Isolation and recognition of keratinolytic bacteria strains based on their biochemical and molecular properties

Increasing amount of resistant keratin wastes which originated from byproducts of agricultural industry is as an environmental issue. Keratinolytic enzymes secreted by bacteria are able to digest insoluble keratin and convert it to valuable products through non polluting processes. The aim of this study was isolation of keratinolytic bacteria strains which resulted to isolation and purification of 120 feather keratinolytic isolates from different environment resources in feather powder medium. Among the 120 isolates tested in vitro, six isolates were found with highest yields and belonged to Bacillus according to obtained results based on biochemical tests and 16S rRNA sequencing analysis. The results were registered in NCBI database. These isolates digested the substrates between ranges of 76-80.8% after 48 hours. Proteolytic and keratinolytic activity were tested at 20, 30, 37 and 50°C temperatures respectively. All of strains were active on SMA media at mentioned temperatures except BK111 which didn’t show proteolytic activity at 50°C. BK206 strain also showed keratinolytic activity in all temperatures while BK107 and BK324 didn’t digest at 50°C. BK111 didn’t show proteolytic activity at 20 and 50°C on FMA medium while BK401, BK402 couldn’t form clear halo on mentioned medium at 20°C. Keratinolytic activities of selected strains were assayed by both keratin azure and azokeratin substrates. The obtained results showed that all strains had significant activities on two substrates. The highest activity in keratine azure and azo keratin substrates were observed in BK324 with 325 u/ml and 5992 u/ml activities respectively after two days incubation. Generally great keratinolytic potential of six novel strains showed their promising application for keratin biodegradation.