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The production of polyhydroxyalkanoates (PHAs) from methane is limited to mesophiles and thus suffers from high energy requirements for cooling. To address this issue, the use of thermophilic processes is gaining interest, as this strategy may deliver improved economic feasibility for PHA production. This study reports the first thermophilic PHA-producing culture grown on methane at 55 °C in fill-and-draw batch reactors. Harvested cells were incubated with various combinations of methane, propionic acid and valeric acid to assess their capacity for the synthesis of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Only PHB was produced when fed with methane alone. The addition of odd-carbon-number fatty acids resulted in higher PHA content with 3 HV fractions in the range of 15–99 mol%, depending on the types of fatty acids added. Acetic acid addition enhanced the synthesis of 3HB monomer, but not of 3 HV. On increasing the temperature to 58 °C, PHA productivity was not significantly affected.

Thermal transitions have been determined for different ternary compositions of polylactide and poly-3-hydroxybutyrate with chitosan from their TGA and DSC data. The sorption capacity of the ternary mixtures for FeIII ion has been evaluated using the Langmuir model and found to increase with the chitosan content.

Commercial paints are produced using components that can be harmful to the environment. In light of this, our study aimed to reduce these drawbacks by investigating water-based paints in which the latex resin (polyvinyl acetate [PVA]) was replaced with poly(3-hydroxybutyrate) (PHB) extracted from Spirulina sp. LEB 18. In addition, C-phycocyanin and phenolic compounds, both also extracted from this microalga, were added to the paints for coloration and antimicrobial properties, respectively. Characterization analyses indicate that paint with 9.2% PHB and 6.1% limonene performs better in the following aspects: density (1.47 g cm −3 ), solids (41.5%) and pigment contents (38.4%), hiding power (94.2%), abrasion resistance (123 cycles), adhesion (5–15% area removed), drying time (90 min), reflectance (90%), and emissivity (0.80). Moreover, the biocolorant C-phycocyanin, besides conferring color, also provides better coverage by the paints. At a concentration of 0.8%, the phenolic compounds are the most effective among the biocides tested. Overall, we found that it is possible to develop a product similar to commercial ones using natural substances extracted from microalgae, which have not yet been used in formulations of paint. Thus, this study contributes to a sustainable alternative for paint formulation.

The main goal of this investigation was setting up a growth strategy to separate H2 evolution from P3HB synthesis in order to increase cumulative P3HB in Rhodopseudomonas cells. The accumulation of poly-3-hydroxybutyrate (P3HB) was investigated culturing Rhodopseudomonas sp. S16-VOGS3 with three carbon substrates either as acetate, butyrate or lactate and with two nitrogen sources either as ammonium or glutamate. The investigation was carried out under several stress conditions caused by single or double nutrient deficiency. The content of P3HB in cell dry weight (CDW) was 21.8% with lactate; 24.6% with acetate and 27.6% with butyrate under sulfur deficient conditions. The P3HB content increased significantly culturing Rhodopseudomonas sp. S16-VOGS3 with butyrate following three phases of growth: phase-1, nutrient sufficient conditions; phase-2, nitrogen-deficiency and phase-3, sulfur-deficient conditions. Under this last phase, the highest P3HB content was achieved (34.4% of CDW). A combined production of P3HB and molecular H2 was obtained when Rhodopseudomonas sp. S16-VOGS3 was cultured with either acetate or butyrate under nitrogen sufficiency (glutamate) or nitrogen deficiency.

Soil burial biodegradation behavior of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx)] was studied based on its copolymer composition determined by thermally assisted hydrolysis and methylation-gas chromatography (THM-GC). The change in copolymer composition of P(3HB-co-3HHx) film samples during soil burial degradation test was monitored in detail by THM-GC. As a result, the copolymer compositions of 3HB units gradually increased, while those of 3HHx units decreased with soil burial time, almost correlating with recovery weight. Based on these results, the biodegradation mechanism of P(3HB-co-3HHx) was elucidated with considering the influence of the crystallinity on the biodegradability. Furthermore, local differences in biodegradability of a given P(3HB-co-3HHx) film after soil burial test were also successfully evaluated from the copolymer compositions obtained by THM-GC.

Bacterially synthesized poly (3-hydroxybutyrate-co-3-hydroxyhexanate) (PHBH) has attracted much attention as biodegradable plastics and potential biomaterials. However, the crystallization rate of PHBH is very low, which limits its application in plastic field. Herein, oxalamide compounds (OXAn) with a formula of C6H5NHCOCONH(CH2)nNHCOCONHC6H5 (n = 2, 4, 8, 12) were tailor-made as nucleators to improve the crystallization behaviors of PHBH. The effect of aliphatic spacer length of OXAn, i.e., -(CH2)n-on the nucleation behavior was investigated. The OXAn would assemble into shish-like superstructures and PHBH crystals preferred to grow on the surfaces of the shish. The crystallization rate of PHBH/OXAn blends increased with the spacer length of OXAn up to n = 8 and then leveled off, which trend was consistent with the nucleation activity (Ψ) and the nucleation constant (Kg) of the OXAn. Meanwhile, the OXAn increased the nuclei density of the PHBH while inhibited its secondary crystallization, resulting in a superior and steady mechanical performance of PHBH materials. This work provides a scientific approach to design the optimal structure of OXAn as nucleators for PHBH materials, which may broaden the application range of PHBH materials.

