![]() Films made from the sodium sulfide–extracted keratin had excellent mechanical properties and was considered to be suitable for industrial applications ( Poole and Church, 2015). Extracted keratin had a molecular weight of 10 kDa (68–70%) and 15–19% of 20 kDa dimers. For extraction, feathers were treated with sodium sulfide under nitrogen atmosphere at 30☌ for 1 h. Sodium sulfide has been demonstrated to be an highly effective reducing agent to extract keratin from feathers with the advantage that the reducing agent gets oxidized and is removed, resulting in chemical residue–free keratin ( Poole and Church, 2015). (2009) with permission from Elsevier.įeathers were solubilized using various reducing agents (thioglycolate, potassium cyanide, or sodium sulfide) to obtain a keratin yield as high as 50% when sodium sulfide was used as the reducing agent ( Gupta, 2012a, 2012b). Digital pictures showing the dissolution of feathers after treating with the enzyme. Although high dissolution of feather could be achieved, it required considerably longer time (up to 4 days) for complete digestion.įigure 14.7. Fig. 14.7 shows the digital picture of feathers before and after enzyme treatment, which shows the complete dissolution ( Khardenavis et al., 2009). Up to 83.6% of the feathers could be solubilized by optimizing the treatment of feathers using the enzyme. ![]() HPC 1383, was isolated from tannery sludge and used to dissolve feathers. In another study, a feather-hydrolyzing enzyme, Serratia sp. Up to 21.6% weight loss was obtained for the feathers, which corresponded to a keratin yield of 17.7%, and the proteins obtained had molecular weight of 11–28 kDa ( Eslahi et al., 2013). Similarly, increasing hydrolysis time up to 4 h increased the total protein extracted beyond which the protein content remained stable. However, the reducing agent was found to decrease the activity. The addition of the surfactant and increasing concentration of the enzyme up to a certain level lead to a substantial increase in enzyme activity. For keratin extraction, feathers were treated with a commercially available protease (Savinase) with or without a reducing agent. Before the enzymatic treatment, feathers were washed with a nonionic detergent and calcium carbonate. The influence of enzyme loading, type of surfactant, concentration of reducing agent, and other parameters were varied using protease (Savinase) as the enzyme ( Eslahi et al., 2013). To avoid chemical extractions, enzymatic approaches (using keratinase) and hot water extraction have been used. Chemical extractions employ toxic and expensive chemicals and moreover destroy vital amino acids and may need multiple extraction steps ( Eslahi et al., 2013). Keratin is extracted from feathers through the cleavage of the intra- and intermolecular disulfide bonds and hydrogen bonds using reduction, oxidation, sulfolysis, and enzymatic and chemical and/or physical treatments.
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