Ignacio Delgado Santamaría’s doctoral research at NMBU reveals that proteins in the expansin superfamily, previously considered non-catalytic, can actually cleave chemical bonds in plant cell walls. This knowledge could transform biotechnological processes for converting plant biomass into valuable products.
His thesis, Plant cell wall-loosening mechanisms: functional insights and evidence for catalysis in fungal expansin-like proteins, provides new insights into how fungi interact with plant cell walls and opens up possibilities for industrial applications.
Below, he answers questions about his research:
Why is this research important?
Understanding how these fungal proteins and enzymes work is industrially important because plant cell walls contain valuable materials. These can be converted into products like biofuels, bioplastics, medicines, adhesives, or fire retardants. Thus, plants offer much more than just food; they are a source of many important products and chemicals of interest.
What were the research goals of your doctoral degree?
In my research group, we study proteins, which are tiny molecules invisible to the naked eye but essential for life. During my PhD, we have worked with proteins from fungi, organisms that include mushrooms but are far more diverse. In nature, fungi interact with plants in various ways. Some fungi feed on and harm living plants, others live in partnership with plants, and some, which my research has focused on, feed on dead plant matter. These fungi play a crucial role in recycling carbon in forests, making it available again for plants and other living organisms.
Fungi break down dead plants using proteins known as enzymes, which act like molecular scissors or glue to cut and reconnect chemical bonds. To understand this, imagine a long chain: an enzyme can cleave and/or rejoin different links in the chain. The plant material that enzymes break down is mainly polysaccharides, complex sugar chains that form the plant cell wall, a protective layer around every plant cell.
What are your most important results, and what is the potential impact of your research?
A special group of proteins that we study are called expansins. Previous to our work, scientists thought they didn’t have enzymatic activity (meaning they were not true enzymes). However, they seemed to help untangle crucial “junctions” or knots in the plant cell wall that hold it together, which is important for processing plant material efficiently. Using the chain metaphor: expansins were thought to separate groups of chains (as if they were magnetized) without cutting the links.
In our research, we discovered that an expansin can actually cut chemical bonds inside a plant cell wall component called xylan. Xylan is widely used in medicine storage, food packaging, wastewater treatment, and is considered a sustainable alternative to plastics and aluminium foil. Our findings are the first demonstration of enzymatic activity for this type of protein, which was a long-standing goal in the field. This discovery could accelerate the breakdown and valorisation of plant biomass, making biotechnological processes more efficient. However, our experiments were conducted at a lab scale, so future work is needed to test how well this works industrially, considering scalability and costs.
We also explored how several fungal expansins affect the plant cell wall. We found that one expansin helps to dismantle the network of cellulose in the plant cell wall—a plant polysaccharide with many uses (such as paper and fabric production, alternative to plastics, thermal and sound insulation, printing or air cleaning). This hints at another potential industrial application.
Just like plants, fungi also have cell walls mainly made of polysaccharides that can be sources of valuable products and chemicals. We studied how fungal expansins impact the degradation of chitin, an essential component of the fungal cell wall. We found that three expansins improve the breakdown of chitin by other enzymes that specialize in degrading it. Considering the applications of chitin (such as wound dressing, fertilizer, cosmetics, prebiotics or vaccines), this discovery may have significant industrial potential.
Overall, this thesis sheds light on the field of expansins, as well as the proteins and enzymes involved in the degradation of plant and fungal cell walls. Given the industrial potential of plants and fungi, we hope that our findings help to steer future research in the field.
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Ignacio Delgado Santamaría
- Education: Biotechnology Degree and Biotechnology and Plant Bioengineering Master, Polytechnic University of Madrid
- Home town: Segovia, Spain
- PhD Faculty: Faculty of Chemistry, Biotechnology and Food Science, NMBU
- Funding: Novo Nordisk Foundation (Emerging Investigator grant) and Research Council of Norway (NorBioLab)
- Main supervisor: Anikó Várnai
- Co-supervisor: Vincent G.H. Eijsink
- Title of thesis: Plant cell wall-loosening mechanisms: functional insights and evidence for catalysis in fungal expansin-like proteins