Effect of proteolytic enzymes on the extent of deproteinisation of Acetes shell residues.

Abstract

The natural biopolymer, chitin is a structural polysaccharide synthesized by numerous living organisms, which has gained great interest due to its versatile biological activities and distinctive physicochemical properties. In spite of the general occurrence of chitin, so far, the major sources are crab and shrimp shells from marine processing wastes. However, the conventional methods of chitin extraction make use of extremely harsh chemicals such as acids and bases at high temperatures for long durations resulting in final inconsistent physicochemical properties in the final product and environmental pollution. Therefore, a much needed alternative eco-friendly approach would be the use of low-cost commercial enzymes such as papain/pepsin for deproteinization of shell wastes. In the present study, protein hydrolysate was produced through enzymatic hydrolysis of paste shrimp (Acetes spp.) which forms a major group of bycatch in Maharashtra and Gujarat Coasts and the residual shell was utilized for bio-extraction of chitin. This facilitates the complete utilization of Acetes spp. for the production of peptides and chitin, both of which act as bioactive molecules. The extraction conditions, viz., enzyme/substrate ratio (E/S), temperature and time were optimized using Response Surface Methodology for attaining maximum degree of deproteinization. For papain and pepsin hydrolysis, the degree of deproteinization was 96.5% and 89.5% respectively while the optimum extraction conditions obtained for papain were: pH-7.0, E/S (%)-2.1 and temperature-52p C and those for pepsin were: pH-3.1, E/S (%)-1.5 and temperature-37p C. These results suggest that enzymatic deproteinization of the shell residue obtained following protein hydrolysate extraction, could be a prominent eco-friendly strategy to produce chitin.