Thua Nao is a Thai traditional fermented soybean food and low-cost protein supplement. Here, we aimed to differentiate the bacteria in Thua Nao from northern Thailand and assess potentially active SCFA-related bacteria. Sixty-six Thua Nao consisting of 30 wet and 35 dried samples were collected from six provinces: Chiang Rai, Chiang Mai, Mae Hong Son, Lampang, Lamphun, and Phayao. Natto, a soybean fermented with starting culture, was also analyzed. Bacterial diversity was significantly higher

more »

... the wet samples than in the dried samples. The dominant phyla were Firmicutes (92.7%), Proteobacteria (6.7%), Actinobacteriota (0.42%) and Bacteroidota (0.26%). The genus Bacillus (67%) was the most represented in all samples. Lactobacillus, Enterococcus, and Globicatella were enriched in the wet samples. Assessment of the SCFA-microbiota relationships revealed that high butyrate and propionate concentrations were associated with an increased Clostridiales abundance, and high acetate concentrations were associated with an increased Weissella abundance. Wet products contained more SCFAs, including acetic (P = 2.8e-08), propionic (P = 0.0044), butyric (P = 0.0021), and isovaleric (P = 0.017) acids, than did the dried products. These results provide insight into SCFA-microbiota associations in Thua Nao, which may enable development of starting cultures for SCFA-enriched Thua Nao production.