Study On Extraction Of Keratin From Poultry Feather And Hydrolysis Of The Keratin To Prepare Peptide Surfactant In Sub-critical Water

Bio-surfactants are eco-friendly surfactants, because of its non-toxic, non-irritating, excellent biocompatibility and environmental compatibility, bio-surfactants have broad application prospects in chemical industry, food industry, pharmaceutical industry, agriculture and so on. Peptides are one kind of bio-surfactants, it can be obtained from hydrolysis of protein. The poultry industry produces a great amount of feather each year in China but most of them are discarded. Feather is mainly composed of protein sources, therefore, this thesis focus on the extraction of keratin with ionic liquid and hydrolysis of keratin into peptide surfactant in subcritical water.The first is the dissolution of feather in ionic liquids(ILs). ILs have drawn intense attention because of superior properties. Several common imidazole ILs were selected to dissolve feathers and [Bmim]Cl has the best dissolution rate. The addition of Na2SO3 to the extracting system should accelerate the dispersion of keratin from feather into liquid phase and increases the dissolution rate and yield of keratin. Some amount of water increases the dissolution of Na2SO3 and decreases of viscosity of IL.The FTIR spectrum of the extracted keratin shows it still forms the secondary structure similar with feather fibers. The analysis of amino acids of feathers and extracted keratin shows the main amino acids are almost the same, indicating that the proteins of extracted keratin and feathers should be the same.The yield of keratin can attain 75.1% under extraction time of 60 min at 90℃, with 20 wt.% of water in IL-water, weight ratio of liquid/feather of 20, and 10 wt.% Na2SO3. IL could be reused up to 3 times with no apparent decrease in the efficiency of the extraction.The second is sub-critical hydrolysis of feather keratin to produce peptide surfactant. Sub-critical water is a green solvent and has broad application prospects. Keratin is hydrolyzed partially through controlling reaction temperature and time. The hydrophilic and hydrophobic groups are released from a dense structure.The liquid product is derivatized by biuret to determine the yield of peptide. The effects of weight ratio, reaction temperature and time were examined. It shows that the hydrolysis rate of keratin was 94.9% and the yield of peptide was 84.8% at following conditions: liquid-solid ratio 10, hydrolysis temperature 180°C and time 60 min.The last are some performance tests of hydrolysate, and the results were compared with the similar performance tests of sodium dodecyl benzene sulfonate(SDBS). Foaming ability gradually increases with increasing concentration, eventually reach equilibrium. Foam stability is basically maintained at around 90%.Foaming ability of peptide is somewhat less than SDBS, while the emulsion ability is a little stronger than SDBS. The emulsion ability of peptide declines sharply when p H value is 4, due to the isoelectric point of the solution is near 4.The surface tension of peptide solution gradually decreases with the increase of concentration. CMC is 2.6 g/L, and the surface tension is 48.2m N/m. Comparing with copper and plastic sheets, the peptide solution has better wettability on glass sheet.