In the present study, we observed that laboratory rats readily consumed lyophilized cells of Cupriavidus necator H16 cultivated using palm oil containing 39 wt% poly(3-hydroxybutyrate) [P(3HB)] as sole diet source. The test animals excreted whitish fecal pellets containing 82–97 wt% P(3HB). The remaining impurities could be easily removed by washing the pellets with water and/or low concentrations of detergent, which resulted in P(3HB) granules of a high purity. The molecular masses and thermal properties of P(3HB) obtained by this method were almost similar to P(3HB) extracted from bacterial cells using chloroform. The method reported here is simple and eliminates the need for solvents and strong chemicals, thus resulting in P(3HB) production that is more ecofriendly.

"Efficient production of poly-3-hydroxybutyrate (P(3HB)) based on glucose-xylose mixtures simulating different types of lignocellulosic hydrolysate (LCH) was addressed using Burkholderia sacchari, a wild strain capable of metabolizing both sugars and producing P(3HB). Carbon catabolite repression was avoided by maintaining glucose concentration below 10g/L. Xylose concentrations above 30g/L were inhibitory for growth and production. In fed-batch cultivations, pulse size and feed addition rate were controlled in order to reach high productivities and efficient sugar consumptions. High xylose uptake and P(3HB) productivity were attained with glucose-rich mixtures (glucose/xylose ratio in the feed=1.5w/w) using high feeding rates, while with xylose-richer feeds (glucose/xylose=0.8w/w), a lower feeding rate is a robust strategy to avoid xylose build-up in the medium. Xylitol production was observed with xylose concentrations in the medium above 30-40g/L. With sugar mixtures featuring even lower glucose/xylose ratios, i.e. xylose-richer feeds (glucose/xylose=0.5), xylonic acid (a second byproduct) was produced. This is the first report of the ability of Burkholderia sacchari to produce both xylitol and xylonic acid." info:eu-repo/semantics/publishedVersion

Systematic methods, such as mathematical programming methods, are traditionally used in decision making concerning capacity planning, especially at tactical and operational level. However, such methods might have the greatest impact at the strategic level where substantial resources are irreversibly allocated. This study proposes a mathematical programming methodology to assist decision makers in strategic (long term) planning for bioprocessing of renewable resources. The novelty lies on the incorporation of significant detail of the bioprocess design in the strategic model and the use of a relatively accurate model for estimating the cost of manufacture of the alternative bioprocesses. A case study demonstrates the advantages of the proposed systematic methodology focusing on optimal screening of 25 bioprocesses for the conversion of molasses, sucrose and glycerol into 11 metabolic products. The methodology was validated via preliminary techno-economic evaluation of the optimum technology-mix involving the production of succinic acid, poly(3-hydroxybutyrate) and 2,3-butanediol.

Hydrolysis of poly(3-hydroxybutyrate) (PHB) was studied using acidic functionalized ionic liquid 1-methyl-3-(3-sulfopropyl)-immidazolium hydrogen sulfate ([HSO 3 -pmim][HSO 4 ]) as catalyst. The influences of experimental parameters, such as reaction temperature, reaction time, the amount of catalyst and mole ratio of water to PHB were investigated. Under the conditions of reaction temperature 160 °C, reaction time 4.0 h, m ([HSO 3 -pmim][HSO 4 ]): m (PHB) = 0.06:1 and n (H 2 O): n (PHB) = 7:1, the conversion of PHB was over 98%. The ionic liquid could be reused up to 6 times without apparent decrease in the conversion of PHB. In addition, the kinetics of the reaction was investigated, the result indicated that hydrolysis of PHB in [HSO 3 -pmim][HSO 4 ] was a first-order kinetic reaction and the activation energy was 171.1 kJ/mol.

Poly-3-hydroxybutyrate is a biopolymer which has shown tremendous potential for replacing conventional petroleum-based plastics for plummeting the plastic pollution problem. However, the production cost of PHB is high which makes it less attractive for commercial use. To tackle this challenge, various researchers suggest the search for low-cost substrates and energy efficient technologies for PHB production. In this regard, the waste generated from fruit processing industries or fruit wastes could be pre-processed and fermented for effectively generating PHB. Therefore, the aim of this review was to focus on the methods of fruit waste pre-processing and the effect of fermentation variables on PHB production using fruit waste as a substrate. The relevant research findings on the use of different microorganisms, PHB production conditions and fruit waste-based substrates are also covered. Analysis of various studies revealed that pineapple and mixed fruit waste are effective for PHB production.

