Abstract
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 °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.
Highlights
Lignocellulosic biomass is a low-cost and renewable material being a substrate to obtain various types of substances
Minced and milled lignocellulosic materials obtained from a variety of species with diversified contents of lignin, cellulose and hemicellulose were investigated
It was observed that for mild alkaline pre-treatment, i.e., NaOH concentration below 4% and temperature below 40 ◦ C, the loss of hemicellulose and lignin is insignificant, and the change in the chemical composition of the material is probably mainly due to dissolution of the extractives in solution
Summary
Lignocellulosic biomass is a low-cost and renewable material being a substrate to obtain various types of substances. Conversion of lignocellulosic biomass through fermentation processes have a great potential for production of many useful products, e.g. biofuels, biomaterials and biochemicals [1]. The development of the world economy implies the need to use renewable non-edible raw materials for production of second-generation biofules [2]. Both lignocellulosic waste as well as special crops with low requirements for cultivation are well suited to the market. Production of second-generation biofuels from lignocellulosic raw materials by fermentative methods requires their processing into fermentable simple sugars. Three main steps influencing the efficiency of the biomass conversion are pre-treatment, enzymatic or acid hydrolysis and fermentation
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