PhD Defence by Yannick Patrice Didion

Principal supervisor
Professor Manuel Pinelo
DTU Chemical Engineering

Co-supervisor
Professor Pablo Ivan Nikel
DTU Biosustain

Examiners
Associate Professor Ioannis Skiadas (Chairman)
DTU Chemical Engineering

Associate Professor Ana Rita Cruz Duarte
Universidade Nova de Lisboa, Portugal

Associate Professor Jakub Zdarta
Poznan University of Technology, Poland

Chairperson at defense
Senior Researcher Merlin Alvarado Morales
DTU Chemical Engineering

The defense will also be held virtually. If you wish to follow the defense virtually you can sign up by sending an e-mail to Merlin Alvarado Morales, meal@kt.dtu.dk, latest 20 March at 9:00. You will then afterwards receive an invitation to join the virtual defense.

Popular summary - A Greener Future for Biodegradable

Plastics Plastics are integral to modern life, but their environmental costs are significant. Most plastics are derived from petroleum, making them difficult to degrade and harmful to ecosystems, while their disposal releases CO2 into the atmosphere. Biodegradable bio-plastics such as Polyhydroxyalkanoates (PHAs) offer a promising alternative. These plastics, produced by bacteria, combine eco-friendliness with versatility, finding applications in packaging, medical devices, and more. However, traditional methods for producing PHAs rely on costly processes and toxic solvents such as chloroform, limiting their large-scale use.

This research sought to overcome some of these challenges by developing potentially greener and efficient methods for extracting PHAs. Central to the study was the use of more sustainable solvents, including biobased solvents and natural deep eutectic solvents (NADESs). NADESs are innovative, low-toxicity solvents derived from natural compounds such as plant-based acids and terpenes. They offer an interesting alternative to conventional organic solvents. By combining enzymatic pre-treatments with NADESs, a process was developed that enabled the efficient extraction of PHAs. One NADES, made from menthol and acetic acid, was very effective, achieving yields and purity levels with clear potential for PHA extarction.

The method was further refined to extract a PHA co-polymer, PHBV, from mixed microbial cultures grown on fruit waste. This extension not only demonstrated the versatility of NADESs but also showcased their potential for use with renewable feedstocks, contributing to waste valorization. The study also took a data-driven approach to solvent design by analyzing the physical and chemical properties of NADESs, such as viscosity and polarity. This allowed the idenitification of factors potentially influencing extraction efficiency and could lead to the development of a more systematic method for selecting optimal solvents.

Furthermore, as it was important to minimize waste the recycling of all solvents used was also achieved.  This research represents a potential step toward more sustainable plastic production. By leveraging greener solvents and innovative extraction techniques, it offers a proof of concept for producing biodegradable plastics in a more responsible manner. The findings pave the way for wider adoption of PHAs, reducing reliance on petroleum-based plastics and hopefully helping to address the global plastic pollution crisis.