Utilization of shrimp waste for the recovery of valuable bioactive compounds

Abstract

Shrimp waste is a major by-product of crustacean processing and represents an interesting source of bioactive molecules. In addition, its use increases the sustainability of processing fishery products. The present study reports a process developed for recovering bioactive molecules from shrimp waste through the use of chemical methods. The samples of shrimp were confirmed to be from the species Haliporoides triarthrus. The recovery of chitin was 30% of the processing waste and 30-60% chitosan (CH) from chitin. CH was characterized by FTIR analysis and exhibited a degree of deacetylation (DDA) of 72%. From the demineralization extract, CaCO3 was extracted and confirmed by FTIR. Based on a kinetic study of acid hydrolysis, it was demonstrated that chitin can be quantitatively hydrolysed into glucosamine (GlN), N-acetyl glucosamine (GlcNAc) and their respective oligomers with 32% hydrochloric acid at 60oC and qualitatively from CH with 32% hydrochloric acid at 80oC. The oligomer mixed fractions were desalted by activated charcoal extraction and the components of each fraction were analysed by TLC and HPLC. Chitooligosaccharides (COS) and N-acetly chitooligosaccharides (NAcCOS) with degrees of polymerization (DP) ranging from 2 to 6 were obtained from CH and chitin, respectively. The antimicrobial activities of chitosan, COS and NAcCOS were investigated against five gram-negative bacteria and five gram-positive bacteria. Chitosan exhibited stronger bacteriostatic effects against gram- positive bacteria than gram-negative bacteria in the presence of 1% chitosan. The oligomers showed no bacteriostatic or bactericidal effects on all tested bacteria. A total 30.74± 0.078 µg.g-1 astaxanthin was extracted with 90% acetone from the species; Haliporoides triarthrus and TLC analysis indicated that the species contained both astaxanthin and its esters.

Chitosan films were obtained by solution casting of blends of chitosan with glycerol, polyethylene glycol 200 (PEG-200) and polyethylene glycol 600 (PEG-600) as plasticizers. Films were characterized by FTIR, XRD diffraction, TGA, and SEM analysis. The tensile strength and elongation at break properties of the films were also evaluated. CH films and CH/GLY blended films were translucent in appearance and the CH/PEG 200 and CH/PEG 600

films were opaque. The CH films yielded mechanically resistant films without the use of a plasticizer. These data point to the feasibility of an integrated process for isolating highly bioactive molecules, such as oligosaccharides, with a broad spectrum of applications from shrimp processing waste.