First, the mechanism of complex enzymes to improve the nutritional value of feed
The reason why compound enzymes can increase the nutritional value of feeds and improve the feeding effect is not that the NSP is hydrolyzed into monosaccharides available to animals to increase the nutritional value of the feeds, but that when the complex enzyme acts on the feed ingredients, it first destroys the plant cell walls. In the intercellular layer, the cell wall structure of the plant is destroyed, and the cellular contents are exposed and release nutrients such as encapsulated protein and starch, which are in contact with the animal's endogenous digestive enzymes and are degraded. At the same time, the viscosity of the intestinal tract is changed and the food is reduced. The negative effect of viscosity on nutrient utilization and absorption.
Second, the defect of enzyme activity evaluation system
1. Determination of enzyme activity at a single pH
Since the range of pH values of digestive chyme in animals is relatively large, simply considering the value of enzyme activity at a certain pH value is not comprehensive, and it is best to measure the enzyme's performance in a wider range of pH values. Special phytase activity was determined in the laboratory using phosphophytase and other sources. Although the enzyme activity was the same at pH 5.5, it was measured at other pH values. The activity was significantly higher than that of other enzymes. Since there were significant differences in the pH values of different parts of the intestine of animals, although the enzyme activity was determined by the national standard, the enzymes of different sources had great differences in the biological activity after being added to the feed. The effect is not the same. The compound effect is more consistent with the actual use of cellulase. The determination of the enzyme activity (CMCase) using hydroxymethyl cellulose as a substrate does not reveal that the C1 enzyme decomposes natural crystalline cellulose into soluble free cellulose, and that FPA is the more reasonable basis for selecting feedstuff cellulase than CMCase. For example, when evaluating the quality of cellulase A and B using hydroxymethyl cellulose as a substrate, cellulase A activity (enzymatic activity of 200) was higher than that of cellulase B (enzymatic activity of 140), but using filter paper As a substrate, cellulase B enzyme activity (enzymatic activity was 20) was higher than cellulase A (enzyme activity was 12).
The substrate chosen for the determination of xylanase is typically birchwood xylan (suitable for papermaking). From the perspective of Feed Enzymes, oat xylan should be used (Table 1). However, even if oat xylan is chosen as a substrate, there are problems because oat xylan (SigmaX0627) is soluble in water, and xylans in feed are mostly insoluble in water.
Effects of Oat Xylan and Birch Xylan on Enzymatic Activity
Oat xylan viability birch xylan vitality
Xylanase A 4 500 1 200
Xylanase B 2 300 6 700
(Lu Wenqing, 2005)
Third, the impact of water on enzyme activity
The effect of moisture on the enzyme preparation has two sides: the water in the reaction medium must reach a certain proportion, and the enzyme preparation can fully exert the enzymatic action on the substrate. When the water content of the medium in which the phytase is located is zero, the phytase is completely absent. active. In vitro tests, the medium moisture content of at least 25%, the reaction can proceed. However, when there is moisture in the environment, the stability of the enzyme activity is affected. At a certain temperature, the higher the moisture content of the sample, the more pronounced the denaturation of the enzyme protein. For example, when the moisture content of the sample is reduced to 10%, the lipase does not start to deactivate until the temperature is increased to 60C. When the moisture content is increased to 23%, apparent deactivation occurs at room temperature.
Fourth, the impact of mineral elements on enzyme activity
Specific metal ions can act as electron transfer carriers to activate enzyme preparations. As phytase in Bacillus has a strong dependence on Ca2+, the phytase is incubated in an environment containing Ca2, and partially inactivated enzyme protein can regain activity of the enzyme (Kerovuo et al., 2000). The source of the enzyme and the concentration of metal ions are different, and the same metal ions have different influence degree and effect on enzyme activity. Ca2+ is a competitive inhibitor of the bacillus phytase. Excess Ca2+ pre-occupies the active site of the substrate and thus inhibits the binding of the enzyme to the substrate. Ca2+ excess inhibits the activity of phytase (Oh et al., 2001). Complexation of Fe2+, Zn2+, Mg, and Cu2+ with phytic acid also inhibited the phytase activity. For Trichoderma reesei GXG"-glucanase, Cu2'and Mn2+ inhibited the enzymatic activity, Zn2' and C02+ had an activating effect, and other ions Ca2', M broad, and K' were different under different concentrations. The role of Li Weifen et al., 2001. Below 5.0 mmol/L of Ca2+, Zn2', and 10.0 mmol/L or less of C02+ have an activation effect on "-glucanase activity, while Cu2+ has an inhibitory effect (Sun Jianyi et al. 2004).
