Bio-refinery of pistachio production by-products

The objective of this thesis was to perform bio-refinery of pistachio production by-products, pistachio hull (PH) and shell (PS). For this purpose, microwave-assisted solvent extraction (MASE) of polar and non-polar compounds from PH was performed. The results showed that the pistachio hull extracts were rich in bioactive compounds such as phenolics, antioxidants and tocopherols. Also, MASE has been shown to be advantageous in extracting bioactive compounds with higher yield, antioxidant activity, and reduced extraction time and solvent consumption. Alkali pre-treatment of PS was carried out by using microwave and/or ultrasound-assisted methods to fractionate PS into hemicellulose solid precipitate and cellulose rich solid phase. The pre-treatment conditions were optimized to obtain maximum hemicellulose and cellulose recoveries and the optimum pre-treatment conditions were determined as ultrasound power of 640 W, microwave power of 248 W and NaOH concentration of 1.58 N for sequential ultrasound-microwave-assisted alkaline pre-treatment (SUMAAP). Under these conditions, the hemicellulose and cellulose recoveries were 66.14% and 90.78%, respectively. SUMAAP increased the hemicellulose recovery with a significant reduction in processing time and amounts of chemical used for the fractionation of PS into hemicellulose and cellulose. Finally, enzymatic hydrolysis of the pre-treated cellulose-rich fractions was performed to produce fermentable sugars and the highest glucose yield of 95.78 mol% obtained after SUMAAP.