Exogenous enzymes in aquaculture: alginate and alginate-bentonite microcapsules for the intestinal delivery of shrimp proteases to Nile tilapia

RODRIGUEZ, YAMILA ELIANA; LAITANO, MARIA VICTORIA; PEREIRA, NAIR DE LOS ANGELES; LÓPEZ-ZAVALA, ALONSO A.; HARAN, NORA SELMA; FERNÁNDEZ GIMENEZ, ANALIA VERÓNICA

AQUACULTURE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018 vol. 490 p. 35 - 43

0044-8486

It has been demonstrated that supplementing diets with exogenous enzymes lead to a better utilization of nutrients improving growth performance. Shrimp processing waste holds digestive proteases with a great potential to be used as feed supplement for Nile tilapia. First, it is necessary to find the best carrier to ensure that exogenous enzymes pass through the gastric environment and reach the intestine where they will act. In the present work, we characterize both sodium alginate (A) and sodium alginate-bentonite (AB) microcapsules to entrap enzymes obtained from Pleoticus muelleri processing waste. Also, we evaluate these encapsulation methods as a strategy to improve intestinal delivery of exogenous enzymes in Oreochromis niloticus in order to enhance their digestion process. The A-enzyme and AB-enzyme solutions were separately extruded into a CaCl2 solution to make capsules containing shrimp enzyme. The effects of different storage methods, in vitro simulation of gastric conditions and exposition to 40°C were studied. In order to evaluate if shrimp enzyme microencapsulated are active when they reach fish gut, animals were exposed to three treatments: (1) fast, (2) diet and, (3) AB capsules + diet. A capsules were more affected by different storage methods than AB ones. The former presented a significant reduction of enzyme activity after the exposition to all storage methods whereas AB capsules showed a decrease in protease activity only when exposed to the freeze-drying process and -80°C. SEM images showed a correlation between decreased enzyme activity and capsule microstructure changes. The best method to store the AB beads is at -20°C. After incubating for 7 hours at 40°C, we observed a notorious reduction in the enzyme activities of both microcapsules class. When we evaluate the enzyme activity of A and AB capsules after being exposed to the in vitro gastrointestinal conditions, we found that at pH 3 capsules prevent enzyme irreversible denaturalization and kept 100% of their activity. However, enzymes contained in both types of microcapsules were severely affected by all pH values below 3. All these results indicate that AB capsules are better vehicles to deliver shrimp enzymes in Nile tilapia. In the bioassay we observed that when fish ate diet and AB capsules the enzyme activity in their intestines was 27 % higher than fish that just consumed the diet. Further trials involving grow bioassays are needed to verify if this shrimp enzyme contained in AB capsules improve fish digestion and lead to bigger fish sizes.