Polyhydroxyalkanoate Copolymers Research Articles

A Statistical approach to optimize the production of Polyhydroxyalkanoates from Wickerhamomyces anomalus VIT-NN01 using Response Surface Methodology

Polyhydroxyalkanoates (PHAs) are three-level group of biodegradable polymers and attractive substitutes over conventional plastics to avoid the pollution problems. The yeast strain isolated from sugarcane juice, identified as Wickerhamomyces anomalus VIT-NN01, was used for the production of polyhydroxyalkanoates (PHA). Response surface methodology (RSM), three-level six variables Box-Behnken design (BBD), was employed to optimize the factors such as pH 8.0, temperature 37°C, sugarcane molasses (35g/L) supplemented with co-substrate palm oil (0.5%),corn steep liquor (2%) after a period of 96h of incubation for the maximum yield (19.50±0.3g/L) of PHA. It was well in close agreement with the predicted value obtained by RSM model yield (19.55±0.1g/L).Characterization of the extracted polymer was done using FTIR, GC–MS, XRD, TGA and AFM analysis. NMR spectroscopic analysis revealed that the biopolymer was poly (3-hydroxybutyrate-co-3-hydroxyvalerate), copolymer of PHA. This is the first report on optimization of PHA production using yeast strain isolated from natural sources.

Medium Chain-Length Polyhydroxyalkanoate Copolymer Modified by Bacterial Cellulose for Medical Devices.

Medium chain-length polyhydroxyalkanoates (mPHAs) are flexible elastomeric biopolymers with valuable properties for biomedical applications like artificial arteries and other medical implants. However, an environmentally friendly and high productivity process together with the tuning of the mechanical and biological properties of mPHAs are mandatory for this purpose. Here, for the first time, a melt processing technique was applied for the preparation of bionanocomposites starting from poly(3-hydroxyoctanoate) (PHO) and bacterial cellulose nanofibers (BC). The incorporation of only 3 wt % BC in PHO improved its thermal stability with 25 °C and reinforced it, increasing the Young's modulus with 76% and the tensile strength with 44%. The percolation threshold calculated with the aspect ratio of the fibers after melt processing was very low and close to 3 wt %. We showed that this bionanocomposite is able to preserve the ductile behavior during storage, no important aging being noted between 3 h and one month after compression-molding. Moreover, this study is the first to investigate the melt processability of PHO nanocomposite for tube extrusion. In addition, biocompatibility study showed no proinflammatory immune response and better cell adhesion for PHO/BC nanocomposite with 3 wt % BC and demonstrated the high feasibility of this bionanocomposite for in vivo application of tissue-engineered blood vessels.

Bioprocess optimization of PHB homopolymer and copolymer P3 (HB-co-HV) by Acinetobacter junii BP25 utilizing rice mill effluent as sustainable substrate

ABSTRACTThe potential use of parboiled rice mill effluent as a cheap substrate for the production of homopolymer and copolymer of Polyhydroxyalkanoates (PHAs) by Acinetobacter junii BP 25 was investigated for the first time. Process optimization by one factor at a time led to homopolymer polyhydroxybutyrate (PHB) production of 2.64 ± 0.18 g/l with 94.28% PHB content using a two-stage batch cultivation mode. BP 25 furthermore produced polyhydroxybutyrate-co-hydroxyvalerate (P3 (HB-co-HV)), with the addition of valeric acid as an additive to the substrate, yielding (2.56 ± 0.12 g/l dry biomass, 2.20 ± 0.15 g/l PHA) a copolymer content of 85.93%. Thus, rice mill effluent can be an effective and relatively low-cost alternative for the production of PHA, replacing the pure substrates.

Effect of glucose and olive oil as potential carbon sources on production of PHAs copolymer and tercopolymer by Bacillus cereus FA11.

In this study, the influence of different physicochemical parameters on the yield of polyhydroxyalkanoates (PHAs) produced by Bacillus cereus FA11 is investigated. The physicochemical factors include pH, temperature, time, inoculum size and its age, agitation speed and composition of the glucose rich peptone deficient (GRPD) medium. During two-stage fermentation, B. cereus FA11 produced a significantly high (p<0.05) yield (80.59% w/w) of PHAs copolymer using GRPD medium containing glucose (15g/L) and peptone (2g/L) at pH 7, 30°C and 150rpm after 48h of incubation. On the other hand, the presence of olive oil (1% v/v) and peptone (2g/L) in the GRPD medium resulted in biosynthesis of tercopolymer during two-stage fermentation and the yield of tercopolymer was 60.31% (w/w). The purified PHAs was characterized by Fourier transform infrared spectroscopy and proton resonance magnetic analysis. Proton resonance magnetic analysis confirmed that the tercopolymer was comprised of three different monomeric subunits, i.e., 3-hydroxybutyrate, 3-hydroxyvalerate and 6-hydroxyhexanoate.

