Polyhydroxybutyrate Content Research Articles

Biopolymer detection in Egyptian microalgae: A pathway to eco-friendly bioplastics

With the increase in pollution resulting from plastic waste, it was a necessity to reduce the danger of its waste to the environment. Hence, replacing traditional plastic with bioplastic is a must. Bioplastic is more environmentally friendly materials, such as plastic made from biological sources. Green and bluegreen microalgae have recently emerged as two of the most valuable sources. This study examines the viability of using microalgal cells to produce biopolymers, such as polyhydroxybutyrate, proteins, and carbohydrates. The study employed spectrophotometric standards to quantify the concentrations of polyhydroxybutyrate (PHB) and carbohydrates. Additionally, the Kjeldahl method was utilised to determine the total protein content. Five green microalgal strains and five blue green microalgal strains were examined. Chlorophyll a was measured to track growth. Growth rate assessments revealed that Selenastrum gracile exhibited the highest chlorophyll a concentration (6.9 μg/L) at 15 days, accompanied by the highest protein content at 41.13 %. Additionally, it displayed a PHB concentration of 325 mg/mL, while exhibiting the lowest carbohydrate levels (12 mg/ml). Polyhydroxybutrate content maximum concentration was detected in Microcystis aeruginosa 720.5 μg/mL, and 31 % concentration in proteins and carbohydrates (12.3 mg/ml). Selenastrum sp. is easily cultivated and offers potential for further research. Its application in bioplastic production, through blending with other polymers, is a promising avenue for future exploration.

Production of Polyhydroxybutyrate by halotolerant Halomonas cerina YK44 using sugarcane molasses and soybean flour in tap water

As environmental pollution intensifies, the interest in bioplastics is growing. The bioplastic polyhydroxyalkanoates (PHAs), which are produced and degraded by microorganisms, have received considerable attention. However, the production cost of PHA is still high, and several ways to increase economy of PHA production have been studied. Therefore, as one way of solution, Halomonas species were screened and evaluated with cheap substrates such as molasses and soybean flour. Among tested strains, Halomonas cerina YK44 was selected and used for polyhydroxybutyrate (PHB) production with molasses and soybean flour together, whose combination was not evaluated well before, in tap water. The medium composition optimization showed maximum PHB production at 4 % sugarcane molasses, 2 % NaCl, 0.05 % soybean flour, and pH 8 in tap water (9.2 g/L DCW, 7.3 g/L PHB, and 79.7 % PHB contents). However, cell growth of halotolerant H. cerina YK44 was disturbed by 0.2 % furfural, which existed in biomass based sugars as inhibitors. Physical and thermal analyses revealed that PHB film started from sugarcane molasses and soybean flour was no different from that initiated from simple sugars (Tm was 175.8 °C and 176.2 °C, PDI was 1.29, and 1.31, respectively).

Evaluating bioproducts production in a purple phototrophic biofilm photobioreactor: Fuel-synthesis wastewater vs. simple substrates

This study evaluated the influence of different carbon sources on purple non-sulphur bacteria (PNSB) biofilm formation, and the production of polyhydroxybutyrate (PHB) and other value-added bio-products. Higher PNSB growth and biofilm formation were observed in fuel-synthesis wastewater (FSW), followed by acetate. Both FSW and acetate cultures contained a large proportion of Rhizobiales, while sugar substrates led to yeast enrichment. Protein contents reached 40–41 % for acetate, which is suitable for single cell protein (SCP) use. The maximum PHB content from the suspended and biofilm growth was obtained from glucose (18.1 ± 0.10 %, 12.9 ± 1.11 %), followed by FSW (14.9 ± 0.25 %, 11.2 ± 0.50 %). FSW showed the highest overall productivity for both protein and PHB. Pigment concentrations were low for all substrates. The study underscores substrate influence on microbial community and bioproducts potential. It highlights FSW as a promising substrate for PNSB, suggesting its treatment integration for resource recovery.

