PHBV Content Research Articles

Optimized batch cultivation and scale-up of Bacillus thuringiensis for high-yield production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Addition of statistically optimized concentration of electron acceptor, propionic acid (1.2 g/L) at different cultivation times (0 h, 14.86 h and 19 h) during batch cultivation of B. thuringiensis in mixed substrate (glucose and glycerol) featured production of 8 g/L of biomass and 3.57 g/L of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) containing 0.805 g/L of 3-hydroxyvalerate concentration. Successful scale up of batch cultivation from 7 L to a 70 L bioreactor was, thereafter, achieved using power/volume (P/V) criteria with maximum PHBV and biomass concentration of 3.57 g/L and 7.15 g/L respectively. Characterization of PHBV so produced was carried out using NMR, FTIR, DSC and TGA to elucidate its structure, thermal properties and stability to map their applications in society. These findings highlight the potential of the optimized batch cultivation and scale-up process in producing PHBV emphasizing its relevance in sustainable biopolymer production.

Biorefinery of volatile fatty acids for the synthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) using Paracoccus sp. TOH: Fermentation performance and metabolic pathway

The residual microbes and uncertain volatile fatty acids (VFAs) components in anaerobic fermentation hydrolysate cause microbial contamination and multi-type polyhydroxyalkanoates (PHA) generation in pure microbial synthesis systems. Meanwhile, the regulation of biosynthesis of poly(3-hydroxybuturate-co-3-hydroxyvalerate) (PHBV), one type of excellent PHA, by re-utilization of waste-organics as carbon substrates is still elusive. In this study, four pretreatment methods for sludge hydrolysate containing 4746 mg-COD·L−1 of VFAs were established to assess the accumulation of PHBV by using Paracoccus sp. TOH as the chassis. Results showed that the autoclaving system exhibited an optimal PHBV concentration of 202.9 mg L−1 with the highest relative abundance of Paracoccus sp. TOH (92.4%). Valeric acid was identified as the primary substrate for 3-hydroxyvalerate accumulation, and the highest PHBV production of 3.76 g L−1 was achieved using 3 g L−1 valeric acid and 5 g L−1 glycerol as co-substrates. The increased carbon metabolism flows through the sequential action of acyl-coenzyme A dehydrogenase and enoyl-coenzyme A hydratase in the fatty acid β-oxidation pathway facilitated PHBV accumulation. This study provides a blueprint for the microbial synthesis of PHBV with oriented acid production from organic wastes.

Large-Scale Preparation of Mechanically High-Performance and Biodegradable PLA/PHBV Melt-Blown Nonwovens with Nanofibers

Biodegradable polylactic acid (PLA) melt-blown nonwovens are attractive candidates to replace non-degradable polypropylene melt-blown nonwovens. However, it is still an extremely challenging task to prepare PLA melt-blown nonwovens with sufficient mechanical properties for practical application. Herein, we report a simple strategy for the large-scale preparation of biodegradable PLA/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) melt-blown nonwovens with high strength and excellent toughness. In this process, a small amount of PHBV is added to PLA to improve the latter’s crystallization rate and crystallinity. In addition, when the PHBV content increases from 0 to 7.5 wt%, the diameters of the PLA/PHBV melt-blown fibers decrease significantly (with the proportion of nanofibers increasing from 7.7% to 42.9%). The resultant PLA/PHBV (5 wt% PHBV) melt-blown nonwovens exhibit the highest mechanical properties. The tensile stress, elongation, and toughness of PLA/PHBV (5 wt% PHBV) melt-blown nonwovens reach 2.5 MPa, 45%, and 1.0 MJ·m−3, respectively. More importantly, PLA/PHBV melt-blown nonwovens can be completely degraded into carbon dioxide and water after four months in the soil, making them environmentally friendly. A general tensile-failure model of melt-blown nonwovens is proposed in this study, which may shed light on mechanical performance enhancement for nonwovens.

