Coffee fermentation with co-inoculated Lactobacillus bulgaricus and Saccharomyces cerevisiae: Accelerated succession strengthens microbial interactions and metabolic function

To investigate the function of co-inoculated fermentation with Lactobacillus bulgaricus and Saccharomyces cerevisiae on the coffee flavor quality, microbial diversity, sensory evaluation and metabolomics techniques were employed for a comprehensive analysis. Based on the analysis results, the predominant microorganisms in natural fermentation (NF) were Weissella , Lactobacillus and Hanseniaspora , whereas were Lactobacillus , Weissella and Saccharomyces in co-inoculated fermentation (CF). Meanwhile, 73 differentially changed metabolites ( P < 0.05, VIP >1, and FC < 0.50 or FC > 2.0) from 2053 non-volatile metabolites were found between NF and CF. NF was classified as premium (79.66); in contrast, CF was classified as fine (82.50) and characterized by the flavor of sweet, nutty, fruity and flowery. Furthermore, 350 volatile compounds with rOAV above 1.0 were considered to directly contribute to the flavor of coffee. Therefore, co-inoculated fermentation with L. bulgaricus and S. cerevisiae is a promising starter culture to obtain high-quality coffee.