Molecular mechanism of enhanced ester synthesis in Monascus – Caproicibacterium co‐culture system based on transcriptomic and flavor metabolomic analysis

Abstract BACKGROUND Ethyl caproate is a key aroma compound in Chinese strong‐flavor Baijiu, yet its biosynthesis remains inefficient in pure cultures due to metabolic bottlenecks. This study investigated the regulatory mechanisms of ester production in Monascus purpureus XTQ under co‐cultivation with Caproicibacterium amylolyticum JSJ through transcriptomic and metabolomic analysis. RESULTS A total of 340 differentially expressed genes were identified in co‐cultures, which were significantly enriched in pathways such as glycolysis, fatty acid metabolism and ester biosynthesis. Notably, acetyltransferase, lipase and the Zn(II) 2 Cys 6 transcription factors were markedly upregulated (3.5‐, 4.5‐ and 28.2‐fold, respectively), functioning as core regulatory elements. Gas chromatography–mass spectrometry analysis showed that the total ester content in the co‐culture significantly increased to 21.74% ( P < 0.05), with specific elevation of characteristic flavor esters including ethyl caproate. Scanning electron microscopy demonstrated the specific adhesion of C. amylolyticum to fungal hyphae, suggesting potential metabolic interactions mediated through physical contact. CONCLUSION These findings provide molecular insights into interspecies metabolic cooperation and offer a theoretical foundation for optimizing microbial co‐culture strategies to enhance flavor profiles in Baijiu fermentation. © 2026 Society of Chemical Industry.