Air-jet spun PHBV/PCL blend tissue engineering scaffolds exhibit improved mechanical properties and cell proliferation

This study aimed to optimize the preparation parameters for air-jet spun blended poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polycaprolactone (PCL) submicron fibrous scaffolds. Blends of PHBV and PCL were made using different weight ratios of polymers and examined for their mechanical, morphological, and biological properties. The 50/50 ratio PHBV/PCL blend scaffolds showed better overall mechanical properties compared to the scaffolds with higher PHBV content and provided better cell attachment and proliferation compared to PCL scaffolds. The incorporation of PCL improved the degree of crystallinity, thermal stability, and mechanical properties of PHBV/PCL blend scaffolds. In vivo subcutaneous implantation and subsequent histological analysis of the implanted scaffolds indicated that the scaffolds were compatible with animal tissues. The findings show that air-jet spun PHBV/PCL blended scaffolds in a 50/50 ratio can be employed in many tissue engineering applications.

Enhanced production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with modulated 3-hydroxyvalerate fraction by overexpressing acetolactate synthase in Cupriavidus necator H16

The elastomeric properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a biodegradable copolymer, strongly depend on the molar composition of 3-hydroxyvalerate (3HV). This paper reports an improved artificial pathway for enhancing the 3HV component during PHBV biosynthesis from a structurally unrelated carbon source by Cupriavidus necator H16. To increase the intracellular accumulation of propionyl-CoA, a key precursor of the 3HV monomer, we developed a recombinant strain by genetically manipulating the branched-chain amino acid (e.g., valine, isoleucine) pathways. Overexpression of the heterologous feedback-resistant acetolactate synthase (alsS), (R)-citramalate synthase (leuA), homologous 3-ketothiolase (bktB), and the deletion of 2-methylcitrate synthase (prpC) resulted in biosynthesis of 42.5 % (g PHBV/g dry cell weight) PHBV with 64.9 mol% 3HV monomer from fructose as the sole carbon source. This recombinant strain also accumulated the highest PHBV content of 54.5 % dry cell weight (DCW) with 24 mol% 3HV monomer from CO2 ever reported. The lithoautotrophic cell growth and PHBV production by the recombinant C. necator were promoted by oxygen stress. The thermal properties of PHBV showed a decreasing trend of the glass transition and melting temperatures with increasing 3HV fraction. The average molecular weights of PHBV with modulated 3HV fractions were between 20 and 26 × 104 g/mol.

Study on the production of high 3HV content PHBV via an open fermentation with waste silkworm excrement as the carbon source by the haloarchaeon Haloferax mediterranei.

Silkworm excrement is hard to be degraded or bio-utilized by environmental microorganisms due to its high content of heavy metals and antimicrobial biomacromolecules in mulberry leaves. In traditional Chinese silk industry, the silkworm excrement results in environmental problems. In this study, the silkworm excrement after chlorophyll ethanol-extraction was researched. An open fermentation strategy was developed using the silkworm excrement as the sole or partial carbon source by haloarchaea to accumulate polyhydroxyalkanoates. As a haloarchaeon with strong carbon source utilization ability, Haloferax mediterranei was found to accumulate a certain amount of poly(3-hydroxybutyrate-co-3-hydroxyvalerate; PHBV) using waste silkworm excrement. The results showed that the addition of silkworm excrement into glucose based fermentation medium can significantly improve the production of PHBV. Using a mixture carbon source including the extract of silkworm excrement and glucose (with a 1:1 carbon content ratio), the yield of PHBV was 1.73 ± 0.12 g/l, which showed a 26% increase than that of fermentation without the silkworm excrement addition. When the NaCl content of medium was set to approximately 15%, fermentation without sterilization was performed using silkworm excrement as the carbon source. Moreover, the addition of the silkworm excrement extract could increase the 3-hydroxyvalerate (3 HV) content of PHBV regardless of the sterilization or non-sterilization fermentation conditions. When using silkworm excrement as the sole carbon source, the 3 HV content was as high as 16.37 ± 0.54 mol %. The real-time quantitative PCR results showed that the addition of the silkworm excrement could specifically enhance the expression of genes involved in the aspartate/2-ketobutyric acid pathway related to 3 HV synthesis in H. mediterranei, and further analysis of the amino acid of the silkworm excrement suggested that the high content of threonine in the silkworm excrement might be the reason for the increase of 3 HV content. Taken together, the success of non-sterile fermentation in hypersaline condition using haloarchaea implied a novel way to reuse the silkworm excrement, which not only reduces the production costs of PHBV, but also is conducive to environmental protection.

