TABLE 2.
Some strains exhibited keratinase activities and are able to degrade feathers.
| Strain | Remarks | References |
| Trichoderma harzianum | A medium containing feather waste was used for enzyme production by strain HZN12 | Bagewadi et al., 2018 |
| Trichoderma atroviride | A 21 kDa keratinase was obtained from F6 strain | Cao et al., 2008 |
| Meiothermus taiwanensis | The strain WR-220 produced a heat stable enzyme with structure determined. The presence of disulfide bonds might be responsible for the high stability | Wu et al., 2017 |
| Fusarium sp. | This strain was found to be efficient in keratin degradation | Cǎlin et al., 2017 |
| Aspergillus niger | Mutants originated from the strain exhibited different keratinase activities | Mazotto et al., 2013 |
| Aspergillus parasiticus | A 36 kDa keratinolytic protease was purified from this strain | Anitha and Palanivelu, 2013 |
| Purpureocillium lilacinum | A 37.0 kDa keratinolytic serine protease was produced by this strain. The enzyme was stable in the presence of organic solvents and detergents | Cavello et al., 2013 |
| Scopulariopsis brevicaulis | A strain was able to produce a 28.5 kDa keratinase | Sharaf and Khalil, 2011 |
| Streptomyces sp. | A proteinase was obtained from strain AB1 with a molecular weight of 29.9 kDa | Jaouadi et al., 2010 |
| Both submerged and solid-state fermentations were used in keratinase production by strain 594 | De Azeredo et al., 2006 | |
| Several strains have been shown to be able to degrade feathers. Antibiotic activity was also observed in these strains | Pettett and Kurtböke, 2004 | |
| Fermentation conditions are critical for keratinase production | Tatineni et al., 2007 | |
| Microsporum canis | The keratinase from this stain was overexpressed and purified from yeast | Descamps et al., 2003 |
| Microsporum gypseum | This strain was used to evaluate keratinase activity. Strains isolated from different resources exhibited different expression levels | Weary et al., 1965; Giudice et al., 2012 |
| Nocardiopsis sp. | A strain was able to produce a variety of alkaline hydrolytic enzymes which were stable under acetic conditions | Mitsuiki et al., 2002 |
| Streptomyces fradiae | A strain was able to produce a 24 kDa keratinase which was active at alkaline pH and also cleaves ester and amide bonds formed by the residues of aromatic and basic amino acids | Galas and Kaluzewska, 1992 |
| Streptomyces albidoflavus | A stain was able to produce at least six proteases when it was grown in feather meal. A new enzyme SAKase with molecular weight of 18 kDa was identified | Bressollier et al., 1999 |
| Streptomyces gulbargensis | A feather degrading strain produced keratinase that was stable at 45°C and pH 9.0 for 120 h | Syed et al., 2009 |
| Streptomyces pactum | A 30 kDa protease was identified. This protease specifically cleaves substrates with Arg and Lys residues at the P1 site | Böckle et al., 1995 |
| Disulfide reduction was observed for the strain | Sangali and Brandelli, 2000 | |
| Streptomyces fradiae | A feather-degrading strain produced a 454 amino acids protease which can be overexpressed in E. coli and resulting product with a molecular weight of 25.6 kDa | Meng et al., 2007 |
| Streptomyces thermoviolaceus | A strain was able to produce keratinase with a molecular weight of 40 kDa | Chitte et al., 1999 |
| Amycolatopsis | The feather-degrading strain grown in feather medium could produce anti-fungus agents | Tamreihao et al., 2017 |
| Actinomadura | A 29 kDa protease was produced by this strain grown in feather medium. The enzyme was stable at higher temperature and in detergent | Habbeche et al., 2014 |
| Scopulariopsis brevicaulis | This strain was able to produce keratinase while this stain might be of secondary importance in the mineralization of keratinic substrates | Filipello Marchisio et al., 2000 |
| Trichophyton mentagrophytes | This strain was able to produce keratinase using keratin-rich material. This stain was able to produce a 41 kDa keratinase whose PI was 3.9 | Yu et al., 1968; Tsuboi et al., 1989 |
| Doratomyces microsporus | A 30 kDa keratinase was purified and able to degrade different keratin materials | Gradišar et al., 2000 |
| Trichophyton rubrum | This stain was able to produce keratinase using different substrates | Sharma et al., 2012 |
| Microsporum canis | The keratinase activity plays a role in virulence of this fungus | Viani et al., 2001 |
| Candida albicans | KPase was able to be produced and exhibited an optimal pH of 4.0 | Negi et al., 1984 |
| Aspergillus flavus | A 31 kDa keratinase was produced when this strain was cultured in a feather-containing medium | Kim, 2007 |
| Candida parapsilosis | Treatment of the strain could enhance keratinase activity | Duarte et al., 2011 |
| Chrysosporium articulatum | A strain was able to produce keratinase using feathers as sole carbon and nitrogen sources | Bohacz, 2016 |
| Aphanoascus fulvesnces | This stain was isolated from soil and able to degrade feathers | Bohacz, 2016 |