A: at present, almost all domestic enterprises producing feed enzymes by liquid fermentation publicize that liquid fermentation products are superior to solid-state fermentation products, and many scientific research workers engaged in animal nutrition research also agree with this view. In fact, this argument is one-sided. Solid state fermentation production exists in developing countries such as China, India and Brazil, and is also highly valued in some developed countries such as Japan and the Netherlands (mainly due to low energy consumption and basically no pollution emission), and the quality of solid-state fermentation products is also very good. Compared with liquid fermentation, solid fermentation products have the following two advantages: ① enzyme protein is a secondary metabolite. Secondary metabolites of mold are usually formed during the differentiation of mold. Liquid culture inhibits the differentiation of mold, so the enzyme production per unit volume of solid-state fermentation is often 5-10 times higher than that of liquid fermentation; ② the raw materials of solid-state fermentation are relatively extensive, and the final product often contains a variety of enzyme activities, which is suitable for use as feed additives. However, the enzyme system of liquid fermentation is often single, and the activity of only one enzyme is higher than that of other components.
There are a lot of non starch polysaccharides in feed materials. The decomposition of these non starch polysaccharides needs the cooperation of one or more groups of enzymes. Non starch polysaccharide enzymes produced by solid-state fermentation usually contain multiple subunits or even multiple enzyme systems. The substrates of solid-state fermentation are basically agricultural and sideline products (mainly wheat bran, soybean meal, corn, etc.), and the induction effect of substrates makes the enzyme system produced by solid-state fermentation have good pertinence, good coordination and scientific proportion. This is also the reason why the effect of enzyme system produced by solid state fermentation in feed is often more significant than that of single enzyme compound produced by liquid fermentation.
There are three kinds of solid-state fermentation: tray type, thick layer ventilation type and drum type. The tray type has the least output, but it has the advantages of simple operation and good product quality.