The “bio-based circular economy”: production of value-added products starting from renewable biomass

In 2022 the “Earth Overshoot Day”, which is the date that marks when all the biological resources that the Earth can renew during the entire year are finished, was calculated to fall on July 28th. Due to human activities and related pollution, the Earth Overshoot Day has fallen earlier every new year: it was conceptualized to clearly show the need to lower human ecological footprint and to find new industrial processes that do not require the over-exploitation of natural resources.

One possible strategy to reduce the depletion of natural resources is “circular economy”, which focuses on the recycling and reutilization of by-products generated from human activities as a starting material to obtain valuable products, thus helping to reduce wastes produced by industrial processes and to enhance the economics of the production chain. An interesting approach is the “bio-based circular economy” model which focuses on the production of value-added products starting from renewable biotic by-product, diminishing the needs to exploit natural resources and making the entire process more sustainable.

In this view, wheat bran and kraft lignin, two renewable low-value by-products obtained in large amounts worldwide could be utilized as starting material to produce bioplastic precursors through a biotechnogical valorization. This biotechnological valorization consists of two main steps: 1) the thermo-enzymatic extraction of chemical compounds from the crude by-product and 2) the biotransformation of the extracted compounds to plastics precursor using an engineered microbial strain. The biotechnological production of plastics using renewable by-product as starting material could help reducing the dependence on petroleum-based feedstock and cope with climate change. Nonetheless, these processes are hampered by the amount of time and money needed to research and develop an efficient industrial-scale production.

In the Protein Factory 2.0 laboratory, we developed a thermo-enzymatic method to extract ferulic acid and vanillin from wheat bran and kraft lignin, respectively. Then, we developed and optimized an engineered Escherichia coli strain expressing up to 6 different recombinant enzymes that converted more than 90% of ferulic acid and vanillin into cis,cis-muconic acid and adipic acid, that are interesting plastic precursors. This study represents a first step toward the development of an industrial-scale bioconversion system for the sustainable utilization of renewable by-products.