Polyhydroxybutyrate Research Articles

High-Yield Production of Polyhydroxybutyrate and Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from Crude Glycerol by a Newly Isolated Burkholderia Species Oh_219

Crude glycerol (CG), a major biodiesel production by-product, is the focus of ongoing research to convert it into polyhydroxyalkanoate (PHA). However, few bacterial strains are capable of efficiently achieving this conversion. Here, 10 PHA-producing strains were isolated from various media. Among them, Burkholderia sp. Oh_219 exhibited the highest polyhydroxybutyrate (PHB) production from glycerol and was therefore characterized further. Burkholderia sp. Oh_219 demonstrated significant tolerance to major growth inhibitors in CG and metabolized the fatty acids present as impurities in CG. Furthermore, the Oh_219 strain was genetically engineered using phaCBP-M-CPF4 and phaJPa to enable the fatty acid-based production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), a component of CG. The resulting strain produced PHBHHx containing 1.0–1.3 mol% of 3HHx from CG. Further supplementation with capric and lauric acids increased the 3HHx molar fraction to 9.7% and 18%, respectively. In a 5 L fermenter, the Oh_219 strain produced 15.3 g/L PHB from 29.6 g/L biomass using a two-stage fermentation system. This is the highest yield reported for PHA production from glycerol by Burkholderia spp. Additionally, PHB produced from CG had a lower melting point than that from pure glycerol and fructose. Taken together, Burkholderia sp. Oh_219 is a promising new candidate strain for producing PHA from CG.

De Novo Assembly of the Polyhydroxybutyrate (PHB) Producer Azohydromonas lata Strain H1 Genome and Genomic Analysis of PHB Production Machinery

Polyhydroxybutyrate (PHB) is a biodegradable natural polymer produced by different prokaryotes as a valuable carbon and energy storage compound. Its biosynthesis pathway requires the sole expression of the phaCAB operon, although auxiliary genes play a role in controlling polymer accumulation, degradation, granule formation and stabilization. Due to its biodegradability, PHB is currently regarded as a promising alternative to synthetic plastics for industrial/biotechnological applications. Azohydromonas lata strain H1 has been reported to accumulate PHB by using simple, inexpensive carbon sources. Here, we present the first de novo genome assembly of the A. lata strain H1. The genome assembly is over 7.7 Mb in size, including a circular megaplasmid of approximately 456 Kbp. In addition to the phaCAB operon, single genes ascribable to PhaC and PhaA functions and auxiliary genes were also detected. A comparative genomic analysis of the available genomes of the genus Azohydromonas revealed the presence of phaCAB and auxiliary genes in all Azohydromonas species investigated, suggesting that the PHB production is a common feature of the genus. Based on sequence identity, we also suggest A. australica as the closest species to which the phaCAB operon of the strain H1, reported in 1998, is similar.

A genome-scale metabolic model for the denitrifying bacterium Thauera sp. MZ1T accurately predicts degradation of pollutants and production of polymers.

The denitrifying bacterium Thauera sp. MZ1T, a common member of microbial communities in wastewater treatment facilities, can produce different compounds from a range of carbon (C) and nitrogen (N) sources under aerobic and anaerobic conditions. In these different conditions, Thauera modifies its metabolism to produce different compounds that influence the microbial community. In particular, Thauera sp. MZ1T produces different exopolysaccharides with floc-forming properties, impacting the physical disposition of wastewater consortia and the efficiency of nutrient assimilation by the microbial community. Under N-limiting conditions, Thauera sp. MZ1T decreases its growth rate and accelerates the accumulation of polyhydroxyalkanoate-related (PHA) compounds including polyhydroxybutyrate (PHB), which plays a fundamental role as C and energy storage in this β-proteobacterium. However, the metabolic mechanisms employed by Thauera sp. MZ1T to assimilate and catabolize many of the different C and N sources under aerobic and anaerobic conditions remain unknown. Systems biology approaches such as genome-scale metabolic modeling have been successfully used to unveil complex metabolic mechanisms for various microorganisms. Here, we developed a comprehensive metabolic model (M-model) for Thauera sp. MZ1T (iThauera861), consisting of 1,744 metabolites, 2,384 reactions, and 861 genes. We validated the model experimentally using over 70 different C and N sources under both aerobic and anaerobic conditions. iThauera861 achieved a prediction accuracy of 95% for growth on various C and N sources and close to 85% for assimilation of aromatic compounds under denitrifying conditions. The M-model was subsequently deployed to determine the effects of substrates, oxygen presence, and the C:N ratio on the production of PHB and exopolysaccharides (EPS), showing the highest polymer yields are achieved with nucleotides and amino acids under aerobic conditions. This comprehensive M-model will help reveal the metabolic processes by which this ubiquitous species influences communities in wastewater treatment systems and natural environments.