Plastic debris surfaces in marine environments provide novel habitats for marine microbes. This type of microbial community is known as a “plastisphere”. Prior metagenomic analyses of plastispheres suggest that the surface of marine plastic debris contain plastic-degrading microbes. Here, we focus on plastisphere as a microbial source. We isolated strain OK12 from plastic bag debris collected from a beach in Japan. The strain grew on a mineral medium supplemented with poly(3-hydroxybutyrate) [P(3HB)] as the sole carbon source. Genetic and biochemical analyses demonstrated that the strain belongs to the genus Nocardioides. In addition, the average nucleotide identity value of the two genomes of the strain OK12 and Nocardioides marinisabuli DSM 18965, a marine species, was 98.3 %, above the 95 % threshold. The strain did not grow above 50 °C, and the optimum temperature for growth was 30 °C. The strain grew and degraded P(3HB) in a broad range of NaCl concentrations (0.01–2.4 M), whereas it did not grow without NaCl, suggesting that the strain is a marine species. The strain degraded the P(3HB) film at a fast rate, despite the fact that the P(3HB) degrading activity in the culture supernatant was low. The strain formed biofilms on the P(3HB) and polypropylene film surfaces. This biofilm formation may have helped the strain to degrade P(3HB).

A poly[(R)-3-hydroxybutyrate] [P(3HB)]-degrading bacterium (strain JKCM-AJ-6,1α) was isolated from coastal seawater near the port of Yaizu, Suruga Bay, Japan. The strain grew well in a marine mineral medium supplemented with P(3HB) powder as the sole carbon source. Phylogenetic analysis revealed that the strain JKCM-AJ-6,1α belonged to the genus Shewanella . The isolate was unable to grow at temperatures above 50 °C, and the optimum range of growth temperatures was 30 °C–37 °C; however, the optimum temperature for degradation of P(3HB) was 15 °C. The maximum specific growth rate (μ = 1.0 h −1 ) was attained at a NaCl concentration of 0.2 M, but the strain was able to grow even in the presence of 0.8 M NaCl. This suggests that the strain is a typical marine bacterium. This is the first report showing P(3HB) depolymerase activity in a member of the genus Shewanella . It is concluded that the genus Shewanella may be one of the key bacterial groups involved in the P(3HB) cycle in marine environments.

We demonstrate a novel strategy to produce ( R )-3-hydroxybutyric acid [( R )-3-HB] using Pseudomonas sp. DS1001a or its extracellular poly (3-hydroxybutyrate) (PHB) depolymerase. While approximately 77.8% PHB was degraded by Pseudomonas sp. DS1001a after 12 h of cultivation, only 1.555 g/l of 3-HB monomer was produced because of assimilation by the strain. About 8.58 g/l ( R )-3-HB was obtained after 8 h of incubation using extracellular PHB depolymerase from Pseudomonas sp. DS1001a. The optimal temperature and pH of PHB depolymerase were 50 °C and 8, respectively. CaCO 3 increased ( R )-3-HB yields to 23.97 g/l by stabilizing the pH of the reaction system. High yields of the ( R )-3-HB product and the low cost of the medium and CaCO 3 indicate the feasibility of bioconversion of low-value PHB waste or industrial leftovers into high-value ( R )-3-HB using extracellular PHB depolymerase.

The addition effects of polymeric materials on natural environments have been mainly evaluated in terms of the relationships between culturable polymer-degrading microorganisms and/or their secreted enzymes and target materials. In this study, we applied metagenome analysis to better understand the change in unculturable microorganismal biodiversity in the four different river samples by using poly (3-hydroxybutyrate) [P(3HB)], a well-studied biodegradable polymer. An inverse relationship between the number of microorganisms and the weight of P(3HB) was observed for all the river samples, while no changes were observed for nondegradable polyethylene. Based on statistical analysis (Chao1 index), the microbial consortia exhibited reduced diversity and tended to converge to similar microbial communities among three of the river samples. This suggests a tight relationship between the biodegradation of P(3HB) and bacterial consortium structure in the river environments. Interestingly, metagenomic sequences corresponding to bacteria that have already been identified as culturable P(3HB) degraders were detected, suggesting a close relationship between the unculturable community and the culturable community. The metagenomic analysis has provided us useful insights into the dynamic changes in the microbial community in the river samples and is applicable for various combinations of environments and biopolymers.

In the present study, media engineering was carried out to optimize various process parameters affecting fermentation for PHB production by Comamonas sp. The optimum conditions for PHB production were yeast extract concentration of 1%, pH 6.0 and inoculum concentration of 5.5%. Under optimized conditions the PHB yield was 0.523 g/g. The extracted polymer was characterized by FTIR and 1H NMR. Nanomatrices and solid walled matrices were prepared using the extracted PHB. Cytotoxic studies revealed that both solid walled and nanomatrices prepared from the extracted PHB showed almost 100% survivals of H9c2 cells. This is the first report on application of extracted PHB from Comamonas sp. as an extracellular matrix for cell culture.

