Background art:
As an efficient biocatalyst, enzyme preparation has been widely used in food, leather and feed industries. The enzyme liquid produced by liquid fermentation is made into dry powder, which is convenient for storage, transportation and processing. Especially feed enzyme preparation, the required cost is lower. Although the cost of spray drying materials is low, it can save the operation processes such as evaporation, crystallization, separation and crushing, and has the advantages of continuous automatic production and stable operation. Because the essence of enzyme preparation is active protein, the general solid enzyme preparation is quickly inactivated in the environment above 60℃, and the activity loss is rapidly accelerated with the increase of environmental temperature, such as the loss of solid cellulase in a water bath at 65 ~ 70℃ for one hour.
Although the preparation of solid enzyme preparation by spray drying has many advantages, it also has disadvantages. At present, the spray drying of enzyme preparation is generally carried out under the conditions of inlet air temperature 100 ~ 160℃ and exhaust air temperature 60 ~ 90℃. The yield of enzyme activity is lower than 70%, and the equipment efficiency is low. For example, in China patent "Thermoneutral Protease Strain, Thermoneutral Protease and Its Production Technology" (application number: 02158191.6), the yield of enzyme activity by spray drying method (the parameters of spray drying are not mentioned) is 68%; In the China patent "Production Technology of Bacillus subtilis and Solid Alkaline Pectinase" (application number 94 105708.9), the inlet air temperature is 160℃, the exhaust air temperature is 80℃, and the enzyme activity yield is less than 10%. The published document "Study on the Preparation Technology of Thermophilic Neutral Protease from Bacillus thermophilus" (Biotechnology, 2003, 13 (4): 26-27) records in experiments that the enzyme activity yield is 75% when the inlet air temperature is 170℃ and the exhaust air temperature is 75℃, but it is easy to stick to the wall in continuous production. The loss of enzyme activity during spray drying means low utilization rate of raw materials, low production efficiency and waste of resources, which leads to high production cost. This has always been a difficult problem to solve.