Hemp extract as a multifunctional stabilizer for polyhydroxybutyrate (PHB) materials: Investigations into anti-aging properties and lifetime control

Hemp extract as a multifunctional stabilizer for polyhydroxybutyrate (PHB) materials: Investigations into anti-aging properties and lifetime control

Exploration of Polyhydroxybutyrate (PHB) Production Potential of Photosynthetic Microbes: A Sustainable Source of Bioplastic.

The present study examined Polyhydroxy butyrate production (PHB) potential of different photosynthetic microbes such as Chlorella vulgaris, Scenedesmus obliquus and Rhodobacter capsulatus-PK under different nutrient conditions. Biodegradable bioplastics, such as Poly-β-hydroxybutyrates (PHB), derived from these microbes provide a sustainable alternative to conventional petroleum-based nondegradable plastics. As the demand for clean and sustainable alternatives rises, bio-plastic is gaining attention as a viable substitute to conventional plastics. However, conventional sources of bio-plastic production have inherent limitations, which can be effectively addressed through the utilization of photosynthetic microbes e.g. microalgae, purple non sulphur bacteria. The production of bioplastic was evaluated by cultivating the microalgae in BG-11, BBM and PNSB in synthetic growth media (MI, MII) with different nitrogen concentrations of 0%, 50% and 100%. The biopolymer (PHB) was obtained from all experiments in a wide range of concentration (7-42.8%) of dry cell weight (DCW). In this study, algal isolate SK1 demonstrated the highest PHB content (42.8%) in BBM under 100% nitrogen starvations rendering the bioplastic exceptionally compatible and suitable for eco-friendly applications. Additionally, various patents cited by different authors on different aspects of microbial bioplastic production. Nutrition depletion such as nitrogen scarcity induced stressful growth conditions that resulted in highest accumulation of the biopolymer PHB. Optimizing nitrogen availability is key to maximizing PHB production, making it a viable sustainable alternative to conventional plastics.

Ecotoxicity of Biodegradable Microplastics and Bio-based Microplastics: A Review of in vitro and in vivo Studies.

As biodegradable and bio-based plastics increasingly replace conventional plastics, the need for a comprehensive understanding of their ecotoxicity becomes more pressing. This review systematically presents the ecotoxicity of the microplastics (MPs) from different biodegradable plastics and bioplastics on various animals and plants. High doses of polylactic acid (PLA) MPs (10%) have been found to reduce plant nitrogen content and biomass, and affect the accumulation of heavy metals in plants. Their phytotoxicity becomes more pronounced when blended with polybutylene adipate terephthalate (PBAT) MPs. Polyhydroxybutyrate (PHB) and polybutylene succinate (PBS) MPs show lower phytotoxicity than PLA MPs. At high doses, PLA and PHB MPs may cause dose-dependent developmental toxicity to aquatic organisms. Nano-PLA could induce oxidative stress and genetic damage in insects, indicating its toxicity could be size-dependent and affected by weathering. PBAT MPs have been observed to affect plant growth at lower concentrations (0.1%) than PLA MPs, while polycaprolactone (PCL) affected seed germination only at high temperatures. PCL MPs and extracts could also cause developmental and reproductive toxicity, alter metabolisms, and induce oxidative stress in aquatic organisms at high concentrations. Polypropylene carbonate (PPC) ( > 40 g/kg) MPs have caused earthworm behavioral changes. Non-biodegradable bioplastics are potentially toxic to embryos, larvae, immune systems, reproductive systems, and endocrine systems of animals. However, it is important to note that toxicity studies are still lacking for biodegradable and bio-based plastics, particularly PHB, PBS, PCL, PPC, starch-based, and non-biodegradable bioplastics. More research into the MPs of these plastics is essential to better understand their ecotoxicity and applicability.

