Mass spectrometry imaging of oligosaccharides following in situ enzymatic treatment of maize kernels

Abstract

In recent years enzymatic treatment of maize has been utilized in the wet-milling process to increase the yield of extracted starch, proteins, and other constituents. One of the strategies to obtain this goal is to add enzymes that break down insoluble cell-wall polysaccharides which would otherwise entrap starch granules. Due to the high complexity of maize polysaccharides, this goal is not easily achieved and more knowledge about the substrate and enzyme performances is needed. To gather information of both enzyme performance and increase substrate understanding, a method was developed using mass spectrometry imaging (MSI) to analyze degradation products from polysaccharides following enzymatic treatment of the maize endosperm. Different enzymes were spotted onto cryosections of maize kernels which had been pre-treated with an amylase to remove starch. The cryosections were then incubated for 17 h. before mass spectrometry images were generated with a MALDI-MSI setup. The images showed varying degradation products for the different enzymes observed as pentose oligosaccharides differing with regards to sidechains and the number of linked pentoses. The method proved suitable for identifying the reaction products formed after reaction with different xylanases and arabinofuranosidases and for characterization of the complex arabinoxylan substrate in the maize kernel. HypothesesMass spectrometry imaging can be a useful analytical tool for obtaining information of polysaccharide constituents and enzyme performance from maize samples.