酱醪中魏斯氏菌的分离及特性分析

Isolation and characterization of Weissella strains from soy sauce moromi mash

【背景】魏斯氏菌广泛存在于发酵食品中,它们与食品发酵进程和风味物质的形成密切相关。酱油发酵过程酱醪中细菌的优势菌属是魏斯氏菌,研究魏斯氏菌的生理和代谢特性对于揭示菌株对环境的适应性和与酱油发酵相关的功能具有重要意义。【目的】从酱油酱醪中分离获得魏斯氏菌属中主要种的菌株,研究它们在酱油发酵过程的数量变化以及菌株的生理和生化特性,阐明菌株对酱油发酵体系的适应性和与酱油发酵相关的特性。【方法】通过菌株绝对数量的定量分析和耐受性比较,以及考察高盐条件下魏斯氏菌合成短链脂肪酸、胞外多糖、生物胺和氨基甲酸乙酯或其前体等特性,研究各类魏斯氏菌对酱油发酵和其安全性的影响。【结果】从高盐稀态酱油的酱醪中共分离得到16株魏斯氏菌,分别属于融合魏斯氏菌(Weissella confusa)、类肠膜魏斯氏菌(Weissellaparamesenteroides)和食窦魏斯氏菌(Weissellacibaria)。其中类肠膜魏斯氏菌可耐受高盐条件,是酱醪中魏斯氏菌属的主要菌种。它们合成短链脂肪酸的能力高于融合魏斯氏菌和食窦魏斯氏菌。酱醪来源的魏斯氏菌合成氨(胺)类危害物的特性区别较大,类肠膜魏斯氏菌的部分菌株产生物胺并可利用精氨酸积累瓜氨酸,食窦魏斯氏菌则能够降解多种生物胺。【结论】揭示了酱醪中主要魏斯氏菌的耐盐特性、在较低温度下生长情况和物质代谢规律,对于阐明魏斯氏菌与酱油发酵相关的功能和特性以及对酱油加工过程安全控制具有重要意义。

[Background] Weissella exists widely in fermented foods. Strains of this genera are involved in fermentation and contribute to the formation of volatile compounds. In soy sauce moromi mash, Weissella is the dominant genera of bacteria. Thus, it is of great importance to characterize their adaption to the environment, as well as properties related to soy sauce fermentation. [Objective] To isolate the main species of Weissella from soy sauce moromi mash, and evaluate their function for soy sauce fermentation by analyzing the dynamic composition of each species and their adaptation to the environment. [Methods] Characteristics of Weissella and their effect on the safety of soy sauce and fermentation process were evaluated by detection of quantity of Weissella during soy sauce fermentation, and their capability in production of short chain fatty acids, extracellular polysaccharides, biogenic amines（BA） and ethyl carbamate or their precursors. [Results] A total of 16 strains of Weissella, including Weissella confusa, Weissella paramesenteroides and Weissella cibaria, were isolated from soy sauce moromi mash. W. paramesenteroides was found to be tolerant to salt stress that confers the main species of Weissella in the moromi mash. The capability of short chain fatty acids synthesis of W. paramesenteroides is higher than that of W. confusa and W. cibaria. Production of toxic ammonia compounds are diverse for Weissella strains. Some strains of W. paramesenteroides produce more than one BAs and accumulate citrulline, the precursor of ethyl carbamate, while W. cibaria degrades a variety of BAs. [Conclusion] The tolerance of Weissella isolated from soy sauce moromi mash to salt stress, their growth at temperature lower than the optimal one, and their metabolisms were disclosed. This is important to elucidate the function and characteristics of Weissella for soy sauce fermentation and safety control in processing.