The terroir of Tempeh: Strong region-specific signatures in the bacterial community structures across Indonesia

Tempeh, a soybean product from Indonesia, is created through fermentation by Rhizopus spp. and associated bacteria. Here, we aim to get an overview of the variability of the tempeh microbiota across Indonesia and disentangle influencing factors. We found high variability in bacterial abundance (10³ – 10⁹ copies g^-1), richness (n_ASV = 40 – 175 ASVs), and diversity (H’ = 0.9 – 3.5) in tempeh. The primary factor affecting this variation was the region, where the tempeh was produced. Interestingly, tempeh samples obtained from geographically close areas tended to share similar bacterial profiles, suggesting a "terroir" of tempeh. Additionally, tempeh wrapped in banana leaves had a higher abundance of enterobacteria in comparison to tempeh wrapped in plastic but also tended to have a higher total bacterial and lactobacilli abundance. Despite all variability, the tempeh core microbiome consists Lactobacillales and Enterobacteriales. This study demonstrates a high variability of bacterial diversity in traditional tempeh from local producers highlighting a strong regional influence across Indonesia.