Skip to main content

Zero Waste Ligno-Cellulosic Biorefineries by Integrated Lignin Valorisation

Periodic Reporting for period 2 - Zelcor (Zero Waste Ligno-Cellulosic Biorefineries by Integrated Lignin Valorisation)

Reporting period: 2018-04-01 to 2019-09-30

Zelcor objective is to demonstrate the feasibility of transforming lignocellulose biorefinery recalcitrant side streams into high added-value biobased products by combining chemical and enzymatic catalysis with insects-based conversion. The project is conceived to avoid waste production by recycling waste bio-based products and improve the sustainability of existing second-generation biorefineries. Through a biorefinery-integrated approach, Zelcor aims to develop efficient and sustainable processes for large-scale production of biomolecules for cosmetics, packaging and chemical industry as well as novel biocatalysts. To reach this aim, the project implies the establishment of a platform for the characterisation of biomolecules along with the elucidation of the structure-function relationships and mechanisms involved in catalytic depolymerisation and bioconversion. Residues from cellulosic ethanol production, lignins from pulping process and lignin-like humins formed by sugars conversion are addressed in the project. All the targeted products are 100% bio-based and obtained by processes driven by green chemistry. They are expected to be safer and more biodegradable than their fossil-based counterparts. Moreover, as bio-based products obtained from industrial wastes, they are likely to reduce the total CO2 emission of the whole value chains.
Lignins and humins from four selected processes were recovered at kilograms scale and implemented for comprehensive structural and functional characterization, including safety profiling, as well as for the development of processes. Variability of the raw materials was investigated and specific valorisation strategies were settled for each type of raw material. In all case however, a fractionation step by water, organic solvent or alkali depending on the material, turned out beneficial to increase the functionality and/or yield of the intermediate products. Humins could find direct uses without further conversion and could alternatively be converted into methyl levulinate and levulinic acid. Four main routes have been explored for lignin conversion: solvent extraction and treatment by an ionic liquid yielding antioxidant extracts, base catalysed depolymerisation yielding aromatic chemical intermediates, dissolution-aggregation technology to recover colloidal lignin particles and use of lignin as substrate for the production of biomass by insects. Termites species able to be reared at large scale and to digest lignin-rich substrates were selected and implemented for the creation of an innovative rearing system that made the breeding operations possible and led to the first production of chitin from termites. Recalcitrant lignocellulosic fractions were successfully used as carbon source for living termites or by microbial consortia cultivated from termite guts. Based on preliminary life-cycle analyses, efforts to improve the environmental fingerprint of all these routes have been made. The possibility to use enzymes for lignin functionalisation was demonstrated (water-solubility increase by enzyme-catalysed sulfation and depolymerisation by tailored enzymatic cocktails). Transcriptomic analysis of four white-rot fungi, and bioinformatics analysis of new bacterial lignin-degrading strains, allowed identification of several new fungal and bacterial lignin-degrading enzymes and accessory enzymes which were expressed and characterised. These enzymes were used for conversion of technical lignins, and large-scale expression of two fungal enzymes and one bacterial enzyme was achieved. All the technical achievements were integrated in a cross-cutting value-chain approach, aiming at providing valuable bio-based products for targeted markets. A mapping of functionalities was established allowing selection of intermediate products for formulation and processing into skin-care cosmetic creams, PE-based packaging materials and aqueous colloidal systems. Down-stream functionalisation was successfully applied to intermediate products to tailor their properties in view of new markets (e.g. water depollution for cationized colloidal lignin particles). The performances of the end-products were confronted to the end-users requirements and to techno-economic analysis in order to define the efforts requested to bring the applications and new technologies to the market.
The selected materials in Zelcor are biorefineries side products for which burning up is usually the most valuable application. A major advance has been made by offering technological solutions to recover higher-value products from these materials, including humins that had hardly been investigated so far. Some of the Zelcor compounds can be potentially developed as new ingredients in industry, in particular in the skin care/cosmetic sector, food packaging, agriculture and bioplastics for several applications. All the tested compounds are characterized by low environmental impact and could compete economically with existing fossil-carbon based products, with a main advantage of multi-functionality. Developing the value chains leading to these new products will help making bio-based industry more economically viable and thus encourages the transition away from a fossil-fuel based society. The knowledge on lignin and humins stability and variability gained through the project will help develop flexible biorefinery processes. The production of new biocatalysts will promote the development of greener routes for lignin functionalisation. A range of bacterial and fungal lignin-oxidising enzymes and accessory enzymes are now available for testing as combined biocatalysts for lignin conversion. Association of lignin-degrading enzymes and accessory enzymes improves the yields and functionalisation degree. A novel enzyme enhancing lignin solubility has been discovered, which opens up new prospects of solvent-free processes. Advances made in the understanding of both bacterial and fungal enzymes activities towards lignins will be useful also for other sectors. Progresses have been made in establishing structure-properties relationships and understanding the reactivity of lignins towards chemical treatments, in particular ionic liquid depolymerizing treatment. Elimination of low-molar mass phenolics prior to the treatment improves the recovery yield of functional intermediate products, which highlights the interest of a cascade process combining solvent extraction and depolymerising treatments. Insights into the safety and eco-toxicity of the selected ionic liquid have been obtained and show that it provides an alternative non-flammable and recyclable reagent for sustainable processes. Using termites as natural biomass utilization systems offers possibility to develop cost-effective and energy-saving strategies for industrial side-streams conversion, especially though processes acting in more environmental-friendly conditions compared to chemical catalysts. A breakthrough has been brought by demonstrating the feasibility of rearing termites with lignocellulosic residues and isolate chitin. Further development of this technology will allow to connect food and non-food value chains.
Zelcor project logo