Impacts of polyhydroxybutyrate (PHB) microplastic exposure on physiology and metabolic profiles of Litopenaeus vannamei

In light of increasing concerns about microplastic pollution, it is crucial to understand the biological impacts of biodegradable PHB microplastics on marine organisms. This study included a 96-h exposure experiment to assess acute toxicity at PHB concentrations of 0 mg/L, 100 mg/L, 500 mg/L and 1000 mg/L. Additionally, a 60-day feeding trial was conducted with PHB concentrations of 0, 0.5, 1.0 and 2.0 g/kg to evaluate the long-term effects on growth, physiological health and metabolic responses of Litopenaeus vannamei. Results from the exposure experiment indicated that PHB microplastics up to 100 mg/L were non-toxic to shrimp. However, the 60-day feeding trial revealed that higher concentrations led to slight reductions in survival rates and growth performance, indicating a concentration-dependent response. Analysis of antioxidant and immune enzymes showed minimal changes across most parameters. However, increases in malondialdehyde content and lysozyme activity at higher PHB levels suggested a stress response. Microbial analysis indicated higher species richness and greater community diversity in the PHB group compared to controls, as evidenced by Chao1, ACE, Shannon and Simpson indices. Linear discriminant analysis revealed that Enterobacteriales and related taxa were more prevalent in the PHB group, while Rhodobacteraceae and associated taxa dominated the control group. Pathway analysis highlighted enhanced signal transduction, cell mobility and metabolic resource reallocation in response to PHB-induced stress. Integrated transcriptomic and metabolomic analyses revealed significant regulatory changes, especially in lipid metabolism pathways. These findings suggest that while PHB microplastics trigger adaptive metabolic responses in shrimp, they do not cause acute toxicity. Significant variations in intestinal microbiome composition reflect potential shifts in gut health dynamics due to PHB ingestion. This study enhances our understanding of the ecological impacts of microplastics and underscores the necessity for further research into the environmental safety of biodegradable alternatives.

Enhancing mechanical performance of solvent-cast 3D printed PCL composites: A comprehensive optimization approach

This study aims to enhance the mechanical properties of 3D-printed scaffolds by optimizing a composite of Poly-ε-caprolactone (PCL), poly-hydroxybutyrate (PHB), and synthetic fluorapatite (FHAp) using Response Surface Methodology (RSM). The research targets the intricate relationships between PCL, PHB, and FHAp concentrations, crucial for achieving optimal tensile, compressive, and flexural strengths. The solvent-cast process successfully yielded FHAp-reinforced PCL composites, confirmed by XRD and FTIR spectra. The findings indicate that an optimal PHB content of over 15 % wt/v and PCL under 10 % wt/v significantly enhance tensile strength, achieving values up to 48 MPa. Compressive strength peaked at PHB concentrations of 13–16 % wt/v and PCL concentrations of 9–13 % wt/v, showcasing effective stress transmission, with the highest recorded value being 90 MPa. Flexural strength exceeded 100 MPa with lower concentrations of PCL and PHB, emphasizing the need for a balance of rigidity and flexibility. The study identifies the optimum composition for these mechanical properties at PCL 9.432 % wt/v, PHB 16.568 % wt/v, and FHAp 24.933 % wt/v, crucial for advanced biomedical implant applications.

PHB+aPHA Blends: From Polymer Bacterial Synthesis through Blend Preparation to Final Processing by Extrusion for Sustainable Materials Design.

The inherent brittleness of polyhydroxybutyrate (PHB), a well-studied polyhydroxyalkanoate (PHA), limits its applicability in flexible and impact-resistant applications. This study explores the potential of blending PHB with a different PHA to overcome brittleness. The synthesis of PHA polymers, including PHB and an amorphous medium-chain-length PHA (aPHA) consisting of various monomers, was achieved in previous works through canola oil fermentation. Detailed characterization of aPHA revealed its amorphous nature, as well as good thermal stability and shear thinning behavior. The blending process was carried out at different mass ratios of aPHA and PHB, and the resulting blends were studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The blends exhibited complex DSC curves, indicating the presence of multiple crystalline forms of PHB. SEM images revealed the morphology of the blends, with PHB particles dispersed within the aPHA matrix. TGA showed similar thermal degradation patterns for the blends, with the residue content decreasing as the PHB content increased. The crystallinity of the blends was influenced by the PHB content, with higher PHB ratios resulting in an increased degree of crystallinity. XRD confirmed the presence of both α and β crystals of PHB in the blends. Overall, the results demonstrate the potential of PHB+aPHA blends to enhance the mechanical properties of biopolymer materials, without com-promising the thermal stability, paving the way for sustainable material design and novel application areas.

