Characterization of Physico-Chemical Changes of Lignin Obtained under Different Conditions of Enzymatic Hydrolysis on an Industrial Scale

Abstract

Research-based on lignin as a bioproduct has grown due to its high availability, reactivity, physicochemical stability, and abundance of different aromatic units. Lignin consists of various functional groups, which can react in various chemical reactions and serve as a raw material in various processes to obtain multiple products. These characteristics make lignin suitable for synthesizing products from natural raw materials, replacing fossil ones. Due to a high aromatic variety and complex structural arrangement, lignin isolation and fractionation are still challenging. The aim and novelty of this work was the modification of severity and enzymatic hydrolysis procedure on an industrial pre-treatment to improve by-products of birch processing as a raw material for the potential production of different products. Lignin from birch wood enzymatic hydrolysis was obtained and marked accordingly: HS (high severity), MS (medium severity), and LS (low severity) lignin. Samples were characterized by ash content, analytical pyrolysis, solubility, and viscosity. HS lignin was characterized by a relatively high carbohydrate content (16%) and lower lignin content (77%). Meanwhile, LS lignin showed increased lignin content (83%) and reduced carbohydrate content (9%). It can be concluded that the delignification process greatly influences the properties of the obtained lignin. HS lignin resulted in a lower polydispersity index (PDI) and more condensed structure, while LS lignin showed a higher PDI but a lower content of carbohydrates. Therefore, looking for a golden middle way is necessary while finding the conditions according to the use field.