Bio-based polylactide/poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PLA/PHBV) blend fibers have been prepared via the conventional melt-spinning and hot-drawing process. The spinnability was optimized by determining the narrow temperature window for each blend via rheological studies. The blend fibers showed unexpectedly improved heat-resistance and softness along with acceptable tensile properties, which was related to the significantly modified crystallization and orientation of PLA with appropriate PHBV addition. The phase morphology of PHBV evolved from finely dispersed nanoscale domains into a unique co-continuous state with increasing content. Correspondingly, the nucleation of PLA was favored at low PHBV content; both the nucleation and crystal growth of PLA were enhanced at medium PHBV content; and the crystallization and melting of PLA were confined at high PHBV content. This opened up a novel and viable way to break the performance bottleneck of traditional PLA fibers.

The non-isothermal melt crystallization kinetics of a series of copoly(ester–urethane)s, PUs, based on poly(3-hydroxybutyrate), PHB, and poly(butylene adipate), PBA, of different PHB content 20, 40, and 60 wt% were studied using DSC at different cooling rates. Various macrokinetic models, namely, Avrami, Tobin, Ozawa, and Mo models were applied to describe the crystallization process of PHB in the PU matrices. Avrami, Tobin, and Mo models could successfully describe the non-isothermal crystallization behavior of PHB segments in all samples, while Ozawa model provides a fair description of the non-isothermal crystallization process of PUs containing only 20 and 40 wt% PHB. The Avrami exponent was found to range from 3.6 to 4.0, while the Tobin exponent was found to range from 2.3 to 3.0. The spherulites shape and size were analyzed using polarized optical microscopy (POM). The results of kinetic parameters showed that the crystallization rate of PHB segments in the investigated PUs was increased with increasing the PHB content. The isoconversional method of Friedman was used to determine the effective activation energy of crystallization of the PUs and the Lauritzen–Hoffman parameters ( K g and U *) were calculated by applying the Vyazovkin method.

Scaffolds play a critical role in bone tissue engineering. Composite scaffolds made of biodegradable polymers and bioactive inorganic compounds have demonstrated superior properties in bone defect repair. In this study, highly bioactive, resorbable poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx)-based scaffolds were prepared using combinational 3-dimensional (3D) printing and surface-doping protocol. Structural and morphological characterization of the composite scaffolds demonstrated the homogenous surface-coating of mesoporous bioactive glass (MBG) throughout their porous framework. These hierarchical scaffolds showed bioactivity superior to that of scaffolds made of pure PHBHHx. MBG coating appeared to provide a better environment for human mesenchymal stem cells (hMSCs) attachment, activity, and osteogenic differentiation. Our study indicates that MBG-coated PHBHHx (PHBM) scaffolds may be excellent candidates for use in bone tissue engineering.

Novel Poly(3-hydroxybutyrate)/Poly(3-hydroxyoctanoate) blends were developed with varying amounts of Poly(3-hydroxyoctanoate), P(3HO) and Poly(3-hydroxybutyrate), P(3HB) for their potential use in various medical applications. These blend films exhibited higher tensile strength and Young’s modulus values compared to neat P(3HO). The overall protein adsorption and % cell viability was also found to be significantly higher in the blend films than the neat P(3HO) film. Hydrolytic degradation was faster in the blend films and the degradation rate could potentially be tailored to achieve the optimum rate required for a particular medical application. Hence, these novel blends were found to be highly biocompatible with surface, mechanical and thermal properties suitable for a range of potential medical applications, a great step forward in the area of medical materials.

Microspheres can be prepared simply by the W 1 /O/W 2 double emulsion-solvent evaporation method. The glycerol density gradient method can be utilized with a homogenizer to produce and separate out homogenized microspheres, with the desired size. Flow cytometer is utilized to measure not only the uniformity of the size of microspheres but also analytical instruments are used to measure their release of drugs. The diameters of microsphere reached the 5 μm–10 μm range when they were prepared with 1% (w/v) P(3HB- co -5%3HV) at a homogenizer speed of 3000 rpm. The microspheres that were separated using the glycerin gradient method and extracted in the 25% concentration zone reveal the size homogeneity determined by flow cytometry analysis. The best microsphere degradation rates were approximately 80% after 72 h of enzyme degradation, as measured using a spectrophotometer, to elucidate the drug-releasing effect of the microspheres. The concentration of trypan blue in the supernatant fluid increased with the duration of the experiment. P(3HB- co -5%3HV)-prepared microspheres with diameters of around 10 μm were engulfed by cells in the cell culture experiments.

Synthetic biology promises to simplify the construction of metabolic pathways by assembling the detached modules of the whole pathway. This gives new approaches for the microbial production of industrial products such as polyhydroxyalkanoates (PHA). In this study, to produce poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) (PHBHHx) by Pseudomonas stutzeri 1317 from unrelated carbon sources such as glucose, the phaC 1- phaZ - phaC 2 operon of P. stutzeri 1317 was knocked out to generate the PHA deficient mutant P. stutzeri 1317LF. Then three modules containing phaC Ah A Re B Re , phaC Ah B Re G Pp and phaC Ah P Ah were introduced into P. stutzeri 1317LF separately. The shake flask results indicated that the precursor supply and PHA synthase activity were the vital factors for the PHBHHx accumulation of P. stutzeri 1317LF. Furthermore, the PHBHHx accumulation of the recombinants from different carbon resources were performed. The highest PHBHHx content was 23.7% (by mass) with 58.6% (by mole) 3HB fraction. These results provide basis for further improving the PHBHHx accumulation of P. stutzeri from unrelated carbon sources.

