Lignin-carbohydrate complexes: Model compounds synthesis

Licentiate thesis, 2015

In lignocellulose there is a recalcitrant interaction by covalent and non-covalent bonds called the lignin-carbohydrate complex. This interaction has been the subject of studies trying to unveil its chemical structure, to understand the mechanims involved in its formation and to determine its influence on practical applications such as the process of turning biomass into ethanol. Through the synthesis of model compounds we aim to further advance the scientific understanding of the lignin-carbohydrate complex. After a general introduction this thesis presents the scale-up and synthesis of ligin model compounds. A 5 L batch reactor was used to perform synthesis on 0.5 kg scale. Reaction conditions were optimized on lab scale before scale-up to ensure a safe and efficient reaction. Lignin model compounds were synthesized to enable the following synthesis of benzyl ether and benzyl ester model compounds that mimic the naturally occurring lignincarbohydrate covalent bond. The benzyl ethers and esters were synthesized via a quinone methide route to afford the products as mixtures of diastereomers. The model compounds were then used as substrates to investigate the hydrolytic properties of a hypothesized lignin-carbohydrate complex cleaving enzyme StGE2. The stability and solubility was also investigated in the optimization process of the enzymatic assay.