Dilute acid pretreatment of rapeseed straw for fermentable sugar generation.

The influence of the main pretreatment variables on fermentable sugar generation from rapeseed straw is studied using an experimental design approach. Low and high levels for pretreatment temperature (140-200 °C), process time (0-20 min) and concentration of sulfuric acid (0.5-2% w/v) were selected according to previous results. Glucose and xylose composition, as well as sugar degradation, were monitored and adjusted to a quadratic model. Non-sugar components of the hydrolysates were also determined. Enzymatic hydrolysis yields were used for assessing pretreatment performance. Optimization based on the mathematical model show that total conversion of cellulose from pretreated solids can be achieved at pretreatment conditions of 200 °C for 27 min and 0.40% free acid concentration. If optimization criteria were based on maximization of hemicellulosic sugars recovery in the hydrolysate along with cellulose preservation in the pretreated solids, milder pretreatment conditions of 144 °C, 6 min and 2% free acid concentration should be used.