Development of Biodegradable Controlled-Release Anti- <i>Phytophthora</i> Formulations Using Poly(3-hydroxybutyrate- <i>co</i> -3-hydroxyvalerate)

In this study, biodegradable controlled-release anti-Phytophthora granules were prepared using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as the polymer matrix and cinnamic acid (CA) as the active compound by the extrusion spheronization method. Two formulations were made with poly(vinylpyrrolidone) (PVP) and poly(vinyl alcohol) (PVA) as the binder, respectively. The size of the granules falls between 2.0 and 0.5 mm. The thermal stability of the formulations was verified using differential scanning calorimetry and thermogravimetric analysis. Combined with Fourier transform infrared spectroscopy, no new functional group was observed, indicating that no chemical interaction was present between the starting materials in the formulations. Release kinetics of the formulations in water and soil were studied and fitted to the Higuchi model, suggesting a Fickian diffusion mechanism governed the drug release. Both formulations show in vitro anti-Phytophthora activity, and the Gompertz equation was used to estimate and describe Phytophthora inhibition. Both formulations achieved over 50% inhibition over 21 days.