Study of nano-hydroxyapatite tagged alkaline protease isolated from Himalayan sub-alpine Forest soil bacteria and role in recalcitrant feather waste degradation.

Purified calcium serine metalloprotease from Stenotrophomonas maltophilia strain SMPB12 exhibits highest enzyme activity at pH 9 and temperature range between 15 °C-25 °C. Enzyme supplemented with 40 µM Ca-Hap-NP (NP-protease) showed maximum elevated activity of 17.29 µmole/min/ml (1.9-fold of original protease activity). The thermostability of the enzyme was maintained for 1 h at 60 °C over an alkaline pH range 7.5-10, as compared to the NP untreated enzyme whose activity was of 8.97 µmole/min/ml. A significant loss of activity with EDTA (1.05 µmole/min/ml, 11.75 %), PMSF (0.93 µmole/min/ml, 10.46 %) and Hg2+ (3.81 µmole/min/ml, 42.49 %) was also observed. Kinetics study of NP-protease showed maximum decreases in Km (28.11 %) from 0.28 mM (NP untreated enzyme) to 0.22 mM (NP-protease) along with maximum increase in Vmax (42.88 %) from 1.25 µmole/min/ml to 1.79 µmole/min/ml at varying temperatures. The enhanced activity of NP-protease was able to efficiently degrade recalcitrant solid wastes like feather to produce value-added products like amino acids and helps in declogging recalcitrant solid wastes. The nano-enabled protease may be utilized in a smaller amount for degrading in bulk recalcitrant solid proteinaceous waste at 15 °C temperature as declogging agents providing an eco-friendly efficient process.