Ethanol production from different agricultural resources with lignosellulosic content

In recent years, increasing population and technology have made necessary the use of renewable energy resources. Bioethanol can be used as an alternative to fossil fuel-based energies. Corn, sugar cane, sugar beet, wheat and barley are the most widely used agricultural resources in the world for bioethanol production. Most of promising new alternative carbon sources that can be used in ethanol production is the most abundant available lignocellulosic biomass in the world. The main objectives of this study were to optimize the dilute acid hydrolysis conditions of lignocellulosic materials such as barley hull (BH), oat hull (OH), wheat bran (WB) and rye bran (RB) using response surface method (RSM), to optimize the detoxification conditions with activated charcoal of the obtained hydrolysates, and to produce ethanol with the yeasts Pichia stipitis ATCC 58784 and ATCC 58785. Temperature (ºC), solid-to-liquid ratio (w/v), dilute sulfuric acid ratio (%, v/v), and hydrolysis time (min) were used as independent variables. For this purpose, the one-factor-at-a-time (OFAT) method was used to determine the range of each parameter for RSM. The optimized conditions of BH were 130ºC, 1:8 (w/v), 1.86% (v/v), and 30 min; the optimized conditions of WB were 121ºC, 1:8 (w/v), 2.66% (v/v), 30 min; the optimized conditions of RB were 130ºC, 1:8 (w/v), 1.58% (v/v), 16 min; and the optimized conditions of OH were 130ºC, 1:8 (w/v), 1% (v/v), 19 min (v/v), respectively. Under these conditions, fermentable sugar concentrations were 76.28, 72.73, 89.42 59.63 g/L, respectively. Following that, the activated charcoal detoxification conditions of the obtained hydrolysates under hydrolysis conditions were optimized in terms of activated charcoal concentration (%), temperature (ºC), and application time (min) by using RSM. After determining the optimal detoxification conditions of hydrolysates, the non-detoxified (for control) and detoxified hydrolysates were used for ethanol production by using the yeasts Pichia stipitis ATCC 58784 and ATCC 58785. At the end of the fermentations, kinetics parameters such as glucose consumption, ethanol production, ethanol production, maximum consumption rate, specific growth rate, doubling time, and sugar utilization were calculated. The highest ethanol concentrations which obtained from the BH, WB, RB, and OH hydrolysates were determined to be 7.68, 7.33, 11.18 ve 4.49 g/L, respectively. The highest results were achieved at the result of fermentations-performed using Pichia stipitis ATCC 58784 and with detoxification process in which the maximum activated charcoal was used. At the end of the studies, ethanol productions were carried out from BH, WB, RB, and OH hydrolysates using the yeast Pichia stipitis. The ethanol yield was increased with the activated charcoal detoxification. This study also indicates that these materials are an alternative carbon source for biotechnological processes.