Enzymatic degradation of dimensionally constrained polyhydroxybutyrate films

Comprehensive Study on the Reinforcement of Electrospun PHB Scaffolds with Composite Magnetic Fe3O4-rGO Fillers: Structure, Physico-Mechanical Properties, and Piezoelectric Response

This is a comprehensive study on the reinforcement of electrospun poly(3-hydroxybutyrate) (PHB) scaffolds with a composite filler of magnetite-reduced graphene oxide (Fe₃O₄-rGO). The composite filler promoted the increase of average fiber diameters and decrease of the degree of crystallinity of hybrid scaffolds. The decrease in the fiber diameter enhanced the ductility and mechanical strength of scaffolds. The surface electric potential of PHB/Fe₃O₄-rGO composite scaffolds significantly increased with increasing fiber diameter owing to a greater number of polar functional groups. The changes in the microfiber diameter did not have any influence on effective piezoresponses of composite scaffolds. The Fe₃O₄-rGO filler imparted high saturation magnetization (6.67 ± 0.17 emu/g) to the scaffolds. Thus, magnetic PHB/Fe₃O₄-rGO composite scaffolds both preserve magnetic properties and provide a piezoresponse, whereas varying the fiber diameter offers control over ductility and surface electric potential.

Characterization and Biotechnological Potential of Intracellular Polyhydroxybutyrate by Stigeoclonium sp. B23 Using Cassava Peel as Carbon Source

The possibility of utilizing lignocellulosic agro-industrial waste products such as cassava peel hydrolysate (CPH) as carbon sources for polyhydroxybutyrate (PHB) biosynthesis and characterization by Amazonian microalga Stigeoclonium sp. B23. was investigated. Cassava peel was hydrolyzed to reducing sugars to obtain increased glucose content with 2.56 ± 0.07 mmol/L. Prior to obtaining PHB, Stigeoclonium sp. B23 was grown in BG-11 for characterization and Z8 media for evaluation of PHB nanoparticles' cytotoxicity in zebrafish embryos. As results, microalga produced the highest amount of dry weight of PHB with 12.16 ± 1.28 (%) in modified Z8 medium, and PHB nanoparticles exerted some toxicity on zebrafish embryos at concentrations of 6.25-100 µg/mL, increased mortality (<35%) and lethality indicators as lack of somite formation (<25%), non-detachment of tail, and lack of heartbeat (both <15%). Characterization of PHB by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC), and thermogravimetry (TGA) analysis revealed the polymer obtained from CPH cultivation to be morphologically, thermally, physically, and biologically acceptable and promising for its use as a biomaterial and confirmed the structure of the polymer as PHB. The findings revealed that microalgal PHB from Stigeoclonium sp. B23 was a promising and biologically feasible new option with high commercial value, potential for biomaterial applications, and also suggested the use of cassava peel as an alternative renewable resource of carbon for PHB biosynthesis and the non-use of agro-industrial waste and dumping concerns.

Enzymatic Hydrolysis of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) Scaffolds

Polyhydroxyalkanoates (PHAs) are hydrolyzable bio-polyesters. The possibility of utilizing lignocellulosic waste by-products and grape pomace as carbon sources for PHA biosynthesis was investigated. PHAs were biosynthesized by employing Cupriavidus necator grown on fructose (PHBV-1) or grape sugar extract (PHBV-2). Fifty grams of lyophilized grape sugar extract contained 19.2 g of glucose, 19.1 g of fructose, 2.7 g of pectin, 0.52 g of polyphenols, 0.51 g of flavonoids and 7.97 g of non-identified rest compounds. The grape sugar extract supported the higher production of biomass and modified the composition of PHBV-2. The biosynthesized PHAs served as matrices for the preparation of the scaffolds. The PHBV-2 scaffolds had about 44.2% lower crystallinity compared to the PHBV-1 scaffolds. The degree of crystallinity markedly influenced the mechanical behavior and enzymatic hydrolysis of the PHA scaffolds in the synthetic gastric juice and phosphate buffer saline solution with the lipase for 81 days. The higher proportion of amorphous moieties in PHBV-2 accelerated enzymatic hydrolysis. After 81-days of lasting enzymatic hydrolysis, the morphological changes of the PHBV-1 scaffolds were negligible compared to the visible destruction of the PHBV-2 scaffolds. These results indicated that the presence of pectin and phenolic moieties in PHBV may markedly change the semi-crystalline character of PHBV, as well as its mechanical properties and the course of abiotic or enzymatic hydrolysis.