Transcriptomics and metabolomics reveal effects of Lactiplantibacillus plantarum NCU116 fermentation on carrot flavor

Lactic acid bacteria (LAB) fermentation is often applied to improve the sensory and nutritional quality of fruit and vegetable juices. In this study, metabolomic analysis was utilized to identify the dynamic changes in flavor compounds, while transcriptomic analysis was conducted to elucidate the biological mechanisms regulating flavor development the fermentation of carrot pulp. The results suggest that compared to non-fermented carrot pulp, fermentation with Lactiplantibacillus plantarum NCU116 (L. plantarum NCU116) exhibited increased levels of organic acids, improved amino acid conversion, reduced terpene and aldehyde odorants, and had higher contents of ketones, alcohols, and esters, which imparted fruity and floral flavors. Moreover, transcriptomic analysis revealed that 1007 and 722 differentially expressed genes (DEGs) were identified in carrot pulp at various stages of fermentation, metabolic pathways associated with these DEGs were predominantly enriched in energy capture and transfer, and metabolism of terpenes, amino acids, and carbohydrates. Therefore, we constructed a metabolic regulatory network of characteristic flavor compounds during carrot pulp fermentation to reveal the relationship between L. plantarum NCU116 and flavor quality formation, identifying key hub genes associated with characteristic flavors. This research lays a theoretical foundation for controlling the removal of off-odors and enhancing aromas in carrot pulp through microbial enzyme systems.