In Vitro Action of Streptomyces griseolus Proteases as Bio-Control on Fasciola gigantic Eggs

This work evaluated the in vitro bio-control action of actinomycetes isolated from Egyptian soil against Fasciola gigantica eggs. In this respect, the identified Streptomyces griseolus was the best parasite-control agent which gave the highest mortality percent applying three methods; the first method was the application of the grown bacterial disks with the eggs at zero time on the medium (2% w/v water-agar) and incubated for 21 days (75.5% mortality), the second method was the incubation of the bacterial disks using the same medium for 5 days before eggs inoculation, after 21 days of incubation the mortality percent was 80.8%. The application of the third method showed a good effect by using all bacterial culture filtrates. S. griseolus filtrate which had the highest lytic enzyme and proteolytic activities reached 2.0 and 660.7 U/ml, respectively, gave the highest mortality (95.5%) of F. gigantica eggs compared to the other bacterial filtrates. The crude culture filtrate and the diluted culture filtrate (1.33 fold) of S. griseolus gave the highest mortality percent against the parasite ́s eggs (95.8 and 94.5%, respectively) compared to the higher diluted filtrates. The culture filtrate of S. griseolus grown on two different media and its partially purified enzyme (precipitated by 60% ammonium sulfate) were tested for their proteolytic activity and inhibitory effect against F. gigantica eggs. Medium no. 2 showed the highest proteolytic activity (1030.3 and 1138.1 U/ml) for the crude and the partially purified enzyme, respectively. While the highest inhibitory effect reached 97.6 and 89.9%, respectively. Finally, the application of crude enzyme filtrate was better than the partially purified one. Streptomyces griseolus was proved as a potential biological control agent for this helminth.