Lignin depolymerization/reconstruction using enzymatic and C-H activation catalysis

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The use of petroleum resources, being not sustainable, leads to CO2 accumulation in the atmosphere, which in turn is the cause of global warming of our planet. Moreover, the earth’s petroleum resources are becoming scarcer and scarcer. Consequently, exploitation of renewable biomass to obtain bulk and speciality chemicals in a sustainable way is becoming “a must” for the present and future generations. Lignocellulosic biomass, consisting mainly of cellulose, hemicellulose and lignin, is produced in large quantities in nature every year. Whereas the sugar part has already been studied extensively for its transformation into low molecular mass chemicals, the lignin part remains largely underexplored. Within this collaborative project between Germany and France, we aim to develop processes allowing the preparation of high added-value molecules starting from polymeric lignin. In the first step, lignin will be depolymerized enzymatically, with a special focus on bacterial -etherases, to yield desired mono-aromatic compounds selectively. In the second step, these are further converted chemically into high added-value chemicals using novel C-H activation catalysis. To provide sufficient quantities of the desired lignin degradation products guaiacylhydroxypropanone (GHP) and (syringylhydroxypropanone (SHP) for chemical upgrading, the enzymatic lignin depolymerisation process will be optimized with regard to efficiency, aromatics yield and the possible combination of different ligninolytic enzyme activities. Moreover, upscaling of the optimized process will be studied. In the monomer upgrading part, emerging protocols will be developed for the conversion of GHP and SHP into 4-chromanones and neoflavanes as well as 1-indanones and dihydrochalcones to serve as building blocks in the synthesis of drugs, agrochemicals and cosmetics, as well as monomers for polymer materials. Overall, the project results are expected to advance the valorization of lignin as a renewable feedstock in view of a future implementation in an industrial context.