Dielectric and free volume of Poly methyl methacrylate/silver nanoparticles- polyhydroxybutyrate nanocomposites (PMMA- AgNP/PHB): positron annihilation lifetime study

Abstract Solution casting technique was used successfully to prepare Poly methyl methacrylate/silver nanoparticles-polyhydroxybutyrate blend with different polyhydroxybutyrate (PHB) concentrations. FTIR results assure and confirm the good compatibility between the two polymers. X-ray results of the PHB/PMMA-AgNP blend show an increase in crystallinity with increasing PHB loading. A non-destructive Positron annihilation lifetime measurements were conducted at room temperature as a function of PHB concentration. Dielectric measurements were performed in the frequency range of 50 Hz to 50 MHz at RT. It was observed that O-Ps lifetime, τ3, O-Ps intensity, I3, free volume hole size, FV, and fractional free volume, FFV, were found to decrease with increasing PHB percentage. The dielectric constant ε/ showed a declined behaviour with increasing PHB content. The fabricated blend shows anomalous behaviour regarding the dielectric properties and free volume properties, assuming that blending PMMA with PHB alters the blend polarization behaviour in an external electric field.

Mechanical and antimicrobial properties of green and photoactive AgTiO2/poly(3hydroxybutyrate) (PHB) electrospun membranes

AbstractThe rise of antibiotic‐resistant microbes and concerns over non‐biodegradable waste highlight the need for innovative materials with integrated functionalities that address these critical issues. In this study, we synthesized poly(3hydroxybutyrate) (PHB) electrospun nanofibers blended with gelatin (Ge) and loaded with photoactive AgTiO2 nanoparticles with improved mechanical and biological properties. Biological tests revealed excellent antibacterial activity of the prepared membrane, with efficiency exceeding 99% against Escherichia coli and 95% against Staphylococcus epidermidis after 90 and 60 min of exposure to low‐power commercial LED lights, respectively. Filtration studies using a dead‐end stainless‐steel cell reveal that both bacteria are eliminated (>99% after one filtration cycle). Results of the viability test showed that blending PHB with Ge improves the membrane's anti‐biofouling properties. The membranes were also characterized using SEM and EDX mapping techniques for morphological and elemental analysis, DSC and TGA to evaluate thermal properties and crystallinity, and FTIR to confirm chemical structure. Moreover, the electrospun membranes exhibited enhanced mechanical properties with the addition of Ge. PHB/Ge/3 wt% AgTiO2 sample showed 2.2 times better tensile strength and 1.89 times improved Young's modulus compared to PHB membranes. Finally, the breakdown of PHB/Ge/AgTiO2 membranes occurred progressively over only 8 weeks, showing the membranes' green and sustainable nature.Highlights Antibacterial efficacy of 99% against E. coli and 95% against S. epidermidis. Microfiltration efficiency >99% achieved in one filtration cycle. Mechanical strength is enhanced by 2.2 times with the addition of gelatin. Effective anti‐biofouling is confirmed by CLSM and SEM tests. Membranes degraded within 8 weeks in natural soil.

Polyhydroxybutyrate Synthesis by the Halophilic Bacterium, Halomonas boliviensis, in Oil Palm EmptyFruitBunch Hydrolysate.

Polyhydroxyalkanoates are biodegradable, natural polyesters with the potential to replace petroleum-based plastics. However, high production costs limit their competitiveness. This study assessed the ability of Halomonas boliviensis, a halophilic bacterium, to synthesize polyhydroxybutyrate (PHB) from an agricultural residue, oil palm empty fruit bunch (OPEFB), in highly saline solutions that minimize contamination risk. OPEFB, containing glucose, xylose, and arabinose, offers a cost-effective alternative to pure sugar substrates and aids in waste management. PHB production from OPEFB was compared with fermentations using these sugars. H. boliviensis successfully synthesized PHB from all substrates, achieving the highest PHB content from glucose (54.63%), followed by xylose (40.18%), OPEFB (33.59%), and arabinose (33.52%). Glucose in the OPEFB hydrolysate was entirely depleted after 72 h, while xylose showed minimal consumption. This research highlights the potential of using low-cost carbon sources like OPEFB for PHB production. Future research should focus on optimizing the fermentation process to increase PHB yields, making it a more viable alternative to traditional plastics.

Producing and Characterizing Polyhydroxyalkanoates from Starch and Chickpea Waste Using Mixed Microbial Cultures in Solid-State Fermentation.

The environmental impact of plastic waste is a growing global challenge, primarily due to non-biodegradable plastics from fossil resources that accumulate in ecosystems. Biodegradable polymers like polyhydroxyalkanoates (PHAs) offer a sustainable alternative. PHAs are microbial biopolymers produced by microorganisms using renewable substrates, including agro-industrial byproducts, making them eco-friendly and cost-effective. This study focused on the isolation and characterization of PHA-producing microorganisms from agro-industrial waste, including chickpeas, chickpeas with bean residues, and starch. Screening via Sudan Black staining identified PHA-accumulating strains such as Brevibacillus sp., Micrococcus spp., and Candida krusei, among others. To assess the potential for PHA biosynthesis, solid-state fermentation (SSF) was conducted using agro-industrial waste as substrates, along with a mixed culture of the isolated microorganisms. The highest observed yield was a PHA accumulation of 13.81%, achieved with chickpeas containing bean residues. Structural and thermal characterization of the PHAs was performed using Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). FTIR-ATR spectra indicated polyhydroxybutyrate (PHB), suggesting it as the synthesized PHA type. This study highlights the potential of agro-industrial waste for sustainable PHA production and eco-friendly bioplastics.

Effects of single or conjoint administration of poly-β-hydroxybutyrate and Bacillus subtilis on growth, antioxidant capacity and apoptosis of common carp (Cyprinus carpio)

