Fermentation performances, bioactivity, and metabolic profiles of fermentated tomato juice by lactic acid bacteria isolated from Chinese traditional fermented foods

Tomato (Lycopersicon esculentum) possess significant beneficial health effects. The aim of this study is to screen a suitable lactic acid strain for the fermentation of tomato juice (TJ) to increase its nutritional value. The fermentation characteristics of 35 strains of lactic acid bacteria isolated from traditional Chinese fermented plant-based foods were evaluated. Subsequently, changes in bioactive compounds and metabolites after fermentation were analyzed. Lactobacillus fermentum 51 isolated from Douzhi (fermented soybean juice), exhibited a stable bacterial count of more than 9 Log CFU/mL in the TJ after 18 h of fermentation, and it maintained a survival rate of 83.15% after undergoing a gastrointestinal simulation model, and the solid-acid ratio was suitable for preferred taste. Moreover, carotenoid content and antioxidant activity enhanced significantly (p < 0.05) in fermented TJ. An untargeted metabolomics analysis showed that 28 differential metabolites were found between the fresh and fermented TJ samples, including organic acids and their derivatives, carbohydrates, and fatty acids, with 13 metabolites up-regulated and 15 down-regulated. Meanwhile, KEGG analysis showed that metabolite changes were significantly enriched in three metabolic pathways: starch and sucrose metabolism, glyoxylate and dicarboxylate metabolism, and the TCA cycle (p <= 0.001). Among the 13 upregulated metabolites were d-threitol, butanedioic acid, and lactic acid, all of which contributed to the enhanced antioxidant activity of fermented TJ. It is thus evident that the fermentation process enriched the metabolic profile of TJ, thereby enhancing its potential health value. This study is benefit to develop probiotic fermented tomato beverages.