Biobased polymer SF/PHBV composite nanofiber membranes as filtration and protection materials

With the emergence of the COVID-19, masks and protective clothing have been used in huge quantities. A large number of non-degradable materials have severely damaged the ecological environment. Now, people are increasingly pursuing the use of environmentally friendly materials to replace traditional chemical materials. Silk fibroin (SF) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) have received increasing attention because of their unique biodegradability and biocompatibility. In this paper, a series of biodegradable SF/PHBV nanofiber membranes with different PHBV content were fabricated by using electrospinning technology. The morphology of the electrospun SF/PHBV composite nanofiber was observed by scanning electron microscopy (SEM). The average diameters of the pure SF, SF/PHBV (4/1), SF/PHBV (3/1), and SF/PHBV (2/1) nanofibers were 55.16 ± 12.38 nm, 75.93 ± 21.83 nm, 69.35 ± 21.55 nm, and 61.40 ± 12.31 nm, respectively. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were used to explore the microstructure of the electrospun SF/PHBV composite nanofiber. The crystallization ability of the composite nanofiber was greatly improved with the addition of PHBV. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated that the thermal stability of SF was better than PHBV obviously, so SF could improve the thermal stability of the composite materials within a certain range. The mechanical properties of the electrospun nanofiber membranes were evaluated by using a universal testing machine. In general, the elongation of the composite nanofiber membranes decreased, and the breaking strength increased with the addition of PHBV. The small pore size of the nanofiber membranes ensured that they had good application prospects in the field of filtration and protection. When the spinning time was 1 h, the filtration efficiency of SF/PHBV/PLA composite materials remained above 95%.

Carbon Capture Utilization for Biopolymer Foam Manufacture: Thermal, Mechanical and Acoustic Performance of PCL/PHBV CO2 Foams.

Biopolymer foams manufactured using CO2 enables a novel intersection for economic, environmental, and ecological impact but limited CO2 solubility remains a challenge. PHBV has low solubility in CO2 while PCL has high CO2 solubility. In this paper, PCL is used to blend into PBHV. Both unfoamed and foamed blends are examined. Foaming the binary blends at two depressurization stages with subcritical CO2 as the blowing agent, produced open-cell and closed-cell foams with varying cellular architecture at different PHBV concentrations. Differential Scanning Calorimetry results showed that PHBV had some solubility in PCL and foams developed a PCL rich, PHBV rich and mixed phase. Scanning Electron Microscopy and pcynometry established cell size and density which reflected benefits of PCL presence. Acoustic performance showed limited benefits from foaming but mechanical performance of foams showed a significant impact from PHBV presence in PCL. Thermal performance reflected that foams were affected by the blend thermal conductivity, but the impact was significantly higher in the foams than in the unfoamed blends. The results provide a pathway to multifunctional performance in foams of high performance biopolymers such as PBHV through harnessing the CO2 miscibility of PCL.

Nonsolvent-induced phase separation of poly(3-hydroxybutyrate) and poly(hydroxybutyrate-co-hydroxyvalerate) blend as a facile platform to fabricate versatile nanofiber gels: Aero-, hydro-, and oleogels

We demonstrated a strategy to prepare different types of 3-D nanofibrous polymeric gels, including hydro-, aero-, and oleogels by nonsolvent-induced phase separation (NIPS). NIPS-derived gel monoliths of poly(3-hydroxybutyrate) (PHB) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) blends were converted into hydrogels and aerogels by solvent exchange and freeze-drying, respectively. The high hydrophobicity and porosity of the nanofibrous PHB/PHBV aerogels enabled them to absorb various oils and swell to 20–30 times their own weight. The pseudo-second-order model was successfully used to describe the oil absorption behavior, and the obtained absorption rate constant increased with increasing PHBV content. The oil-swollen aerogels were highly elastic, thereby indicating that NIPS-derived aerogels are an excellent template for the fabrication of oleogels. With an increase in the PHBV ratio, the gels exhibited reduced modulus and collapse strength but increased collapse strain, thereby revealing higher ductility by compression. The rapid separation and re-binding of the liquid phase entrapped in the nanofiber network resulted in the unique thixotropic properties of the hydro- and oleogels. Indomethacin, a hydrophobic model drug, was successfully incorporated into injectable self-healing oleogels containing soybean oil and aerogels. These gels exhibited excellent cytocompatibility, and a better sustained drug release was observed for the oleogels compared to the aerogels.

