Bioprospecting Psychrotrophic Bacteria for Serine-Type Proteases from the Cold Areas of Western Himalayas

Bioprospecting Psychrotrophic Bacteria for Serine-Type Proteases from the Cold Areas of Western Himalayas:

Abstract

The aim of present study was to analyze the prevalence of protease diversity among psychrotrophic bacteria in Lahaul and Spiti of the Western Himalayas. A total of 459 bacteria were screened and protease activity was observed in 150 isolates at 5 °C. Furthermore, 55 isolates showed protease activity up to pH 10 at 5 °C. Based on the hydrolytic zone, 22 isolates were selected for protease quantification. The protease activity varied from 58–377 U mL⁻¹ at 10 °C, 49–396 U mL⁻¹ at 28 °C and 31–407 U mL⁻¹ at 37 °C. Similarly, protease activity ranged from 36–353 U mL⁻¹ at pH 7, 40–306 U mL⁻¹ at pH 9 and 33–304 U mL⁻¹ at pH 10. The isolates were identified based on 16S rRNA gene sequencing and showed phylogenetic relationship to Arthrobacter belonging to the class Actinobacteria, Bacillus, Exiguobacterium, Paenibacillus, and Planomicrobium to Bacilli, and Pseudomonas, Serratia, and Stenotrophomonas to Gammaproteobacteria. Zymogram analysis revealed variations in protease isoforms ranging from 20 to 250 kDa which were strongly inhibited in the presence of phenylmethylsulfonyl fluoride, thus indicated serine-type nature. The extensive number of serine proteases among these bacteria was confirmed by annotating genomes of the reported genera for prevalence of protease isoforms. The properties of proteases including low-temperature activity with alkaline stability and detergent compatibility suggested their suitability as bio-additives in laundry.