Microstructural and Physicochemical Analysis of Collagens from the Skin of Lizardfish (Saurida tumbil Bloch, 1795) Extracted with Different Organic Acids

Abstract

Marine fish collagen has attracted considerable attention due to its characteristics, including its biodegradability, biocompatibility, and weak antigenicity, and is considered a safer material compared to collagen from terrestrial animals. The aim of this study was to extract and characterize collagen from the skin of lizardfish (Saurida tumbil Bloch, 1795) with three different acids. The yields of acetic acid-extracted collagen (AESkC), lactic acid-extracted collagen (LESkC), and citric acid-extracted collagen (CESkC) were 11.73 ± 1.14%, 11.63 ± 1.10%, and 11.39 ± 1.05% (based on wet weight), respectively. All extracted collagens were categorized as type I collagen with mainly alpha chains (α1 and α2) detected and γ and β chains to some extent. Fourier transform infrared (FTIR) spectra showed an intact triple-helical structure in the AESkC, LESkC, and CESkC. UV-vis spectra and X-ray diffraction further demonstrated the similarity of the extracted collagens to previously reported fish skin collagens. AESkC (Tmax = 40.24 °C) had higher thermostability compared to LESkC (Tmax = 38.72 °C) and CESkC (Tmax = 36.74 °C). All samples were highly soluble in acidic pH and low concentrations of NaCl (0–20 g/L). Under field emission scanning electron microscopy (FESEM) observation, we noted the loose, fibrous, and porous structures of the collagens. The results suggest that the lizardfish skin collagens could be a potential alternative source of collagen, especially the AESkC due to its greater thermostability characteristic.

Physicochemical and Microstructural Analyses of Pepsin-Soluble Collagens Derived from Lizardfish (Saurida tumbil Bloch, 1795) Skin, Bone and Scales

“…The differences in the peaks might be due to sample preparation that was arranged in a random order. Moreover, our previous reports on acid-extracted collagens also exhibited two diffraction peaks [ 25 , 26 , 27 ] and other previous reports of carp ( C. carpio ) scale collagen [ 52 ], golden pompano ( T. blochii ) skin and bone collagen [ 7 ] and tilapia ( O. niloticus ) skin collagen [ 53 ]. Furthermore, d(Å) was used to predict the minimum value of repeated spacing d (Å).…”

“…This finding was in accordance with the study of fish-bone collagen from grass carp ( C. idellus ) [ 14 ] and Spanish mackerel ( S. niphonius ) [ 15 ]. However, for lizardfish skin, the pepsin-aided treatment yielded a lower collagen percentage (3.50 ± 0.11%) than the acid-aided process (11.73 ± 1.14%), as reported in our previous work [ 26 ], and other fish, including sturgeon ( H. huso ) [ 16 ], sailfish ( Istiophorus platypterus ) [ 34 ] and Spanish mackerel ( S. niphonius ) [ 15 ]. It was suggested the acid solutions increased the extractability of solubilized skin collagen, resulting in less collagen in the undissolved matter, and the final PSC obtained was also lower.…”

“…After alkaline treatment, fish bone and scales were subjected to demineralization by suspension in 0.5 M EDTA-2Na at a ratio of 1:10 ( w / v ) for 48 h, and the solution was changed every 16 h. The suspended samples were then washed with cold distilled water for 30 min, and the distilled water was replaced every 10 min. In terms of lizardfish skin, a defatting process was performed by adding 10% butyl alcohol at the ratio of 1:10 ( w / v ) for 24 h, and the solution was periodically changed every 12 h. In the present study, we used undissolved matter from our previous acids extraction processes [ 25 , 26 , 27 ]. All undissolved samples were isolated in an acidic condition by adding 0.5 M of acetic acid and 1.5% ( w / w ) of pepsin from a bovine origin (Himedia, Maharashta, India) at a solid–liquid ratio of 1:15 ( w / v ) for two days with continuous stirring.…”

“…Yields of PSSC, PSBC and PSCC were measured based on the wet weight of undissolved matter obtained from our previous works [ 25 , 26 , 27 ], and the formula is described below: …”

“…The utilization of by-products from lizardfish, particularly the skin, bones and scales, could be utilized to the maximum. The production of acid-soluble collagens from the skin, bone and scales of lizardfish and their physicochemical properties have been evaluated in our previous works [ 25 , 26 , 27 ]. This study was conducted to further extract collagen from the undissolved matter from acid-aided collagen-extraction studies by using the pepsin enzyme in order to maximize the output.…”