Institute of Subtropical Agriculture, Chinese Academy of Sciences
Key Research and Development Project of Hunan Province (2022NK2010)
镉作为一种毒性极大的重金属，极易在稻米中富集，严重危害食用者的身体健康。我国是水稻生产大国，但稻米镉超标事件时有发生，对食品安全构成严重威胁，因此迫切需要研究和开发镉污染稻米防治措施和“镉大米”安全利用技术。常德米粉生产过程可使镉超标稻米的镉含量低于国家标准（0.2 mg/kg），本研究对该过程的降镉效应从微生物角度进行探究。利用Illumina MiSeq高通量测序技术分析大米发酵液中细菌的种群组成结构特征；同时通过传统的微生物分离培养方法获取纯菌株并进行16S rRNA基因测序鉴定；在此基础上，以镉含量重度超标的稻米为试验材料，探究分离菌株的降镉效果。研究表明，发酵液中优势属为乳杆菌属（Lactobacillus）。通过分离培养共获得58株菌，其中乳杆菌属的菌株占比最大，发酵乳杆菌（Lactobacillus fermentum）、德氏乳杆菌（Lactobacillus delbrueckii）、乳酸片球菌（Pediococcus acidilactici）、枯草芽孢杆菌（Bacillus subtilis）均表现出一定的降镉效果。其中，乳酸片球菌P1和发酵乳杆菌L4的降镉能力最强，发酵48 h的降镉量可达到0.55 mg/kg。菌种添加后发酵体系pH值降低，乳酸含量升高，从而有利于蛋白结合态镉的溶出，可能是米粉加工过程中稻米镉含量降低的主要微生物作用机制。稻米粉碎可提高功能微生物活性，提升降镉效率。本研究证明大米发酵液中存在高效降镉的菌株可有效降低镉超标稻米镉含量，可为降镉微生物菌株挖掘以及镉超标稻米有效利用提供新思路。
Cadmium (Cd) is a toxic heavy metal and can easily accumulate in rice grains, which is harmful to human health. China is the largest producer of rice, but the “cadmium rice” incident occurs frequently and has posed a serious threat to food safety. Therefore, it is urgent to study and develop effective measures to prevent rice Cd contamination and to safely utilize “cadmium rice”. The Changde rice noodles production process could reduce the Cd content of Cd contaminated rice below the national standard (0.2 mg/kg). In this study, the mechanism of Cd reduction in this process was investigated from the perspective of microorganisms. The composition and structure of the bacterial community during the rice fermentation was analyzed via high-throughput sequencing. Meanwhile, bacteria were isolated using the traditional culture method and identified by 16S rRNA gene sequencing. And then the Cd removal efficiency of the isolated strains was investigated. The results showed that the dominant bacterial group in the fermentation broth is Lactobacillus. Meanwhile, a total of 58 strains were isolated from fermentation broth, and Lactobacillus strains accounted for the largest proportion. Strains of Lactobacillus fermentum, Pediococcus acidilactici, Bacillus subtilis, Lactobacillus delbrueckii showed Cd reducing capability. Strain P. acidilactici P1 and L. fermentum L4 had the highest Cd removal ability, reducing up to 0.55 mg/kg Cd during a 48 h fermentation. After addition of these strains, the pH value of the fermentation system decreased and the content of lactic acid increased, which was conducive to the dissolution of cadmium-binding protein. This could be the main microbial mechanism for decreasing Cd content during the rice noodles production process. Rice grinding can improve the activity of functional microorganisms and Cd reduction efficiency. This study demonstrated that the highly efficient Cd-removing strains in the rice fermentation broth could effectively reduce the Cd content of the Cd contaminated rice, providing new possibilities for the effective use of rice with excess Cd.
徐文华,张文钊,侯海军,魏文学,盛荣. 发酵对米粉生产的降镉作用及其微生物学机理[J]. 农业现代化研究, 2023, 44(2): 359-369
XU Wen-hua, ZHANG Wen-zhao, HOU Hai-jun, WEI Wen-xue, SHENG Rong. Cadmium reducing effect of fermentation on rice noodles production and its microbiological mechanism[J]. Research of Agricultural Modernization, 2023, 44(2): 359-369