Efficient removal of lignin in tobacco stems with choline chloride-based deep eutectic solvents

Tobacco stems are a by-product of the tobacco industry and a valuable natural resource. To enhance the quality of tobacco stems, the efficiency of five binary and ternary deep eutectic solvents (DES) composed of choline chloride (ChCl), ethylene glycol (EG), urea, lactic acid (LA), and Gamma-Valerolactone (GVL) for the pretreatment of tobacco stems was investigated with the aim of reducing the lignin content. The experimental analysis showed that all the prepared DES were effective in the removal of lignin from tobacco stems. In particular, the ternary DES system composed of ChCl, LA, and EG ([Ch][LA] 5 [EG] 0.6 ) was the most effective for the pretreatment of tobacco stems, achieving a lignin removal efficiency of 85.9 % at 100°C for 4 h. Under these conditions, a tobacco stem residue rich in cellulose fractions was obtained. The pretreatment of tobacco stems with DES can effectively reduce the lignin content in the stems and the phenolics in the combustion smoke of the stems after delignification, leading to an improvement in the sensory quality of tobacco flake cigarette products.