Jury :

• Vincent SENEZ, Director of Research, University of Lille - Thesis supervisor
• Rénato FROIDEVAUX, Professor, Institut Charles Viollette (ICV) / ProBioGEM - Thesis co-director
• Catherine SARAZIN, Professor, Enzymatic and Cellular Engineering (GEC), University of Picardie Jules Verne - Examiner
• Yannick COFFINIER, Research Fellow, Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN) - Examiner
• Gabrielle POTOCKI-VERONESE, Research Director, Toulouse Biotechnology Institute (TBI) - Rapporteur
• Gérard MORTHA, Professor, International School of Paper, Printed Communication and Materials, Grenoble INP - Rapporteur

Summary:

The rising price of fossil fuels, uncertainty about their long-term availability and environmental concerns are driving research into the exploitation of abundant, renewable raw materials with high value-added potential. Alternative technologies are also being sought with the aim of reducing environmental damage, particularly in terms of carbon dioxide emissions. Lignocellulosic biomass falls within these criteria, and there has been a great deal of interest in its recovery in recent years (mainly lignin, which is the second most abundant compound in lignocellulosic biomass after hemicellulose). Lignin is a complex phenolic polymer that is recalcitrant due to its insolubility in aqueous media. Its valorisation by enzymatic depolymerisation therefore represents a major challenge with the aim of obtaining low molecular weight compounds with high added value, such as vanillin. The enzymatic depolymerisation of lignin requires the use of mediator(s), which are small molecules that act as intermediates in the laccase oxidation reaction (known as the "Laccase-Mediator System" (LMS)). A very wide variety of lignins, enzymes and mediators are present due to their very varied sources, making it necessary to develop tools for screening all these enzymatic conditions on lignins. However, the insolubility of lignins in aqueous media (the optimum medium for enzymatic reactions) makes it difficult to depolymerise them enzymatically in liquid media. Under these conditions, we have developed an enzymatic screening tool that can be used to visualise enzymatic depolymerisation in solid media (lignin in the form of solid films or solid microdeposits). Lignin in the form of solid films was produced using the spin-coating technique and in the form of solid micro-deposits using inkjet printing technology.

Abstract:

The increase in the price of fossil fuels, the uncertainty of their long-term availability and environmental concerns are guiding research towards the exploitation of abundant, renewable raw materials with a high added value potential. Alternative technologies are also being sought to reduce environmental damage, particularly in terms of carbon dioxide emissions. Lignocellulosic biomass falls within these criteria and its valorization (mainly lignin, which is the second most abundant compound of lignocellulosic biomass after hemicellulose), is of great interest in recent years. Lignin is a complex phenolic polymer but recalcitrant because of its insolubility in aqueous media. Its valorization by enzymatic depolymerization thus represents a major challenge in order to obtain compounds of low molecular weight with high added value such as vanillin. The enzymatic depolymerization of lignin requires the use of mediator(s) which are small molecules acting as intermediates in the laccase oxidation reaction (called "Laccase-Mediator System" (LMS)). A great diversity of lignins, enzymes and mediators are present from their very varied source, which makes it necessary to develop tools to screen all these enzymatic conditions on lignins. However, the insolubility of lignins in aqueous media (optimal activity medium for enzymatic reactions) makes their enzymatic depolymerization in liquid medium difficult. Under these conditions, we developed an enzymatic screening tool to visualize an enzymatic depolymerization in solid medium (lignin in the form of solid films or solid micro-deposits). Lignin in the form of solid films has been produced by the spin-coating technique and in the form of solid micro-deposits by inkjet printing technology.