耐镉乳酸菌对重金属镉的吸附机制

The cadmium removal mechanism of lactobacillus strains

对17株实验室保藏的标准乳酸杆菌进行了重金属镉耐受性(最低抑菌浓度MIC)测定,筛选出4株对镉具有高耐受性的乳酸杆菌(MIC≥4.0 g/L)。通过原子吸收分光光度法测定4株高耐受乳酸菌具有较强的镉离子吸附能力(>27%,100 mg/LCd^(2+)溶液)。以1株在镉耐受性实验中MIC最低(10 mg/L)的植物乳杆菌LAB-54(Lactobacillus plantarum ATCC 8014)作为对照,采用傅氏转换红外光谱(Fourier transform infrared spectroscopy,FTIR)、扫描电镜(SEM)结合研究分析1株在镉耐受MIC较高的鼠李糖乳杆菌LAB-5(Lactobacillus rhamnosus ATCC 53103)与镉吸附前后的细胞微观结构及形态变化,证明了细胞组成成分参与了镉离子与乳酸菌的相互作用,参与官能团有羟基(O—H)、羧基(C O)、磷酸基(P O)、酰胺基(N—H)、烃基(C—H)。镉离子使细胞的微观结构受到了严重破坏,镉吸附机制包括胞外的络合反应、离子交换、物理吸附(静电引力),微沉淀(胞外及胞内)和胞内扩散。

17 standard Lactobacillus strains were selected by MIC test against cadmium. Among them, 4 strains showed high resistance to Cd （ MIC ≥4.0 g/L）. The selected bacteria were assessed in vitro for their ability to remove Cd （ 〉 27% in 100 mg/L Cd2 ＋ solution）. To clarify the removal mechanism of Lactobacillus rhamnosus ATCC 53103 （LAB-5 strain） , fourier transform infrared spectroscopy （FTIR） and scanning electron microscopy （SEM） were used to structurally and morphologically characterize the interaction of bacteria and Cd ion. LAB-54 （Lactobacillus plantarum ATCC 8014） , a Cd-sensitive strain, was used as control. Results indicated that hydroxyl （O-H） , carboxyl （C = O）, phosphoryl （P = O）, amide （N--H） and hydrocarbonyl （C-H） groups were involved in biosorption process. Cd removal mechanisms of LAB might include complexation, ion exchange, physical adsorption （electrostatic interaction）, precipitation and diffusion. Cell microstructure was heavily damaged by treatment with Cd2 ＋ ion. Distorted, sunken, rough, crumpled, cracked and perforated cells were observed.