Traditional fermented foods of Indonesia harbour functionally redundant but phylogenetically diverse taxa

Fermented foods represent complex microbial ecosystems that contribute to food quality, functionality, and potential health benefits, yet many traditional fermented foods remain poorly characterized. The aim of this study was to study microbial diversity, and functional potential of underexplored traditional Indonesian fermented food. The fermented products displayed substantial variation in bacterial richness, ranging from 65 to 614 bacterial amplicon sequence variants across samples. The microbial communities were dominated by bacterial taxa affiliated with the orders Bacillales and Lactobacillales, alongside fungal taxa from the order Mucorales. The plant-based products i.e. tape ketan and tape singkong had a higher bacterial abundance but lower diversity than animal-based terasi. We found significant correlations between bacterial and fungal communities dominated by positive cooccurrence patterns and highly complex networks especially in terasi. Each food product was characterized by a unique functional profile of genes linked to beneficial metabolic functions (biosynthesis of bacteriocins, short-chain fatty acids, and vitamins) but tape ketan samples demonstrated the highest diversity and abundance of them. Metagenome assembled genomes reflect a high diversity of health beneficial properties as well as substrate-specific degradation capabilities. Traditional Indonesian fermented foods harbour functionally redundant but phylogenetically diverse taxa offering a potential source for probiotic traits and functional food development.