The preparation medium of soybean cake powder needs to be filtered. When preparing with dry powder, it is necessary to contact the air during the preparation process, so we usually prepare the culture medium, adjust the PH, and then filter it with a filter bottle in the ultra-clean table. After suction filtration, take 5ml and put it in a culture bottle, and cultivate it in an incubator for 3 days. If no pollution is found, it can be used.