SO 2 ‐catalysed steam pretreatment of quinoa stalks

BACKGROUND Quinoa is a pseudo‐cereal grown predominantly in South America. The quinoa stalks are lignocellulosic residues, which have a limited use today. The objective of the current study was to assess the potential of this material as a source of monosaccharides for fermentation purposes by means of steam pretreatment giving sugars from the hemicellulose part, and enzymatic hydrolysis of the solid fraction obtained. SO 2 catalysed steam pretreatment was carried out with a holding time of 5 min at temperatures between 180 and 220°C. The pretreatment was carried out at two different scales, a small reactor of size 0.5 L and a somewhat larger reactor of size 10 L, to allow comparison of scale effects in the pretreatment. RESULTS The highest xylose yield in the liquid phase, obtained after pretreatment at 210°C, was 80%. In the smaller scale unit, longer residence times were needed. The enzymatic hydrolysis, at an enzyme loading of 15 FPU g ‐1 glucan and a WIS loading of 2%, resulted in a glucose yield of 70% based on the original glucan. The overall sugar yield, including the xylan hydrolysed in the enzymatic treatment, at dilute conditions was 75%. CONCLUSIONS SO 2 catalysed pretreatment of quinoa straw followed by enzymatic hydrolysis gave a relatively good sugar yield. However, the yield obtained was somewhat lower than previously reported for similar materials, such as wheat straw and sugarcane bagasse, steam pretreated with SO 2 . © 2013 Society of Chemical Industry