Optimization of integrated alkaline–extrusion pretreatment of barley straw for sugar production by enzymatic hydrolysis
•A new integrated alkaline–extrusion pretreatment is studied on barley straw biomass.•Mild alkali and temperature conditions were tested.•Enzymatic digestibility of biomass increased up to 5 times with alkaline–extrusion.•No sugar degradation products were produced during the pretreatment.
In this work, an integrated one-step alkaline–extrusion process was tested as pretreatment for sugar production from barley straw (BS) biomass. The influence of extrusion temperature (T) and the ratio NaOH/BS dry matter (w/w) (R) into the extruder on pretreatment effectiveness was investigated in a twin-screw extruder at bench scale. A 23 factorial design of experiments was used to analyze the effect of process conditions [T: 50–100 °C; R: 2.5–7.5% (w/w)] on composition and enzymatic digestibility of pretreated substrate (extrudate). The optimum conditions for a maximum glucan to glucose conversion were determined to be R = 6% and T = 68 °C. At these conditions, glucan yield reached close to 90% of theoretical, while xylan conversion was 71% of theoretical. These values are 5 and 9 times higher than that of the untreated material, which supports the great potential of this one-step combined pre-treatment technology for sugar production from lignocellulosic substrates. The absence of sugar degradation products is a relevant advantage over other traditional methods for a biomass to ethanol production process since inhibitory effect of such product on sugar fermentation would be prevented.
Journal: Process Biochemistry - Volume 48, Issues 5–6, May–June 2013, Pages 775–781