2.2. Screening for extracellular keratinase production on solid
screening media
Initial screening for extracellular keratinolytic protease activity
was undertaken by applying extracellular fermented hydrolysate
into a well on milk agar and keratin plates prepared as described by
Paul et al. (2013a). The previously maintained media components
were autoclaved separately and cooled to 50 C before mixing:
0.25 g skim milk powder in 50 mL distilled water and 2 mL of
keratin solution (0.125 g mL1) in 48 mL of distilled water and
incubated at 45 C for 42 h. For detection of extracellular keratinolytic
protease activity, plates were flooded with 10% tannic acid
(Saran et al., 2007) after incubation and examined for hydrolysed
zones indicating milk protein and keratin hydrolysis.