This study aims to assess single or conjoint administration of poly-β-hydroxybutyrate (PHB) and Bacillus subtilis on growth, the function and morphology of hepatopancreas and intestines, antioxidant capacity, inflammation and apoptosis in common carp (Cyprinus carpio). In this study, four diets were formulated according to a 2 × 2 factorial design, including control diet (without PHB and B. subtilis), B. subtilis diet (with 1 × 108 CFU/g B. subtilis), PHB diet (4%PHB) and PHB+B. subtilis diet (with 4%PHB and 1 × 108 CFU/g B. subtilis). Common carp (3.50 ± 0.03g) were allocated into 4 groups (3 replicates per group, 30 fish per replicate) and fed for 8 weeks. Results demonstrated that single or conjoint administration of 4%PHB and 1 × 108 CFU/g B. subtilis promoted the growth performance and feed utilization, with interaction (P<0.05). 4%PHB and 1 × 108 CFU/g B. subtilis increased the levels of protease in intestines, lipase and amylase in hepatopancreas and intestines, AST and ALT in hepatopancreas, intestinal permeability (DAO, D-LA, 5-HT and ET-1), intestinal tight junction protein-related mRNA, intestinal growth indexes (fold height and muscular layer thickness), antioxidant capacity (CAT, T-AOC, T-SOD and GSH-PX in hepatopancreas and intestines, Nrf2, SOD, CAT and GSH-PX mRNA in hepatopancreas and intestines, HO-1 mRNA in hepatopancreas), anti-inflammatory and anti-apoptosis (TGF-β, IL-10 and Bcl-2 mRNA in hepatopancreas and intestines) (P<0.05), decreased the levels AST and ALT in serum, intestinal growth indexes (lamina propria width), oxidative stress indicator (MDA) and Keap1 mRNA in hepatopancreas and intestines, pro-inflammatory and pro-apoptosis (NF-κB, TNF-α, IL-1β, IL-6, Bax, Caspase-3, Caspase-8 and Caspase-9 mRNA in hepatopancreas and intestines) (P<0.05), improved the morphology of hepatopancreas and intestines. Whereas the levels of protease in hepatopancreas were only increased by 1 × 108 CFU/g B. subtilis (P<0.05), the levels of HO-1 mRNA in intestines were only up-regulated by 4%PHB (P<0.05). Furthermore, the interaction between 4%PHB and 1 × 108 CFU/g B. subtilis was discovered for the levels of AST, ALT and 5-HT in serum, intestinal Occludin mRNA, MDA in hepatopancreas and intestines, Keap1, HO-1 and IL-1β mRNA in hepatopancreas, GSH-PX mRNA in hepatopancreas and intestines, Bcl-2 and Caspase-3 mRNA in intestines (P<0.05). In conclusion, this study indicated that conjoint administration of 4%PHB and 1 × 108 CFU/g B. subtilis had synergistic promotion on the growth performance, digestive function, antioxidant capacity, hepatopancreatic and intestinal functions of common carp.

Biofabrication of polyhydroxybutyrate (PHB) in engineered Cupriavidus necator H16 from waste molasses

BackgroundCupriavidus necator H16, a native polyhydroxybutyrate (PHB) producer, has emerged as a promising candidate for sustainable bioproduction to replace conventional plastics. However, most fermentation processes still rely on expensive substrates. Therefore, developing an eco-friendly bioprocess for PHB using waste materials is urgent and essential. MethodAn engineered strain Lgg-H16, incorporating galactose permease (galP) and glucokinase (glk), was employed to boost glucose uptake and phosphorylation. Then, biomass and PHB production were improved by fine-tuning the carbon, nitrogen, and phosphorus ratios. Yeast extract was supplemented as an additional nutrient, and a tailored feeding strategy was applied to maximize PHB output. To lower the manufacturing costs, waste molasses from the sugar industry, was utilized for fed-batch fermentation. The physical properties of the PHB, such as molecular weight and crystallinity, were analyzed using differential scanning calorimeter (DSC) and gel permeation chromatography (GPC), respectively. Significant resultsEngineered Lgg-H16 strain exhibited a 2.15-fold increase in specific growth rate compared to the wild type with a C:N:P ratio of 20:1:18, as well as supplemented 2 g/L yeast extract in the medium. PHB yield reached 17.4 g/L with 70 % content from waste molasses in fed-batch fermentation with an atomizer to increase gas dispersion, costing only 1 % of pharmaceutical-grade glucose. All physical properties of the PHB produced by Lgg-H16 were comparable to commercial product, supporting this promising bioprocess by using the low-cost feedstocks for high-value bioplastic PHB.

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.

Electrospinning of Poly-3-Hydroxybutyrate Fibers Loaded with Chlorophyll for Antibacterial Purposes.

This work is devoted to the creation of biocompatible fibrous materials with a high antimicrobial effect based on poly-3-hydroxybutyrate (PHB) and chlorophyll (Chl). The data obtained show the possibility of obtaining fibrous materials from PHB and Chl by electrospinning methods. The obtained electrospun matrices were investigated by the SEM, DSC and FTIR methods. Various key properties of the matrices were evaluated, including hydrophilicity and mechanical strength, as well as photodynamic and light-dependent antimicrobial effects against the conditionally pathogenic microorganism Staphylococcus aureus. The results demonstrate a significant improvement in electrospinning properties for a concentration of 0.5% Chl and a reduction in fiber formation defects, as well as an increase in the strength of nonwovens. It was found that the antimicrobial potential of Chl-PHB (with concentrations of Chl of 1.25 and 1.5%) is higher than that of Chl in free form. It was also determined that irradiation increases the inhibitory effect of Chl, both in free form and in the form of a complex with a polymer.

