Streptomyces sp. MM-3 from rhizosphere of Psidium Guajava: A potential candidate for protease with dehairing properties

Soil is the richest medium for isolation of microbial flora especially genus Streptomyces as potent source of extracellular enzymes. Soil samples from rhizosphere of guava plant (Psidium guajava) were screened for proteolytic bacteria. Among all isolates, Streptomyces sp. MM-3 showed best proteolytic activity by utilizing agro-based substrates like malt, soybean, wheat bran and peels of ground nuts as carbon/nitrogen sources. Optimum incubation time for enzyme production was 96h (420U/ml), while optimum age and size of inoculum was 24 h (95 U/ml) and 10% (482 U/ml), respectively. Maximum units of protease were observed with 0.5% starch (396U/ml) and 1% gelatin (439 U/ml). Application of partially purified protease on sheep and goat skins resulted in a highly promising dehairing efficiency as an alternative of lime-sulfide chemical unhairing process. Enzyme-treated dehaired leather was processed further through other pre-tanning steps like liming, fleshing, deliming and pickling. Final leather crust from chrome blue pelt showed high degree of tear strength (40.93 ± 4.21) N/mm k=2, good tensile strength (16.58 ± 2.31) N/mm k=2 and elongation (155.08 ± 5.97) N/mm k=2 comparing to lime-sulfide unhairing process. Other significant advantages of enzymatic dehairing were total recovery of hairs, simplification of pre-tanning process and reduction in use of sodium sulfide. Thus producer strain Streptomyces sp.MM-3 of soil origin emerged as a potential candidate for the production of protease using low-cost production medium to be utilized by leather industry.