This work is concerned with the melting behaviour and accuracy of differential scanning calorimeter (DSC) analyses of poly(3-hydroxybutyrate) (PHB), a semi-crystalline thermoplastic polymer completely biodegradable and biocompatible, and obtained from renewable resources. Melting parameters of PHB were determined for the first fusion event applying standard experimental procedures for thermal analysis, using heating rates ranging between 1 °C/min and 20 °C/min. The analyses of DSC energy flow scans showed a complex melting peak that may be resolved into three elementary peaks having different intensities at different melting temperatures. Peak temperatures depend on heating rate, while the total crystallinity detected was independent of the rate. A study of 24 DSC runs showed good temperature reproducibility (±0.5 °C), but poor reproducibility of mass crystallinity (±10%).

The biodegradable polyester poly-(3-hydroxybutyrate) (PHB), produced by Ralstonia eutropha in batch and fed-batch processes, was purified by electrofiltration. The protein film on PHB granules determines their high negative zeta potential, enabling the application of electrofiltration as an integrated technology in the downstream processing of PHB. In order to determine the optimal purification parameters, various pressure and electric field strength conditions were tested. Electrofiltration of PHB at 4bars and 4V/mm provided an up to four times higher concentration factor than conventional filtration. FT-Raman spectroscopy demonstrated that electrofiltration did not result in structural changes to the products. The study demonstrates the efficiency and practical advantages of electrofiltration as a promising downstream step in the PHB production technology.

In this paper, we report a systematic study of the dielectric relaxation spectroscopy of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) polyester which has potential applications as a “green” dielectric material in electronic devices. The dielectric spectra was measured over a wide frequency range (100 ∼ 107 Hz) from −100 to 60 °C. A glass and a sub-glass transition relaxations were observed in the dielectric spectra of PHBHHx. In addition, a nearly constant loss behavior was found by analyzing the dielectric and conductivity spectra.

Sucrose has several advantages over glucose as a feedstock for bioprocesses, both environmentally and economically. However, most industrial Escherichia coli strains are unable to utilize sucrose. E. coli W can grow on sucrose but stops growing when sucrose concentrations become low. This is undesirable in fed-batch conditions where sugar levels are low between feeding pulses. Sucrose uptake rates were improved by removal of the cscR gene, which encodes a protein that represses expression of the sucrose utilization genes at low sucrose concentrations. Poly-3-hydroxybutyrate (PHB) was used as a model compound in order to assess the effect of improved sugar utilization on bio-production. In the cscR knockout strain, production from sucrose was improved by 50%; this strain also produced 30% more PHB than the wild-type using glucose. This result demonstrates the feasibility of utilizing sucrose as an industrial feedstock for E. coli-based bioprocesses in high cell density culture.

Polyhydroxyalkanoates (PHAs) are biodegradable plastics. Currently most PHAs are produced using microbial fermentation. The separation of PHAs is a key factor in the design of a successful production scheme. This study chose a recombinant Escherichia coli to produce poly(3-hydroxybutyrate) (PHB), an important one among PHAs; and to use different separation methods to recover PHB. The diversity of PHB obtained by different separation methods was characterized. Among different methods used, sodium dodecyl sulfate (SDS)–NaOH method was selected as the best in separation from the results obtained from experiments using a combinatorial design. In the combinatorial design, only 16 runs are needed to generate 150 sets of experimental data. By using a two-stage design, PHB with a purity of 99% was obtained when the first-stage digestion used SDS digestion method (50 °C, 125 rpm, biomass/digestion solution (100 g/L) = 1/10 (w/v) and 10 min) and the second-stage used NaOH method (50 °C, 125 rpm, biomass/digestion solution (1 M) = 1/10 (w/v) and 10 min).

The effect of 7 mT (milliTesla) SMF (static magnetic field) on poly-3-hydroxybutyrate (PHB) production was studied at an acetate concentration of 260 Cmmol l−1 and temperature of 10 °C. The SMF decreased the specific acetate uptake rate by 29%, but increased the maximum PHB content and the yield of PHB on acetate by 32 and 28% respectively. The ratio qP/(qS − qP), which described specific PHB production rate over the difference between specific acetate uptake rate and specific PHB production rate, was introduced for evaluation of the ratio of carbon flux into PHB synthesis and into the TCA (tricarboxylic acid) cycle. This value reached 2.3 when activated sludge culture was exposed to magnetic field of 7 mT, which was 1.1 times higher than the qP/(qS − qP) value obtained without magnetic exposure. Therefore, the SMF promoted diversion of more acetyl-CoA towards PHB synthesis and could offset adverse effects of high acetate concentration and low temperature. These results provide evidence that SMF enhances PHB production by activated sludge.

