TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: In modifying erythromycin bacterial residue, the erythromycin bacterial residue is fresh wet bacterial residue which has just left factory; it is also dry bacterial residue which has passed dry disposition. The proportion of original accessories is that, 50-70% erythromycin bacterial residue; the accessories are 2-3 kinds of grain stillage, meal, bran or chaff, the added proportion is 5-30%. The fermented mixed flora is Trichosporon cutaneum, Bacillus pumilus and Aspergillus niger. The quantity of fermenting mixed flora (T. cutaneum, B. pumilus and A. niger) is 3:1:1. The added compound enzyme preparation comprises high activity beta -glucanase, high activity protease and high activity cellulose. The quantity of every added compound enzyme preparation is 0.1-0.3% according to dry material of raw material. The water content of solid fermentation substrate is 45-65%; the original water content which is selected preferably is 55%. The temperature of solid fermentation is 30-55 degrees C, when the temperature is higher than 55 degrees C, it should cool down by stirring up and venting. The fermenting time of solid fermentation is 45-60 hours; the preferable selecting time is 55 hours. Making up fermentation substrate, adding some industrial and agricultural byproduct (grain stillage, meal, bran, chaff, etc.) with good air permeability and higher protein content in erythromycin bacterial residue (dry residue or wet residue) to be accessories, the sort of added accessories are 2-3 kinds, mixing original accessories equally, making water content from 45-65%; inoculating mixed bacterial residue of T. cutaneum, B. pumilus and A. niger according to 3-5% of dry weight of material, simultaneously adding in compound enzyme preparation, mixing bacteria, enzyme and fermenting substrate adequately; fermenting for 45-60 hours at 30-55 degrees C, drying material, drying it until water content of material is less than or equal to 12%; scattering and screening by 60-80 meshes; packing and getting erythromycin bacterial residue modified culture medium products.