Biodegradative controlled natural toxin release from Pimelea trichostachya-poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biocomposites: Towards a sustainable intra-ruminal device

To address the need to develop rumino-reticulum devices (RRDs) for prolonged delivery of natural toxins that can protect Australian cattle from the fatal Pimelea poisoning by stimulating their own detoxification capability, a range of melt-extruded biocomposites were prepared from two formats of Pimelea plant materials (these being ground Pimelea plant particles and their derived ethanol extracts) combined with the biodegradable biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). To explore the close to end-of-life biodegradation and natural toxin release behaviors of these materials in the rumen environment, they were incubated for less than 29 days in anaerobic and aqueous sewage sludge using the mesophilic biochemical methane production (BMP) assay. Characterization of the composites over time (and thus over different degrees of biodegradation) using Xray computed tomography scanning (& mu;-CT), differential scanning calorimetry (DSC), size exclusion chromatography (SEC), and quantification of the residual polymer contents by weight, confirmed that there was a consistent surface biodegradation mechanism. The biodegradation kinetics were well simulated using a parallelmass-loss model combined with an adapted Gompertz model, confirming that initial microorganism growth in biofilm formation/biomass adaptation is the rate-limiting step. The natural toxin release kinetics were obtained by determining the concentrations of the principal natural toxin, simplexin, in the biocomposites before and after biodegradation using an optimized analytical methodology based on ultra-high performance liquid chromatography hyphenated with a quadrupole Orbitrap mass spectrometry (UHPLC-Q-Orbitrap-MS). These release kinetics were appropriately described by a new model that considered the interplay of burst release, toxin adsorption, and biodegradation. These findings will not only aid the future RRD design by identifying that the Pimelea plant extracts are preferred as the toxin source, but also extend the understanding of the anaerobic biodegradation of PHBV-based biocomposites and highlight the need to consider toxin sorption effects in controlled release formulations.

Automated summary

In this study, melt-extruded biocomposites were prepared by combining Pimelea plant materials with the biodegradable biopolymer PHBV. The biodegradation and natural toxin release behaviors of these materials were investigated in the rumen environment. The findings will contribute to the development of rumino-reticulum devices and provide insights into the anaerobic biodegradation of PHBV-based biocomposites and the sorption effects of toxins in controlled release formulations.