Chicken feathers comprise _ % of our waste. In the US alone, 2 billion pounds of
chicken feathers are produced by the poultry industry.
(http://www.ars.usda.gov/is/kids/animals/story1/story1.htm). Chicken feathers, by
nature, are made up of over 90% protein (Cheng-cheng et al., 2007). And this protein is
none other than keratin. It’s actually the most abundant protein. It is not easily degraded
due to its tightly packed structural arrangement which is in the form of alpha keratin or
beta keratin. The key to its stability lies on the cross-linking by disulfide bonds,
hydrophobic interactions, and hydrogen bonds. Such stability renders keratin water-
insolube and non-degradable by the enzymes papain, trypsin and pepsin. (Gradisar et
al., 2005). In a study conducted by Onifade et al., 1998 and Gousterova et al., 2005, as
cited in the journal of Cheng-Cheng et al., 2007, the build-up of chicken feathers in the
environment and landfills would only result to future pollution problems and protein
wastage. More so, its accumulation could serve as a breeding ground for a variety of
harmful pathogens (Chandra, 2002).
Considering that chicken feathers have a high protein content it could also be
used as an animal feed, but first its protein must be degraded (Tapia and Contiero,
2008). Yet this is said to need so much water and energy (Frazer, 2004). Old methods
of degrading the chicken feathers such as alkali hydrolysis and steam pressure cooking
are no longer advisable. They cause so much energy wastage and they unfortunately
destroy the configuration of proteins. (Cheng-cheng et al., 2007).
Incineration is also a method used in degrading such waste but it causes so much
energy loss and carbon dioxide build-up in the environment. Other methods of disposal
are landfilling, burning, natural gas production and treatment for animal feed. But
subjecting it to burning and land filing costs a lot and it contributes air, soil and water
contamination. (Joshi et al., 2007).
A wiser suggestion or approach would be the use of microbes in degrading these
chicken feathers. (Cheng-cheng et al., 2007). Such approach is said to an economical
and environment-friendly alternative (Joshi et al., 2007). Experiments that tested on the
degradation of chicken have already been done. In fact, studies have already proven
that keratinolytic microbes such as Bacillus (Maczinger et al., 2003; Rodziewicz and
Wojciech, 2007; Joshi et al.,2007) , fungi ( Gradisar et al., 2005) and actinomycetes
(Gousterova et al., 2005). The enzymes that perform keratin degradation are called
keratinase, which could degrade feathers and make it available for its use as animal
feed, fertilizer and natural gas. The enzymes are said to degrade the beta-keratin
component and the main idea behind such biodegradation is that the microbes use the
feather as their carbon, nitrogen, sulfur and energy for their nourishment. (Joshi et
al.,2007 ; Manczinger et al., 2003).
Keratinases isolated from microbes have various economic uses. Aside from its
feather degrading capacity, it could be used in the leather industry as an agent in
dehairing leather. Its by-product, the feather hydrolysate, could also be used as animal
feed additive. (Joshi et al., 2007). Furthermore, potentially, the said hydolysate could be
used in the generation of organic fertilizer, edible films and amino acids which are
considered rare, as cited by Brandelli in the journal of Joshi et al., 2007.
In terms of experimental procedures, various methods are used in determining
the keratinolytic ability, which means it could produce keratinase and hence degrade
chicken feather, of microbes. A particular study by Tapia and Contiero 2008, used a
feather meal agar, wherein the feather served as the source of carbon, nitrogen, sulfur
and energy, in cultivating the isolated microbe Streptomyces. The growth, which
occurred on the 10th day of incubation, through colony formation of the microbe
indicated that it utilized the feather as a source of its nutrients. After which, its
keratinolytic activity was tested using a modified keratin azure protocol. Another study
by Maczinger et al. 2003 focused on the isolation of a microbe from the poultry waste
that could degrade feathers. During the preliminary elimination, they cultured the
different population of bacteria found in a partially degraded feather in a basal medium
with sterilized feathers serving as its source of carbon, nitrogen and sulfur. It was then
rotated in an orbital shaker for 10 days. After 4 days, one flask which showed a visual
degradation of the feather. A dilution series was made afterwards so as to isolate and
culture the bacteria that just degraded the feather. The strain was identified as Bacillus
lichenformis strain K-508. And the confirmation of the keratinolytic activity was done by
using the azokeratin as a substrate assay.
Isolation of a new microbial organism that could degrade chicken feather will help
in the degradation of the chicken feathers which is now becoming a burden in the
society both internationally and locally. The microbe could potentially provide the
keratinase that could be used in compost technology (Maczinger et al., 2003) or in the
conversion of feather to feedstock meal additives (Tapia and Contiero, 2008).