基于微生物菌群调控的枯草芽孢杆菌改善低盐发酵鱼露品质作用机制

Bacillus subtilis B-2 Improved the Quality of Low-Salt Fermented Fish Sauce through Regulating the Microbial Community

以高产蛋白酶耐盐菌株Bacillus subtilis B-2作为鱼露发酵剂,研究加菌发酵对低盐鱼露发酵过程中微生物菌群、生物胺和氨基酸态氮(amino acid nitrogen,AAN)的影响。16S rRNA基因高通量测序结果显示,加菌发酵能够显著降低微生物群落的丰富度和均匀度,Bacillus始终占主导地位,腐败微生物丰度显著降低。加菌发酵能够显著抑制组胺、腐胺、尸胺和酪胺的生成,其含量在发酵末期较自然发酵鱼露分别下降了25.9%、35.6%、23.6%和9.3%。加菌发酵可显著增加低盐鱼露的AAN含量,发酵15 d可达1.23 g/100 mL,明显高于自然发酵鱼露(0.79 g/100 mL)。相关性网络图分析结果显示,Brevibacterium、Dietzia、Paracoccus、Aequorivita、Brachybacterium丰度的下降是低盐自然发酵鱼露发酵末期微生物菌群多样性下降的主要原因;在低盐自然发酵鱼露和低盐加菌发酵鱼露中,Stenotrophomonas均与多种生物胺呈显著正相关,表明其在低盐鱼露生物胺产生中发挥核心作用。对比两种鱼露发酵末期微生物菌群和品质指标,结果显示,B. subtilis B-2代谢是加菌发酵鱼露腐败微生物种类和丰度下降、AAN含量提高以及关键生物胺含量下降的主要原因。B. subtilis B-2有望开发为鱼露专用发酵剂,用以改善低盐快速发酵鱼露的品质和食用安全性。

In this study,the effect of fermentation with Bacillus subtilis B-2,a salt-tolerant strain capable of producing high yield of protease,on the microbial community and the contents of biogenic amines and amino acid nitrogen(AAN)during the fermentation of low-salt fish sauce.The results of high-throughput 16S rRNA gene sequencing showed that fermentation with B-2 reduced the richness and evenness of the microbial community,Bacillus was dominant throughout the fermentation process and the abundance of spoilage microorganisms significantly decreased.B-2 significantly inhibited the formation of histamine,putrescine,cadaverine,and tyramine,and their contents at the end of fermentation decreased by 25.9%,35.6%,23.6%and 9.3%,respectively,compared with those in naturally fermented fish sauce.The content of AAN in low-salt fish sauce was significantly improved by inoculated fermentation,reaching 1.23 g/100 mL after 15 days of fermentation,which was significantly higher than that of naturally fermented fish sauce(0.79 g/100 mL).The correlation network map showed that the decrease in the abundance of Brevibacterium,Dietzia,Paracoccus,Aequorivita,and Brachybacterium was the major reason for the decrease in microbial diversity at the late stage of fermentation of naturally fermented fish sauce.The abundance of Stenotrophomonas showed a significantly positive correlation with the contents of many biogenic amines in naturally fermented and B-2 fermented fish sauce,suggesting its important role in the formation of biogenic amines in low-salt fish sauce.Comparative analysis of the microbial community and quality attributes at the end of fermentation showed that the metabolism of B-2 was the main reason for the decrease in the species and abundance of spoilage microorganisms,the increase in AAN content,and the decrease in the contents of key biogenic amines.B.subtilis B-2 is expected to be developed as a special fermentation starter for fish sauce to improve the quality and safety of rapidly fermented low-salt fish sauce.