Efficient production of polyhydroxybutyrate using lignocellulosic biomass derived from oil palm trunks by the inhibitor-tolerant strain Burkholderia ambifaria E5-3.

Lignocellulosic biomass is a valuable, renewable substrate for the synthesis of polyhydroxybutyrate (PHB), an ecofriendly biopolymer. In this study, bacterial strain E5-3 was isolated from soil in Japan; it was identified as Burkholderia ambifaria strain E5-3 by 16S rRNA gene sequencing. The strain showed optimal growth at 37°C with an initial pH of 9. It demonstrated diverse metabolic ability, processing a broad range of carbon substrates, including xylose, glucose, sucrose, glycerol, cellobiose, and, notably, palm oil. Palm oil induced the highest cellular growth, with a PHB content of 65% wt. The strain exhibited inherent tolerance to potential fermentation inhibitors derived from lignocellulosic hydrolysate, withstanding 3g/L 5-hydroxymethylfurfural and 1.25g/L acetic acid. Employing a fed-batch fermentation strategy with a combination of glucose, xylose, and cellobiose resulted in PHB production 2.7-times that in traditional batch fermentation. The use of oil palm trunk hydrolysate, without inhibitor pretreatment, in a fed-batch fermentation setup led to significant cell growth with a PHB content of 45% wt, equivalent to 10g/L. The physicochemical attributes of xylose-derived PHB produced by strain E5-3 included a molecular weight of 722kDa, a number-average molecular weight of 191kDa, and a polydispersity index of 3.78. The amorphous structure of this PHB displayed a glass transition temperature of 4.59°C, while its crystalline counterpart had a melting point of 171.03°C. This research highlights the potential of lignocellulosic feedstocks, especially oil palm trunk hydrolysate, for PHB production through fed-batch fermentation by B. ambifaria strain E5-3, which has high inhibitor tolerance.

Biosynthesis of polyhydroxybutyrate from methane and carbon dioxide using type II methanotrophs

Methane (CH4) and carbon dioxide (CO2) are the dominant greenhouse gases (GHGs) that are increasing at an alarming rate. Methanotrophs have emerged as potential CH4 and CO2 biorefineries. This study demonstrated the synchronous incorporation of CH4 and CO2 into polyhydroxybutyrate (PHB) for the first time using 13C-labeling experiments in methanotrophs. By supplying substantial amounts of CO2, PHB content was enhanced in all investigated type II methanotrophic strains by 140 %, 146 %, and 162 %. The highest content of PHB from CH4 and CO2 in flask-scale cultivation reached 38 % dry cell weight in Methylocystis sp. MJC1, in which carbon percentage in PHB from CO2 was 45 %. Flux balance analysis predicted the critical roles of crotonyl-CoA carboxylase/reductase and phosphoenolpyruvate carboxylase in CO2 recycling. This study provided proof of the conversion of GHGs into a valuable and practical product using methanotrophic bacteria, contributing to addressing GHG emissions.

Stability and release mechanism of double emulsification (W1/O/W2) for biodegradable pH-responsive polyhydroxybutyrate/cellulose acetate phthalate microbeads loaded with the water-soluble bioactive compound niacinamide

Microbeads of biodegradable polyhydroxybutyrate (PHB) offer environmental benefits and economic competitiveness. The aim of this study was to encapsulate a water-soluble bioactive compound, niacinamide (NIA), in a pH-responsive natural matrix composed of PHB and cellulose acetate phthalate (CAP) by double emulsification (W1/O/W2) to improve the encapsulation efficiency (%EE) and loading capacity (%LC). PHB was produced in-house by Escherichia coli JM109 pUC19-23119phaCABA-04 without the inducing agent isopropyl β-D-1-thiogalactopyranoside (IPTG). The influences of PHB and polyvinyl alcohol (PVA) concentrations, stirring rate, PHB/CAP ratio and initial NIA concentration on the properties of NIA-loaded pH-responsive microbeads were studied. The NIA-loaded pH-responsive PHB/CAP microbeads exhibited a spherical core-shell structure. The average size of the NIA-loaded pH-responsive microbeads was 1243.3 ± 11.5 μm. The EE and LC were 33.3 ± 0.5 % and 28.5 ± 0.4 %, respectively. The release profiles of NIA showed pH-responsive properties, as 94.2 ± 3.5 % of NIA was released at pH 5.5, whereas 99.3 ± 2.4 % of NIA was released at pH 7.0. The NIA-loaded pH-responsive PHB/CAP microbeads were stable for >90 days at 4 °C under darkness, with NIA remaining at 73.65 ± 1.86 %. A cytotoxicity assay in PSVK1 cells confirmed that the NIA-loaded pH-responsive PHB/CAP microbeads were nontoxic at concentrations lower than 31.3 μg/mL, in accordance with ISO 10993-5.

