OPTIMIZATION OF INTEGRATED ALKALINE-EXTRUSION PRETREATMENT OF BARLEY STRAW FOR SUGAR PRODUCTION BY ENZYMATIC HYDROLYSIS

Abstract

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 10 temperature (T) and the ratio NaOH/BS dry matter (w/w) into the extruder on pretreatment effectiveness was investigated in a twin-screw extruder at bench scale . A 23 factorial response surface design of experiments was used to analyze the effect of process conditions [T: 50- 100ºC; NaOH/BS ratio: 2.5-7.5% (w/w)] on composition and enzymatic digestibility of pretreated substrate. The optimization of these process variables for a maximum glucan to 15 glucose conversion was determined to be at 6% NaOH/DM and 68ºC. 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