Characteristics of Pseudomonas stutzeri Oxidation of As(III)/Sb(III)

Abstract

Heavy metal pollution, especially arsenic (As) and antimony (Sb) pollution, seriously threatens people’s health and the ecological system. It is a common occurrence for As and Sb to coexist in the environment as inorganic species, including trivalent/pentavalent As or trivalent/pentavalent Sb. In addition, trivalent As and trivalent Sb are more toxic and difficult to remove than pentavalent As and pentavalent Sb. Therefore, the simultaneous pre-oxidation of trivalent As and trivalent Sb to pentavalent As and pentavalent Sb is a very critical step in the process of pollution control. A strain of Pseudomonas stutzeri, by which trivalent As/trivalent Sb can be oxidized to pentavalent As/pentavalent Sb, was selected, and its oxidation characteristics were studied in detail. The oxidation mechanism was thoroughly analyzed through a series of experiments and characterization. The results indicated that Pseudomonas stutzeri could tolerate trivalent As (577 mg/L) and trivalent Sb (1752 mg/L); the highest oxidation ratio of trivalent As was 53.05% and that of trivalent Sb was 83.05%. According to the cytotoxicity assay, the largest inhibition ratio was 89.22% for trivalent As and 74.98% for trivalent Sb under 5 mM of trivalent As/trivalent Sb stress. In addition, the minimum inhibitory concentrations of trivalent As and trivalent Sb were 0.22 mM and 0.43 mM, respectively. The results of Raman and FTIR spectroscopy analyses revealed that the peak vibration intensity of all strains under trivalent As and trivalent Sb stress was weaker than that of the control group. Therefore, it could be concluded that the toxicity of trivalent As for Pseudomonas stutzeri is greater than that of trivalent Sb according to the maximum concentration tolerated by Pseudomonas stutzeri and the minimum inhibitory concentrations. The oxidation ratio of trivalent Sb for Pseudomonas stutzeri is higher than that of trivalent As, with both trivalent As and trivalent Sb being bonded to the organic groups. The simultaneous oxidation of Sb(III) and As(III) by Pseudomonas stutzeri suggests its potential as a candidate for bioremediation of environments contaminated with these elements. This study provides a theoretical basis and guidance for the microbial oxidation of trivalent As and trivalent Sb.