Isolation, identification and some cultural conditions of a protease-producing thermophilic Streptomyces strain grown on chicken feather as a substrate

Six strains of thermophilic actinomycetes were isolated from soil using an enrichment technique with feathers as the sole carbon and nitrogen source. They showed clear proteolytic activity on casein-agar medium. The most acti ve strain was tentatively identified as Streptomyces thermonitrificans. Thi s isolate was grown in a basal medium with feathers and/or other carbon and nitrogen sources. Supernatant from centrifuged cultures was examined for p rotease activity and temperature and pH optima were determined for enzyme a ctivity. Optimum proteolytic activity on basal liquid medium containing 1% chicken feather pieces was obtained at 50 degrees C. in a medium adjusted a t pH 8 and incubated for 72 h at 150 rpm. Proteolytic activity was further increased by 1.5% feather pieces and the time required for maximal activity was 96 h. The keratinolytic activity of S. thermonitrificans was examined by incubation with native chicken feather pieces and it was found that it i s significantly active. The degradation of whole intact feathers by S. ther monitrificans was obtained after 48 h of incubation at 50 degrees C. The pH and temperature optima for proteolytic activity were 9.0 and 50 degrees C, respectively. The proteolytic activity was stable at 40 degrees C for I h. The proteolytic activity was inhibited by DFP but not by EDTA or pCMB. The se results inidicated that the enzyme(s) can be classified as an alkaline p rotease. (C) 1999 Elsevier Science Ltd. All rights reserved.