Isothermal microcalorimetry analysis of microencapsulated Yamadazyma mexicana LPa14: release and antifungal activity against Colletotrichum gloeosporioides

Abstract

Anthracnose caused by Colletotrichum is the most significant disease in avocado. Since its quiescent infection begins in the field, preharvest control is crucial. Applying microencapsulated Yamadazyma mexicana LPa14 in preharvest may prevent pathogen establishment and reduce production losses. However, the evaluation of the release and the antagonistic activity of microencapsulated yeasts is essential to ensure the efficacy of a bioformulation. Due to the limitations of traditional techniques, isothermal microcalorimetry (IMC) is proposed as an innovative, accurate, and sensitive technique for measuring the heat generated during biological processes. This work aimed to evaluate the release of microencapsulated Y. mexicana and its antifungal activity against Colletotrichum gloeosporioides from avocado fruit using IMC and traditional microbiological techniques. The intermediate release rate of the bioformulation was compared with low and high release rate treatments, and Pearson correlation was used to associate the release rates with the thermokinetic parameters. For the confrontation test, the thermogenic curves of yeast (1.14 × 10⁶ and 3.16 × 10⁷ cells/mL) and fungus were recorded, the co-culture curves were deconvoluted and the thermokinetic parameters: lag phase (λ), maximum growth rate (µ_Max), total heat (Q_t), and time to peak (T_p) were obtained. The release rates were inversely correlated with Q_t. In vitro, C. gloeosporioides inhibition was yeast concentration-dependent, with no differences between fresh (56.78–68.24%) and microencapsulated (54.21–70.90%) yeast, as well as for the thermokinetic values. In the confrontation assay, at 3.16 × 10⁷ cells/mL, the yeast and confrontation curves showed a similar pattern, with no significant differences between µ_Max, λ phase, Q_t, and T_p, indicating complete fungal inhibition. Instead, at 1.14 × 10⁶ cells/mL, the yeast and fungus growth is affected, indicating incomplete inhibition below this concentration. In conclusion, the IMC is suitable for in vitro testing, as it provides insights into the release dynamics and antifungal activity of microencapsulated biocontrol agents. This study is crucial for enhancing the efficacy and practical application of bioformulations for fungal diseases management.