Proteomics and Metabolomics Reveal that an Abundant α‑Glucosidase Drives Sorghum Fermentability for Beer Brewing

Sorghum (Sorghum bicolor), a grass
native to Africa, is a popular alternative to barley for brewing beer.
The importance of sorghum to beer brewing is increasing because it
is a naturally gluten-free cereal, and climate change is expected
to cause a reduction in the production of barley over the coming decades.
However, there are challenges associated with the use of sorghum instead
of barley in beer brewing. Here, we used proteomics and metabolomics
to gain insights into the sorghum brewing process to advise processes
for efficient beer production from sorghum. We found that during malting,
sorghum synthesizes the amylases and proteases necessary for brewing.
Proteomics revealed that mashing with sorghum malt required higher
temperatures than barley malt for efficient protein solubilization.
Both α- and β-amylase were considerably less abundant
in sorghum wort than in barley wort, correlating with lower maltose
concentrations in sorghum wort. However, metabolomics revealed higher
glucose concentrations in sorghum wort than in barley wort, consistent
with the presence of an abundant α-glucosidase detected by proteomics
in sorghum malt. Our results indicate that sorghum can be a viable
grain for industrial fermented beverage production, but that its use
requires careful process optimization for efficient production of
fermentable wort and high-quality beer.