Mirko Bunzel

Our research focuses on plant cell wall polymers. Plant cell walls mostly comprise non-starch polysaccharides, but also lignin and structural proteins. We strive to develop methods to understand the chemical structures of polysaccharides and lignin as both technofunctionality and potential health benefits of these components are dependent on their chemical structures. Also, we aim to understand which factors affect the composition and the structures of the cell wall polymers and how these structures are altered during processing. This includes the finding of suitable processing conditions to produce, for example, prebiotic carbohydrates, to increase or decrease viscosity, or to generate the starting materials for hydrogel formation. With hydrogels being one example, plant based polymers have the potential to replace synthetic polymers in many applications. 

I am a chemist at heart, although of course I also appreciate food. So I started my studies with both chemistry and food chemistry. After three years, however, I focused on food chemistry because I really liked the applied nature of food chemistry. Following my studies, I completed a practical year, the prerequisite for becoming a state-certified food chemist in Germany. To gain more experience in research, I did my PhD at the Department of Biochemistry and Food Chemistry at University of Hamburg. During my doctoral studies, I also gained my first research experience in the United States, at the Dairy Forage Centre in Madison, WI, where I had the privilege of working with John Ralph, who is both a great researcher and person. As I really enjoyed research, I did my habilitation, which is the equivalent of being an Assistant Professor in the US, back at the University of Hamburg. After I finished my habilitation, I became an Associate Professor at the University of Minnesota before I took the position as a Full Professor at the Karlsruhe Institute of Technology (KIT). Here, I am also responsible for both the undergraduate and graduate studies in Food Chemistry. 

As I am basically a carbohydrate chemist, I look at plant protein research from a slightly different angle. As sustainability is certainly one of the biggest issues today and the use of plant proteins is also closely linked to sustainability, I believe that we need to produce plants in a sustainable way and be able to utilize the plant in its entirety, both sensibly and profitably. Of course, this also includes the by-products of the plant after protein extraction. Secondly, people here in Germany like plant-based products because of the sustainability and animal welfare aspects, but consumers are sometimes concerned that plant-based foods still contain many additives to imitate animal products. Therefore, we need to steer and improve the functionality of plant-based proteins. However, we must always remember that despite all the sustainability, animal welfare, and health aspects, consumers will only demand purely plant-based products if they taste good!

My group aims to contribute to both aspects just mentioned. Firstly, we want to understand the structure-function relationships of polysaccharides in order to define high-value applications for the by-products after protein extraction, which are highly enriched with plant cell wall polymers. We still have a long way to go here. The next step is and will certainly be to find sustainable and economically feasible ways to modify the polysaccharides according to our needs. This is an important aspect of our work as cell wall polysaccharides have a large natural diversity that depends on many factors, including genomics and environmental influences. So we need to learn how to deal with this structural diversity, which - seen positively - of course also brings great versatility to these polysaccharides. We are also interested in whether we can utilize by-products to influence the functionality of plant proteins.

We always have projects focusing on the improvement of polysaccharide analytical techniques. We aim to utilize the full spectrum of chromatography and spectroscopy capabilities to understand the fine structure of plant cell wall polymers. For example, we apply two-dimensional HSQC-NMR experiments and mass spectrometry coupled to ion exchange chromatography in order to improve our profiling approaches for oligosaccharides that are liberated from polysaccharides. We also endeavor, in collaboration with processing partners, to affect the technofunctional properties of by-product polymers and to find potential applications where these polymers can replace less sustainable polymers, such as synthetic polymers or chemically modified polymers.

From my experience as a consumer, I really like pea and sunflower proteins. Both are found in great tasting plant-based hamburger patties. From a scientific point of view, I am particularly interested in the by-products. In this context, I appreciate the botanical diversity of cell wall polymers. By-products from wheat have a completely different composition than by-products from peas, which in turn are very different from by-products from lupines. Here again, this polysaccharide diversity and versatility is a boon and a bane!