Biopolymers: unravelling the next generation materials
Oeiras, 7 September 2020
Polymers are widely present in our daily life, from fashion to construction, or even in sophisticated medical implants and scaffolds. However, a significant change is occurring, leading to a growing demand for polymers derived for renewable resources. Plant polyesters - a kind of complex natural plastic -, can play a key role in this paradigm shift as the basis for new materials.
On the cell wall of plants, one can find cutin and suberin, which are among the most abundant plant polymers. These plant polyesters, considered as promising substitutes to petroleum-based plastics, have unique properties, but important aspects of their molecular chemistry and functional behaviour remain obscure.
A team of researchers at ITQB NOVA led by Cristina Silva Pereira has developed an innovative methodological approach, which allows extracting biopolymers without losing its original “skeleton”. This new method opens a window of opportunity to enlighten the structure and function of highly complex plant polymers.
Suberin - plant polyester against bacteria
On a first approach, described in Materials Today Bio, researchers focused on suberin, a biopolymer present in the well-known material cork. This interesting molecule is also considered by many as a key green polymer to fight climate change impacts in plant productivity.
Nuclear Magnetic Resonance (NMR) spectroscopy has helped researchers reach for the first time a wide-range characterisation that reveals the structure of suberin in great detail, both in its purified (ex-situ) form and in cork (in-situ). With this technique, it was possible to look at suberin with its polymeric form preserved, and identify specific functional groups crucial for its molecular organisation.
While unravelling new chemical details of suberin, researchers founded an unexpected feature: its ability to form molecular structures with bactericidal activity. “It was crucial to look at the polymer as a whole, from the chemical perspective while bearing in mind the role it plays in the plant”, highlights Cristina Silva Pereira.
The work resulted from a collaborative project with researchers from the University of Gdańsk (Poland), the University of Oxford (UK) and the University of Helsinki (Finland).
Innovative cutin extraction towards solving molecular puzzles
With the previously established NMR methods, researchers developed a new approach to recover and solve the molecular structure of another biopolymer, the cutin. This green polyester is present on plant cuticle, a sort of film that 
constitutes the protective layer of the aerial parts of plants like leaves or fruits.
In the study, now published in Plant Physiology, the researchers of the Silva Pereira lab together with researchers from the Fruit Biology and Pathology - INRAE/ Univ. Bordeaux (France), University of Gdańsk (Poland) and University of Sheffield (UK), established a new cutin extraction method that is applicable to a wide range of plant species and tissues.
The NMR analysis was performed at CERMAX - Centro de Ressonância Magnética António Xavier, which hosts an 800 MHz spectrometer with a high magnetic field and a cryogenic probe which increases its sensitivity, allowing unparalleled studies of biological systems.
The extraction of the biopolymer used an ionic liquid, which coupled with cryogenic milling enabled to see in a liquid state what is supposedly not soluble. With this approach, it was possible to preserve the structure of cutin in a near-native state, that was until now partially unsolved. In addition, this is a faster and simpler method. “These are very promising steps and could lead to settling the puzzles of both cutin and suberin polymer biosynthesis”, says Silva Pereira.
This breakthrough method and the molecular knowledge of biopolymers can be essential to develop a new generation of materials, as well as to solve several unknowns, from the understanding of the ability of plants to adapt to climate change to the polyesters functions and their impact on plant evolution.
ITQB NOVA researchers - Cristina Silva Pereira, Vanessa G. Correia, Artur Bento and Carlos Moreira
In the news:
- Portugueses procuram alternativa sustentável ao plástico, in Diário de Notícias, 03.09.2020
Original Papers:
Plant Physiology | doi.org/10.1104/pp.20.01049
New ionic liquids extraction method that preserves molecular structure from cutin highlighted by solution NMR
Carlos J.S. Moreira, Artur Bento, Joana Pais, a Johann Petit, Rita Escórcio, Vanessa G. Correia, Ângela Pinheiro, Łukasz P. Haliński, Oleksandr O. Mykhaylyk, Christophe Rothan, Cristina Silva Pereira*
Materials Today Bio | doi.org/10.1016/j.mtbio.2019.100039
The molecular structure and multifunctionality of the cryptic plant polymer suberin
V.G. Correia, A. Bento, J. Pais, R. Rodrigues, Ł.P. Halinski, M. Frydrych, A. Greenhalgh, P. Stepnowski, F. Vollrath, A.W.T. King, C. Silva Pereira*
Read the profiles of the first authors in Plant Physiology:
