LAUSR

Abstract Several microbial proteases were reported for dehairing; however, they become unstable and lose the activity at alkaline conditions during the process. Hence, there is a need for protease that withstands its activity at high pH. This work attempts to screen and isolate alkaline protease from marine Streptomyces. An alkaline protease producing strain Streptomyces sp. GS-1 was isolated from the backwaters of Munanbam and Valapad, Kerala, India. Growth characteristics and protease production were investigated in 10 different basal media (BM) supplemented with four different substrates viz. skim milk, casein, wheat bran and rice bran. Maximum protease production was detected in BM2 medium with wheat bran after 9.5 days of incubation. The activity of extracted protease was found to be 341 U/ml and a correlation coefficient of 0.9532 between growth and enzyme production was observed. The crude enzyme exhibited maximum activity at 45 °C and pH 8.5. The Km and Vmax values of the enzyme were determined as 5.29% and 32.25 μmol l−1 min−1 mg−1, respectively, using 1% casein as substrate. The enzyme sustained its activity at high temperature (50 °C for 8 h), alkaline pH (8–10) and in the presence of metal ions and organic solvents. The purified enzyme was inhibited by phenylmethylsulphonyl fluoride (PMSF) suggesting it belongs to serine protease. The enzyme displayed dehairing property and successfully removed the hair follicles as tested in goat hide. Thus, the enzyme extracted from Streptomyces sp. GS-1 was found to be effective in dehairing during leather processing.