A large number of researches and practical applications have shown that feed enzyme preparations as feed additives can eliminate anti-nutritional factors, supplement the lack of endogenous enzymes in animals, make nutrients more easily absorbed, and effectively improve feed utilization, thereby expanding the available feed. Resources, reduce feed costs and reduce environmental pollution caused by livestock manure, and achieve a series of purposes such as improving feed flavor and promoting animal feeding. The application of feed enzyme preparation not only promotes the growth of animals, but also prevents and controls animal diseases. Compared with the application of antibiotics and various hormone substances, it has excellent safety. Therefore, feed enzyme preparations have attracted the attention of the feed industry worldwide.
Feed enzymes can be divided into two categories according to their functions. One type is enzymes that promote digestion of macromolecular substances in the digestive tract, mainly cellulase, hemicellulase, pectinase, amylase and protease. The other type is an enzyme that aims to eliminate anti-nutritional factors such as phytic acid, saponin and phytoenzyme in feed. The main role is to eliminate or inhibit the anti-nutritional factors in the feed, thereby greatly improving the nutritional value of the feed, xylanase and phytase belong to this category. This type of enzyme is more important than the first type of enzyme, because most of the enzymes in the first type of enzyme, the animal itself, added to the feed only to supplement the endogenous deficiency; and the second type of enzyme monogastric animal If it is not available, and the anti-nutritional factors such as phytic acid are not eliminated, it can not only combine with the nutrients of the feed itself to form indigestible substances, greatly reduce the nutritional value of the feed itself, but also endogenous enzymes with the animal itself. The combination forms an inactive substance and reduces the digestion and absorption of nutrients in the feed by the animal. China's feed is mainly based on vegetable cakes and other agricultural and sideline products. The content of anti-nutritional factors in feed is quite rich. Therefore, it is especially important to add the second type of enzyme to the feed.
With the addition of the WTO in China, the feed safety requirements for animal products are getting higher and higher, and the use of antibiotics and various hormones will be banned. It is imperative to strengthen the research and refining of feed enzymes.
1 Feed enzyme preparation granulation purposes and requirements
The amount of feed enzyme added in the feed is related to the enzyme concentration of the product, generally 100-300 g/t. The granulation has the following advantages: 1) Improve fluidity and facilitate uniform mixing. 2) Prevent dust generation and contribute to environmental protection. 3) Prevent the separation of the mixed components, increase the density and specific gravity by granulation, and prevent the negative pressure airflow of the system from being carried away during the mixing process. 4) Prevent sticking or agglomeration into pieces. 5) Improve solubility. 6) Reduce the inactivation of the enzyme during secondary granulation (ring granulation). 7) If the pellets are coated, the enzyme preparation can be slowly released or enteric-coated. 8) Improve product value and so on.
Since the amount of feed enzyme added is small compared with the amount of the feed itself, it is required that the feed enzyme has a small particle size, and generally has a particle size of about 40 mesh, which is advantageous for uniform mixing of the feed enzyme and the feed. Because it is required to prepare a large amount of feed enzyme microparticles (pill) with a uniform size of about 40 mesh, and there is no excessive temperature generation during the granulation process, so as not to damage the activity of the enzyme, the granulation technology and equipment for the feed enzyme have High requirements and difficulty.
2 preparation method of feed enzyme pellets
2.1 Fluidized bed spray granulation method
The fluidized bed coating machine was pioneered by Wurster and is a commonly used method for preparing pharmaceutical pellets abroad. It is also useful for preparing enzyme preparations such as the preparation of BOSPRO phytase pellets. The device consists of an air compression system, a power heating system, a spray system and a control system. Figure 1 is a top spray fluidized bed granulation by placing the material in a fluidization chamber. The screen at the bottom of the fluidization chamber is thinner and made of stainless steel. A certain temperature of hot air flows through the screen into the fluidization chamber. The drug and the auxiliary materials are suspended and mixed in the fluidization chamber, and the powder begins to aggregate into the pellets; when the particle size reaches the specified requirement, the spraying is stopped, and the formed small pellets are dried in the original fluidization chamber. During the whole process, the micro-powder trapping device is always in a vibrating state, and the micro-powder is continuously shaken into the fluidized bed, and continues to contact the droplets or wet particles to form a ball. The coating process of the pellets is also carried out in the fluidized bed, i.e., granulation, drying and coating are completed in one step. In this process, the pellets are always in a fluidized state, which can effectively prevent the adhesion of the pellets during the coating process; the two most critical process parameters in the top spray fluidized bed granulation are the spray air pressure ( Volume) and hydraulic feed rate, air inlet temperature and volume have little effect on particle formation, but when the strength of the binder decreases, the influence of these secondary parameters will increase, and the type and concentration of binder also play an important role in particle size formation. effect. Generally, the particles prepared by the top spray method are porous and have a loose structure, have a low density, are easily decomposed in water, have poor true sphericity, and have poor uniformity in size.
Fluidized bed granulation In addition to the top spray structure, tangential spray (rotation) and bottom spray are two other common structures, as shown in Figures 2 and 3, respectively. The main feature of the tangential spray device is that the rotating disc is adjustable. During processing, three kinds of mechanical forces: the centrifugal force generated by the rotation of the disc and the lift and gravity generated by the air through the disc gap move, mix and granulate the particles. These forces are similar to a rotating spiral that provides excellent mixing and uniform granzyme content. The granules produced by the tangential spray are denser than those obtained by the top spray, and the true sphericity of the granules is high. Most of the granules to be coated are selected by tangential spray granulation, which is due to the surface of the granules prepared by the rotor. The shape is smooth and close to a spherical shape, which is more suitable for coating.
The bottom spray is mainly used for the coating of the pellets, and the bottom spray is characterized by an air distribution plate and a partition plate, which are combined to fluidize the particles through the separator (coating area). The nozzle is mounted at the bottom of the product container and in the center of the coating area. The short distance between the coating material and the granules minimizes spray drying time, and the bottom spray fluidized bed has excellent coating uniformity and coating efficiency.
Fluidized bed technology is widely used in granulation and coating, and each of the three fluidized bed processes has unique properties. The advantages, limitations, and applications of each method are relevant, and an understanding of each fluidized bed process, material properties, and end product requirements helps to select the best process for a particular application. The fluidized bed spray granulation drying process is an organic combination of fluidization technology, atomization technology and drying technology.
2.2 Extrusion spheronization granulation
2.2,1 basic principle of extrusion spheronization granulation
The preparation of feed enzyme preparation pellets by extrusion spheronization requires at least two extruders and a spheronizer to complete the granulation process. The preparation process can be roughly divided into four steps: 1) preparing the desired powder and Mix the right amount of binder and water evenly. 2) The uniformly mixed material is extruded into strips of equal diameter through an extruder. 3) The strip material is cut into a uniform cylinder in the friction disc rotated by the rounding machine, and the cylindrical particles are gradually trimmed into a size gauge and a sphere under the combined action of shearing force, centrifugal force and interaction between the pellets. Good pellets. 4) The collected pellets are dried.
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