Optimization of Keratin Hydrolysate Extraction from Tannery Sheep Hair Waste

Abstract

Tannery hair wastes are becoming a challenge for tanners regarding environmental pollution control and human health. In this study, an experiment had been designed to hydrolyse sheep hair in an alkaline medium, and the operational condition for the alkaline extraction of KH has been modeled and optimized. The structure, morphology, functional groups, particle size, and molecular mass of the KH extracts were evaluated experimentally by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), particle size analysis, and SDS-PAGE analysis, respectively. FTIR analysis of the extract confirmed the presence of carboxylic, amide, and aldehyde functional groups and alkyl side chains of amino acids. The molecular weight of the extracted keratin ranges between 3–15 kDa, and X-ray diffraction (XRD) analysis showed an amorphous form of structure with two peaks at 2 theta of 9.36° and 21.16° due to α -helix and β - sheet structure in keratin. Response surface methodology (RSM) coupled with BOX-Behnken design was applied as a statistical tool to investigate the effect of extraction time, the concentration of the hydrolysing agent, and temperature on the response variable (yield of keratin protein). The concentration of the hydrolysing agent was found to be the most significant factor affecting the speed of extraction, but its gradual increase tends to affect the protein content of the extract. Optimum parameters of 0.5 N, 80°C, and 3.5 hr were obtained for the concentration of NaOH, temperature, and extraction time, respectively, with a maximum average protein yield of 91.5% and a percentage total nitrogen content of 14.6% using the Kjeldahl method and 86.57% using the biuret test method.

Keratin hydrolysate as a chrome exhaust aid and keratin filler in leather processing: A cleaner technology approach for tannery solid waste management and leather manufacturing

“…This indicates that the experimental extract has relatively less hazardous inorganic oxides and salinity compared with most commercial retanning agents and the higher ash percentage indicates an excessive amount of the hydrolyzing agent employed. The findings suggests that the lesser ash contents are more likely to be green because ash content is a key feature of any retanning agents manufactured and employed in the leather manufacturing [ 40 ]. Furthermore, one of the biggest issues facing the tanning industry is the treatment of wastewater containing a high salt load.…”

“…The extracted keratin has been used for a wide range of applications, such as for fertilizer industries [ 27 ]; for industries producing animal feeds [ 28 , 29 ]; as a biomaterial for example, for the production of keratin-based bioplastic films from chicken feathers [ 21 , 30 , 31 ]; as a biomedical material using sodium sulfide-based extraction [ 32 ]; as an industrial application of tannery wastewater treatment to adsorb chromium [ 12 , 33 ]; and as a replacement for salt in textile processing to enhance dyestuff uptake [ 26 , 34 ]. Therefore, many keratin sources, including waste chicken feathers, wool waste from the textile and wool processing industries, hog hair, horn meal, hoofs, nails and tannery hair waste, have been used for the extraction of keratin hydrolysate [ 27 , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] ]. It is slowly becoming more common to produce biobased retanning and chrome exhaust aids, as well as use them in the production of leather.…”

Process optimization, antioxidant, antibacterial, and drug adjuvant properties of bioactive keratin microparticles derived from porcupine (Hystrix indica) quills

“…It has been found that the rate of protein solubilization is directly proportional to the hydrolyzing agent concentration and temperature when keratin is extracted from sheep’s hair. The types and numbers of bonds in the polypeptide are primarily connected to the optimum parameters, which were discovered to be 80 °C, 0.5 N, and 3.5 h. The protein’s sulphide link is easily broken by temperature, allowing the protein to disintegrate ( Mengistu, Angassa & Tessema, 2023 ). In other reports, the yield percentage and absorption of extracted keratin in hydrolysate increase in response to change in the extraction time, NaOH concentration, and pH ( Teklemedhin, 2018 ).…”

Amino Acids Isolation from α-keratin of Javanese Goat (Capra hircus) Hair and Garut Sheep (Ovis aries) Hair Waste Using Acid Hydrolysis Method as BCAA Supplement

“…However, it is still higher than the keratin yield from sheep hair hydrolyzed with Br ions at 100°C and sheep hair hydrolyzed with choline thioglycolate at 130 °C 38 (Table 1). This is attributed to the influence of the temperature used during hydrolysis 36,39 . Keratin precipitation occurs due to the addition of HCL.…”

“…These are rich in cysteine and contain fewer amounts of hydroxyproline and proline amino acids. However, β-keratins are present in the hard tissue protein of bird feathers, fish scales, nails, and others 8 .…”