Metabolomic studies allow the identification of dissimilar behaviour of ligninolytic bacteria on different technical lignins
Résumé
Lignin is a renewable source of aromatic molecules which is present in large quantities throughout the world in plant biomasses and as by-products of certain industries (paper industry, wood industry,...). Lignin is mainly burned and used to produce energy because of its complex structures and chemical compositions. Lignin can be degraded and transformed by microbial and enzymatic processes known to be respectful of the environment. Biological valorization remains challenging as biocatalysts are not sufficiently effective and efficient. Moreover, the complexity and heterogeneity of lignins are a barrier to their use. Understanding the microbial behavior on lignins by finding some markers of their efficient transformation could lead to the development of effective biological routes to valorize the aromatic moieties of these polymers. In Nature, several micro-organisms are able to degrade lignins [1]. Ligninolytic bacteria have some interesting features in term of ligninolytic enzymes productions, utilization of aromatic compounds as carbon source, their metabolization via various intracellular pathways and finally some productions of molecules of interest [2]. In this work, we use multiple approaches (growth kinetics studies, ligninolytic activities quantification, IRTF and metabolomic studies by ultra-high performance liquid chromatography - electrospray ionisation - high-resolution multiple-stage tandem mass spectrometry (UHPLC-ESI-HRMS)) to study the behaviour of two ligninolytic bacteria Pandoraea norimbergensis [3] and Comamonas composti [4], during their growth on lignins with different structures and origins (Kraft and Protobind lignins). Results showed that growths profiles, lignin modifications, consumption and production of phenolic monomers and oligomers vary within bacteria and according to the lignin used. The targeted bacteria behave differently on the two lignins. This study demonstrates that the efficient transformation of lignins requires a suitable combination of biocatalysts (bacteria)/lignins. Micro-organisms used must be selected on the basis of their metabolic capacities, as well as the structure and composition of the substrates to be valorized.
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