Determination of the Amino Acid Composition of Gelatin Extracted from Marine Fish Scales and Polymer Blends Characterization

Abstract

Whereas marine fish processing in Kenya is on one hand an important contributor to Kenya’s food production and economy, it is on the other hand a source of bio waste disposed to the environment. Most of the by products, including fish skin, scales and bones, which are disposed as waste, can be utilized in the making of important products hence eliminating the environmental menace they pose. This study sought to utilize scales in the extraction of the protein gelatin. Gelatin in this study was extracted by an enzymatic process from the scales of three marine fish species; Lutjanus sebea (Red snapper), Lethrinus harak (Black spot emperor) and Scalus ghobban (Blue barred parrot fish). Concentration of the bacteria, Bacillus cereus, for mass production of enzyme was done in a fermentation medium using a bio reactor. Scales were hydrolysed at 45ºC and the pH maintained at 12. Complete hydrolysis took between 20 and 23 days for all species. The yield for dry gelatin was between 28.2% and 41.4% for the marine fish scales under study. Fourier transform infrared spectra showed the presence of amide bands and two other additional absorption bands indicating the presence of amide bonds for all the three fish species under study. The amino acid composition analysis for gelatin obtained from the fish species showed the presence of 16 amino acids. Glycine was the most abundant (35%), followed by Alanine, both adding up to around 50% of the total amino acid composition for all three marine fish species studied. Proline was higher for red snapper at over 14.2% compared to 11.1% and 11.6% for blue barred parrot fish and black spot emperor respectively. Polymer blends of three different compositions were prepared comprising of gelatin obtained from blue barred parrot fish scales and PLA. Thermal analysis of these polymer blends was conducted via TGA and DSC. Miscibility and compatibility were confirmed but were dependent on PLA/gelatin composition. The good yield of gelatin obtained in this study shows that alkaline protease was effective in the extraction of gelatin from the scales of the three marine fish species and that the scales are suitable sources of gelatin. This study also showed an improvement caused by polymer blending with the TGA analysis of the three polymer blends of amorphous PLA and gelatin showing slower rates of thermal decomposition than either of the polymers before blending.