Isolation of three novel Antarctic psychrotolerant feather-degrading bacteria and partial purification of keratinolytic enzyme from Lysobacter sp. A03

Abstract

Three psychrotolerant bacteria (designated as A03, A08 and A17U) were isolated from penguin feathers collected in the Elephant Island, Antarctic. They were able to grow in feather meal as sole carbon and nitrogen source at 9 °C, 20 °C and 30 °C. Based on 16S rDNA sequencing, the strains were identified as belonging to the genera Lysobacter, Arthrobacter and Chryseobacterium, respectively. The isolate Lysobacter sp. A03 was capable to degrade feather meal almost completely in 7 days of cultivation at 20 °C, which was also the optimal growth temperature for Arthrobacter sp. A08 and Chryseobacterium sp. A17U. Despite the optimum growth temperature of the isolates was in the range of psychrotolerant microorganisms, the enzyme extracts showed maximum caseinolytic and keratinolytic activities under temperatures between 15 and 20 °C above that point, which is expected when enzymes are isolated from their source organism. For Lysobacter sp. A03, proteolytic activity was strongly inhibited by serine protease inhibitor PMSF, while for Arthrobacter sp. A08 and Chryseobacterium sp. A17U the enzymatic activity was inhibited by EDTA and partially inhibited by PMSF and 1,10-phenantroline. These results were in agreement with those found in zymograms. The protease of Lysobacter sp. A03, partially purified by two-step ion exchange chromatography, was only inhibited by PMSF. The peptide bands were analyzed by mass spectrometry resulting in the absence of significant homology to other Lysobacter proteins or microbial proteases of NCBI database. The production of keratinolytic proteases by these cold-adapted bacteria can be valuable for the reduction of energy costs in the application of enzymes in industrial processes as an alternative to mesophilic and thermophilic microorganisms.