Hao Kongli, Zhang Zihui, Wang Binsong, Zhang Jie, Zhang Guocai
Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Sciences, Northeast Forestry University, Harbin 150040, China.
School of Chemistry and Material Sciences, Heilongjiang University, Harbin 150080, China.
Iran J Biotechnol. 2022 Jan 1;20(1):e3001. doi: 10.30498/ijb.2021.275524.3001. eCollection 2022 Jan.
Chromium is one of the most used toxic heavy metals. A large amount of chromium waste is discharged into the environment every year, causing serious environmental pollution, especially the pollution of soil and water by hexavalent chromium. Eliminating hexavalent chromium is the primary challenge to achieve a pollution-free environment.
This study aims to understand the mechanism of 's reduction of hexavalent chromium through enzymatic characteristic, oxidative stress response, and reduction product.
The strain ZJH-1 was isolated and stored in our laboratory. The hexavalent chromium uses 1,5-diphenyl carbazide method (DPC) to measure. The UV spectrophotometer was used to measure the intracellular antioxidant enzyme activity, and the kit was used to measure the activity of catalase and glutathione reductase. The reduction products were analyzed by ultraviolet full-wavelength scanning and FTIR.
The reduction of hexavalent chromium by ZJH-1 is accompanied by an increase in active oxygen and antioxidant levels. Chromate reductase mainly exists in the extracellular fluid, and the carboxyl, amide, hydroxide and other groups of the cell wall are involved in the bioremediation of Cr(VI) by complexing with Cr(VI) and Cr(III). After ZJH-1 was treated with different concentrations of Cr(VI), the expression of proteins with molecular weights of 15 kDa, 18 kDa, 35 kDa, 62 kDa, and 115 kDa increased significantly. This strain is the most suitable for chromate reductase (CChR). The optimum temperature is 40℃ and the optimum pH is 7.0. Cu2+ can enhance the activity of chromate reductase. At the optimum temperature and pH, the chromate reductase Km of this strain is 0.40 μmol and Vmax is 14.47 μmoL.L·min.
The bioremediation of Cr(VI) by ZJH-1 is attributable to the reduction product (Cr(III)) that can be removed in the precipitate and can be fixed on the cell surface and accumulated in the cell.
铬是最常用的有毒重金属之一。每年大量的铬废物排放到环境中，造成严重的环境污染，尤其是六价铬对土壤和水体的污染。消除六价铬是实现无污染环境的主要挑战。
本研究旨在通过酶学特性、氧化应激反应和还原产物来了解菌株对六价铬的还原机制。
菌株ZJH-1由本实验室分离保存。采用二苯碳酰二肼法（DPC）测定六价铬。用紫外可见分光光度计测定细胞内抗氧化酶活性，试剂盒测定过氧化氢酶和谷胱甘肽还原酶活性。通过紫外全波长扫描和傅里叶变换红外光谱对还原产物进行分析。
ZJH-1对六价铬的还原伴随着活性氧和抗氧化水平的增加。铬酸盐还原酶主要存在于细胞外液中，细胞壁的羧基、酰胺基、羟基等基团通过与Cr(VI)和Cr(III)络合参与Cr(VI)的生物修复。ZJH-1经不同浓度Cr(VI)处理后，分子量为15 kDa、18 kDa、35 kDa、62 kDa和115 kDa的蛋白质表达显著增加。该菌株最适合铬酸盐还原酶（CChR）。最适温度为40℃，最适pH为7.0。Cu2+可增强铬酸盐还原酶的活性。在最适温度和pH条件下，该菌株的铬酸盐还原酶Km为0.40 μmol，Vmax为14.47 μmoL·L-1·min-1。
ZJH-1对Cr(VI)的生物修复归因于还原产物（Cr(III)），其可在沉淀物中去除，并可固定在细胞表面并在细胞中积累。
