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

Abstract

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.