Investigation of the effect of temperature and alkaline concentration on the solubilization of phenolic acids from dilute acid-pretreated wheat straw

• CA and FA in WS were observed as the major phenolic acids.
• The amount etherified FA in WS was higher than CA.
• The amount of esterified CA in WS was higher than FA.
• The effect of temperature was higher than alkaline on the production of phenolics.
• WS can serve as potential renewable source for the production phenolic acids.

This work deals with the investigation of the effect of alkaline concentration and temperature on the solubilization of phenolic materials from wheat straw, an abundant agricultural waste found in Turkey. The solid residue obtained after dilute acid pretreatment of wheat straw (SPWS) was treated by alkaline to solubilize the lignin to phenolic acids. Four different alkaline concentrations at 120 °C and seven different temperatures with 2 M NaOH were evaluated for the degree of solubilization of the phenolic materials, and the antioxidant activities of the soluble phenolic materials were determined. It was found that coumaric and ferulic acids were the major phenolic acids in all of the conditions tested. The highest antioxidant capacity of the hydrolysate of SPWS was obtained with 2 M NaOH at 150 °C where DPPH*, FRAP and TEAC values were found to be 3.23, 10.27 and 13.70 μmol/g WS, respectively.