Remediation of copper-contaminated soils and growth enhancement of Pakchoi (B. chinensis L.) via biofertilizers composed of new Bacillus amyloliquefaciens SYNU1

Excessive copper contaminants are  harmful to soil, microbes, plants and humans and can be remediated by biosorption. Applying biofertilizers to remediate copper-contaminated soil is an environmentally friendly way.

In this study, we identified a new strain, Bacillus amyloliquefaciens SYNU1, based on morphological, biochemical, physiological and phylogenetic analyses. It has been cultured on Luria–Bertani (LB) medium and absorbs soluble Cu²⁺ from pH 3.5–5 and 25–40 °C at Cu²⁺ concentrations of 100 mg L⁻¹. The results showed that the maximum adsorption capacity of copper by strain SYNU1 is 53.09% w/w. Furthermore, microbe fertilizers were made based on strain SYNU1, these fertilizers were allowed to ferment for 15 days, and they were used for remediation of copper-contaminated soil and growth tests of Pakchoi (B. chinensis L) in pot experiments. The results showed that the growth of Pakchoi planted in copper-contaminated soil at concentrations ranging from 50 to 200 mg kg⁻¹ was inhibited, and its growth indices, such as plant height, fresh weight and dry weight, decreased significantly with increasing copper concentration. Compared with the control, the increases in plant height, fresh weight and dry weight of Pakchoi treated with biofertilizer were 10.37, 65.3 and 67.78%, respectively, indicating that biofertilizer could significantly promote the growth of Pakchoi.

Bacillus amyloliquefaciens SYNU1 is useful for the bioremediation of Cu²⁺-contaminated soil in Northeast China.