Method for increasing content of manganese ions in bacillus subtilis and complex microbial inoculant

The invention provides a method for increasing the content of manganese ions in bacillus subtilis. According to the method, bacillus subtilis and clostridium butyricum are simultaneously fermented and cultured in a culture medium rich in manganese ions. The bacillus subtilis strain is a bacillus subtilis NT66 strain which is preserved in the China General Microbiological Culture Collection Center of Institute of Microbiology, Chinese Academy of Sciences in No.3, No.1 yard, Beichen West Road, Chaoyang District, Beijing on November 8th, 2021, and the preservation number is CGMCC No.23751. According to the method, the bacillus subtilis strain domesticated by high manganese ions and the clostridium butyricum are co-cultured according to a certain proportion, so that the quantity of the bacillus subtilis can be increased, the content of small peptides in the domesticated bacillus subtilis strain is effectively increased, and the prepared bacterium product can effectively enhance the animal immunity, promote the gr