The persistence of conventional synthetic plastic in the environment is increasingly considered as a source of ecological problem and has been motivated the research of biodegradable and biocompatible polymers. Polyhydroxyalkanoates (PHAs) are thermoplastic polyesters synthesized by several bacteria and Cupriavidus necator is the known one. Due to the high production cost of PHAs, the use of a cheaper carbon source or nutritional supplements are required in order to reduce the production cost. The aim of this research was to investigate the influence of biodiesel of rice bran oil as a low cost nutritional supplement in cultures of C. necator in mineral medium on the cell growth and production of poly(3-hydroxybutyrate) - P(3HB). For this, C. necator was cultivated in shake flasks of 500 mL with 150 mL of mineral medium at 30 °C for 24 h in 150 rpm. Samples were removed each 4 h for evaluation. The results demonstrate that the addition of biodiesel of rice bran oil as nutritional supplement in the culture of C. necator was viable, since its addition allows a cell growth with substrate consume reduction. Besides, the P(3HB) yield was 61% and 150% superior when biodiesel was used compared to the control medium using 30 g L − 1 and 15 g L − 1 , respectively.

The orientation of poly(3-hydroxybutyrate) (PHB) and poly(lactic acid) (PLA) segments in PHB/PLA blend films cast from chloroform solutions with compositions PHB O) bands of the blend components, it was derived that the PLA chains orient in the direction of elongation while the PHB chains orient perpendicular to the drawing direction. PHB homopolymer and PHB/PLA blend films with PHB > PLA compositions could only be oriented by cold drawing in ice water after quenching from the melt. The IR-dichroic effects of films drawn under these conditions indicate for both blend components a chain alignment parallel to the drawing direction.

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) is a potential material for tissue engineering applications because of its excellent biodegradable and biocompatible properties. The aim of this study is to present a close picture of the interaction between human mesenchymal stem cells (hMSCs) and the surface characteristics of PHBHHx membranes. The surface characteristics of PHBHHx membranes were created by using compression-molding, solvent-casting, and electrospinning methods. The behaviors of the hMSCs performed differently on those membranes. The highly porous electrospun PHBHHx membranes are better substrates for culturing hMSCs as they can keep higher cell viability than the compression-molded PHBHHx membranes. Aggregation and cluster formation of hMSCs were found only on the cast PHBHHx membranes.

The thermal degradation of poly(3-hydroxybutyrate) (PHB) was investigated by kinetic analyses in detail to clarify its complex degradation behavior, resulting in a finding of mixed mechanisms comprising at least a thermal random degradation with subsequent auto-accelerated transesterification, and a kinetically favored chain reaction from crotonate chain ends. The thermal degradation behavior of PHB varied with changes in time and/or temperature. From the kinetic analysis of changes in molecular weight, it was found that a non-auto-catalytic random degradation proceeding in the initial period was followed by an auto-accelerated reaction in the middle period. From the kinetic analysis of weight loss behavior, it is proposed that there are some kinetically favored scissions occurring at the chain ends, where the degradation proceeded by a 0th-order weight loss process in the middle stage. The observed 0th-order weight loss process was assumed to be an unzipping reaction occurring at ester groups neighboring the crotonate end groups.

Principal component analysis-based two-dimensional (PCA2D) correlation spectroscopy combined with the eigenvalue manipulating transformation (EMT) technique by lowering the power of a set of eigenvalues associated with the original data was applied to the temperature-dependent infrared-reflection absorption (IRRAS) spectra of spin-coated films of biodegradable P(HB-co-HHx) (HHx = 3.8, 7.2, and 10.0 mol%) copolymers. The PCA2D correlation spectra for P(HB-co-HHx) (HHx = 10.0 mol%) copolymer is completely different from those for P(HB-co-HHx) (HHx = 3.8 and 7.2 mol%) copolymers. In the synchronous PCA2D correlation spectra, the intensity changes of the bands at 1136 and 1282 cm−1 changed greatly as HHx mol% of P(HB-co-HHx) copolymers increases. Furthermore, EMT technique accentuates the contribution of intensity of band enhanced the minor PCs, seems to preferentially emphasizes the behavior of amorphous components of during the heating process.

Radiation-induced graft polymerization of vinyl acetate (VAc) onto poly(3-hydroxybutyrate) (PHB) film was carried out. At a degree of grafting higher than 5%, the grafted films (PHB-g-VAc) completely lost the enzymatic degradability that is characteristic of PHB due to the grafted VAc covering the surface of the PHB film. However, the biodegradability of the PHB-g-VAc films was recovered when the films were saponified in alkali solution under optimum conditions. Graft chains of the PHB-g-VAc film reacted selectively to become biodegradable polyvinyl alcohol (PVA). The biodegradability of the saponified PHB-g-VAc film increased rapidly with time.

