Date of Award
2024
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Doctor of Philosophy
School
School of Science
First Supervisor
Professor Michelle Colgrave
Second Supervisor
Doctor Jean-Philippe Ral
Third Supervisor
David Moody
Fourth Supervisor
Doctor Angéla Juhász
Fifth Supervisor
Hugh Dunn
Abstract
Barley (Hordeum vulgare L.) is one of the earliest domesticated cereal crops. It is used in world malt barley production, where Australia is a major exporter, representing more than 30 per cent of the world's trade. Barley is the grain of choice for malt production due to its high starch-to-protein ratio and enzyme levels that can be harnessed during germination. Malt is produced by a process called malting, which involves a three-stage controlled germination of malting barley grain. This process uses enzyme activation and de novo enzyme synthesis to modify the physical structure of the hard barley grain to friable malt ready for brewing, distilling, or food manufacture. However, the malting process is energy-intensive, requiring essential utilities and direct input costs. Therefore, traits that improve the barley grain's malting phenotype could be potential targets for improved malting practices and sustainability.
This PhD thesis focuses on developing and applying proteome-wide investigation to understand the impacts of controlled germination on malting barley grain modification. To achieve this goal, we combined proteomic technologies, biochemical assays, and compositional analysis to investigate barley grain malting phenotypes for a more informed selection of barley varieties with enhanced malt quality characteristics. The study focused on two InterGrain malt barley genotypes: (1) IGB1467, an InterGrain trial breeding line with a unique phenotype that modified efficiently at a 2% lower moisture level than (2) Flinders, an InterGrain premium malt variety.
We used bottom-up proteomic analysis involving high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) and various data acquisition methods, such as (1) discovery or shotgun proteomics; (2) multiple reaction monitoring (MRM); and (3) sequential window acquisition of all theoretical fragment ion mass spectra (SWATH-MS). Qualitative and quantitative data is explored via bioinformatics and database technologies to identify key protein groups and differentially abundant proteins (DAPs) over the malting time course in the two malting barley genotypes. The proteomic data was mapped to metabolic pathways and correlated with malting barley biochemical, compositional and malt quality analyses, providing insight into the impact of key protein abundance pattern changes.
This study highlights differing responses in IGB1467 and Flinders due to low[1]oxygen submergence stress during malting, the influence of aquaporins on grain water uptake and the role of reactive oxygen species (ROS) during controlled germination. All of these factors influence overall grain modification and final malt quality.
Understanding differences in mechanisms underpinning the malting phenotype will potentially lead to the development of new barley varieties with improved processability for efficient malting practices that drive energy savings and environmental sustainability. In addition, this knowledge will be valuable to the Australian barley industry in maintaining its competitive advantage globally by providing a proteomic understanding of germination to improve the selection of barley varieties with internationally competitive malting quality characteristics.
DOI
10.25958/rqy1-1g75
Access Note
Access to this thesis is embargoed until 31 May 2026
Recommended Citation
O'Lone, C. E. (2024). Proteomic understanding of grain germination to improve the selection of barley varieties with internationally competitive malting quality characteristics. Edith Cowan University. https://doi.org/10.25958/rqy1-1g75