Abstract
In black feathers, melanin is embedded in keratin matrix that makes feather more resistance to the microbial degradation. Chryseobacterium sp. RBT previously isolated from the poultry waste disposable site revealed strong sulfitolytic and keratinolytic activities. Maximum keratinase activity was observed at 48 h (89.12 U ml−1) showed 83 % of native black feather degradation. The concentration of free sulfhydryl groups released during degradation was 0.648 × 10−4 M (12 h), 2.144 × 10−4 M (96 h), and however, declined on prolong incubation to 1.752 × 10−4 M (120 h). Melanin was released in the degradation medium after microbial exploitation of black feather. After purification, melanin was dark brown colored powder insoluble in water, 5 M HCL, ethanol, methanol, benzene, chloroform, and acetone; whereas, soluble in KOH and NaOH. On exposure to oxidizing and reducing reagents feather melanin showed decolorization, while formed a brown precipitate when reacted with FeCl3. The spectroscopic characterization of isolated melanin demonstrated absorption at infra-red region. Similarly, UV–visible scan confirmed that increase in the wavelength progressively declined the absorbance of pigment. The crude keratinase enzyme (2 % v/v) produced during degradation showed complete dehairing of goat skin within 20 h.
Highlights
In birds, feather pigmentation mainly depends on the components, such as keratin and melanin, having different refractive indexes
The native black feathers were degraded (83 %) within 48 h, by releasing melanin embedded in the feather matrix (Fig. 1)
An increase in the pH from 7.5 to 8.8 was observed. This tendency of medium alkalinity was attributed due to the deamination reactions leading to release of ammonia from protein, peptides, and amino acids. Such increase in pH during feather degradation is the important indication of high keratinolytic potential of the microorganisms (Riffel et al 2003)
Summary
Feather pigmentation mainly depends on the components, such as keratin and melanin, having different refractive indexes. Melanin is embedded in the b-keratin matrix arranged in a complex array of feather barbules (Durrer 1986). Melanin provides structural rigidity to feathers by cross-linking with proteins and making them more resistant against feather feeding microorganisms and ecto-parasites (Burtt 1986; Goldstein et al 2004; Gunderson et al 2008). Wilson et al (2007) in their study with archaeological contexts found that microbial activity degraded only keratin without affecting the melanin. Goldstein et al (2004) and Gunderson et al (2008) demonstrated the degradation of melanized feathers using Bacillus licheniformi and B. licheniformi OWU 138B and concluded that melanized feathers where unable to biodegrade
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