Evaluation of Xylan Extraction Yield with Alkaline Pretreatment Coupled with Steam from Pistachio Shell

Pistachios are grown in hot, dry, and salt-rich area of some regions, such as the Mediterranean, Middle East, and the United States. Pistachio shell is produced in large quantities in most pistachio recording terminals and pistachio processing units in different parts of the Iran, which has no special application. The aim of this study was to create added value for this by-product by producing xylan. Chemical analysis of pistachio shell indicated that this lignocellulosic biomass, along with cellulose, contained 42.2% hemicellulose. Xylan in the pistachio shell was extracted using different levels of 4, 8, 12, and 16% sodium hydroxide or potassium hydroxide at two temperatures (25 °C/ 16 hours and steam treatment (121 °C, 15 lb/in2, 45 min). Statistical analysis indicated that variant levels of alkali and different temperatures had a significant effect on the true recovery of xylan extraction (p <0.05). The maximum true recovery of xylan extracted from pistachio shell with an average of 20.34 and in fact the relative recovery of 48.4%, belonged to the treatment with sodium hydroxide 16% in combination with steam. The results obtained from high performance liquid chromatography were confirmed by FT-IR, which characterized preliminary structure features of the extracted pistachio shell xylan. The treatment used enabled the recovery of xylan from this hard lignocellulosic biomass that can be used in food and pharmaceutical industries.