Production of electrospun nanofiber mat from fish skin gelatin

Abstract

Gelatin from nile tilapia (Oreochromis niloticus) skin was prepared by deproteinization in 0.4% w/v NaOH. Swelling process was carried out by soaking the pretreated skin in 0.4% w/v HCl. Then gelatin was extracted using distilled water at 70 °C for 1.5 hours. The gelatin solution were evaporated and dried at 50 °C for 18 hours. The yield of gelatin was 18% (wet basis). The gelatin contained protein as the major composition and low fat and ash contents. Gel strength and viscosity at 80 s-1 shear rate of 6.67% w/v gelatin were 328 g and 17.79 cP, respectively. Amino acid compositions of fish skin and porcine skin gelatin were quite similar. The main amino acids contents of gelatin from nile tilapia skin were glycine, alanine, glutamic acid, proline, arginine, and hydroxyproline. Similar protein patterns were observed for fish skin and porcine skin gelatin. In the electrospinning study, 40% v/v acetic acid and 80% v/v formic acid concentration gave smooth and uniform ultra fine fibers with an average diameter of 233 nm and 137 nm, respectively. The viscosity of gelatin solution increased while the conductivity decreased when the solvent concentration increased causing the fiber diameter to increase. The resulting smooth and uniform ultra fine fibers with an average diameter between 208 nm and 316 nm were obtained when using 17, 20, and 23% w/v gelatin concentrations in acetic acid solvent. In formic acid solvent, 20, 23, and 26% w/v gelatin concentrations gave smooth and uniform ultra fine fibers with an average diameter between 238 nm and 284 nm. The viscosity and conductivity of gelatin solution and fiber diameter were found to increase with increasing gelatin concentration. The tensile strength and Young’s modulus of gelatin nanofibers mats increased when the mats were crosslinked with glutaraldehyde. Elongation of the crosslinked and non-crosslinked gelatin nanofibers mats at all gelatin concentrations did not differ significantly (P> 0.05). The colour of the crosslinked gelatin nanofiber became visibly yellowish.