Green tea residue extract as a fermentation matrix improves yeast growth and linoleic acid enrichment in Pichia kudriavzevii HJ2

Green tea residues from simulated brewing were converted into a fermentation matrix. • TREM promoted P. kudriavzevii HJ2 growth and linoleic acid enrichment. • Lipidomics showed lower TAG and higher GP signals in TREM. • EGCG partially reproduced linoleic acid enrichment and lipid profile responses. • TREM shifted the fatty acid profile of HJ2 without strain engineering. Tea residues are food processing byproducts rich in nutrients and polyphenols, but their potential as fermentation matrices for improving yeast growth and cellular lipid quality remains underexplored. In this study, green tea residues (GTRs) were generated through a simulated tea brewing process and used to prepare tea residue extract medium (TREM), and the effects of TREM on Pichia kudriavzevii HJ2 were evaluated. Compared with basal control medium (BCM), TREM supported higher biomass accumulation and faster reducing sugar consumption. Extracellular metabolomics showed decreases in selected phenolic and nitrogenous compounds, while transcriptomics indicated higher expression of fatty acid synthesis and desaturation genes, including ACS1/2, ACC1, FAS1/2, OLE1 , and the putative FAD2 gene. Compared with BCM, TREM shifted the cellular fatty acid profile toward linoleic acid (LA) enrichment, increasing the LA proportion from 12.43% to 22.84% and LA content from 7.39 to 11.73 mg/g dry cell weight. Lipidomic profiling further revealed reduced triacylglycerol signals, increased glycerophospholipid signals, and enrichment of LA-containing phospholipids. Consistent with these lipid changes, the proportion of propidium iodide-positive cells decreased from 44.57% to 20.80%. Supplementation with epigallocatechin-3-gallate (EGCG; 20 mg/L) partially reproduced the LA enrichment and lipid remodeling observed in TREM but did not reproduce the growth-promoting effect. Collectively, these findings indicate that GTRs can be converted into a fermentation matrix that improves HJ2 growth and its lipid quality without strain engineering.