Phytoextraction of toxic trace elements by Sorghum bicolor inoculated with Streptomyces pactum (Act12) in contaminated soils.

The increasing industrial, mining and agricultural activities have intensified the release of potential toxic trace elements (PTEs), which are of great concern to human health and environment. The alarming increase in PTEs concentration, stress the need for biotechnological remediation approaches. In order to assist phytoextraction of PTEs, different combinations of Streptomyces pactum (Act12) with biochar were applied to mining and industrial polluted soils of Shaanxi and Hunan Provinces of China, respectively. Act12 affected soil physico-chemical properties in both soils. Bioavailable Zn and Pb increased due to microbial activities, while Cd decreased by adsorption on biochar surface. Phytoextraction of Zn and Pb occurred in TG and CZ soil, while Cd uptake decreased in iron rich CZ soil by conflicting effect of siderophores. Cd in sorghum shoot was below detection level, but uptake increased in the roots due to minimum available fraction in TG soil. Biochar reduced the shoot and root uptake of Cd. Sorghum shoot, root dry weight and chlorophyll significantly increased after Act12 and biochar application. β-glucosidase, alkaline phosphatase and urease activities were significantly enhanced by Act12. Antioxidant enzymatic activities (POD, PAL and PPO) and lipid peroxidation (MDA) were decreased after the application of Act12 and biochar by reduced PTEs stress. Act12 and biochar can be used for different crops to enumerate the transfer rate of PTEs into the food chain.