Non-isothermal melt- and cold-crystallization and subsequent melting behavior of poly(3-hydroxybutyrate) (PHB) have been investigated by differential scanning calorimetry (DSC). The crystallization kinetics was studied by a direct fitting of the experimental data to various macrokinetic models, namely Avrami, Tobin and Ozawa models. All of the macrokinetic models were found to describe the experimental data for both the melt- and the cold-crystallization processes fairly well. For both the melt- and the cold-crystallization processes, the inversed half-time of crystallization and both the Avrami and the Tobin rate constants were all found to increase with increasing cooling or heating rate. For the melt-crystallization process, the Ozawa rate constant was found to decrease, while, for the cold-crystallization process, it was found to increase, with increasing temperature. Finally, the effective energy barrier for both the melt- and the cold-crystallization processes was found to decrease in its magnitude with increasing relative crystallinity.

The auto-gelling and drug release properties of the thermosensitive chitosan-β-glycerophosphate formulation were investigated. According to rheological study, gelation lag time of chitosan/β-glycerophosphate (GP) solutions varied from 2 to 60min with different deacetylation degree of chitosan, pH, gelation temperature, and the particles in the sol. The gelation properties were also found to influence the release profiles of a hydrophilic drug, 5-fluorouracil (5-FU). Morphological examination by scanning electron microphotography demonstrated that large “pores” occurred during the gel-forming process, which created hydrophilic environment and led to the rapid initial release of the drug (85% in first 8h). Poly-3-hydroxybutyrate (PHB), a biodegradable material, was applied here as scaffold to capture 5-FU into microparticles with high encapsulation efficiency by solvent-nonsolvent method. Combination of these microparticles into the chitosan-β-GP formulation could drop the rapid initial release from 85% down to 29% in the optimized PHB content (75%, by mass). The release could sustain for about 10 months. This study provided an understanding of the potential of injectable implant using thermosensitive chitosan-β-GP formulation containing PHB based particles for the water soluble drugs that need the property of long-term delivery.

Hydroxyapatite (HAP) was blended into poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) to make films and scaffolds. After HAP blending, mechanical properties of PHB including compressive elastic modulus and maximum stress showed improvement and osteoblast responses including cell growth and alkaline phosphatase activity were also strengthened. On the other hand, scaffolds made of PHBHHx blended with HAP had an adverse effect. No remarkable change on degradation of PHB or PHBHHx blended with HAP, respectively, was observed in simulated body fluid. Scanning electron microscopy examination revealed that osteoblast responses to HAP incorporation may be related to surface morphology and to the exposed HAP particles on polymer surface. All these results indicated that the blending of HAP particles into PHBHHx scaffolds fabricated by salt leaching was unable to either strengthen its mechanical properties or enhance osteoblast responses. Although HAP is bioactive and osteoconductive, its blending with PHBHHx did not generate a better performance on bone reconstruction.

Fungal degradation of biodegradable plastics such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) occurred only on the surface covered with fungal hyphae capable to excrete depolymerase, and the fungal degradation of PHBV film was described mathematically. The surface growth of fungi was derived from the notion of equivalent symmetric tree model and was expressed for the two different growth phases, exponential phase and deceleration phase. PHBV degradation by fungi was expressed in terms of the degradation capability of a fungal hypha and the fraction of fungal biomass contributing to PHBV degradation. The proposed growth and degradation models simulated the experimental data obtained from fungal PHBV degradation in soil well and gave insight into fungal PHBV degradation process.

Rabbit bone marrow cells were inoculated on 3D scaffolds of poly(lactic acid) (PLA), poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) to evaluate their in vitro biocompatibilities. It was found that PHBHHx had the best performance on attachment, proliferation of bone marrow cells. The cells on PHBHHx scaffolds presented typical osteoblast phenotypes: round cell shape, high alkaline phosphotase (ALP) activity, strong calcium deposition, and fibrillar collagen synthesis. After incubation for 10 days, cells grown on PHBHHx scaffolds were approximately 2x10(5)ml(-1), 40% more than that on PHB scaffolds and 60% more than that on PLA scaffolds. ALP activity of the cells grown on PHBHHx scaffolds was up to about 65U/g scaffolds, 50% higher than that of PHB and PLA, respectively. The scanning electronic microscopy (SEM) results showed that PHBHHx scaffolds had the appropriate roughness for osteoblast attachment and proliferation comparing with PHB and PLA. All these indicated that PHBHHx was a suitable biomaterial for osteoblast attachment, proliferation and differentiation from bone marrow cells.

The noncrystalline structures of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymers were studied by variable temperature solid-state wide-line 1H NMR and solid-state high-resolution 13C NMR spectroscopy. It is found that at room temperature there exists a rich and rigid component in the noncrystalline region of PHB and PHBV. The content of this component decreases with the increase in 3-hydroxyvalerate content in PHBV and with the increase in temperature. The brittleness of PHB may be partly attributed to the rigidness of the noncrystalline region at room temperature, while the improvement of the properties of PHBV may come from the enhanced mobility of the noncrystalline region.

