Construction of transgenic Bacillus mucilaginosus strain with improved phytase secretion

Aims: To construct a transgenic Bacillus mucilaginosus strain to increase the secretion capability of a wild‐type isolate of B. mucilaginosus D4B1 to hydrolyse phytate phosphorus, which can be used as a microbial fertilizer in field application. Methods and Results: We constructed a phytase secreting expression vector pSP43 with a mini‐Tn5 transposon and a Aspergillus fumigatus phytase expression cassette. The vector pSP43 was successfully transferred into the wild‐type B. mucilaginosus using the particle bombardment method, and three transgenic strains with a stable copy of phytase expression cassette integrated into the chromosome of the B. mucilaginosus by Tn5 transposition were selected. The phytase activity of the engineered strains increased 36–46‐fold when compared with the wild‐type strain of D4B1. Conclusions: The A. fumigatus phytase gene can be expressed under the direction of p43 promoter in B. mucilaginosus. The expression protein is secreted extracellularly and newly constructed strains showed a high phytase activity. Significance and Impact of the Study: A transgenic Bacillus strain by the particle bombardment method was constructed.