Integrated transcriptomic and metabolomic analyses reveal monoterpenoid biosynthesis in Aspergillus cristatus during tea infusion fermentation

Monoterpenoids are key contributors to the characteristic aromas of fermented tea, but their formation by Aspergillus cristatus remains unclear. In this study, liquid-state fermentation of a tea infusion was tracked through inoculation with A. cristatus , monoterpenoid profiles, sensory analysis, and transcriptomics were generated at three fermentation stages with or without glucose supplementation. A. cristatus promoted monoterpenoid accumulation as fermentation progressed, and glucose supplementation induced earlier and stronger accumulation of key odor-active compounds. Gas chromatography–olfactometry coupled with aroma extract dilution analysis and odor activity value analyses identified linalool, α -terpineol, geranial, neral, geraniol, citronellol, β -ocimene, nerol, and β -myrcene as major odor-active monoterpenoids in TG12. Transcriptomic analysis indicated activation of the MVA pathway, and AcGal4 was identified as a putative regulatory factor associated with Acerg20 and AcTPS . AcTPS was functionally validated in vitro as a nerol synthase. These findings could assist in the targeted regulation of sensory characteristics of fermented tea.