Evaluation of the microencapsulation process of conidia of Trichoderma asperellum by spray drying.

Microencapsulation of microorganisms has been studied to increase product shelf life and stability to enable the application in sustainable agriculture. In this study, the microencapsulation of Trichoderma asperellum conidia by spray drying (SD) was evaluated. The objective was to assess the effect of drying air temperature and wall material (maltodextrin DE20, MD20) concentration on the microencapsulation and to identify the optimum conditions to produce, in high yield, microparticles with low moisture, high conidial viability and conidial survival. Microparticles were characterized in terms of morphology, particle size, and shelf life. A central composite rotatable design (CCRD) was used to evaluate the effect of operating parameters on drying yield (DY), moisture content, conidial viability (CV), and conidial survival (SP). Microencapsulation experiments were carried out under optimum conditions to validate the obtained model. The optimum temperature and MD20/conidia dry weight ratios were 80 °C and 1:4.5, respectively, which afforded a drying yield of 63.85 ± 0.86%, moisture content of 4.92 ± 0.07%, conidial viability of 87.10 ± 1.16%, and conidial survival of 85.78 ± 2.88%. Microencapsulation by spray drying using MD20 as wall material extended the viability of conidia stored at 29 °C compared with the control. The mathematical models accurately predicted all the variables studied, and the association of the microencapsulation technique using DE20 maltodextrin was able to optimize the process and increase the product's shelf life. It was also concluded that high inlet air temperatures negatively affected conidia survival, especially above 100 °C.