Increasing the Greenness of Lignocellulosic Biomass Biorefining Processes by Means of Biocompatible Separation Strategies

Abstract

The extraction of phenolic acids from wheat straw (WS) using more environmentally friendly and competitive means is targeted in the present work. The ability of Tween 20 (polyoxyethylene (20) sorbitan monolaurate) as a phenolics extractant in aqueous solutions of a biocompatible ionic liquid (choline dihydrogencitrate) obtained after biomass hydrolysis has been demonstrated. To accomplish the extraction as required, the existence of biphasic areas in model aqueous ternary systems from 20 to 60 °C was ensured as a prior step to evaluate the extraction yields and partition coefficients of ferulic and p-coumaric acids at different Tween 20 concentrations. It was observed that the surfactant content turned out to be a key parameter to attain high extraction levels of phenolic acids (up to 97% of total phenols, 89% of ferulic acid, and 93% of p-coumaric acid at the greatest surfactant concentration). Furthermore, at this surfactant concentration, the total phenols content (TPY) after extraction was 4.51 mg of gallic acid equivalent (GAE)/g of WS dry basis (d.b.), antioxidant activity TEAC (Trolox equivalent antioxidant capacity) was 4.26 μmol equivalents of Trolox (TRE)/g WS d.b., and antioxidant activity for DPPH (2,2-diphenyl-1-picrylhydrazyl) was 0.458 μmol TRE/g WS d.b. The proposed extraction method did not entail bioactivity impairment, as reflected the analysis of free radical scavenging capacity and trolox equivalents antioxidant capacity.