8-74: Isolation and characterization of lignin from ionic liquid pretreated biomass using new generation enzymes for the production of value-added lignin by-products

A process based on enzymatic hydrolysis and fermentation is a promising route in converting lignocellulosic biomass to ethanol. However, the components of biomass (cellulose, hemicellulose, and lignin) are intricately bound together, thereby requiring suitable pretreatment of the substrate prior to hydrolysis. Ionic liquids (ILs) being non volatile, non-flammable and recyclable, are gaining wide recognition as green solvents for pretreating biomass. From an economic standpoint, it is necesary to facilitate the production of value-added products from all components of biomass, including lignin, given its interesting functionalities and properties owing to its complex aromatic nature. Structurally, lignin consists of three units (p-coumaryl, coniferyl and sinapyl alcohol) that are incorporated in the form of phenylpropanoids: p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) respectively.

The IL pretreatment process & strategic choice of enzymes result in almost carbohydrate-free (mostly lignin) residue after hydrolysis. In this regard, our approach not only provides high saccharification yields but also nearly pure lignin that can be processed into value-added products. This is unique in the sense that lignin is obtained as a residue rather than being dissolved and precipitated as in other current methods. In view of this, our study addresses: (1) the isolation of high quality lignin from IL pretreated biomass subjected to enzymatic hydrolysis, using new generation enzyme mixtures, and (2) the characterization of recovered lignin using chromatographic, spectroscopic, and thermal methods in order to assess its usability for further processing to produce value-added products including flame retardant materials, mixed phenolics, fibers, adhesives, fillers, surfactants, etc.