Five, dosage forms of enzyme preparations
The enzyme preparation can improve the resistance to high temperature through some physical treatments, mainly including adding a carrier to adsorb the original enzyme and coating the original enzyme. Enzymatic coating treatment can improve the thermal stability of the enzyme to some extent. Pichford (1992) reported that the stabilization of the enzyme can increase the retention rate of the enzyme after 75-C granulation from 48% to 76%, while the survival rate of the enzyme activity after 95-qC granulation increased from 12% to 34%.
The prerequisite for the enzyme to function is that the enzyme that reaches the site of action of the digestive tract is active, so it should be noted whether the coated enzyme can be released at the appropriate site of the digestive tract to achieve the purpose of catalyzing the substrate. Guss (2000) tested three types of phytase (powder, granule, and coating) in phosphatized corn-soybean meal diets. The test results were coated phytase groups. Weight gain is lower than the other two groups. This may be due to the slow release of coated phytase activity in the intestinal tract of animals.
Sixth, the digestive tract environment
As a biologically active protein, the enzyme preparation is affected by the environment of the digestive tract, and the whole digestive tract forms a physiological pH line (Table 2). The enzyme activity characteristics and the physiological characteristics of the animal's gastrointestinal tract, especially with the same pH value, can fully play the catalytic activity of the enzyme. Whether the exogenous enzyme can adapt to the pH line in the digestive tract and whether it causes reversible or irreversible denaturation of the enzyme protein are all factors that need to be considered when using the complex enzyme. For example, pepsin is rapidly inactivated at pH 6~7, pH1. 0 to 5.0 is very stable. The optimum pH of the general fungal cellulase is 4.0~6.0, while the optimum pH of the bacterial cellulase is 6. 0~7.0 (Wood, 1995). The acidic conditions in the anterior segment of the digestive tract are suitable for enzymes derived from fungi, and the feed cellulases are mostly fungal-derived acidic enzymes.
In general, the pH of the chyme after eating in the pig stomach is around 4.7. However, commercial phytase currently on the market mostly has the highest activity at pH 5.5, and the enzyme activity decreases significantly at pH 4.5. The phytase gene was successfully modified and modified by the feedstuff of the Academy of Agricultural Sciences. The phytase developed in the special section R-phosphorus pig had the highest enzyme activity between 4.0 and 5.0, which was significantly higher than that of the original phytase. Improve the effect of adding in the pig feed.
VII. Differences in reactions of different animals to enzymes
Different types of animals, there are differences in the use of enzyme preparation effects, the effect of adding enzyme preparations in poultry feed is slightly better than in pig feed, the main reasons are:
(1) The relatively high pH of poultry fleas favors the activity of most enzymes, and enzyme preparations are more inactive in poultry than in poultry.
(2) The content of water in the intestinal contents of pigs is higher than that of poultry, the dry matter content (10%) is significantly lower than that of poultry (20%), and the content of intestinal contents is lower than that of poultry. Therefore, the compound enzyme is added to the food. The decrease in viscosity is more effective, and the decrease in viscosity makes the absorption of nutrients more rapid.
(3) The ratio of intestine volume to total intestine of pigs is much higher than that of poultry. The species and number of microorganisms in the intestine of pigs are also higher than those of poultry. The fermentation of microorganisms in the hindgut can release some fatty acids and provide part of the energy.
With the deepening of the research on the enzymatic characteristics of various Single Enzymes, and the more scientific and rational combination of compound enzymes, they all help to increase the effect of enzyme preparations in feed and promote the use of enzyme preparations in feed. However, at the same time, it is also necessary to realize that there are still many issues in the application of enzyme preparations that need further study. The intrinsic characteristics and external linkages of enzyme preparations need to be further studied and discussed in order to promote the effective absorption and utilization of feed nutrients and promote healthy green environmental protection animal husbandry. development of.