A Sustainable Approach for the Synthesis of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Biocomposite by Employing Corncob-Derived Nanocellulose as a Reinforcing Agent

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a copolymer synthesized by Bacillus megaterium co-utilizing cheese whey and food waste hydrolysate for its one-step production. The optimized substrate ratio of 60:40 (v/v) manifested maximum biomass of 3.09 ± 0.12 g/L and PHBV yield of 2.0 ± 0.3 g/L. Batch kinetics study revealed maximum biomass and PHBV yield of 3.05 ± 0.07 g/L and 2.175 ± 0.06 g/L respectively, with 71.43 ± 0.28% g/g PHBV content. The integration of corncob-derived nanocellulose into PHBV was confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) analysis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyzed the thermal characteristics of the PHBV biocomposite, where the highest degradation temperature was obtained at 790 °C, thus exhibiting high thermal stability. The mechanical properties such as Young's modulus, elongation at break, and tensile strength of the biocomposite was comparatively higher than PHBV and was found to be 40 MPa, 5.310%, and 11.110 MPa, respectively. The enhanced thermal and mechanical characteristics of PHBV biocomposite proves that the corncob-derived nanocellulose can be employed as a reinforcing agent.

Biopolymer Composite Nanofibers Electrospun from Regenerated Silk Fibroin and PHBV: Fabrication Method, Morphology and Thermal Stability

Silk fibroin (SF) and polyhydroxyalkanoate (PHA) have received increasing attention in recent years because of their unique biodegradability and biocompatibility. Studies on SF or PHA-based materials that are intended for use as biomaterials have attracted great attention, but few studies have been conducted on SF/PHA composite materials. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymers with varying ratios of the 3-hydroxyvalerate (HV) component are the most widely used member of PHAs. In this study, SF/PHBV composite nanofibers were prepared by electrospinning. The stability of the mixed solution of SF/PHBV was explored first. Fourier transform infrared (FTIR) spectroscopy was used to study the composition of the precipitates caused by mixing the SF solution with the PHBV solution. The morphology of the electrospun SF/PHBV composite nanofibers was observed by scanning electron microscopy (SEM). The average diameters of the pure PHBV, pure SF, SF/PHBV (the content ratio of solute SF/PHBV (w/w) was 10/1), and SF/PHBV (the content ratio of solute SF/PHBV (w/w) was 4/1) nanofibers were 495.12 ± 82.27, 67.88 ± 14.52, 171.10 ± 40.38, and 149.70 ± 28.57 nm, respectively. To discuss the influence of the electrospinning parameters on the spinning stability and morphology of the electrospun SF/PHBV (10/1) composite nanofibers, a univariate analysis experiment was designed. When the applied voltage was 15 kV, the feeding rate was 0.3 mL/h, and the tip-to-collector distance was 13 cm, the spinning stability, uniformity and formability of the SF/PHBV (10/1) composite nanofibers were excellent. In addition to FTIR analysis, X-ray diffraction (XRD) was also used to explore the structure of the electrospun SF/PHBV composite nanofibers. As the content of PHBV increased, the crystallinity of the SF/PHBV composite nanofibers could be improved. The thermogravimetric analysis (TGA) results indicated that the thermal stability of SF was better than that of PHBV. As the content of PHBV increased, the thermal stability of the SF/PHBV composite nanofibers would decrease.

Design and fabrication of bone tissue scaffolds based on PCL/PHBV containing hydroxyapatite nanoparticles: dual-leaching technique.

