Secretion of a trypsin-like thiol protease by a new keratinolytic strain of Bacillus licheniformis

Abstract

When cultured in feather-containing broth with a growth optimum of pH 7.0 and 47°C, a Bacillus licheniformis strain exhibited a high chicken feather-degrading activity. A trypsin-like protease was isolated from its ferment broth and was partially characterized. The enzyme was constitutively secreted and was highly active towards N-benzoyl-Phe-Val-Arg- p-nitroanilide as chromogenic substrate. Its pH optimum was 8.5 and it exhibited the highest activity at 52°C. Fractionation on Sephadex G-100 column revealed that its molecular mass was about 42 kDa. The enzyme, which is new for the genus Bacillus, is a thiol protease, as tosyl- L-phenylalanine chloromethyl ketone, tosyl- L-lysine chloromethyl ketone, phenylmethylsulfonyl fluoride and ethylenediamine tetraacetate did not inhibit it, while HgCl 2 and para-chloromercuribenzoate lowered its activity.