Cellulases present in the digestive tract of the shrimp Litopenaeus vannamei

Abstract

Cellulases have been classified as endoglucanases. This is the only enzyme capable of degrading cellulose, which gives an immense importance in the processes of the food chain, being cellulose the most abundant source of carbon on earth. Cellulases and related enzymes are widely used in various industrial processes. Cellulose is used as a nutritional source for several organisms, initially it was thought that only microorganisms may degrade this polymer however cellulases have been reported in many animal groups. In this paper, we present the preliminary identification and characterization of cellulases in the shrimp Litopenaeus vannameiduring its larval and adult stages. In adults and f different sub-stages of L. vannamei were collected in culture tanks in comercial shrimp farms in the Santa Elena Peninsula and Muisne, in the provinces of Esmeraldas and Santa Elena, respectively. The hepatopancreas, larval stages and intestines were homogenized in a Braun-Melsungen homogenizer. Carboxymethyl cellulose (CMC) of medium viscosity was used as a substrate. To measure enzymatic activity 3,5 dinitrosalicylic acid (DNS) was added. The cellulase activity was determined based on the amount of reducing groups released. To try to determine the presence of endogenous cellulases, that is produced by shrimp, samples were submitted to antibiotics and later assayed. In sub-stage zoeal 3, a cellulase with an optimal pH range between pH 6.5 and pH 9.5 was determined. In samples of adult shrimp hepatopancreas two optimum pH were determined: one in the acid range (pH 4-6) and one in the basic range (pH 10-11), while in the intestine only one in an acidic pH range (pH 4-6) was determined. The cellulase activity detected in the ontogenetic development of the shrimp was low and unstable, a condition also reported in the comparative analysis of digestive enzymes in four other species of crustaceans. The relative activity of the two enzymes is similar in the hepatopancreas and each of these have an activity four times greater than that found in the intestine. These results suggest the presence of two possible cellulases, one could be transported from the hepatopancreas into the intestine but more tests are needed to get more conclusive results. The cellulase activity at basic pH (10.5) may be a cellulase produced endogenously by the shrimp. The data reported in this study of enzyme production capabilities shrimp can be the basis for future research projects aimed at optimizing procedures shrimp farming