Scaffolds are the important part of the tissue-engineering field that are made from different biomaterials using various techniques. In this study, new scaffold based on polycaprolactone (PCL) and poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV) containing hydroxyapatite nanopraticles (n-HA) were fabricated using the dual-leaching technique (DLT). Morphology, porosity, degradation rate, Fourier transfer infrared ray (FTIR) spectra, surface, and mechanical properties as well as capacity of cell binding and cell proliferation on the constructed scaffolds were evaluated. FTIR analysis showed that n-HA particles have some interest interactions with polymeric chains. The best 3D-structure was seen in PCL70PHBV30 scaffold using the scanning electron microscopy (SEM) and its structure improved in the presence of 3, 5 wt% of n-HA. Results of energy dispersive x-ray analysis (EDXA, map of Ca) showed that the nanoparticles have the uniform distribution within the fabricated scaffolds. Porosity analysis showed that the particulate salt leaching technique is a successful approach to building a 3D structure. Increasing of PHBV content and n-HA up to 3 and 5 wt% in the PCL matrix led to increase porosity in all samples. Mechanical properties analysis showed that values of compression modulus and strength are decreased with addition of PHBV and HA nanoparticles. These results were directly in line with the results of morphology and porosity. Cell culture experiments demonstrated that the PCL/PHBV/nHA nanocomposite scaffold has a better tendency of proliferation to cells than that of the pure PCL/PHBV scaffold. All of these results suggest promising potentials of the developed PCL/PHBV/nHA scaffolds in this study desire for bone tissue engineering.

Mechanical properties of cold-drawn films of ultrahigh-molecular-weight poly(3-hydroxybutyrate-co-3-hydroxyvalerate) produced by Haloferax mediterranei

We investigated the biosynthesis and properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) produced by Haloferax mediterranei NBRC14739T from glucose. When H. mediterranei grew on 5 g/L glucose in flask culture, 43.7 wt% PHBV with 12 mol% 3-hydroxyvalerate (3HV) accumulated intracellularly. Size-exclusion chromatography revealed that this polymer had a weight-average molecular weight (Mw) and polydispersity (Mw/Mn) of 4.7 × 106 g/mol and 1.7, respectively. Increasing the glucose concentration in the flask cultures slightly promoted cell growth and increased the PHBV content but had less effect on molecular weight. Scale-up cultivation in a 5-L jar yielded 4.0 g/L PHBV from 20 g/L glucose with a Mw of up to 5.0 × 106 g/mol. These results showed that H. mediterranei can produce ultrahigh-molecular-weight (UHMW) PHBV from glucose. UHMW-PHBV (7 mol% 3HV, Mw = 4.4 × 106 g/mol) was used to prepare cold-drawn films, the mechanical properties of which were characterized. The films were produced by tenfold cold drawing, followed by annealing at 100 °C, and had a tensile strength and Young’s modulus of 258.7 MPa and 0.90 GPa, respectively. We investigated the biosynthesis and properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) produced by Haloferax mediterranei from glucose. Size-exclusion chromatography revealed that PHBV produced by H. mediterranei in flask cultures had a weight-average molecular weight of 4.7 × 106 g/mol, demonstrating production of ultrahigh-molecular-weight (UHMW) PHBV. The UHMW-PHBV (7 mol% 3-hydroxyvalerate, Mw = 4.4 × 106 g/mol) obtained by jar fermenter cultivation was used to produce tenfold cold-drawn films with a tensile strength of 258.7 MPa. This suggests that UHMW-PHBV has a potential for practical, strong films.

Nanocomposites from functionalized bacterial cellulose and poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Bacterial cellulose (BC) sponges are valuable materials for tissue engineering and regenerative medicine due to their biocompatibility and nano-sized fibrous network with interconnected open porosity. However, their instability in physiological environment and poor mechanical properties are the main issues that need to be solved in order to obtain appropriate three-dimensional scaffolds for tissue formation. In this work, a bacterial polyester, poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and a simple impregnation method were used to improve the properties of BC sponges for biomedical application. Highly hydrophilic BC was surface functionalized by amination (BCA) to improve its affinity to PHBV. PHBV uptake in BC and BCA sponges depended on the PHBV concentration and was confirmed by Fourier transform infrared spectroscopy and by the increase in density after impregnation. SEM investigation showed that PHBV was deposited on the BC nanofibrous network, in some conditions forming a tridimensional honeycomb ordered structure with uniform micrometer pores. Thermogravimetric and kinetic analyses showed a delay in the thermal degradation for the BCA nanocomposites sponges compared to the BC ones and an increase in the activation energy of degradation compared to neat PHBV. Better compression strength was obtained for BCA/PHBV nanocomposite sponges due to the increased interactions between the polymer and the aminated cellulose substrate. Swelling tests showed that BC and BCA sponges did not resist and completely disintegrated in 90 min of incubation in phosphate-buffered saline, but a good stability in this simulated physiological environment was obtained after impregnation with PHBV. The swelling degree varied between 1200% and 2400% for BC/PHBV and between 700% and 1200% for BCA/PHBV sponges, which are high enough to allow the diffusion of water and the transport of nutrients. Therefore, these easily obtained BC/PHBV and BCA/PHBV nanocomposite sponges, with improved properties, could be a promising option for tissue engineering scaffolds.

