Feather keratin hydrolysates: enzymatic method
Bacillus subtilis AMR was inoculated in a medium
containing yeast extract 0.5%, peptone 0.5%, KCl 2.0%
and sucrose 2.0%. After 48 hours at 28°C the bacteria
were washed three times with saline 0.85%. The inoculums
(108cell/ml) were added to 1 L of feather medium
(yeast extract 0.01%, KCl 2.0% and supplemented with
chicken feather 1%). The feathers were obtained from
poultry waste and were previously washed with water
and detergent, delipidated with chloroform: methanol
(1:1, v/v) and dried at 60°C before use. The culture
was grown for 5 days at 28°C/ rev min−1 in an orbital
shaker. The crude feather keratin hydrolysate was obtained
by centrifugation for 20 min at 2000 g. The supernatant
containing the hydrolysates was concentrated further by
ultrafiltration (Millipore) in an Amicon YC 05 system (1000
Daltons, NMWL, Nominal Molecular Weight Limit). The
hydrolysates recovered corresponded to the enzymatic
keratin hydrolysates.
Keratinases and gelatinase assays