Enzyme Assay To Determine Optimum Crude Papain Level On Plant Protein Diets For Nile Tilapia (Oreochromis Niloticus)

Abstract

This study was conducted to evaluate the chemical composition, enzymatic activity and optimum crude papain level incorporation in plant protein based diets for Nile tilapia. The crude papain extract (CPE) was collected from unripe paw paw fruits and enzymatic activity determined by tyrosine method. The CPE was used to assay In vitrorelative protein digestibility (IVRPD) using pH drop method. A diet (Diet 1) was formulated to contain 300g/kg crude protein (CP) using fishmeal (FM), soybean meal (SBM), canolameal (CM) and sunflower meal (SFM). The FM was replaced (10% CP basis) with either SBM, CM, or SFM (Diet 2, 3, & 4, respectively). In a factorial design the four diets were treated with 0.02%, 0.04%, 0.06% and 0.08% of CPEin triplicates and subjected to IVRPD. Crude papain extract and pure papain (standard) had protease activity of 1.9u/mg and 1.55 u/mgat pH 7.5, respectively. Diet 1 had highest (P<0.05) digestibility (39.96%) and replacement of FM by SBM, CM and SFM reduced the digestibility to 35.84, 34.82 & 33.27%, respectively. Addition of CPE at 0.06% recorded the highest (P<0.05) IVRPD (39.16%). In conclusion, CPE can be used in plant protein based diets for Nile tilapia at 0.06%.