Accumulation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Azotobacter vinelandii with different 3HV fraction in shake flasks and bioreactor.

In the present study, the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by Azotobacter vinelandii was evaluated in shake flasks and bioreactors, utilizing different precursors and oxygen transfer rates (OTRs). In shake flask cultures, the highest PHBV yield from sucrose (0.16gg-1) and 3-hydroxyvalerate (3HV) fraction in the PHA chain (27.4mol%) were obtained with valerate (1.0g L-1). In the bioreactor, the cultures were grown under oxygen-limited conditions, and the maximum OTR (OTRmax) was varied by adjusting the agitation rate. In the cultures grown at low OTRmax (4.3mmol L-1h-1), the intracellular content of PHBV (73% w w-1) was improved, whereas a maximum 3HV fraction (35mol %) was obtained when a higher OTRmax (17.2mmol L-1h-1, to 600rpm) was employed. The findings obtained suggest that the PHBV production and the content of 3HV incorporated into the polymer were affected by the OTR. Based on the evidence, it is possible to produce PHBV with a different composition by varying the OTR of the culture; thus, the approach in this study could be used to scale up PHBV production.

A Study on the Synthesis of Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) by Bacillus megaterium Utilizing Cheese Whey Permeate

Cheese whey permeate, a processed by-product of the dairy industry, was utilized as the sole carbon source for the production of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) from Bacillus megaterium. In the present study, propionic acid was co-fed as an internal plasticizer to synthesize PHBV co-polymer. Cultivation parameters such as time, propionic acid, C/N ratio were optimized by investigating several parameters that affect the production of PHBV. The maximum PHBV content of 86.6% and the highest PHBV yield of 3.64 g/L were achieved at 72 h, 0.1% propionic acid content, and C/N ratio of 15. The presence of PHBV in the extracted sample was confirmed by gas chromatography–mass spectroscopy (GC–MS) and Fourier transform-infrared spectroscopy analysis, and further, the morphology was studied by scanning electron microscopy analysis. Mechanical characterization revealed that PHBV has a tensile strength of 4.41 MPa, which was higher than polyhydroxybutyrate with 3.37 MPa. The PHBV biopolymer was observed to be thermally stable between 100–400 °C. The melting point, crystallization temperature and glass transition temperature of PHBV were measured to be 116.60 °C, 108.92 °C and 87.88 °C respectively. The synthesized PHBV nanoparticles had an average diameter of 343.3 nm, and the zeta potential was found to be—21.3 mV.

FABRICATION AND THERMO-MECHANICAL CHARACTERISTICS OF PHBV/LATEX/VEGETABLE OIL COMPOSITES-MODIFYING ON BIOCOMPOSITES

Polyhydroxybutyrate-co-hydroxyvalerate (PHBV, P) and natural latex (L) are mixed together to improve biostructures due to very stiff PHBV and high resilient natural latex. Another raw material added in PHBV/L mixtures is a vegetable oil which is vary between virgin coconut oil (VC) and cooking coconut oil (CC). Then, the three mixtures are known for P-L-C biocomposites. These three different components among PHBV, natural latex, and the coconut oil are considered to obtain their proper mechanical properties. The 2% and 3% (w/v) of PHBV concentrations (2P, 3P) in chloroform are started as the main component, and mixed to natural latex (L) and coconut oil (VC or CC) as the blended films in the ratio of 12:8:1, 10:10:1, 8:12:1, and compared to 6:4:1, 5:5:1, 4:6:1, respectively. The blends are specified the thermal property by the differential scanning calorimetry and also distinguished with their crystallinity. Besides, they are also characterized the tensile strength by universal testing machine. The degree of crystallinity is inversely proportional to the melting temperature particularly for 3Px-Lx-C1. The 3% w/v of PHBV-Latex-Coconut oil blends presents higher melting temperature than the 2% w/v of PHBV-Latex-Coconut oil mixtures. Adding coconut oil mixes show a lower melting temperature at 166-167oC when is compared to the mixture without coconut oil at 168-169oC. The virgin coconut oil mixes specify no inconsistency of the melting temperature, enthalpy, and degree of crystallinity. The addition of the coconut oil can diminish the 50% of tensile strength and the 6-7% of tensile modulus. The cooking coconut oil added in the 2% w/v PHBV-Latex matrix affects a 10% increase in tensile modulus related to the 3% w/v PHBV-Latex matrix. The appearance of the coconut oil in the blend is suitable for conformity of plastic deformation.

