Expression of the Bacillus licheniformis PWD-1 keratinase gene in B. subtilis

The kerA gene which encodes the enzyme keratinase was isolated from the feather-degrading bacterium Bacillus licheniformis PWD-1. The entire gene, including pre-, pro- and mature protein regions, was cloned with Pker, its own promoter, P43, the vegetative growth promoter, or the combination of P43-Pker into plasmid pUB18. Transformation of the protease-deficient strain B. subtilis DB104 with these plasmids generated transformant strains FDB-3, FDB-108 and FDB-29 respectively. All transformants expressed active keratinase in both feather and LB media, in contrast to PWD-1, in which kerA was repressed when grown in LB medium. With P43-Pker upstream of kerA, FDB-29 displayed the highest activity in feather medium. Production of keratinase in PWD-1 and transformants was further characterized when glucose or casamino acids were supplemented into the feather medium. These studies help understand the regulation of kerA expression and, in the long run, can help strain development and medium conditioning for the production of this industrially important keratinase.