Sour soup is a traditional plant-based fermented food from Qiandongnan Prefecture, Guizhou Province, China. It is divided into two types: white sour soup and red sour soup. White sour soup is made by semi-anaerobic fermentation of oryza sativa var. glutinosa washing water in earthenware jars for 7–10 days. Red sour soup is prepared by crushing and mixing solanum lycopersicum , red capsicum annuum , and zingiber officinale with oryza sativa var. glutinosa washing water at a ratio of 3:1:0.5:5, followed by semi-anaerobic fermentation for 10–15 days. To date, no study has systematically compared the bacterial community and functional differences between the two types of sour soup. In this study, six samples of each type were analyzed by 16 S rRNA gene sequencing and PICRUSt2 functional prediction. The results showed that their community structures were significantly separated ( p < 0.05). White sour soup was dominated by Proteobacteria (93.66%) and enriched with Lactobacillus (LDA = 3.63), Acetobacter (LDA = 5.67), and Clostridiales (LDA = 4.21). Red sour soup exhibited higher diversity, with Proteobacteria decreasing to 39.09% and co-existing with multiple other phyla including Chloroflexota (19.72%), and specifically enriched with Akkermansia (LDA = 4.26). Functionally, white sour soup showed higher predicted abundances in host circulatory system (FC = 3.26, p < 0.001) and host immune system (FC = 1.65, p < 0.01) pathways, whereas red sour soup showed higher abundance in the host digestive system pathway (FC = 0.46, p < 0.01). This study systematically reveals, for the first time, raw material-driven bacterial differentiation and provides a theoretical foundation for the functional development of traditional fermented foods.
Zhou et al. (Sat,) studied this question.