Short communication Potential use of wool-associated Bacillus species for biodegradation of keratinous materials A. Catarina Queiroga a, b , Manuela E. Pintado a , F. Xavier Malcata c, d, * a CBQF/ESB, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200-072 Porto, Portugal b Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Tapada da Ajuda, P-1349-017 Lisboa, Portugal c ISMAI e Instituto Superior da Maia, Avenida Carlos Oliveira Campos, Castêlo da Maia, P-4475-690 Avioso S. Pedro, Portugal d CEBAL e Centro de Biotecnologia Agrícola e Agro-alimentar do Baixo Alentejo e Litoral, Rua Pedro Soares, Apartado 6158, P-7801-908 Beja, Portugal article info Article history: Received 26 July 2011 Received in revised form 12 December 2011 Accepted 13 December 2011 Available online 5 March 2012 Keywords: Hair Nail Feather Keratinase Protease Novel strains abstract Five wool-degrading bacterial strains were selected from a set of 115 isolates from a less conventional source, i.e., the wool of Portuguese Merino sheep, based on their promising keratinolytic abilities. All selected strains belong to the genus Bacillus, probably Bacillus subtilis/licheniformis, according to 16S rRNA sequencing. They were able to grow on and hydrolyse feathers and wool (in both native and milled forms), and human hair and nails to a lesser extent. The maximum keratinase activity was recorded on milled chicken feathers. Biodegradation of such keratin-rich matrices increased the amount of soluble proteins in the fermentation broth and implied the action of extracellular enzymes from those adventitious micro- organisms. Therefore, such novel strains have a potential for effective use in solid waste management strategies encompassing keratin-rich materials based on submerged fermentation. Concomitantly, the nutritional value of the broth may be improved for eventual formulation of animal feed. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Keratin-rich materials, such as hair, wool, feather, horn, hoof, claw, nail, and beak, are quite abundant in nature. In view of the intrinsic stability and insolubility of these proteins, said materials are resistant to degradation carried out by most proteo- lytic enzymes (Lateef et al., 2010). The complex structure of a- and b-keratins e including the presence of a high degree of disulfide crosslinking, numerous hydrogen bonds, and strong hydrophobic interactions, has been implicated in their recalcitrant characteris- tics (Riessen and Antranikian, 2001; Riffel and Brandelli, 2006). Despite the great resistance of keratins to enzyme attack, keratin-rich materials do not accumulate in nature to excessive levels. This suggests the existence of natural decomposers (or users) of such matrices (Lucas et al., 2003). Keratinolytic activity has indeed been reported in several fungi, and especially gram-positive bacteria (Gradisar et al., 2005); those best studied to date are keratinases from dermatophytic fungi, as well as from bacteria belonging to the Bacillus and Streptomyces genera (Daroit et al., 2009). Textile and agro-industrial processes produce large amounts of keratin-rich wastes that pose serious environmental and sanitary problems. Hence, efficient ways to degrade/recycle them are urged. Classical processing of keratinous wastes from the poultry and leather industries encompasses alkali hydrolysis and steam pressure-cooking, which release digestible dietary proteins that are safe for animal feeding (Mazotto et al., 2010). However, these physicochemical treatments are expensive and energy-consuming, and lead as well to loss of integrity of certain amino acids (Haddar et al., 2010). Hence, establishment of low-environmental-footprint conditions is urged in the search for cleaner processes. Keratinases have received increased interest with realization that microbial degradation of keratin-rich matrices occurs spon- taneously in nature e so alternative, eco-friendly routes were hypothesized to upgrade agro-industrial byproducts under mild reaction conditions (Adıgüzel et al., 2009; Haddar et al., 2010). Furthermore, microbial keratinases may have applications in the textile industry (e.g., modification of wool fibers) and in the phar- maceutical industry (e.g., production of bioactive peptides, as well as personal-care hair-removal and peeling agents). Finally, kerati- nases have been reported in the production of bio-hydrogen, biodegradable films, and keratin composites; and in medicine, keratinases may find applications in breakdown of prions and * Corresponding author. Instituto Superior da Maia, Avenida Carlos Oliveira Cam- pos, Castêlo da Maia, P-4475-690 Avioso S. Pedro, Portugal. Tel.: þ351 968 017 411. E-mail address: fmalcata@ismai.pt (F.X. Malcata). Contents lists available at SciVerse ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod 0964-8305/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.ibiod.2011.12.013 International Biodeterioration & Biodegradation 70 (2012) 60e65