Isolation of a feather-degrading strain of bacterium from spider gut and the purification and identification of its three key enzymes

A novel feather-degrading bacterium named CA-1 was isolated from the gut of the spider Chilobrachys guangxiensis, which degrades native whole chicken feathers within 20 h. The CA-1 was confirmed to belong to Stenotrophomonas maltophilia based on morphologic and molecular analysis. Maximum feather degradation activity of the bacterium was observed at 37 °C in basal feather medium (NaCl 0.5 g/L, KH2PO4 0.3 g/L, K2HPO4 0.4 g/L, feather powder 10.0 g/L, pH 8.0), which was inhibited when glucose and ammonium nitrate were added in the medium. Furthermore, the purified enzymes under the optimal and suppressive conditions were analyzed respectively by SDS-PAGE and LC–MS/MS. Three enzymes, namely alkaline serine protease (29.1 kDa), ABC transporter permease (27.5 kDa), and alkaline phosphatase (40.8 kDa), were isolated and identified from the supernatant of the optimal culture and were considered to play principal roles. On the other hand, the potential synergic effects of the three proteins in S. maltophilia CA-1 feather degradation system were analyzed theoretically. CA-1 may product outer-membrane vesicles comprised of membranes and periplasmic proteins in the feather medium. The newly identified CA-1 and its synergic enzymes provide a new insight into further understanding the molecular mechanism of feather degradation by microbes. They also have potential application in cost-effectively degrading feathers into feeds and fertilizers through careful optimization and engineering of the three newly identified enzymes.