Short communicationRational protein engineering approaches to further improve the keratinolytic activity and thermostability of engineered keratinase KerSMD

- Site-directed mutagenesis increased secretion and catalytic activity of FDD.
- C-terminus fusion increased thermostability and substrate specificity of DDF.
- Y215F showed 3-fold increase of extracellular activity compared to FDD.
- DDFD owned outstanding performance between t1/2 and keratinolytic activity.

Keratinase has great potential to convert poultry waste into feed or fertilizers. In order to obtain excellent keratinase variants with improved thermostability and activity to degrade feather waste, we did rational protein engineering approaches. Using site-directed mutagenesis on keratinase FDD, two variants (Y94F and Y215F) showed higher extracellular keratinolytic activity and specific activity in Escherichia coli expression system. The C-terminus fusion on keratinase DDF created a new variant DDFD with the highest substrate specificity and keratinolytic activity of 6220 ± 20 U/mg. Besides, the performance of thermophilicity and theromostability of the variants was evaluated. The A218S and A218G showed more than 30% improvement of relative activity at 70 °C while DDFD owned the most outstanding comprehensive performance between half-life (t1/2 = 146 min) and keratinolytic activity. It is highly effective to obtain excellent keratinases by site-directed mutagenesis and C-terminus fusion based on model structure analysis, and it provides possibility of industrial application of new keratinases.