Evaluation of the bacteriostatic effect of hop leaves for the treatment of bovine waste

Abstract

Hops are a fast-growing perennial plant common in temperate countries. The cones are used in the brewing industry, as their glands secrete the substance lupulins, which contain alpha and beta acids responsible for giving aroma and bitterness to beer, in addition to conserving it. Brazil is one of the largest cattle breeders in the world and consequently generates a large volume of manure, which contains several pathogens. The reuse of hops crop residues as a possible antimicrobial agent in the treatment of bovine manure can be a sustainable alternative for small rural producers. The bacteriostatic action of the hops was evaluated from the pool of bacteria isolated from bovine manure and were stored at -20 ° C until the experiment was carried out. By means of infusion for 48 hours, aqueous extracts of the leaves of the hops grown in 2 types of soil (mixed and sandy) were prepared, with 4 hours in homogenization in the shaker at 90 rpm and sterilized by filtration. For the bacteriological test, from the initial concentration of 0.28 g / mL, 5 serial dilutions were performed in triplicates with 10 μL of the bacterial suspension. After 24 hours of incubation at 37 ° C, bacterial colonies were counted (visual and Pour Plate). The results indicated a growth above 10,000 colony-forming units in all dilutions, making quantification impossible, that is, in the tested concentrations the extracts did not show bactericidal action on the evaluated microbiota. Thus, given the results, it is necessary to establish the limit concentration to enable the bacteriostatic action of the hops extracts in bovine manure.