Effects of methane to oxygen ratio on cell growth and polyhydroxybutyrate synthesis in high cell density cultivation of Methylocystis sp. MJC1.

Polyhydroxybutyrate (PHB) production through CH4 conversion by methanotrophs offers a solution for greenhouse gas emissions and plastic waste concerns. In this study, we aimed to achieve high cell density cultivation of Methylocystis sp. MJC1 for efficient PHB production. Cultivating MJC1 using CH4 and air (3:7, v/v) yielded a final cell density of 52.9 g/L with a 53.7% (28.4 g/L) PHB content after 210 h, showcasing PHB mass production potential. However, long-term cultivation led to a low volumetric productivity of 0.200g/L/h. To address this, we conducted cultivation at various O2/CH4 ratios using O2 instead of air, which significantly improved the PHB productivity. Under high O2 conditions (O2/CH4 ratio of 1.5), biomass productivity increased 1.51-fold compared to that under low O2 conditions in the same time frame; however, PHB accumulation was delayed. Using an equal ratio of CH4 and O2 induced active cell growth and selective PHB production, achieving the highest PHB productivity (0.365 g/L/h) with a final cell density of 55.9 g/L and PHB content of 61.7% (34.5 g/L) in 162 h. This study highlighted the significance of the O2/CH4 ratio in CH4 conversion and PHB production by M. sp. MJC1.

Experimental investigation of PCL‐based composite material fabricated using solvent‐cast 3D printing process

AbstractBone tissue engineering relies on scaffolds with enhanced mechanical properties, achievable through 3D printing techniques. Our study focuses on enhancing mechanical properties using a solvent‐cast 3D printing method. For this, poly‐ε‐caprolactone (PCL) reinforced with polyhydroxybutyrate (PHB), and synthetic fluorapatite (FHAp) nanopowders were utilized, immersed in a solution of dichloromethane (DCM) and dimethylformamide (DMF). Sol–gel method was used to synthesized FHAp, and the XRD pattern confirmed crystalline FHAp presence, with notable peaks at 2θ values of 31.937°, 33.128°, 32.268°, and 25.864°. Moreover, composites exhibited nonchemical PCL‐PHB/FHAp interactions, with PHB and FHAp crystallographic planes evident. Surface roughness, assessed via RMS values, showed progressive increases with higher PHB and FHAp content. Tensile strength peaked at 19% wt/v of PHB, with varied effects of FHAp. Compressive strength reached its apex at 30% wt/v of FHAp, with higher PHB content consistently enhancing strength. Flexural strength notably increased with PHB, peaking at 19% wt/v, and further with FHAp. Young's modulus rose with both PHB and FHAp content. Hardness increased with PHB and FHAp, notably peaking at 30% wt/v of FHAp. Cell viability improved with PHB, showing varied responses to FHAp. Hemocompatibility evaluations indicated low hemolysis percentages, especially in balanced PHB/FHAp compositions. These findings highlight the crucial role of composite compositions in tailoring mechanical and biological properties for optimal bone scaffold design, promising advancements in tissue regeneration technologies.

Production of polyhydroxybutyrate from industrial flue gas by microbial electrosynthesis

The aim of this work was to produce the biopolymer polyhydroxybutyrate (PHB) from industrial flue gas as CO2 source and electrolysis originating hydrogen via microbial electrosynthesis. Besides the laboratory experiments, the experiments were carried out under industrial conditions directly on-site in a cogeneration plant. We were able to demonstrate that the use of flue gas as a CO2 source has no detectable negative effect on bacterial growth and PHB production in comparison to a pure gas mixture. In an electrochemical H-cell 333 ± 44 mg L−1 PHB were obtained, which corresponds to a PHB content of 43 ± 3 % of the cell dry weight. By using flue gas for the production of the biopolymer PHB, not only CO2 emissions are reduced, but also possible environmental pollution from non-biodegradable plastics. To the best of our knowledge, this is the first time that the production of PHB from flue gas has been demonstrated using Cupriavidus necator.

