College of Food Science and Technology, Key Laboratory of Environment Correlative Dietology, Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, China.
College of Resources and Environment, Huazhong Agricultural University, P R, Wuhan, 430070, China.
Environ Sci Pollut Res Int. 2020 May;27(14):16745-16753. doi: 10.1007/s11356-019-06832-1. Epub 2020 Mar 4.
Shewanella oneidensis MR-1 (MR-1)-impregnated alginate capsules with 3D porous structure were prepared through cation crossing-linking and was used for the Cr(VI) reduction and removal. After being encapsulated by alginate, the endurance of the MR-1 was largely enhanced under conditions of high Cr(VI) concentrations (up to 4 mM) and low pH (pH 5). The Cr(VI) reduction over the MR-1-impregnated alginate capsules could be fitted by pseudo first-order kinetic model. With the Cr(VI) initial concentration increasing from 1 to 4 mM, the first-order rate constant for the encapsulated MR-1 (k) and free cells (k) fell by 26.3% and 82.4%, respectively. At pH 5, the k value was 0.19 h, which was about 3.7 times higher than k. Moreover, the encapsulated MR-1 held 90.5% of the Cr(VI) reduction ability after 15 days of resting time, while the free MR-1 held 19.7%. After bioreduction, 73.6% of total chromium was adsorbed on the MR-1 impregnated Ca-alginate capsules. XPS results showed 85% of the adsorbed chromium was Cr(III). The mechanism for chromium removal over the MR-1-impregnated Ca-alginate capsules was proposed with the following steps: (1) Cr(VI) was bioreduced via the encapsulated MR-1; (2) the reduced soluble Cr(III) was adsorbed by alginate selectively. In the study, the Ca-alginate shell of the cabbage-like MR-1 impregnated capsules could be a shelter for encapsulated MR-1 to endure unfavorable conditions (e.g., low pH and high concentration of Cr(VI)) and immobilize the soluble chromium. Considering the obtained capsules derived from biomolecules were environment-friendly, the MR-1-impregnated Ca-alginate capsules were potential for the application in the remediation of environmental pollution. Graphical abstract.
Shewanella oneidensis MR-1（MR-1）负载的海藻酸钠胶囊具有 3D 多孔结构，通过阳离子交联制备而成，用于 Cr（VI）的还原和去除。在高 Cr（VI）浓度（高达 4 mM）和低 pH（pH 5）条件下，用海藻酸钠包封后，MR-1 的耐受性大大提高。MR-1 负载的海藻酸钠胶囊上的 Cr（VI）还原可以用拟一级动力学模型拟合。随着 Cr（VI）初始浓度从 1 增加到 4 mM，封装的 MR-1（k）和游离细胞（k）的一级速率常数分别下降了 26.3%和 82.4%。在 pH 5 时，k 值为 0.19 h，约为 k 的 3.7 倍。此外，封装的 MR-1 在 15 天的休眠时间后保持 90.5%的 Cr（VI）还原能力，而游离的 MR-1 保持 19.7%。生物还原后，73.6%的总铬被负载在 MR-1 浸渍的 Ca-海藻酸钠胶囊上。XPS 结果表明，85%的吸附铬为 Cr（III）。提出了 MR-1 浸渍 Ca-海藻酸钠胶囊去除铬的机制，包括以下步骤：（1）Cr（VI）通过包封的 MR-1 进行生物还原；（2）还原的可溶性 Cr（III）被海藻酸钠选择性吸附。在该研究中，白菜状 MR-1 浸渍胶囊的 Ca-海藻酸钠壳可以作为包封的 MR-1 的庇护所，使其能够耐受不利条件（例如低 pH 和高浓度 Cr（VI））并固定可溶性铬。考虑到获得的胶囊来源于生物分子，是环境友好的，MR-1 浸渍的 Ca-海藻酸钠胶囊有望应用于环境污染的修复。
