Enzymatic Hydrolysis of Blue Crab (Callinectes Sapidus) Waste Processing to Obtain Chitin, Protein, and Astaxanthin-Enriched Extract
Abstract
Blue crab’ waste is a good source of valuable substances although only few studies are related to its use, especially concerning the enzymatic hydrolysis and recovery of compounds such as astaxanthin. Besides, the reuse of crab waste may reduce environment al pollution, add value to this residue and promote a social responsibility in several small fishery communities. Therefore, this study aimed to recover protein, chitin, and astaxanthin from blue crab waste by means of enzymatic hydrolysis with alcalase an d bromelain. High hydrolysis efficiency, defined by hydrolysis degree (DH), was achieved with 3% alcalase (E/S), recovering 30% of protein in 120 minutes reaction. The highest extraction yield (3.1 ± 0.4% - w/w) and astaxanthin content (97.7 ± 14.3% μg astaxanthin /gresidue ) were from demineralized sample under acid process (DERS), before carotenoid recovery. Thermogravimetric analysis of the sample with enzymatic deproteinization presented higher thermal stability and mass loss. The enzymatic hydrolysis of t he blue crab processing waste proved to be efficient for the production of protein hydrolysates, mostly using 3% of alcalase enzyme related to the substrate (E/S). Additionally, it was possible to obtain chitin and astaxanthin -enriched extract from the hydrolyzed residue with enzymes, similar to what obtained through an alkaline deproteinization process and, consequently, promote improvements in the blue crab waste environmental management.
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Introduction
Crustaceans are among the most profitable marine products. In 2012, were processed approximately 6,446,818 t of crustaceans in the world [1] and their industrialization generates a large amount of highly perishable waste, which most often is irregularly discarded.
The blue crab waste is basically composed by chitin, protein, minerals, fatty acids, and carotenoids, primarily astaxanthin [2– 4]. Chitin and carotenoids have particular biological activity and can be used as additives for pharmaceutical and food industries.
Therefore, the use of crustaceans wastes is an interesting research topic, in particular concerning blue crab waste, which is very scarce in scientific literature and is one of the most important commercial seafood from the Brazilian South coast. The reuse of this residue could have a positive impact, environmentally and economically, for several small Brazilian fishery communities.
Chitosan, derived from the chitin deacetylation, has been intensively applied in different areas: agriculture (pesticides and fertilizers), water treatment (flocculants for clarification and removal of metal ions), food industry (dietary fibers, cholesterol reducers, preservatives, fungicides, bactericides, fruit coatings), cosmetic industry (skin exfoliators, acne treatments, hair moisturizers, toothpaste), and pharmaceutical industry (antitumors, hemostatics, and anticoagulants). However, its extensive application is in biomedical area (surgical sutures, dental implants, bone reconstitution, controlled release of drugs in animals and humans, materials encapsulation) [5,6].
The recovery of chitin from crustacean waste usually consists of three steps: demineralization, deproteinization, and discoloration. Deproteinization is often performed with the use of chemical products and heating with temperatures above 90°C, which can cause degradation of some amino acids [7], and leads to waste disposal problems, because neutralization of the wastewater are necessary [8]. Therefore, the use of commercial proteases has been proposed as an environmentally friendly method to deproteinize crustacean wastes in order to obtain protein hydrolysates of high nutritional value [9–11], that can be used as a source of protein in the diet of humans and in animal nutrition [12–14].
After the enzymatic hydrolysis process is possible to use insoluble part to recover pigments in the form of a lipid–carotenoid extract, astaxanthin is the main carotenoid present, and solvents or supercritical CO can be used to recover it [11,15]. 2 Astaxanthin presents important applications in nutraceutical, cosmetic, food, and animal feed industries. The most important astaxanthin attributes are the pigmentation capacity and the antioxidant potential. The diverse biological functions of astaxanthin has attracted academic interest due to its benefits to human health (Guerin et al., 2003).
Therefore, considering the environmental, economical, and process aspects discussed above, the aim of this study was to optimize chitin, protein, and astaxanthin extract recovery from blue crab (Callinectes sapidus) waste processing through enzymatic hydrolysis processes using alcalase and bromelain enzymes.
Conclusion
This study revealed the practical relevance of blue crab waste processing as a proper source of proteins, chitin, and carotenoids. Protein hydrolysis using the enzyme alcalase at 3% [E/S] obtained the best degree of hydrolysis, resulting in approximately 30% of protein material after 120 minutes of reaction, as well as similar composition of blue crab deproteinization in soluble fraction. Alcalase 3% also yielded high values of soluble protein, approximately 3.5 times higher than the soluble fraction without the presence of enzymes. The enzyme bromelain had low DH efficiency in for the studied concentrations of 1% and 3% (E/S).
Extracts obtained from insoluble fraction of the enzymatic hydrolysis in this study indicate that blue crab waste presents a proper source of astaxanthin. Its antioxidant activity can be compared to that of positive controls such as standard astaxanthin and BHT, particularly in the case of the extract hydrolyzed using bromelain 1% (E/S), which indicates that they can be used in other systems as natural antioxidants.
The FTIR, TG and SEM analyses of chitins obtained from enzymatic hydrolysis showed characteristics similar to those reported in the traditional literature. It was also possible to assess that the enzymatic treatment to obtained hydrolyzed pr otein does not change the structure of chitin drastically. It is possible to conclude that the enzymatic hydrolysis, a deproteinization environmentally friendly method, of blue crab waste ( Callinectes sapidus ) processing can be used to produce, protein concentrated, chitin and astaxanthin enriched ex tract, and the use of crustacean waste, associate to enzymatic deproteinization is a promising clean technology for the disposal and management of the crustacean waste.
