Breeding of Bacillus mucilaginosus HJ07 mutated by UV/NTG and its effects on microbial leaching of bauxite

An original strain Bacillus mucilaginosus HJ07 was screened from bauxite sampled from Henan Province of China. It was induced mutagenesis by ultraviolet (UV) radiating and nitrosoguanidine (NTG) culturing, and then was used for bioleaching silicon from bauxite. After treated by 120 s UV radiating and 600 mg·L^-1 NTG culturing, its kill rates are 89% and 90%, and its positive mutation rates are 16.5% and 18.7%, respectively. Two mutant strains UV-2 and NTG-5 were screened from a large number of mutant strains, and they have better bioactivity and de-silicon efficiency than HJ07 strain. In comparison with HJ07 strain, the time that UV-2 and NTG-5 strains reach stable growth in bauxite bioleaching systems shortens by 48 h and 24 h, respectively, and they have higher bacterial concentrations. After 12 d bioleaching, SiO₂ mass concentrations in leachates of UV-2 and NTG-5 stains improve by about 25.6% and 12.5%, and the time that UV-2 and NTG-5 strains reach the leaching terminal point shortens by 3 d and 2 d, respectively. UV-2 and NTG-5 strains can produce much more organic acids and extracellular polymeric substances than HJ07 strain. Moreover, mineral particle surfaces leached by UV-2 strain are eroded much more obviously and covered with a thicker layer of zooglea.