Spontaneous fermentation tunes purine metabolism of tomato by modifying bacterical diversity: Based on metabonomics and microbiomics

Guizhou's tomato sour soup (TSS) is a spontaneous fermented food enjoyed by the Miao and Dong ethnic groups. This study utilized non-targeted UPLC-Q/TOF-MS-based metabolomics and Illumina Miseq sequencing for assessing the metabolic changes occurring between fresh tomatoes and TSS. The pH value, titratable acidity, lactic acid and acetic acid content of the fermented tomato were measured as 3.18, 33.44 mmol/100 g, 41.78 g/kg, and 3.98 g/kg, respectively. TSS identified a total of 1,502 metabolite ion features. Compared to fresh tomatoes, TSS exhibited lower levels of nucleic acids and peptides, but higher content of organic acids and lipids. Through fermentation, about 26 metabolism pathways, including nucleotide metabolism, purine metabolism, pyrimidine metabolism and alanine, were significantly altered. The analysis indicated a negative association between the purine content (including Guanine monophosphate (GMP), adenosine, guanine, uracil, uridine, and inosine) and the presence of Brevibacterium, Nocardiopsis, Serratia, Sutterella, Limnobacter, and Collinsella. Additionally, certain purines were found to be negatively correlated with Lactobacillus, Bifidobacterium, and Akkermansia. This study highlights the potential of TSS as a valuable resource for isolating purine-degrading bacteria and suggests its potential as a healthy food option for individuals with hyperuricemia (HUA) and gout.