Physico-chemical characteristics and fibril-forming capacity of carp swim bladder collagens and exploration of their potential bioactive peptides by in silico approaches
Introduction
India is the second largest producers of freshwater fish in the world after China. Catla (Catla catla) is second most important species after rohu (Labeo rohita) with an estimated production of 2-4 t/ha [1]. In fish shop and fish-processing factories, catla processing generates a large amount of by-products (∼ 50-80% of total fish weight) that is discarded as non-edible by-product/waste (Skins, scales, bones, fins and swim bladders) [2]. These by-products, especially swim bladders are an excellent raw material to obtain the high-value bioactive molecules such as collagen, gelatin and so on. Swim bladder (air bladder) is an internal gas-filled organ found in bony fishes [3].
Collagen has a triple helical molecule that contains three polypeptide α-chains that are coiled around each other and composed of (Glycine-X-Y)n, where X and Y are often proline and hydroxyproline, respectively. Presently, 29 different collagen types (type I–XXIX) have been identified so far [4], [5]. Type I is the most common form of collagen in the vertebrate connective tissues. Collagen and its derivatives have potential commercial value for a broad range of pharmaceutical, cosmetic, food and biomedical industries applications [6], [7], [8]. The skin and bone of land based animals (bovine and porcine) have been the conventional sources of collagen. However, the use of bovine and porcine collagens have raised serious problems regarding consumers health due to the outbreak of bovine spongiform encephalopathy, transmissible spongiform encephalopathy, foot-and-mouth disease, and other prions diseases, as well as ethical problems among the religious communities [6]. Therefore, there is a strong necessity to find out the alternative sources of collagen. Aquatic species and their processing by-products have been recognized as potential alternative sources, owing to their availability, lack of disease risk, lack of dietary restriction, and high collagen yields. Incorporation of collagen derived bioactive compounds can be an innovative approach to the production of functional food and nutraceutical products with potential health-promoting properties [7]. Development of the bioactive collagen hydrolysate is an important area of research due to their various food and biotechnological industries relevant applications. Carp collagens contain a high amount of glycine and proline amino acid residues that can serve as a potential precursor of bioactive peptides. Fish collagen hydrolysates have the biological and pharmacological properties (anti-inflammatory, antimicrobial, antitumor, antiviral, anti-ageing and radical scavenging activities) due to the presence of the specific peptides and amino acids [8]. In the past decades, in silico approaches (BLAST, BIOPEP, PeptideRanker, Pepdrew, Pepcalc, ToxinPred) have been successfully applied to predict potential biological activity of hydrolysate/peptides [9], [10], [11], [12], [13]. Moreover, in silico analysis is time-saving and more economical methods as compared with traditional experiments.
Therefore, the objectives of this investigation were to characterize the catla swim bladder collagens with fibril-forming capacity and their revalorization for the development of antioxidative hydrolysate/peptides by computational approaches. To the best of our knowledge, the extraction and characterization of collagens from catla swim bladder are not reported so far. In addition, the potential antioxidant activities of catla swim bladder collagen hydrolysates/peptides have not been reported in the literature.
Section snippets
Collection and pre-treatment of swim bladder
The swim bladders of catla (Catla catla) were collected immediately after slaughter of fish from the local fish market (Devaraja fish market, Mysuru, India). The collected swim bladders were transported in child condition to Meat and Marine Sciences Department, CSIR-Central Food Technological Research Institute, Mysuru within 30 min. Swim bladders were washed thoroughly three to four times with chilled tap water and then with chilled demineralized water (∼ 4 °C), within 1 h after the collection.
Proximate composition of catla swim bladder
Catla swim bladder has 82.8 ± 2.01% moisture content, on wet weight basis. The ash, fat and protein content of catla swim bladders were 0.50 ± 0.01%, 4.7 ± 0.01%, 83 ± 1.2% (dwb), respectively. These results are in agreement with results of Kaewdang et al. [3]. The proximate compositions of our finding are also in agreement with the proximate composition of the rohu swim bladder in our previous study (unpublished data).
Yield
The yield of collagens (ASC and PSC) from catla swim bladder was determined after
Conclusion
The swim bladder collagens of Indian freshwater carp were successfully extracted and characterized with well-maintained triple helical structure and fibril-forming capacity. The present study highlighted that in silico and in vitro digestions of carp collagen chains using papain and pepsin effectively generated the antioxidative peptides that provide a basis for the development of carp collagen as a precursor of antioxidative peptides in the food industries. Therefore, the utilization of fish
Conflict of interest
The authors declare that we have no conflict of interests.
Acknowledgement
Gaurav Kumar Pal gratefully acknowledge the Department of Science and Technology (DST), New Delhi, India for the award of DST-INSPIRE-SRF Fellowship (IF-131071). Authors thank Director, CSIR-CFTRI, Mysuru for his encouragement and permission to publish this work.
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