Abstract
Lignocellulosic biomass can be converted to energy via several routes. One of them is hydrolysis to sugars with subsequent transformation to fuels and chemicals. Due to the crystalline structure of lignocellulose, pretreatment is a prerequisite to achieving increased enzymatic hydrolysis’ rates. The objective of this study was to determine the optimum extrusion operating conditions for glucose and xylose production from Miscanthus. Extrusion was conducted in a high shear extruder (single screw type) with compression ratio 3:1. Barrel temperature and screw speed, along with sample moisture content and particle size were the parameters evaluated using Response surface methodology (RSM). Conversion rate to glucose and xylose was monitored after enzymatic hydrolysis with low enzyme loadings (5 FPU g-1 of cellulase complex and 18 CBU g-1 of B-glucosidase). The optimum conditions for the glucose production (3.63 g L-1) were: barrel temperature 150 °C, screw speed 2.5 Hz, moisture content 20% and particle size 2 mm; the optimum conditions for the xylose production (0.78 g L-1) were: barrel temperature 150 °C, screw speed 1.67 Hz, moisture content 15% and particle size 2 mm. Hence, under controlled conditions, extrusion resulted in better digestibility of Miscanthus and as such it can be utilized as a source of glucose and xylose in ethanol production.
Highlights
Ethanol is a well-established liquid biofuel, which can be produced from different biomass feedstocks and conversion technologies
Samples of various particle sizes (0.67, 1.00, 1.50, 2.00, 2.33 mm) and moisture contents, which were achieved by rehydration, (13.34, 15.00, 17.50, 20.00, 21.66%) were conditioned and extrusion processed at different barrel temperatures (83.39, 100.00, 125.00, 150.00, 166.61 °C) and screw speeds (1.39, 1.67, 2.09, 2.5, 2.78 Hz)
Since glucose and xylose are predominant sugars in lignocellulosic biomass (Dien et al, 2006), yields of these sugars were used as reference in evaluating the enzymatic hydrolysis efficiency
Summary
Ethanol is a well-established liquid biofuel, which can be produced from different biomass feedstocks and conversion technologies. Biomass resources have become very important for their use as bioenergy supplies, and research and development efforts directed towards commercial production of ethanol have increased (Voca, Kricka, Janusic, & Matin, 2007). On commercial basis, it is still produced from sugar and starch-based materials, such as sugarcane and corn; a concern for the continued growth of this first-generation biofuel is the availability of raw feedstock at a reasonable cost (Voca et al, 2009), and, more importantly, food versus fuel dilemma regarding the risk of diverting farmland or crops for liquid biofuels production in detriment of the food supply on a global scale. Due to their abundance and low costs, lignocellulosic biomass is especially interesting as a source of fermentable sugars
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