Pretreatment of lignocellulosic feedstock to produce fermentable sugars for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production using activated sludge

The goal of this research was to release fermentable reducing sugar from lignocellulose (poplar) by hot water pretreatment, and then employed to synthesize poly(3-hydroxybutyrate-co-3-hydroxy-valerate) (PHBV) using activated sludge to replace traditional petroleum-based polymers. The orthogonal experiment was used to optimize the conditions of different pretreatment temperature, pretreatment time, enzymatic hydrolysis temperature and enzymatic hydrolysis time and the optimal condition for producing sugars was pretreated at 200 °C for 30 min and enzymatic hydrolysis at 45 °C for 3d. A maximum yield was 530.3 mg/g of reduced sugar, while the furfural and 5-HMF produced in the optimum conditions were 512.61 mg/L and 239.34 mg/L. Moreover, the effects of increasing concentration of hot water pretreated poplar hydrolysates (500–1700 mg/L) on PHBV production were investigated. Poplar hydrolysate (1700 mg/L) exhibited maximum PHBV concentration of 637.556 mg/L.

POLY(HYDROXYBUTYRATE-CO-HYDROXYVALERATE) MICRONIZATION BY SOLUTION ENHANCED DISPERSION BY SUPERCRITICAL FLUIDS TECHNIQUE

ABSTRACT Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biodegradable polymer used for a wide range of applications, especially in biomedical and food industry, for which bioactive compound encapsulation is noteworthy. This work aimed to micronize PHBV by Solution Enhanced Dispersion by Supercritical Fluids technique and evaluate possible changes in polymer crystallinity. A 23 Central Composite Design with 3 central points was used to analyze the influence of pressure, temperature and PHBV concentration on particle size produced. Micronized particles were mostly spherical with sizes from 210 to 720 nm, and free of organic solvents. PHBV crystallinity degree was approximately 20% higher when polymer was processed at 8 MPa compared to that processed at 10 and 12 MPa, as well as to the raw polymer. Results suggest versatility in PHBV application according to SEDS process parameters and the possibility of its use in drug delivery systems.

Acetic Acid as an Indirect Sink of CO2 for the Synthesis of Polyhydroxyalkanoates (PHA): Comparison with PHA Production Processes Directly Using CO2 as Feedstock

White biotechnology is promising to transform CO2 emissions into a valuable commodity chemical such as the biopolymer polyhydroxyalkanaotes (PHA). Our calculations indicated that the indirect conversion of acetic acid from CO2 into PHA is an interesting alternative for the direct production of PHA from CO2 in terms of CO2 fixation, H2 consumption, substrate cost, safety and process performance. An alternative cultivation method using acetic acid as an indirect sink of CO2 was therefore developed and a proof-of-concept provided for the synthesis of both the homopolymer poly(3-hydroxybutyrate) (PHB) and the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The aim was to compare key performance parameters with those of existing cultivation methods for direct conversion of CO2 to PHA. Fed-batch cultivations for PHA production were performed using a pH-stat fed-batch feeding strategy in combination with an additional Dissolved Oxygen (DO)-dependent feed. After 118 h of fermentation, 60 g/L cell dry matter (CDM) containing 72% of PHB was obtained, which are the highest result values reported so far. Fed-batch cultivations for PHBV production resulted in 65 g/L CDM and 48 g/L PHBV concentration with a 3HV fraction of 27 mol %. Further research should be oriented towards process optimisation, whole process integration and design, and techno-economic assessment.