Synthesis of plastein from prawn processing plant wastewater

K. Madzlan, S. Mamot, H. Osman and A. Noor Rehan

Abstract

The precipitate of prawn processing wastewater was hydrolysed with bromelain yielding an approximate degree of hydrolysis of 84.56 ± 0.77% after 24 h of hydrolysis. The protein hydrolysates were then assayed for plastein reaction with bromelain and papain at enzyme/substrate ratio of 1:100 and 2:100 respectively and substrate concentration of 40% (w/v) for 24 h. The hydrolysis of protein yielded 31.30 ± 4.14% of protein hydrolysate. The lipid content decreased considerably to 2.30 ± 0.23% for protein hydrolysate compared to the starting material, while its protein content increased to 81.88 ± 0.20%. Plastein yields of 27.35% and 26.77% were found for papain and bromelain respectively, when trichloroacetic acid was used as the precipitating agent. However, when plastein was precipitated by ethanol the yield was found to be 47.46% and 45.19% for papain and bromelain respectively. The amino acid composition of protein hydrolysate and plastein precipitated with ethanol was generally similar to the starting material. However the amino acid content of plastein precipitated with trichloroacetic acid was slightly lower. Electrophoresis analysis of the prawn protein precipitate showed the presence of two major bands with a molecular weight of 14.2 KDalton and 29.5 KDalton. In contrast, no band was detected in the hydrolysate which indicated that proteins had been hydrolysed into small peptides and amino acids. Electrophoresis analysis of plastein synthesized by papain showed the presence of one major band with molecular weight of 2.8 KDalton. Meanwhile, synthesis with bromelain showed the presence of two bands with a molecular weight of less than 6.5 KDalton and 3.5 KDalton.

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