Fractionation and thermal characteristics of biosynthesized polyhydoxyalkanoates bearing aromatic groups as side chains

Two polyhydroxyalkanoate (PHA) copolymers, poly(3-hydroxybutyrate-co-3-hydroxy-3-phenylpropioate) [P(3HB-co-3H3PhP)] and poly(3-hydroxybutyrate-co-3-hydroxy-4-phenylbutyrate) [P(3HB-co-3H4PhB)], both bearing aromatic side chains, were biosynthesized by recombinant Ralstonia eutropha fed with a respective precursor for the aromatic unit. As bacterial PHA copolymers generally exhibit broad comonomer compositional distribution, the as-biosynthesized samples, P(3HB-co-18 mol% 3H3PhP) and P(3HB-co-11 mol% 3H4PhB), were fractionated into several fractions with narrow comonomer compositional distribution using a chloroform/n-hexane mixed solvent. When the fractionated samples were aged under ambient conditions, the P(3HB-co-3H3PhP) fraction with 12 mol% 3H3PhP exhibited a melting temperature (Tm) of 132–148 °C, whereas the fractions with 15–21 mol% 3H3PhP did not exhibit melting behavior. As for P(3HB-co-3H4PhB), all fractions with a range of 4–15 mol% 3H4PhB exhibited Tm in the range 105–151 °C. The glass transition temperature (Tg) of these copolymers increased with increasing aromatic unit content, and the highest Tg of 20 °C was observed for the fraction with 21 mol% 3H3PhP. On the basis of the results presented here, the effects of aromatic comonomers on the thermal properties of the resulting copolymers are discussed. Two polyhydroxyalkanoate copolymers, poly(3-hydroxybutyrate-co-3-hydroxy-3-phenylpropioate) [P(3HB-co-3H3PhP)] and poly(3-hydroxybutyrate-co-3-hydroxy-4-phenylbutyrate) [P(3HB-co-3H4PhB)] were biosynthesized. The as-biosynthesized polymers were fractionated into several fractions with narrow comonomer compositional distribution using a chloroform/n-hexane mixed solvent. Using these fractions, the effects of aromatic comonomers on the thermal properties were investigated.

Production and characterization of medium-chain-length polyhydroxyalkanoate copolymer from Arctic psychrotrophic bacterium Pseudomonas sp. PAMC 28620

Arctic psychrotrophic bacterium Pseudomonas sp. PAMC 28620 was found to produce a distinctive medium-chain-length polyhydroxyalkanoate (MCL-PHA) copolymer when grown on structurally unrelated carbon sources including glycerol. The maximum MCL-PHA copolymer yield was obtained about 52.18±4.12% from 7.95±0.66g/L of biomass at 144h of fermentation when 3% glycerol was used as sole carbon and energy source during the laboratory-scale bioreactor process. Characterization of the copolymer was carried out using fourier transform infrared spectroscopy (FTIR), gas chromatography–mass spectrometry (GC–MS), proton (1H) and carbon (13C) nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), differential scanning calorimeter (DSC) and thermo-gravimetric analysis (TGA). The copolymer produced by Pseudomonas sp. PAMC 28620 consisting of four PHA monomers and identified as 3-hydroxyoctanoate (3HO), 3-hydroxydecanoate (3HD), 3-hydroxydodecanoate (3HDD) and 3-hydroxytetradecanoate (3HTD). An average molecular weight of the copolymer was found approximately 30.244kDa with polydispersity index (PDI) value of 2.05. Thermal analysis showed the produced MCL-PHA copolymer to be low-crystalline (43.73%) polymer with great thermal stability, having the thermal decomposition temperature of 230°C–280°C, endothermic melting temperature (Tm) of 172.84°C, glass transition (Tg) temperature of 3.99°C, and apparent melting enthalpy fusion (ΔHm) about 63.85Jg−1.

Composite properties and biodegradation of biologically recovered P(3HB-co-3HHx) reinforced with short kenaf fibers

A compression-molded green composite material comprising of bacterially synthesized poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx)] and short kenaf fibers (KF) was prepared in the present study. Accordingly, P(3HB-co-3HHx) was produced by the Cupriavidus necator Re2058/pCB113 using the palm oil as the sole carbon source, while the polyhydroxyalkanoate (PHA) copolymer with ∼99% purity was recovered from the bacterial cells using a newly reported solvent-free biological recovery method. Experimental results showed that P(3HB-co-3HHx) containing 30 wt % KF possessed the highest flexural strength and similar or better comparable mechanical performance compared to that of the low density polyethylene (LDPE), LDPE/KF composites and high density polyethylene (HDPE). Water absorption and soil burial tests were also performed to evaluate the durability of the P(3HB-co-3HHx)/KF composites. As compared to that of the pristine P(3HB-co-3HHx), it was determined that P(3HB-co-3HHx)/KF composites demonstrated higher water absorption percentage and showed higher percentage of weight loss during the soil degradation study. Burkholderia sp., Streptomyces sp., Amycolatopsis sp. and Streptacidiphilus sp. that involved in the biodegradation of P(3HB-co-3HHx)/KF composites during the soil degradation study were successfully isolated and characterized. These species had the capability to degrade the composite material in vitro.

Co-metabolism of substrates by Bacillus thuringiensis regulates polyhydroxyalkanoate co-polymer composition

Polyhydroxyalkanoate (PHA) production by Bacillus thuringiensis EGU45 was studied by co-metabolism of crude glycerol (CG) (1%, v/v), glucose (0.05–0.5%, w/v) and propionic acid (0.05–0.5%, v/v) under batch (shake flask) culture conditions. Glycerol+PA combination resulted in 15–100mg/L PHA co-polymers with a HV content of 33–81mol%. The addition of NH4Cl (0.5%, w/v) to CG+PA enhanced PHA production by 1.55-fold, with a HV content of 58–70mol%. The time period of incubation of PA to the feed: CG+glucose was optimized to be 3h after initiation of fermentation. The PHA contents were found to be stable at 1900–2050mg/L up scaling from 0.4 to 2.0L feed material. Biochemical characterization through GC–MS of PHA co-polymer revealed the presence of 3-hydroxydecanoate (3-HDD), 3-hydroxyoctadecanoate (3HOD), 3-hydroxyhexadecanoate (3HHD).

Characterization of the depolymerizing activity of commercial lipases and detection of lipase-like activities in animal organ extracts using poly(3-hydroxybutyrate-co-4-hydroxybutyrate) thin film.

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] is one of the polyhydroxyalkanoate (PHA) copolymers which can be degraded by lipases. In this study, the depolymerizing activity of different known commercial lipases was investigated via microassay using P(3HB-co-92 mol % 4HB) thin film as substrate. Non-enzymatic hydrolysis occurred under conditions in which buffers with pH 12 and 13 were added or temperature of 50 °C and above. Different concentrations of metal ions or detergents alone did not cause the film hydrolysis. The depolymerizing activity of lipases on P(3HB-co-4HB) was optimum in the pH range of 6–8 and at temperatures between 30 and 50 °C. Addition of metal ions and detergents in different concentrations was also shown to cause variable effects on the depolymerizing activity of commercial lipases. Pancreatic extracts from both mouse and chicken showed similar depolymerizing activity as the commercial lipases on the P(3HB-co-4HB) film. The presence of lipolytic enzymes in the organ extracts was confirmed with another lipase activity assay, p-nitrophenyl laurate assay. For the first time this has produced a direct evidence for the involvement of lipase-like enzymes from animal in the degradation of this PHA. Lipase is most likely the enzyme from pancreas that was involved in the degradation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-016-0230-z) contains supplementary material, which is available to authorized users.

Copolymers of polyhydroxyalkanoates and polyethylene glycols: recent advancements with biological and medical significance

AbstractCopolymers of polyhydroxyalkanoates (PHAs) and polyethylene glycols (PEGs) have gained high significance for biological and medical applications within the past few years. PHAs are natural biopolymers (hydrophobic biopolyesters), which can be produced microbially and also synthetically, and PEGs are biocompatible hydrophilic polyethers, which are frequently used in medicine to enhance the effect of bioactive compounds. Both polymers can be conjugated with a variety of other polymers, and in particular the conjugation with each other affords hydrophobic − hydrophilic PHA‐PEG copolymers with high significance as biomaterials. This paper describes selected recent developments in this field with a focus on synthetic approaches and the suitability of the resulting copolymers for applications in drug delivery and tissue engineering. © 2016 Society of Chemical Industry

Microbial Cometabolism and Polyhydroxyalkanoate Co-polymers

Polyhydroxyalkanoate (PHAs) are natural, biodegradable biopolymers, which can be produced from renewable materials. PHAs have potential to replace petroleum derived plastics. Quite a few bacteria can produce PHA under nutritional stress. They generally produce homopolymers of butyrate i.e., polyhydroxybutyrate (PHB), asa storage material. The biochemical characteristics of PHB such as brittleness, low strength, low elasticity, etc. make these unsuitable for commercial applications. Co-polymers of PHA, have high commercial value as they overcome the limitations of PHBs. Co-polymers can be produced by supplementing the feed with volatile fatty acids or through hydrolysates of different biowastes. In this review, we have listed the potential bacterial candidates and the substrates, which can be co-metabolized to produce PHA co-polymers.

Novel polyhydroxyalkanoate copolymers produced in Pseudomonas putida by metagenomic polyhydroxyalkanoate synthases.

Bacterially produced biodegradable polyhydroxyalkanoates (PHAs) with versatile properties can be achieved using different PHA synthases (PhaCs). This work aims to expand the diversity of known PhaCs via functional metagenomics and demonstrates the use of these novel enzymes in PHA production. Complementation of a PHA synthesis-deficient Pseudomonas putida strain with a soil metagenomic cosmid library retrieved 27 clones expressing either class I, class II, or unclassified PHA synthases, and many did not have close sequence matches to known PhaCs. The composition of PHA produced by these clones was dependent on both the supplied growth substrates and the nature of the PHA synthase, with various combinations of short-chain-length (SCL) and medium-chain-length (MCL) PHA. These data demonstrate the ability to isolate diverse genes for PHA synthesis by functional metagenomics and their use for the production of a variety of PHA polymer and copolymer mixtures.

Evaluation of the effects of crude glycerol on the production and properties of novel polyhydroxyalkanoate copolymers containing high 11‐hydroxyoctadecanoate by Cupriavidus necator IPT 029 and Bacillus megaterium IPT 429

Crude glycerol (CG), a by‐product from biodiesel production, is a carbon source with potential as feedstock for polyhydroxyalkanoate (PHA) production. PHAs are biological macromolecules synthesized by microorganisms as intracellular carbon and energy storage granules. PHA production and its properties were investigated using Cupriavidus necator IPT 029 and Bacillus megaterium IPT 429 cultivated with CGs from different origins. The highest PHA extraction percentage (71.56% [w/v]) occurred when C. necator IPT 029 metabolized CG 3 (from the processing of biodiesel from castor bean oil). The gas chromatography–mass spectrometry analyses revealed novel PHA constituents as building blocks of medium (3‐hydroxytetradecanoate) and long (11‐hydroxyoctadecanoate) chains. Molar mass distribution revealed range of 121–6900 kDa. The initial degradation temperature ranged from 181.83 to 287.50°C and the crystallinity ranged from 35.30 to 66.70%. The results obtained indicate that C. necator IPT 029 from CG 3 could produce copolymers with industrially applicable thermophysical properties. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Use of thiol-ene click chemistry to modify mechanical and thermal properties of polyhydroxyalkanoates (PHAs)

In order to diversify the number of applications for poly[(R)-3-hydroxyalkanoates] (PHAs), methods must be developed to alter their physical properties so they are not limited to aliphatic polyesters. Recently we developed Escherichia coli LSBJ as a living biocatalyst with the ability to control the repeating unit composition of PHA polymers, including the ability to incorporate unsaturated repeating units into the PHA polymer at specific ratios. The incorporation of repeating units with terminal alkenes in the side chain of the polymer allowed for the production of random PHA copolymers with defined repeating unit ratios that can be chemically modified for the purpose of tailoring the physical properties of these materials beyond what are available in current PHAs. In this study, unsaturated PHA copolymers were chemically modified via thiol-ene click chemistry to contain an assortment of new functional groups, and the mechanical and thermal properties of these materials were measured. Results showed that cross-linking the copolymer resulted in a unique combination of improved strength and pliability and that the addition of polar functional groups increased the tensile strength, Young's modulus, and hydrophilic profile of the materials. This work demonstrates that unsaturated PHAs can be chemically modified to extend their physical properties to distinguish them from currently available PHA polymers.