Resource recovery through bioremediation of fuel-synthesis wastewater in a biofilm photobioreactor using purple non-sulfur bacteria: A circular bioeconomy approach

In the current era of wastewater treatment, integrating reusable water production with resource recovery is a key goal. This study aims to treat fuel-synthesis wastewater (FSW), intending to recover various resources, including polyhydroxybutyrate (PHBs), single cell protein, bacteriochlorophylls, carotenoids, and coenzyme Q10 from suspended and biofilm growth to decrease the harvesting costs. The study considered the treatment process, biofilm growth, and resource recovery potential in a mixed-culture system enriched with purple non-sulfur bacteria for treating FSW. Specifically, the effects of four different FSW strengths (25–100 %) and nitrogen sufficiency (N+) or deficiency (N−) were evaluated in eight biofilm photobioreactors. This study observed a direct correlation between the concentration of FSW and PHB content; specifically, as the FSW content decreased from 100 % (undiluted) to 25 % the PHB content decreased. The undiluted condition achieved 17 % dry cell weight as PHB in the suspended growth and 22.6 % in the biofilm growth under N− condition. The protein content ranged between 33 and 44 %, and the presence of nitrogen had a slight positive effect on higher protein content. No trend was observed for carotenoids or bacteriochlorophylls in the N− condition. In contrast, for the N+ condition, the concentration of bacteriochlorophylls increased with decreasing wastewater concentration under suspended growth, while it decreased with decreasing wastewater concentration under biofilm growth. Coenzyme Q10 concentration was enhanced under the most growth-limited condition (25 %, N−). PHB and protein content of these resources seem most promising when using N− and N+ conditions, respectively.

Poly(3-hydroxybutyrate) production from cassava processing wastes by Paracoccus sp. through high cell density cultivation: Effects of substrates limitation and kinetic analysis

Polyhydroxybutyrate (PHB) is bioplastic that has been recognized as a viable alternative to petroleum-based ones, owing to its biodegradability and biocompatibility. However, its use has long been hampered by its high selling price, caused mainly by using costly fermentation feedstock. In the present study, cassava pulp (CP) was investigated as an alternative low-cost carbon source for a high cell density cultivation of Paracoccus sp. KKU01 for PHB production. CP was hydrolyzed enzymatically, and the resulting hydrolysate was used as the base medium to optimize the bacterial growth conditions, i.e., medium compositions and dissolved oxygen setpoints, attaining as high as 40.9 ± 0.0 g/L of biomass. The optimum growth conditions were subsequently used in 4 fed-batch fermentation regimes, and Regime 2, where complete medium (CP hydrolysate supplemented with other nutrients) was fed twice followed by twice feedings of concentrated CP hydrolysate (CPH), was found to give highest biomass and PHB production of 114.5 ± 1.3 and 47.8 ± 3.9 g/L, respectively, with 41.8 ± 2.9% PHB content and yield of 0.12 kg/kg-CP. PHB productivity was 0.80 ± 0.06 g/(L·h). Logistic and Luedeking-Piret models were used successfully to describe the profiles of bacterial growth and PHB production, respectively. Curve fitting using the Luedeking-Piret model revealed that PHB synthesis and PHB turnover occurred simultaneously during the process. Overall, the results demonstrated that cassava processing wastes are feasible feedstock for PHB production by Paracoccus sp. KKU01.

Polyhydroxybutyrate (PHB)-Based sustainable bioplastic derived from Bacillus sp. KE4 isolated from kitchen waste effluent

