Dynamic changes in physic-chemical properties and bacterial community during natural fermentation of tomatoes

Abstract This study revealed for the first time the dynamic changes of bacterial community and physic-chemical properties in the process of tomatoes fermentation. In the early phase of fermentation, Proteobacteria and Firmicutes account for 86.04% and 9.97%, respectively. Then, Firmicutes replaced Proteobacteria to be the dominant phylum from day 10. Among then, Lactobacillus decreased from 20 to 30 days and then rapidly increased. The total sugar showed a gradual decreased while the nitrite content increased in the early phases. The total acid content increased from initial 0.6% to 2.03% on day 30, mainly including citric acid, malic acid and lactic acid. In the later stages, the number of microorganisms and bacterial community tended to be stable, along with the content of organic acids and nitrite. During fermentation, the physic-chemical parameters inevitably change, mainly due to microbial metabolism, affecting in turns the development of the micro-ecosystem. These results contribute to our knowledge about bacterial participation in the process of fermentation and will help improve the quality of fermented food and vegetables.

摘要 本研究首次揭示了番茄发酵过程中细菌群落与理化特性的动态变化规律。发酵初期，变形菌门（Proteobacteria）与厚壁菌门（Firmicutes）的相对占比分别为86.04%与9.97%；至发酵第10天，厚壁菌门取代变形菌门成为优势菌门。其中乳杆菌属（Lactobacillus）的相对丰度在发酵第20至30天呈下降趋势，随后快速回升。总糖含量随发酵进程逐渐降低，而亚硝酸盐含量在发酵初期呈上升态势。总酸含量从初始的0.6%升至发酵第30天的2.03%，所涉及的主要有机酸为柠檬酸、苹果酸与乳酸。发酵后期，微生物总量与细菌群落结构趋于稳定，有机酸及亚硝酸盐含量亦保持平稳。发酵过程中，理化参数不可避免地发生变化，这主要源于微生物的代谢活动，而代谢产物又反过来影响微生态系统的演替。本研究结果有助于加深对细菌参与发酵过程的认知，同时可为提升发酵果蔬的产品品质提供理论支撑。