid concentration. The liquid fraction from this pretreatment had the following average composition (in g/L): glucose, 27.5; xylose, 19.2; acetic acid, 4.5. Fermentation of pentoses and hexoses was performed whit ethanologenic Escherichia coli at 37ºC, pH 7.0, 300 rpm, under microaerobic conditions, and the syrup was amended with phosphate and ammonia salts. Total sugars were converted to ethanol with yields above 90% of the theoretical.