Efficacy of tebuconazole embedded in biodegradable poly-3-hydroxybutyrate to inhibit the development of Fusarium moniliforme in soil microecosystems.

BACKGROUND: An important line of research is the development of a new generation of formulations with targeted and controlled release of the pesticide, using matrices made from biodegradable materials. In this study, slow-release formulations of the fungicide tebuconazole (TEB) have been prepared by embedding it into the matrix of poly-3-hydroxybutyrate (P3HB) in the form of films, microgranules and pellets. RESULTS: The average rates of P3HB degradation were determined by the geometry of the formulation, reaching, for 63 days, 0.095-0.116, 0.081-0.083 and 0.030-0.055 mg day-1 for films, microgranules and pellets respectively. The fungicidal activity of P3HB/TEB against the plant pathogen Fusarium moniliforme was compared with that of the commercial formulation Raxil Ultra. A pronounced fungicidal effect of the experimental P3HB/TEB formulations was observed in 2-4 weeks after application, and it was retained for 8 weeks, without affecting significantly the development of soil aboriginal microflora. CONCLUSION: TEB release can be regulated by the process employed to fabricate the formulation and the fungicide loading, and the TEB accumulates in the soil gradually, as the polymer is degraded. The experimental forms of TEB embedded in the slowly degraded P3HB can be used as a basis for developing slow-release fungicide formulations. © 2016 Society of Chemical Industry.

Microbial Degradation of Polyhydroxyalkanoates with Different Chemical Compositions and Their Biodegradability.

The study addresses degradation of polyhydroxyalkanoates (PHA) with different chemical compositions-the polymer of 3-hydroxybutyric acid [P(3HB)] and copolymers of P(3HB) with 3-hydroxyvalerate [P(3HB/3HV)], 4-hydroxybutyrate [P(3HB/4HB)], and 3-hydroxyhexanoate [P(3HB/3HHx)] (10-12 mol%)-in the agro-transformed field soil of the temperate zone. Based on their degradation rates at 21 and 28 °C, polymers can be ranked as follows: P(3HB/4HB) > P(3HB/3HHx) > P(3HB/3HV) > P(3HB). The microbial community on the surface of the polymers differs from the microbial community of the soil with PHA specimens in the composition and percentages of species. Thirty-five isolates of bacteria of 16 genera were identified as PHA degraders by the clear zone technique, and each of the PHA had both specific and common degraders. P(3HB) was degraded by bacteria of the genera Mitsuaria, Chitinophaga, and Acidovorax, which were not among the degraders of the three other PHA types. Roseateles depolymerans, Streptomyces gardneri, and Cupriavidus sp. were specific degraders of P(3HB/4HB). Roseomonas massiliae and Delftia acidovorans degraded P(3HB/3HV), and Pseudoxanthomonas sp., Pseudomonas fluorescens, Ensifer adhaerens, and Bacillus pumilus were specific P(3HB/3HHx) degraders. All four PHA types were degraded by Streptomyces.

Experimental wound dressings of degradable PHA for skin defect repair.

The present study reports construction of wound dressing materials from degradable natural polymers such as hydroxy derivatives of carboxylic acids (PHAs) and 3-hydroxybutyrate/4-hydroxybutyrate [P(3HB/4HB)] as copolymer. The developed polymer films and electrospun membranes were evaluated for its wound healing properties with Grafts-elastic nonwoven membranes carrying fibroblast cells derived from adipose tissue multipotent mesenchymal stem cells. The efficacy of nonwoven membranes of P(3HB/4HB) carrying the culture of allogenic fibroblasts was assessed against model skin defects in Wistar rats. The morphological, histological and molecular studies revealed the presence of fibroblasts on dressing materials which facilitated wound healing, vascularization and regeneration. Further it was also observed that cells secreted extracellular matrix proteins which formed a layer on the surface of membranes and promoted the migration of epidermal cells from the neighboring tissues surrounding the wound. The wounds under the P(3HB/4HB) membrane carrying cells healed 1.4 times faster than the wounds under the cell-free membrane and 3.5 times faster than the wounds healing under the eschar (control).The complete wound healing process was achieved at Day 14. Thus the study highlights the importance of nonwoven membranes developed from degradable P(3HB/4HB) polymers in reducing inflammation, enhancing angiogenic properties of skin and facilitating better wound healing process.

Constructing herbicide metribuzin sustained-release formulations based on the natural polymer poly-3-hydroxybutyrate as a degradable matrix.

Polymer poly(3-hydroxybutyrate) [P(3HB)] has been used as a matrix in slow-release formulations of the herbicide metribuzin (MET). Physical P(3HB)/MET mixtures in the form of solutions, powders, and emulsions were used to construct different metribuzin formulations (films, granules, pellets, and microparticles). SEM, X-Ray, and DSC proved the stability of these formulations incubated in sterile water in vitro for long periods of time (up to 49 days). Metribuzin release from the polymer matrix has been also studied. By varying the shape of formulations (microparticles, granules, films, and pellets), we were able to control the release time of metribuzin, increasing or decreasing it.

Cell growth and accumulation of polyhydroxyalkanoates from CO2 and H2 of a hydrogen-oxidizing bacterium, Cupriavidus eutrophus B-10646.

Synthesis of polyhydroxyalkanoates (PHAs) by a new strain of Cupriavidus - Cupriavidus eutrophus B-10646 - was investigated under autotrophic growth conditions. Under chemostat, at the specific flow rate D=0.1h(-1), on sole carbon substrate (CO2), with nitrogen, sulfur, phosphorus, potassium, and manganese used as growth limiting elements, the highest poly(3-hydroxybutyrate) [P(3HB)] yields were obtained under nitrogen deficiency. In batch autotrophic culture, in the fermenter with oxygen mass transfer coefficient 0.460 h(-1), P(3HB) yields reached 85% of dry cell weight (DCW) and DCW reached 50 g/l. Concentrations of supplementary PHA precursor substrates (valerate, hexanoate, γ-butyrolactone) and culture conditions were varied to produce, for the first time under autotrophic growth conditions, PHA ter- and tetra-polymers with widely varying major fractions of 3-hydroxybutyrate, 4-hydroxybutyrate, 3-hydroxyvalerate, and 3-hydroxyhexanoate monomer units. Investigation of the high-purity PHA specimens showed significant differences in their physicochemical and physicomechanical properties.