Protocol for the Extraction of Lignin from Brewer’s Spent Grain Using Deep Eutectic Solvents

The agro-food industry annually produces tons of lignocellulosic waste with an intrinsic high value. Specifically, lignin—an underrated bioresource that is mostly burned for energy production—has a tremendous potential as source of high-value chemicals. A promising lignin valorization requires an efficient extraction process able to recover high-purity lignin with considerable yields. Hence, we describe a protocol to extract lignin from a relevant agro-food residue—brewer’s spent grain—through the use of a deep eutectic solvent system, which has been proven an excellent potential to promote the fractionation of high-purity lignin from lignocellulosic material. The biomass is subjected to a hydrolysis at 120 °C for 5 h, and the lignin is further recovered by precipitation with distilled water. This protocol gives simple and detailed recommendations to effectively recover lignin from brewer’s spent grain contributing to the valorization of this abundant residue.