Bio-nanocomposite was prepared by impregnation of bacterial cellulose into the poly(3-hydroxybutyrate) (PHB). The morphology was examined by field emission scanning electron microscopy, which showed the well-dispersed bacterial cellulose nanofibrils in PHB. The changes in the crystallinity of PHB caused by incorporating the bacterial cellulose were investigated by X-ray diffraction. The result indicates that the bacterial cellulose nanofibrils probably help the PHB molecules to crystallize. An increase in the mechanical properties was observed by impregnating bacterial cellulose as reinforcement into the PHB matrix. The biocompatibility of nanocomposite was preliminarily evaluated by cell-adhesion studies using Chinese Hamster Lung (CHL) fibroblast cells. The cells incubated with nanocomposite scaffold for 48 h were capable of forming cell adhesion and proliferation, which shows much better biocompatibility than pure PHB.

A continuous culture system consisting of two chemostats in series was used to investigate the kinetics of poly-3-hydroxybutyrate (PHB) formation by Ralstonia eutropha . The cells of R. eutropha grew under glucose-limited conditions in the first-stage and accumulated PHB under nitrogen-limited conditions in the second-stage. The carbon/nitrogen ( C / N ) ratio in the second fermenter was controlled by feeding the fermenter with a fresh glucose solution. The biokinetics of R. eutropha in different nutrient conditions were studied at various steady states by controlling the dilution rates. The cell growth, glucose utilization and PHB formation under the nitrogen-rich conditions followed a Monod model very well. PHB was accumulated substantially under nitrogen-limited conditions, and the specific PHB synthetic rate was dependent on C / N molar ratio, which also closely approximated a Monod model.

Bacterial homo poly(3-hydroxybutyrate) (PHB) was melt spun into fibers and the relations among the processing conditions, crystalline structures, and the mechanical properties were investigated. WAXD patterns of PHB fibers indicate a broad reflection which cannot be assigned to any plane in the orthorhombic system of PHB, although most strong reflections can be assigned to the planes in the orthorhombic system. It has been reported that the broad reflection is assigned to be β-zigzag form, which occurs by the stretching of the amorphous tie molecules between lamellae. When annealed under high tension, this broad reflection tended to be stronger, while it became significantly weak when annealed without tension. These results suggest that the annealing without tension makes the amorphous tie molecules crystallized into orthorhombic form, while annealing under high tension makes the molecules in the amorphous region stretched and increased the fraction of the β-zigzag form.

A new method for the recovery of poly(3-hydroxybutyrate) (PHB) from Alcaligenes eutrophus was reported. This process involved the use of a surfactant–chelate aqueous solution. The key factors that influenced the purity, recovery rate and Mv of recovered PHB were investigated. The purity and recovery rate were determined by the amount of surfactant, the ratio of chelate to dry biomass, pH value, temperature and treatment time, whereas the Mv was affected by pH value and temperature. The optimal recovery conditions were a 0·12:1 surfactant-to-dry biomass ratio, a 0·08:1 chelate-to-dry biomass ratio, a pH value of 13, a 50°C temperature and a 10-min treatment time. Under such conditions, a purity of 98·7%, a recovery rate of 93·3% and a Mv of 316000 were obtained. The original Mv was 402000.

The effects of fermentation performance on the final production cost of poly(3-hydroxybutyrate) [P(3HB)] were examined. Two processes for the production of P(3HB) byAlcaligenes latus from sucrose with the recovery method of surfactant-hypochlorite digestion were designed and subsequently analysed. The actual fermentation results that were different in the final P(3HB) content, P(3HB) yield and P(3HB) productivity were used in the simulations. The production cost of P(3HB) was significantly lower with higher P(3HB) content due to the reduction in polymer recovery cost. The cost of raw materials (mainly sucrose) was also lower with higher P(3HB) content since the process yielding higher P(3HB) content also resulted in higher P(3HB) yield on carbon source. The direct fixed capital-dependent costs decreased with increasing productivity. By employing the fermentation process that resulted in high P(3HB) concentration, P(3HB) content and P(3HB) productivity of 98.7 g/l, 88.3% and 4.94 g P(3HB)/l/h, respectively, the final production cost of P(3HB) was as low as US $2.6/kg P(3HB).

The spherulitic structure, growth rates and melting behaviour of blends of bacterially produced poly(d(−)-3-hydroxybutyrate) (PHB) and poly(l-lactide) (PLLA) were investigated using polarized light microscopy. Results indicated that low-molecular-weight PLLA (Mn = 1759) was miscible in the melt over the whole composition range, whereas a blend of high-molecular-weight PLLA (Mn = 159 400) with PHB showed biphasic separation, in accordance with calculations based on Flory-Huggins theory. Two types of spherulite were formed on cooling, relating to the crystallization of PHB and PLLA respectively. In some blends, spherulites of opposite type interpenetrated when the growth fronts met. It is proposed that lamellae belonging to one type of spherulite continued to grow in the interlamellar regions of the other type of spherulite.