Aleksander Riise Hansen has conducted his Ph.D. thesis in BioValue’s project 3.

Below is a short summary of his findings and information on the defense.


Ph.D. title: Development and applications of advanced probing tools for cell wall biology

Lignocellulosic biomass is mainly composed of plant cell walls that are unique highly complex structures comprised of diverse classes of polysaccharides, proteoglycans and polyphenolics with multiplexed roles throughout the life of a plant. Understanding the biology of this special cellular organelle also facilitates cell wall-based industrial applications, however, it requires a variety of sensitive and specific detection methods for separate cell wall components including their alternating molecular characteristics in vitro as well as in situ. Cell wall component-directed molecular detection probes represent an essential asset. Up to date, a relatively large set of probes has been produced. Currently, this main set consists of monoclonal antibodies, carbohydrate-binding modules, synthetic antibodies produced by phage display and small molecular probes.

The objectives of this Ph.D. study are to expand the set of probes against polysaccharides found primarily in the plant cell wall, and to develop methods of analysis based on the new probes and use these methods to address problems of fundamental as well as of applied nature. The main objectives was to established method for comprehensive microarray profiling to determine optimal hydro thermal pre-treatment severity levels from corn stover waste streams. In order to improve existing detection methods new probes was developed from the model grass Brachypodium distachyon using a naïve human single domain antibody library.

This first part of the thesis therefore comprises an introduction to the plant cell wall, to its constituent biopolymers, its diversity in composition and finally methods of analysis, both the methods that I have developed and used and methods that are complementary. Chapter 2 highlights the impact of hydrothermal pretreatment on enzymatic digestibility of 3 grass species for lignocellusic biomass conversion. As a function of pre-treatment severity, an increase in glucose yield from Cellic CTec3 (Novozymes, Denmark) enzyme cocktails was observed for all 3 biomasses. CoMPP showed a removal of detectible pectin and lower levels of the XG, xylan and mannan derived antibody signals. Even through pectin are low in grass feedstocks, the loss of pectin and other soluble cell wall polysaccharides from pre-treatments might still not outweigh the benefits of increased fermentable yield. The yield comes primarily from the xylan and cellulose degradable components of the enzymatic cocktail. The later chapters describes the use of phage display for developing new antibodies for cell wall analysis by shotgun selection. Common for those aims was the data readout from the various carbohydrate detection methods including antibodies.

Even though most of the major polysaccharide classes of the cell wall are represented by one or more probes, there is still a notable lack of probes against lignin, RG-II and cellulose substructures. To date, even for well studies terrestrial plants like Arabidopsis or grass speices , there exists an enormous number of permutations of unidentified or uncharacterized cell wall domains with important functions, and limited experimental studies how they are interconnected. Discovering these and interpreting the results obtained maybe critical for chemical engineers towards a more effective deconstruction and bio-valorization.

We hope that you will participate at Aleksander’s defense:

Time: Mondag 15/1 2018 at 13 o’clock

Place: to be announced shortly

Main supervisor: Professor MSO William Willats, previously at Institute of Plant and Environmental Sciences / Plant Glyco biology, University of Copenhagen.

Contact information: Aleksander Riise Hansen, e-mail: arh@plen.ku.dk

Defense title: Development and applications of advanced probing tools for cell wall biology