The Role of Chemical Treatments on Curaua Fibers on Mechanical and Thermal Behavior of Biodegradable Composites

Biodegradable composites combining thermoplastic polymers and natural fibers could originate materials with synergetic mechanical and thermal properties, keeping their biodegradability. This paper describes biodegradable polymers’ mechanical and thermal properties, such as polylactic acid (PLA) and polyhydroxybutyrate (PHB) reinforced with curaua fibers. To improve the interface between matrix and reinforcement, the curaua fibers were treated by two routes: (1) treatment with hot water and subsequent mercerization with NaOH; (2) treatment with chlorite and subsequent mercerization with NaOH. The composites of PLA and PHB reinforced with natural or modified fibers (10 and 20 wt%) were obtained by extrusion and injection molding. The influence of fiber content and treatment on composite properties was studied by tensile and flexural tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results showed the removal of hemicellulose and lignin from the fibers, increasing their crystallinity and slightly decreasing their thermal stability after chemical treatments. Also, the DSC technique showed that the insertion of the curaua fibers increased the crystallinity index of all composites/PLA. The mercerized-curaua (20 wt%)/PLA composite showed the best result in the mechanical behavior, both in tensile and bending tests. The PHB composite, reinforced with curaua fibers and treated with hot water and mercerization (20 wt%), showed the best result regarding mechanic performance. To conclude, all composites improved mechanical properties compared to pure polymers.

Bioplastic’s Valorisation by Anaerobic Co-Digestion with WWTP Mixed Sludge

Bioplastics are designed to degrade at the end of their lifecycle, but effective management of their end-of-life phase and integration into existing organic waste management systems remain significant challenges. Some bioplastics decompose under anaerobic conditions, with the anaerobic digestion (AD) process being a potential solution for their disposal. AD is a promising technology for valorising organic wastes, enabling biomethane production, reducing carbon footprints, and promoting product circularity. This study focuses on evaluating the continuous co-digestion of bioplastics with mixed sludge from an urban wastewater treatment plant (WWTP). Polyhydroxybutyrate (PHB) was the selected bioplastic, as various studies have reported its high and rapid degradation under anaerobic mesophilic conditions. PHB’s biodegradability under typical WWTP anaerobic digestion conditions (35 °C, 20-day retention time) was assessed in batch tests and the results indicate that PHB degradation ranged from 68 to 75%, depending on particle size. To further explore the potential of AD for PHB valorisation, the feasibility of anaerobic co-digestion of PHB with WWTP sludge was tested on a continuous laboratory scale using two digesters: a conventional digester (CSTR) and an anaerobic membrane bioreactor (AnMBR). The results indicated complete degradation of PHB, which led to higher biomethanisation percentages in both digesters, rising from 58% to 70% in the AnMBR and from 44% to 72% in the CSTR. The notable increase observed in the CSTR was attributed to changes in microbial populations that improved sludge biodegradability.

Functionalisation of polyhydroxybutyrate for diagnostic uses

Polyhydroxybutyrate (PHB) is a biodegradable and biocompatible biopolyester, naturally produced and self-assembled as spherical inclusions inside bacteria. These PHB particles contain a hydrophobic PHB core covalently coated with PHB synthase (PhaC), which serves as an anchoring linker for foreign proteins of interest. Protein engineering of PhaC enables the display of biologically active protein functions on the surface of PHB particles suitable for different applications. Many biomolecules, such as e.g. antigens, enzymes, fluorescent proteins were immobilized to PHB particles and exhibited superior functionalities when compared to their respective soluble counterparts. Recently, PHB particles have been successfully applied for various diagnostics applications. This mini review provides an overview of the unique design space of PHB particles towards the development of safe and cost-effective diagnostic tools, and highlights the important research progresses of manufacturing PHB particles-based diagnostics.

