Process Biochemistry 46 (2011) 1731–1737 Contents lists available at ScienceDirect Process Biochemistry journal homepage: www.elsevier.com/locate/procbio Total solubilisation of the chicken feathers by fermentation with a keratinolytic bacterium, Bacillus pumilus A1, and the production of protein hydrolysate with high antioxidative activity Nahed Fakhfakh ∗ , Naourez Ktari, Anissa Haddar, Ibtissem Hamza Mnif, Ines Dahmen, Moncef Nasri Laboratoire de Génie Enzymatique et de Microbiologie, Université de Sfax, Ecole Nationale d’Ingénieurs de Sfax, B.P. 1173-3038, Sfax, Tunisia article info Article history: Received 14 January 2011 Received in revised form 26 May 2011 Accepted 27 May 2011 Keywords: Feather protein hydrolysate Antioxidant activity Animal feed Bacillus pumilus abstract A feather protein hydrolysate was effectively produced using the keratinolytic bacterium Bacillus pumilus strain A1. In fact, complete feather degradation was achieved in medium containing up to 50 g/l of raw feathers. Cultivation of 50 g/l of feathers for two days, at 45 ◦ C and at initial pH of 10.0, resulted in maxi- mum production of amino acids and peptides (42.4 g/l). The feather protein hydrolysate (FPH) presents a very high in vitro digestibility (98%) compared with that of the untreated feathers (2%). Furthermore, the antioxidant activities of FPH were evaluated using in vitro antioxidant assays, such as 1,1-diphenyl- 2-picrylhydrazyl (DPPH) radical-scavenging activity and reducing power. Interestingly, FPH presents an important antioxidant potential with an IC 50 value of 0.3 ± 0.01 mg/ml. These results indicate that FPH may be useful as supplementary protein and antioxidants in animal feed formulations. © 2011 Published by Elsevier Ltd. 1. Introduction Feathers are produced in large amounts as a waste by-product at poultry-processing plants, reaching millions of tons annually throughout the world. Feathers, consisted mainly of keratin char- acterized by its high recalcitrant nature, could be an important protein source in animal feedstuff. Currently, some industries produce feather meal by steam pressure cooking, which require high-energy input. The resulted feather meal is deficient in methionine and histidine which limit its use in animal feed [1]. Nutritional enhancement of feathers can be achieved by hydrolysis with feather-degrading microorganisms. Hydrolysis of kerati- nous wastes by microorganisms possessing keratinolytic activity represented an attractive alternative method for their efficient bioconversion and improving their nutritional value. The poten- tial applications of such microbial keratinases have been recently reported by Gupta and Ramnani [2]. In fact, several microorgan- isms were known to degrade keratinous substrates such as fungi [3–5], actinomycetes [6,7] and some Bacillus species [8–13]. Chick- ens fed by feather hydrolysate produced by Bacillus licheniformis and supplemented with amino acids grow as well as chickens fed by soybean meal [14]. ∗ Corresponding author. Tel.: +216 74274088. E-mail address: nahedfakh zouari@yahoo.fr (N. Fakhfakh). In recent years, hydrolysed proteins from many animal and plant sources have been found to possess antioxidant activity, such as milk casein [15], soybean [16], rice bran [17], quinoa seed protein [18], canola [19], egg yolk protein [20] and porcine myofibrillar proteins [21]. However, no antioxidant activity was reported in the poultry feather protein hydrolysate. To the best of our knowledge, this is the first report highlighting the antioxidant potential of such keratinous waste hydrolysate which could be an important protein source in feed formulations for fish or domestic animals. Fish feeds containing high levels of polyunsaturated fatty acids are susceptible to lipid oxidation. Presently, fish feeds are protected with synthetic antioxidants, mainly ethoxyquin (EQ) and butylated hydroxytoluene (BHT) [22]. Recently, there is a substantial carry- over of these antioxidants to the fish fillet and the mandatory 2 weeks starvation period before slaughter of farmed fish is not suf- ficient for clearance of these antioxidants from the fillet [22,23]. Therefore, a switch to natural antioxidants in fish feed ingredi- ents would be an advantage both for the aquaculture industry and with regard to consumer health and well-being. Furthermore, the relationship between nutrition and animal health has long been recognized. Animal’s morbidity and mortality can be explained partly by impaired immune responsiveness. Therefore, the role of natural antioxidants in immunity and health in food animals is of prime importance [24]. This study reports the production of feather protein hydrolysate (FPH) by Bacillus pumilus A1, isolated from a local slaughter house 1359-5113/$ – see front matter © 2011 Published by Elsevier Ltd. doi:10.1016/j.procbio.2011.05.023