A study of the properties and efficacy of microparticles based on P(3HB) and P(3HB/3HV) loaded with herbicides

The wide use of pesticides in agriculture has caused uncontrolled distribution of these chemicals in the environment, calling for the development and investigation of new environmentally friendly formulations, which would reduce human impact on nature. In the present study, the metribuzin (MET), tribenuron-methyl (TBM), and fenoxaprop-P-ethyl (FPE) herbicides were encapsulated in microparticles of degradable microbial polymers - polyhydroxyalkanoates (PHAs) - of two types - poly-3-hydroxybutyrate [P(3HB)] and poly(3-hydroxybutyrate-co-3-hydroxyvalerate [P(3HB/3HV)]. The use of P(3HB) resulted in higher yields of microparticles (63% to 79%) and larger sizes of the particles, whose average diameter was 0.60 +/- 0.06-0.75 +/- 0.11 mu m, while the average diameter of copolymer particles varied between 0.43 +/- 0.12 and 0.55 +/- 0.05 mu m. Encapsulation efficiency was rather determined by the type of herbicide and its solubility, varying from 24.7% to 48.2%. In vitro herbicide release from microparticles to water was affected by herbicide solubility and PHA chemical composition. The readily soluble MET showed the highest release rate, and over 30 days, 64% and 78% of the encapsulated amounts were released from P(3HB) and P(3HB/3HV) microparticles, respectively. High herbicidal activity of microparticles loaded with metribuzin and tribenuron-methyl was demonstrated in the laboratory stands of the Elsholtzia ciliata weed plant.