Proteomic profiling of barley spent grains guides enzymatic solubilization of the remaining proteins
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Within the brewing industry, malted barley is being increasingly replaced by raw barley supplemented with exogenous enzymes to lessen reliance on the time-consuming, high water and energy cost of malting. Regardless of the initial grain of choice, malted or raw, the resultant bulk spent grains are rich in proteins (up to 25% dry weight). Efficient enzymatic solubilization of these proteins requires knowledge of the protein composition within the spent grains. Therefore, a comprehensive proteomic profiling was performed on spent grains derived from (i) malted barley (spent grain A, SGA) and (ii) enzymatically treated raw barley (spent grain B, SGB); data are available via ProteomeXchange with identifier PXD008090. Results from complementary shotgun proteomics and 2D gel electrophoresis showed that the most abundant proteins in both spent grains were storage proteins (hordeins and embryo globulins); these were present at an average of two fold higher in spent grain B. Quantities of other major proteins were generally consistent in both spent grains A and B. Subsequent in silico protein sequence analysis of the predominant proteins facilitated knowledge-based protease selection to enhance spent grain solubilization. Among tested proteases, Alcalase 2.4 L digestion resulted in the highest remaining protein solubilization with 9.2 and 11.7% net dry weight loss in SGA and SGB respectively within 2 h. Thus, Alcalase alone can significantly reduce spent grain side stream, which makes it a possible solution to increase the value of this low-value side stream from the brewing and malt extract beverage manufacturing industry.
KeywordsBarley spent grain Proteomics Enzymatic solubilization Hordein Mass spectrometry
This research was supported by Biomedical Research Council (BMRC), Agency for Science, Technology and Research and a joint research collaboration fund between Bioprocessing Technology Institute, Agency for Science, Technology and Research, Singapore, and NESTEC LTD, Switzerland.
X Bi designed and supervised the study. L Ye, A Lau, L Zheng, and K Tan performed the experiments. L Ye, X Bi, A Lau, YJ Kok, and D Ng analyzed the data and wrote the manuscript. J Muller, C Vafeiadi, D Ow, and E Ananta gave valuable suggestions during experimental design and revised the manuscript. All authors read and approved the final manuscript.
Compliance with ethical standards
This article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
The authors declare that they have no competing interests.
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