Effect of Bacillus cereus mutant strain S458-M on active phosphorus and crucian carp in culture systems

Certain bacterial strains could efficiently improve the conversion of insoluble phosphorus to active phosphorus due to their phosphate-solubilizing ability, but there is little research on its specific effects on aquaculture. In this study, a mutant strain Bacillus cereus S458-M was obtained via compound mutagenesis of UV and LiCl. We found it exhibited higher phosphate-solubilizing ability and phytase activity than the original strain S458-1 reported in our previous report. The sequence analysis of phytase gene (phyC) in S458-M revealed mutations in amino acids 81, 89 and 148. Its predicted protein contained an additional Ca2+ binding site that might be associated with higher phytase activity. To verify phosphate-solubilizing and probiotic properties of S458-M, no bacteria (CG: control group), S458-1 (LS: 1 × 105 CFU/mL; HS: 1 × 107 CFU/mL) and S458-M (LM: 1 × 105 CFU/mL; HM: 1 × 107 CFU/mL) were supplemented into aquaculture water separately. The results showed that S458-M could improve the concentration of active phosphorus in aquaculture water and enhance the antioxidant ability of crucian carp. Overall, S458-M obtained by UV-LiCl mutagenesis could support the application of phosphate-solubilizing bacteria in aquaculture water. •UV-LiCl mutagenesis was used in the genetic mutation of Bacillus cereus S458-M.•S458-M exhibited higher phosphate-solubilizing ability and phytase activity.•An additional Ca2+ binding site was observed in the predicted phytase of S458-M.•S458-M could improve the concentration of active phosphorus in aquaculture water.•S458-M could enhance the antioxidant ability of crucian carp.