Isolation of Thermoanaerobacter keratinophilus sp nov., a novel thermophilic, anaerobic bacterium with keratinolytic activity

Several thermophilic anaerobic bacteria with keratinolytic activity growing at temperatures between 50 degreesC and 90 degreesC were isolated from samples collected on the island of Sao Miguel in the Azores (Portugal). On the basis of morphological, physiological, and 16S rDNA studies, the isolate 2KXI was identified as a new species of the genus Thermoanaerobacter, designated Thermoanaerobacter keratinophilus. This strain, which grows optimally at 70 degreesC, pH 7.0, and 0.5% NaCl, is the first member of the genus Thermoanaerabacter that has been described for its ability to degrade native keratin. Around 70% of native wool was solubilized after 10 days of incubation under anaerobic conditions. The strain was shown to possess intracellular and extracellular proteases optimally active at 60 degreesC, pH 7.0, and 85 degreesC, pH 8.0, respectively. Keratin hydrolysis was demonstrated in vitro using a sodium dodecyl sulfate gel containing feather meal. The extracellular protease responsible for breaking down keratin fibers was purified to homogeneity in only one step by applying hydxoxyapatite column chromatography. The enzyme belongs to the serine-type proteases and has a molecular mass of 135 kDa.