Production and partial characterization of Duddingtonia flagrans (AC001) crude extract and its in vitro larvicidal action against trichostrongylid infective larvae

The production and partial characterization of Duddingtonia flagrans (AC001) crude extract and its in vitro larvicidal action against trichostrongylid infective larvae from sheep were studied. D. flagrans was grown in liquid medium with glucose, casein, bibasic potassium phosphate (K₂HPO₄), magnesium sulfate (MgSO₄), zinc sulfate (ZnSO₄), ferrous sulfate (FeSO₄), and copper sulfate (CuSO₄). The proteolytic activity was measured within varied pHs and temperatures. To determine the thermostability, the crude extract was incubated at 28°C for 72 h. To study the effect of different chemical compounds on the activity of the crude extract, the samples were incubated in solutions containing (10 mM): calcium chloride (CaCl₂), copper II sulfate (CuSO₄), zinc sulfate (ZnSO₄), magnesium sulfate (MgSO₄), inhibitor phenylmethylsulfonyl fluoride (PMSF), and 0.5% SDS. Results showed that the highest activity obtained (79.23 U/mL) was at pH 9.0, while the optimum temperature was 60°C (119.6 U/mL). The thermostability analysis demonstrated that after 72 h the activity was maintained or increased. It was found that the CuSO₄, ZnSO₄, and PMSF strongly inhibited the proteolytic activity. Moreover, the MgSO4 and SDS, caused a weak inhibition of the proteolytic activity. There was a significant (P<0.01) reduction in number of treated L₃ when compared to control (94.2%). The results suggest that the crude extract produced by D. flagrans (AC001) in liquid medium exerted larvicidal activity on trichostrongilid L₃ and therefore may contribute to a large-scale industrial production.