Profiling of cool-season forage arabinoxylans via a validated HPAEC-PAD method

Glenna E Joyce; Isabelle A Kagan; Michael D Flythe; Brittany E Davis; Rachel R Schendel

doi:10.3389/fpls.2023.1116995

Profiling of cool-season forage arabinoxylans via a validated HPAEC-PAD method

Front Plant Sci. 2023 Mar 13:14:1116995. doi: 10.3389/fpls.2023.1116995. eCollection 2023.

Authors

Glenna E Joyce¹, Isabelle A Kagan², Michael D Flythe^{1

2}, Brittany E Davis^{1

2}, Rachel R Schendel¹

Affiliations

¹ Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, United States.
² Forage-Animal Production Research Unit, U.S. Department of Agriculture, Agricultural Research Service (USDA-ARS), Lexington, KY, United States.

Abstract

Cool-season pasture grasses contain arabinoxylans (AX) as their major cell wall hemicellulosic polysaccharide. AX structural differences may influence enzymatic degradability, but this relationship has not been fully explored in the AX from the vegetative tissues of cool-season forages, primarily because only limited AX structural characterization has been performed in pasture grasses. Structural profiling of forage AX is a necessary foundation for future work assessing enzymatic degradability and may also be useful for assessing forage quality and suitability for ruminant feed. The main objective of this study was to optimize and validate a high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) method for the simultaneous quantification of 10 endoxylanase-released xylooligosaccharides (XOS) and arabinoxylan oligosaccharides (AXOS) in cool-season forage cell wall material. The following analytical parameters were determined or optimized: chromatographic separation and retention time (RT), internal standard suitability, working concentration range (CR), limit of detection (LOD), limit of quantification (LOQ), relative response factor (RRF), and quadratic calibration curves. The developed method was used to profile the AX structure of four cool-season grasses commonly grown in pastures (timothy, Phleum pratense L.; perennial ryegrass, Lolium perenne L.; tall fescue, Schedonorus arundinaceus (Schreb.) Dumort.; and Kentucky bluegrass, Poa pratensis L.). In addition, the cell wall monosaccharide and ester-linked hydroxycinnamic acid contents were determined for each grass. The developed method revealed unique structural aspects of the AX structure of these forage grass samples that complemented the results of the cell wall monosaccharide analysis. For example, xylotriose, representing an unsubstituted portion of the AX polysaccharide backbone, was the most abundantly-released oligosaccharide in all the species. Perennial rye samples tended to have greater amounts of released oligosaccharides compared to the other species. This method is ideally suited to monitor structural changes of AX in forages as a result of plant breeding, pasture management, and fermentation of plant material.

Keywords: endoxylanase; hemicellulose; hydroxycinnamic acid; pasture grass; plant cell wall.

Grants and funding

This study was funded by the U.S. Department of Agriculture, Agricultural Research Service as part of National Program 215; Grass, Forage, and Rangeland Agroecosystems. USDA is an equal opportunity provider and employer. This work was also supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, Hatch Project KY007112 under Accession #1021937.