An extracellular serine protease of an isolate of Duddingtonia flagrans nematophagous fungus

Abstract This study aimed to present a protease produced by Duddingtonia flagrans fungus (AC001), and to evaluate its activity in the biological control of cyathostomin infective larvae (L3). The crude extract from D. flagrans grown in liquid medium was applied first to a DEAE-Sepharose™ and later to a CM-Sepharose™ ion exchange column. Protease activity was determined under different pHs and temperatures. Subsequently, the effects of metal ions and phenylmethylsulfonyl fluoride (PMSF) inhibitor on activity were evaluated. Next, the protease activity in the biological control of nematodes was tested. A new 38 kDa serine protease (Df1) was purified. Optimum activity was obtained at pH 8.0 and 60°C; CuSO4, ZnSO4 and PMSF strongly inhibited the activity. Df1 (AC001) showed an L3 reduction rate of 58%. In conclusion, a serine protease produced by D. flagrans (AC001) has been isolated, which is effective in the in vitro destruction of cyathostomin L3.