Production of co-polymers of polyhydroxyalkanoates by regulating the hydrolysis of biowastes

Production of polyhydroxyalkanoate (PHA) co-polymers by Bacillus spp. was studied by feeding defined volatile fatty acids (VFAs) obtained through controlled hydrolysis of various wastes. Eleven mixed hydrolytic cultures (MHCs) each containing 6 strains could generate VFA from slurries of (2% total solids): pea-shells (PS), potato peels (PP), apple pomace (AP) and onion peels (OP). PS hydrolysates (obtained with MHC2 and MHC5) inoculated with Bacillus cereus EGU43 and Bacillus thuringiensis EGU45 produced co-polymers of PHA at the rate of 15–60mg/L with a 3HV content of 1%w/w. An enhancement in PHA yield of 3.66-fold, i.e. 205–550mg/L with 3HV content up to 7.5%(w/w) was observed upon addition of OP hydrolysate and 1% glucose (w/v) to PS hydrolysates. This is the first demonstration, where PHA co-polymer composition, under non-axenic conditions, could be controlled by customizing VFA profile of the hydrolysate by the addition of different biowastes.

&lt;i&gt;Pseudomonas aeruginosa&lt;/i&gt; MTCC 7925 as a Biofactory for Production of the Novel SCL-LCL-PHA Thermoplastic from Non-Edible Oils

Novel short-chain-length-long-chain-length polyhydroxyalkanoate (SCL-LCL-PHA) copolymer production was examined with Pseudomonas aeruginosa MTCC 7925 under supplementation of non-edible oils such as karanja, jatropha, mahua, and castor oils, and their respective cakes for cost reduction. Polymer yield reached up to 4.66 g/l (63.7% dry cell wt., dcw) with a mol fraction of 89.7:4.2:2.7:3.4 of 3- hydroxybutyric acid (3HB): 3-hydroxyvaleric acid (3HV): 3-hydroxyhexadecanoic acid (3HHD): 3-hydroxyoctadecanoic acid (3HOD) units under the interactive condition of low nitrogen concentration with 0.5% (v/v) jatropha oil in combination with its cake extract, followed by 3.94 g/l (59.6% dcw) with a mol fraction of 91.6:3.3:2.5:2.6 of 3HB: 3HV: 3HHD: 3HOD with castor oil and its cake extracts. The novel co-polymer not only depicted material properties analogous to the common plastics but also better melting temperature (Tm), glass-transition temperature (Tg), elongation-to-break value and Young’s modulus than the homopolymer of poly-3-hydroxybutyrate (PHB). As compared to our previous report where palm oil and its cakes were used, a cost reduction of 54% was observed with the non-edible jatropha oil with its cakes. This opens up possibility for further study at pilot-scale level for low-cost production and future recommendations. Keywords: Low-cost carbon sources, NH4NO3, KH2PO4, Polyhydroxyalkanoates, Pseudomonas aeruginosa MTCC 7925, Non-edible oils, SCL-LCL-PHA co-polymer

Bioconversion of crude glycerol to polyhydroxyalkanoate by Bacillus thuringiensis under non-limiting nitrogen conditions

Glycerol has emerged as a cheap waste material due to blooming biodiesel manufacturing units worldwide. The need is to exploit the crude glycerol (CG) to produce useful products such as polyhydroxyalkanoate (PHA). Bacillus thuringiensis EGU45 was found to produce 1.5–3.5gPHAL−1 from feed containing 1–10% CG (vv−1) and nutrient broth (NB, 125mL) without any acclimatization. B. thuringiensis EGU45 could produce PHA at the rate of 1.54–1.83gL−1, from 1% CG (vv−1) on media having high nitrogen contents: (i) NB, (ii) NB+0.5% NH4Cl (wv−1), and (iii) peptone+yeast extract+0.5% NH4Cl (wv−1). B. thuringiensis EGU45 was able to produce co-polymer of P(3HB-co-3HV) with 13.4% 3HV content on high N containing feed supplemented with propionic acid. This is the first report demonstrating the abilities of B. thuringiensis to convert CG into PHA co-polymer under non-limiting N conditions.

