Fermented vegetable flavors are closely associated with microbial metabolism. Here, shifts in flavor metabolites and their correlations to the structure and function of fermentative microbial communities were explored during the spontaneous fermentation process of potherb mustard ( Brassica juncea var. multiceps ), a traditionally fermented vegetable from China. Halophilic bacteria (HAB, i.e. , Halomonas , Salinivibrio , and Vibrio ) and lactic acid bacteria (LAB, i.e. , Lactobacillus -related genera and Weissella ) became highly abundant after potherb mustard fermentation. Further, HAB and LAB abundances exhibited significant, positive correlations with metabolites important in fermented potherb mustard flavoring (e.g., organic acids, amino acids, alcohols, aldehydes, and nitriles). Metagenomic analysis indicated that Halomonas , Salinivibrio , Weissella , and Lactobacillus -related genera were likely actively engaged in pyruvate metabolism (ko00620) and citrate cycle (TCA cycle, ko00020), leading to higher lactic and acetic acid concentrations, along with lower pH, which would affect levels of volatile isothiocyanates and nitriles that contribute to flavoring of fermented potherb mustard. Further, HAB and LAB were the primary populations inferred to be responsible for amino acid and fatty acid metabolism in addition to the biosynthesis of numerous volatile flavor compounds. This study highlights the predominance and importance of LAB and HAB during spontaneous fermentation of potherb mustard and provides new insights into their roles in this process.
The fermentation of navel orange juice with lactic acid bacteria (LAB) has rarely been investigated. In this study, an autochthonous LAB strain isolated from navel orange, Lactiplantibacillus paraplantarum M23, was found to effectively ferment navel orange juice, producing a juice with enhanced functional activities and organoleptic quality. The viable bacterial count in the fermented orange juice remained consistently above 8.51 log CFU/mL throughout the entire 7-day fermentation period. The content of vitamin C (VC), total phenolic content (TPC), total flavonoid content (TFC), and hesperidin in the fermented orange juice increased by a maximum of 28.88, 1.21, 1.13, and 1.16 times, respectively, compared to the unfermented orange juice. The fermented juice exhibited significantly higher antioxidant activity than the unfermented juice, with an increase of up to 255 % and 347 % based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric ion reducing antioxidant power (FRAP) assays, respectively. This may be attributed to the increase in VC and flavonoids, as demonstrated by Pearson's correlation analysis. Additionally, the fermented orange juice demonstrated improved α-glucosidase inhibition, anti-MRSA, and anti-glycation activities compared to the unfermented juice. Furthermore, the fermented juice notably reduced the levels of NO and ROS in Raw 264.7 cells without any negative impact on cell viability. The findings of this study may help in the development of nutritious and healthy fermented navel orange juice products, and serve as a reference for the production of fermented beverages from other fruits using autochthonous strains.
危险品化学品经营许可证（带存储）