MICROENCAPSULATION DE BIOPESTICIDES POUR APPLICATION EN AGRICULTURE
Sensitivity to environmental variations and high volatilization of biopesticides (essential oil and bacteria) drastically reduce the useful lives and efficiency in the field. The microencapsulation method with natural materials enables the formation of a physical barrier that protects and ensures viability, properties optimization, and increased shelf life of these products. Thus, the objective is to evaluate the encapsulation effect of essential oils and Bacillus amyloliquefaciens CBMAI 1301 to control Botrytis cinerea, Colletotrichum glocosporioides, and Corynespora cassiicola. The effect of rosemary, cinnamon cassia, cardamom, clove, eucalyptus, ho wood, sweet orange, tea tree, and thyme oils on pathogens was evaluated. The ideal encapsulation conditions of the bacterium (with alginate) and of the essential oil (with alginate and chitosan), was determined by means of a Design of experiment. The essential oils of cinnamon, cloves, and thyme obtained the best antimicrobial activity with the lowest concentrations (fungicide < 2 μL/mL and bactericide > 250 μL/mL). The agitation speed, polymer and surfactant concentration were significant factors for both encapsulation processes. Under these conditions, spherical microcarriers with continuous walls, diameters of less than 150 μm, and high encapsulation efficiency (EE) were obtained. EE of up to 93% and 94% were achieved for the microcarriers of clover leaf oil and B. amyloliquefaciens, respectively. All four formulations of essential oil microcarriers showed fungicidal activity for the three fungi. The two formulations containing chitosan showed greater compatibility with the B. amyloliquefaciens strain, recovering cell growth after 24 h and contact, better physicochemical stability, and lower phytotoxicity compared to free oil. For microcarriers containing B. amyloliquefaciens fungicide inhibition of 40, 38 and 56% was obtained for B. cinerea, C. glocosporioides and C. cassiicola, respectively, low physicochemical stability and no leaf phytotoxicity. Thus, it is possible to obtain microcarriers for application as a sprayable biopesticide, maintaining efficiency, reducing the oils phytotoxicity, and enabling the compatibility between oil and bacteria.