Effect of Oligo-Hydroxyalkanoates on Poly(3-Hydroxybutyrate-co-4-Hydroxybutyrate)-Based Systems

This study presents the utilization of oligo-hydroxyalkanoates obtained from controlled degradation of poly(3-hydroxybutyrate) as additives in a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer matrix (P(3HB-co-4HB)). These oligomers are compared to a conventional biobased plasticizer, used as reference, based on a monoglyceride acetate obtained from hydrogenated castor oil. Different multiphase systems are elaborated with these additives and characterized. Thermal and mechanical properties demonstrate that the monoglyceride acetate is as an efficient plasticizer increasing the elongation of the P(3HB-co-4HB) films while decreasing their maximum strength and elastic modulus. On the contrary, the addition of oligo-PHB results in an increased crystallinity of the matrix, thus improving the maximum strength and elastic modulus of the corresponding films. The oligomers act as an efficient reinforcing agent. Mobility brought by the oligomers induces a rearrangement of the P(3HB-co-4HB) with an increase of the chain rearrangement. Interestingly, the simultaneous addition of both additives results in significantly reduced T-g and improved elongation at break, as expected from an efficient plasticizer, but it also leads to P(3HB-co-4HB) films retaining relatively high strength and modulus values, thanks to the reinforcement ability of the oligo-PHB additive. Thermal characterization finally demonstrated that such mixed additives system results in greatly improved thermal stability of the polyhydroxyalkanoate copolymer matrix.

Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyalkanoates) by recombinant Escherichia coli from glucose

The polyhydroxyalkanoate (PHA) copolymers consisting of short-chain-length (scl) and medium-chain-length (mcl) monomers have various properties ranging from stiff to flexible depending on the molar fraction of the monomer compositions. It has been reported that PhaG, which is first known as a (R)-3-hydroxyacyl-acyl carrier protein (ACP)-CoA transferase, actually functions as a 3-hydroxyacyl-ACP thioesterase, and the product of PP0763 gene from Pseudomonas putida KT2440 has a (R)-3-hydroxyacyl (3HA)-CoA ligase activity (Wang et al., Appl. Environ. Microbiol., 78, 519-527, 2012). In this study, we found a new (R)-3HA-CoA ligase (the product of PA3924 gene) from Pseudomonas aeruginosa PAO. The PA3924 gene was coexpressed with PHA synthase 1 gene (phaC1Ps) and phaGPs gene from Pseudomonas sp. 61-3, and β-ketothiolase gene (phbARe) and acetoacetyl-CoA reductase gene (phbBRe) from Ralstonia eutropha in Escherichia coli LS5218 at 25°C. As a result, the copolymer containing 94.6mol% 3-hydroxybutyrate (3HB) and 5.4mol% mcl-3-hydroxyalkanoates (3HA) consisting of C8, C10, C12 and C14 was synthesized by recombinant E.coli LS5218 from glucose as the sole carbon source. The concentration of P(3HB-co-3HA) (scl-co-mcl-PHA) synthesized by the recombinant E.coli LS5218 harboring phaC1Ps, phaGPs, phbABRe and the PA3924 genes was approximately 7-fold higher than that of the recombinant LS5218 harboring phaC1Ps, phaGPs, phbABRe and the PP0763 genes. The number-average molecular weight of the P(3HB-co-5.4% 3HA) copolymer was 233×10(3), which was relatively high molecular weight. In addition, the physical and the mechanical properties of the copolymer were demonstrated to improve the brittleness of P(3HB) homopolymer.

Impact of different by-products from the biodiesel industry and bacterial strains on the production, composition, and properties of novel polyhydroxyalkanoates containing achiral building blocks

The potential of crude glycerol (CG) from different origins as carbon sources in the production of polyhydroxyalkanoate (PHA) copolymer using Cupriavidus necator IPT 027 and Burkholderia cepacia IPT 438 was investigated in this study. Different variables were kept constant during the subsequent microbial growth and PHA production. A maximum cell accumulation of 71.07% (w/v) was obtained when C. necator IPT 027 was cultivated with CG II (originated from the processing of biodiesel from residual fats and oils). The gas chromatography–mass spectrometry (GC–MS) analyses revealed novel PHA-constituents as building blocks of medium chains (3HTD) and long (15HPD and 11HHD) chains. Analyses of molar mass distribution revealed weight average molar masses (Mw) in the range of 552–8240kDa and polydispersity indexes (PDIs) in the range of 1.6–2.2. The melting temperature ranged between 139.8 and 175.9°C. The crystallinity was verified by X-ray diffraction (XRD) (35.92–66.07%) and differential scanning calorimetry (DSC) (33.30–57.80%). High decomposition temperatures (291.6–348.9°C) were also observed. All PHAs presented Fourier transform infrared (FTIR) spectra that were similar to the FTIR spectra reported in the literature. The results obtained from this study indicate that C. necator IPT 027 and B. cepacia IPT 438 cultivated from different by-products from the biodiesel industry were capable of producing PHA copolymers that are suitable for industrial applications.