Partial purification, characterization and application of thermoalkaliphilic proteases from Priestia endophytica, Lysinibacillus cresolivorans and Bacillus subtilis isolated from desert soil

Aims: Thermophilic proteases are important industrial enzymes because they can be used at high temperatures in various bioprocessing schemes. The bacterial population of the Cholistan desert was explored for thermophilic proteases and their industrial applications. Methodology and results: Three bacterial isolates K1, K5 and K7 were found promising protease producers. These isolates were preliminary identified as Bacillus based on morphological characteristics and biochemical tests (positive for catalase, oxidase and citrate tests, and negative for indole and urease tests). The isolates K1, K5 and K7 were further identified as Priestia endophytica, Lysinibacillus cresolivorans and Bacillus subtilis, respectively by phylogenetic analysis. The isolates grew best at 50 degrees C and P. endophytica (K1), L. cresolivorans (K5) and B. subtilis (K7) produced larger zones of hydrolysis at 37 degrees C, 45 degrees C and 50 degrees C at pH 7, respectively. The optimum temperature where protease activity was maximum was 65 degrees C for P. endophytica and L. cresolivorans and 55 degrees C for B. subtilis, and the optimum pH was 9. Conclusion, significance and impact of study: The proteases produced by these isolates were found active at high temperatures (45 degrees C to 85 degrees C) and high pH (9-12), which make them industrially important thermoalkaliphilic proteases. These proteases successfully de-haired cow's skin and de-stained blood from cotton cloth pieces, which are rarely tested applications of these proteases.