Awamori fermentation test and 1-octen-3-ol productivity analysis using fatty acid oxygenase disruptants of Aspergillus luchuensis

1-Octen-3-ol is a major aroma component of awamori, a traditional distilled liquor produced in Okinawa Prefecture, Japan. As 1-octen-3-ol is thought to affect the sensory properties of awamori, it is important to fully characterize the compound's biosynthetic pathway and control mechanism. We previously reported that the fatty acid oxygenase ppoC (ppo: psi-produced oxygenase) of Aspergillus luchuensis is directly involved in the production of 1-octen-3-ol in rice koji (Kataoka et al., J. Biosci. Bioeng., 129, 192–198, 2020). In the present study, we constructed A. luchuensis ppoD disruptants to characterize the role of ppo genes in 1-octen-3-ol biosynthesis. A small-scale awamori fermentation test was performed using ppoA, ppoC, and ppoD single disruptants (ΔppoA, ΔppoC, and ΔppoD, respectively), along with the parent strain, ΔligD. 1-Octen-3-ol was not detected in the distillate prepared using the ΔppoC strain. We conclude that A. luchuensis ppoC is the only 1-octen-3-ol–producing factor in the awamori brewing process. Because ΔppoA and ΔppoD slightly enhanced 1-octen-3-ol productivity, these two genes may play a role in negatively controlling 1-octen-3-ol biosynthesis.