Extraction and Characterization of Gelatin from Lates niloticus Scales and Potential Industrial Applications

Abstract

This study sought to extract and characterize gelatin from Lates niloticus (Nile perch) scales, then blend it with polyvinyl alcohol (PVA). Hydrolysis of the scales was done using a crude alkaline protease harvested from a bacterium, Bacillus cereus strain wwcp 1, obtained from Lake Bogoria and the resulting solution lyophilized to obtain gelatin powder. The yield was calculated based on the dry weight of the scales and was shown to be 16.3%. The sample was characterized using infrared spectroscopy and showed peaks at 3442 cm-1, 1653 cm-1 and ~ 1590 cm-1 corresponding to Amide A, Amide I and Amide II bands respectively. Amino acid analysis of the sample was done using an Agilent 1260 HPLC. Glycine was the most abundant amino acid (21.7%), followed by proline (14.6%) and alanine (11.8%). Isoleucine, Histidine and Tyrosine were the least abundant (1.8, 1.4 and 0.9% respectively). Polyvinyl alcohol-gelatin blend films of various compositions ranging from 10% to 90% PVA were prepared by solution casting method, Differential Scanning Calorimetry (DSC) and Thermo-gravimetric Analysis (TGA) tests showed the films had glass transition, melting and thermal decomposition onset temperatures intermediate between those of the respective individual polymers ( PVA and gelatin). The thermal stability of the films reduced with the increase in the amount of the less thermally stable constituent. Lastly, potential applications of the prepared blend films were investigated. Batch experiments to assess the potential of the polymer blend films as adsorbent material were done using Methylene Blue dye. The films were found to adsorb up to 64% of the dye. The percent dye removal varied with initial concentration of the dye and contact time.