Petrochemical-derived plastics pose a major threat to the biosphere and the environment due to their acute or long-term toxicity. Therefore, to ensure sustainability, it is essential to find an effective replacement for synthetic plastics with natural and ecofriendly biomaterial. In this context, production of polyhydroxybutyrate (PHB) was produced by the Bacillus sp. KE4 using glucose as the carbon source, and a maximum dry cell weight (DCW) of 4.4 g/l with a PHB concentration of 3.1 g/l, PHB yield of 0.15 g/g was obtained, and the PHB content was 70.4% of the DCW. The extracted biopolymer was characterized using FTIR, GC-MS, 1H NMR, and 13C NMR which confirmed the structure of the biopolymer as PHB. The findings of TGA, DTG, DTA and DSC studies corresponded to PHB's excellent thermal stability. PHB biopolymer has a melting temperature of 168.7 °C and a maximum degradation temperature of 273 °C. The weight average molar mass (Mw), number average molar mass (Mn), and polydispersity index (PDI) of the extracted PHB was 1,55,436 g mol−1; 1,43,258 g mol−1; and 1.08, respectively. The XRD analysis validated the material's partly crystalline nature. FESEM-EDS and XPS were employed to determine the elemental composition of the purified PHB film. The Young's modulus, tensile strength and elongation at break showed rigid and brittle nature of PHB. Using open windrow composting method, the extracted PHB biopolymer film was assessed to determine its biodegradability. Within 28 days of soil burial, it was found that the biopolymer film had degraded by 61.34%. Cytotoxicity assessment in HepG2 cells indicated that PHB is non-cytotoxic in nature. The results have showed that the biomaterial is environmentally benign, biodegradable, and biocompatible; therefore, it may find its diverse application covering packaging, medicine, agriculture and allied fields.

Exogenous Trehalose Improves Growth, Glycogen and Poly-3-Hydroxybutyrate (PHB) Contents in Photoautotrophically Grown Arthrospira platensis under Nitrogen Deprivation.

Glycogen and poly-3-hydroxybutyrate (PHB) are excellent biopolymer products from cyanobacteria. In this study, we demonstrate that nitrogen metabolism is positively influenced by the exogenous application of trehalose (Tre) in Arthrospira platensis under nitrogen-deprived (-N) conditions. Cells were cultivated photoautotrophically for 5 days under -N conditions, with or without the addition of exogenous Tre. The results revealed that biomass and chlorophyll-a content of A. platensis experienced enhancement with the addition of 0.003 M and 0.03 M Tre in the -N medium after one day, indicating relief from growth inhibition caused by nitrogen deprivation. The highest glycogen content (54.09 ± 1.6% (w/w) DW) was observed in cells grown for 2 days under the -N + 0.003 M Tre condition (p < 0.05), while the highest PHB content (15.2 ± 0.2% (w/w) DW) was observed in cells grown for 3 days under the -N + 0.03 M Tre condition (p < 0.05). The RT-PCR analysis showed a significant increase in glgA and phaC transcript levels, representing approximately 1.2- and 1.3-fold increases, respectively, in A. platensis grown under -N + 0.003 M Tre and -N + 0.03 M Tre conditions. This was accompanied by the induction of enzyme activities, including glycogen synthase and PHA synthase with maximal values of 89.15 and 0.68 µmol min-1 mg-1 protein, respectively. The chemical structure identification of glycogen and PHB from A. platensis was confirmed by FTIR and NMR analysis. This research represents the first study examining the performance of trehalose in promoting glycogen and PHB production in cyanobacteria under nitrogen-deprived conditions.

Production, optimization, scale up and characterization of polyhydoxyalkanoates copolymers utilizing dairy processing waste

The microbial biotransformation using low-cost feedstock to produce biopolymers (degradable), an alternative to petrochemical-based synthesis plastics (non-degradable), can be a beneficial approach towards sustainable development. In this study, the dairy industry processes waste (whey) is used in polyhydroxyalkanoate (PHA) copolymer production. Initial screening suggested that Ralstonia eutropha produced higher PHA as compared to Bacillus megaterium. A central composite rotatable design-based optimization using two process variables (amino acid and tween-80) concentration remarkably influenced PHA co-polymer production under physiological conditions of pH (7), temperature (37 °C), and agitation rate of 150 rpm. High polyhydroxybutyrate (PHB) mass fraction yield of 69.3% was observed as compared to predicted yield of 62.8% from deproteinized whey as feed. The combination of tryptophan (50 mg L−1) and tween-80 (3 mL−1) enhanced R. eutropha mass gain to 6.80 g L−1 with PHB contents of 4.71 g L−1. Further, characterization of PHA and its copolymers was done by ESI–MS, FTIR, and TEM. On upscaling up to 3.0 L, the PHA contents and yields were noted as quite similar by R. eutropha. This study demonstrates that dairy waste processing waste can be potentially utilized as inexpensive feed for producing high content of biopolymers to develop a sustainable system of waste management.

