An unfolded protein response-inducible protein (ULI1) mediates aromatic alcohols biosynthesis through reinforcing the Ehrlich pathway in Saccharomyces cerevisiae

Aromatic alcohols such as 2-phenylethanol (2-PE) and tryptophol (TOL) possess diverse biological functions. Here, an unfolded protein response-inducible gene ULI1 and an aldehyde dehydrogenase gene ALD3 in Saccharomyces cerevisiae were disrupted using the CRISPR-Cas9 system. Fermentation assays revealed that both the ULI1 frameshift (Kmuli1) and knockout (KΔuli1) mutants exhibited significantly reduced 2-PE and TOL yields relative to the wild-type strain KMLY1-6, retaining 46.32 and 64.54% for 2-PE, and 34.61 and 77.73% for TOL, respectively. In contrast, ALD3 knockout moderately elevated 2-PE and TOL production by 4.98 and 20.57%, respectively. These results indicate that both ULI1 and ALD3 mediate the biosynthesis of 2-PE and TOL in S. cerevisiae. To further confirm the role of ULI1, three chromosomal integration expression (CIE) strains (KXuli1, KXIIuli1, KΔald3uli1) and one plasmid-based expression (PBE) strain (BY4741/pY26-uli1) were constructed. Compared with the control KMLY1-6, the CIE strains increased 2-PE and TOL production by 10.13-12.91% and 25.76-29.28%, respectively. Meanwhile, the PBE strain produced significantly higher levels of 2-PE and TOL than the empty vector control (BY4741/pY26), with maximum increases of 38.80% and 30.86% detected at 60 h of cultivation. To further elucidate the molecular mechanism of ULI1 in 2-PE and TOL biosynthesis, comparative transcriptomic analysis for Kmuli1 vs. KMLY1-6, together with transcriptomic and proteomic analyses for BY4741/pY26-uli1 vs. BY4741/pY26, was performed. Multi-omics results revealed that ULI1 reinforces the Ehrlich pathway, modulates metabolic flux, maintains mitochondrial structure and cellular protein homeostasis, and coordinates stress responses with metabolic redistribution. Collectively, ULI1 acts as a novel regulatory hub linking stress tolerance and cellular homeostasis, and facilitates aromatic alcohol biosynthesis by strengthening the Ehrlich pathway in S. cerevisiae.