Species identification and mutation breeding of silicon-activating bacteria isolated from electrolytic manganese residue.

A strain of silicon-activating bacteria was isolated from electrolytic manganese residue (EMR); identified as a species of Ochrobactrum by integrated microscopic morphological characteristics, biochemical index determination, and clone analysis (i.e., results of 16S rRNA sequence); and temporarily named as Ochrobactrum sp. T-07 (T-07). The optimal growth conditions of the strain T-07 were obtained as follows: temperature of 30 °C, initial pH of 7.0, shaking speed of 180 rev. min-1, and loading volume of 100 mL. In order to enhance its activation activity of silicon, T-07 went through the ultraviolet (UV) mutagenesis and nitrosoguanidine (NTG) mutagenesis breeding, and the mutant strain T-07-B with higher activity was obtained. Under the optimal fermentation condition (leaching time of 20 days, temperature of 30 °C, initial pH of 7, pulp concentration of 5%, shaking speed of 180 rev. min-1, and particle diameter of EMR ≤ 180 μm), the available silicon content in the supernatant reached 98.8 mg L-1, which was 2.4 times of the original strain T-07. Therefore, T-07 can be used as a good backup in developing biological silicon fertilizer for plants.