Controlled release of papain encapsulated in chitosan hydrogels and study of nematicidal action on Panagrellus sp.

Abstract

Alternatives to the use of chemical products traditionally used to combat agricultural pests and diseases have been a concern for society. Thus, based to sustainable agriculture, the use of enzymes has grown as an alternative to the control with traditional. However, some limitations prevent greater effectiveness of action of these important biological catalysts, such as variations in pH and temperature, the presence of inhibitory ions, among others. In this study, papain, a plant enzyme, was incorporated into chitosan hydrogels by cross-linking with glutaraldehyde at different concentrations (0; 0,25 %; 0,5 %; 0,75 %; 1 %). The results of scanning electron microscopy showed a difference in the porous morphology of the different treatments compared to chitosan without crosslinking and the FTIR analysis suggests crosslink formation in the hydrogels. The enzymatic activity of free papain was reduced by approximately 57 % of the initial value. On the outher hand, the results indicate that the activity of the enzyme released from some hydrogels increased and the diffusion of papain probably occurred in the solution from the surface of the formed chitosan hydrogels, represented by a parabolic diffusion model. The mortality of Panagrellus sp., a model nematode, was evaluated and the treatments with hydrogels demonstrated high mortality of Panagrellus sp. above 80 % after 5 days. The hydrogels containing papain were effective in the mortality of the nematodes evaluated and constituted a slow release system, sustainable environmentally, as it has the potential to reduce the number of applications needed to control pests and diseases in agriculture.