Optimization of Saccharification Conditions of Lignocellulosic Biomass under Alkaline Pre-Treatment and Enzymatic Hydrolysis

Pre-treatment is a significant step in the production of second-generation biofuels from waste lignocellulosic materials. Obtaining biofuels as a result of fermentation processes requires appropriate pre-treatment conditions ensuring the highest possible degree of saccharification of the feed material. An influence of the following process parameters were investigated for alkaline pre-treatment of Salix viminalis L.: catalyst concentration (NaOH), temperature, pre-treatment time and granulation. For this purpose, experiments were carried out in accordance to the Box-Behnken design for four factors. In the saccharification process of the pre-treated biomass, cellulolytic enzymes immobilized on diatomaceous earth were used. Based on the obtained results, a mathematical model for the optimal conditions of alkaline pre-treatment prediction is proposed. The optimal conditions of alkaline pre-treatment are established as follows: granulation 0.75 mm, catalyst concentration 7%, pre-treatment time 6 h and temperature 65 degrees C if the saccharification efficiency and cost analysis are considered. An influence of the optimized pre-treatment on both the chemical composition and structural changes for six various lignocellulosic materials (energetic willow, energetic poplar, beech, triticale, meadow grass, corncobs) was investigated. SEM images of raw and pre-treated biomass samples are included in order to follow the changes in the biomass structure during hydrolysis.