Abstract by Jonatan Riber Granborg

The use of industrial enzymes has grown over the past decades with one of the applications being enzyme-assisted wet-milling of maize kernels. Here the industrial enzymes are used to break down biopolymeric structures, such as arabinoxylan, to increase the separation and yield of the valuable end products e.g., starch, proteins and maize oil.

In this thesis two research articles describing methods for in situ analysis of degradation products formed from maize arabinoxylan after enzymatic treatment by Matrix-Assisted Laser Desorption Ionization (MALDI) imaging are presented.

One method was developed to compare solutions with different xylanases and auxiliary enzymes after applying the solutions by droplet deposition to the endosperm of cryosectioned maize kernels. Each cryosection was applied with three enzyme solutions and incubated for 17 hours. After incubation, the formed oligosaccharide degradation products were analyzed by MALDI imaging. The MALDI imaging analysis proved capable of detecting oligosaccharides with a variety of decorations to the xylan backbone including, acetyl groups, ferulic acids, hexuronic acids and methylated hexuronic acids. Furthermore, it made it possible to show distinct differences in which oligosaccharides were formed as degradation products for the enzyme solutions and thereby compare the enzyme performance.

The other method was used to describe the distribution of arabinoxylan degradation products in different morphological regions of the maize kernel. Here xylanases were applied by spray application to cryosectioned maize kernels originating from two different kernels. The method was able to show how the formed oligosaccharides were located in the different regions of the kernels. The method thereby provided new insights to differences in the arabinoxylan substrate depending on the morphological region of the kernel in addition to the information gained on enzyme performance.

Overall, the MALDI imaging methods provided a valuable contribution to analysis of enzyme degradation products of cell-wall polysaccharides in maize.

In addition to the two research articles the thesis also includes a review article describing the current state and future perspectives for Mass Spectrometry Imaging (MSI) in studies drug distribution and drug metabolism.