Fabrication of electrospun nanofiber from a blend of PVC and PHB

Abstract In this work, the fabrication process of electrospun nanofibers from a blend of polyhydroxy butyrate (PHB) and polyvinyl chloride (PVC) has been investigated. PVC/PHB nanofibers have been fabricated from solutions using different PVC and PHB ratios. The influence of technical parameters of the electrospinning process on the fabrication, morphology, and diameter of nanofibers has been evaluated. The chemical structure and thermal properties of PVC/PHB have been studied. The results show that the diameter of PVC/PHB nanofibers increases as the PHB content increases. In addition, the optimal technical parameters of the electrospinning process for each PVC and PHB ratio are different. Infrared spectroscopy analysis revealed an enhancement of the crystalline phase of the polymer composite with increasing PHB content. The thermal properties of PVC/PHB nanofibers were evaluated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The change in PHB ratios leads to a change in the glass transition temperature of PVC/PHB nanofibers. The thermal degradation process of PVC/PHB includes two steps. Increasing the PHB content leads to an enhancement in the mechanical strength of PVC/PHB nanofiber mats; however, it also results in a reduction in tensile elongation. Based on the results of structural, morphological, interaction analysis, and mechanical properties of PVC/PHB nanofibers, this study contributes to the optimization of the fabrication of nanofibers from PVC and PHB. PVC/PHB nanofibers have the potential to be used for air filtration applications.

A multi-objective optimization approach for the production of polyhydroxybutyrate via Chlorogloea fritschii under diurnal light with single-stage cultivation

The present study aims to optimize the nutrients for maximization of cyanobacterial biomass with high content of polyhydroxybutyrate (PHB), a bioplastic, and recovery of biomass by auto-sedimentation under diurnal light mimic to sunlight. The multi-objective optimization with desirability approach was used to improve dry cell weight (DCW), PHB content (% w/w), and auto-sedimentation concentration factor (SCF) of biomass. Initially, NaNO3, K2HPO4, TRACE (micronutrient solution), Na2EDTA, and MgSO4.7H2O were screened as important media compositions. Screening was followed by the application of response surface methodology for the development of a model used in multi-objective optimization. The optimized media selected from many optimal solutions, a set of Pareto solutions generated by multi-objective optimization was validated in a flat panel photobioreactor. Using a single-stage cultivation strategy under diurnal light, Chlorogloea fritschii TISTR 8527 has shown capability to produce DCW of 1.23 g/l with PHB content of 31.78 % and SCF of 93.63 with optimal media. This leads to the enhancement of both PHB content (2.72 fold) and SCF (1.64 fold) were observed when compared to the non-optimal medium. This is the first multi-objective optimization study for media optimization using cyanobacteria reported till now under diurnal light mimic to sunlight for bioplastic production.

Optimization of polyhydroxybutyrate (PHB) production by Priestia megaterium ASL11 and glycerol and thermoplastic properties of PHB-based films

The production of polyhydroxybutyrate (PHB) by Priestia megaterium ASL11 was elucidated with various carbon sources. The optimized conditions for PHB production were as follows: C/N ratio of 6.99; mixture of 3% (v/v) glycerol, 0.079% (w/v) malt extract and 0.35% (w/v) sodium ammonium phosphate; initial medium pH of 8.0; and incubation time of 120 h. These optimal conditions increased the PHB concentration (g/L), PHB yield, and PHB content produced by ASL11 from 0.32, 0.13, and 15.8% (using glucose) to 0.92, 0.78 and 49.6% (using glycerol), accounting for 2.9-, 6.0- and 3.1-fold increases, respectively. FTIR analysis of the ASL11-PHB film revealed carbonyl (1720 cm−1) and alkane (1453–1379 cm−1) groups similar to those of standard PHB, and GC/MS analysis confirmed that the characteristics of PHB obtained with ASL11 were consistent with those of standard PHB. The ASL11-PHB film was resistant to heat (90–175 °C) and pH values from 5 to 10 and had a melting temperature of 165.1 °C, indicating typical thermobioplastic properties. The ASL11-PHB film could be completely dissolved in sulfuric acid, which is less toxic than chloroform. The mechanical properties of the ASL11-PHB film showed a low Young's modulus with an elongation at break of 5.27%, indicating brittle behavior with low mechanical strength. Thus, the ASL11-PHB film should be blended with other materials to reinforce the film strength and reduce its brittleness for future applications. Moreover, the studies of PHB production under optimal condition by ASL11 needs to be scaled up from the laboratory scale to the pilot scale.