Repeated Fed-Batch Culture Strategy for the Synthesis of Polyhydroxybutyrate (PHB) Biopolymers from Sugar Cane Juice Using Azotobacter vinelandii.

In this research work, a main biopolymer group of polyhydroxyalkanoates (PHAs) in the form of polyhydroxybutyrate (PHB) was synthesised by a pure bacterial strain of Azotobacter vinelandii via repeated fed-batch fermentation. An agricultural crop, sugar cane, was used as the sole carbon source. Firstly, batch fermentation was investigated considering variations in incubation times (24 h, 48 h, and 96 h). The highest dry cell weight (DCW) and PHAs of 5.15 ± 0.04 g/L and 4.00 ± 0.04 g/L were obtained after 48 h of incubation time. The optimum time obtained was further varied to investigate the effect of the sugar concentrations in the medium. It was found that bacteria could grow very well and produced the highest DCW and PHAs (11.17 ± 0.15 g/L and 8.77 ± 0.06 g/L) when the culture medium with a 100 g/L sugar concentration was added. Later, repeated fed-batch fermentation was carried out to improve productivity. The results obtained revealed that PHA production was increased in the next cycle of the process. Furthermore, the final productivity (0.104 g/L·h) was increased 1.65-fold compared to the first cycle (0.063 g/L·h). Moreover, the culture strategy showed remarkable results, with reductions in both fermentation time and preparation cost.

Modification of Poly(3-Hydroxybutyrate) with a Linear Polyurethane Modifier and Organic Nanofiller-Preparation and Structure-Property Relationship.

The growing demand for products made of polymeric materials, including the commonly used polypropylene (PP), is accompanied by the problem of storing and disposing of non-biodegradable waste, increasing greenhouse gas emissions, climate change and the creation of toxic products that constitute a health hazard of all living organisms. Moreover, most of the synthetic polymers used are made from petrochemical feedstocks from non-renewable resources. The use of petrochemical raw materials also causes degradation of the natural environment. A potential solution to these problems is the use of biopolymers. Biopolymers include biodegradable or biosynthesizable polymers, i.e., obtained from renewable sources or produced synthetically but from raw materials of natural origin. One of them is the poly(3-hydroxybutyrate) (P3HB) biopolymer, whose properties are comparable to PP. Unfortunately, it is necessary to modify its properties to improve its processing and operational properties. In the work, hybrid polymer nanobiocomposites based on P3HB, with the addition of chain, uncross-linked polyurethane (PU) and layered aluminosilicate modified with organic salts (Cloisite®30B) were produced by extrusion process. The introduction of PU and Cloisite®30B to the polymer matrix (P3HB) influenced the processing parameters beneficially and resulted in a decrease in the extrusion temperature of more than 10 °C. The influence of the simultaneous addition of a constant amount of PU (10 m/m%) and the different amounts of nanoadditives (1, 2 and 3 m/m%) on the compatibility, morphology and static mechanical properties of the resulted nanobiocomposites were examined. The component interactions by Fourier transformation infrared spectroscopy (FTIR) analysis, nano- and microscale structure studies using small-angle X-ray scattering (SAXS) and morphology by scanning electron microscopy (SEM) were carried out, and the hardness and tensile strength of the obtained polymer nanobiocomposites were determined. FTIR analysis identified the compatibility of the polyester matrix, PU, and organomodified montmorillonite, the greatest being 3 m/m% Cloisite30B content. The addition of PU to the polyester elasticizes the material and decreases the material's strength and ductility. The presence of nanoclay enhanced the mechanical properties of nanobiocomposites. The resulting nanobiocomposites can be used in the production of short-life materials applied in gardening or agriculture.

Optimized Polyhydroxybutyrate Production by Neobacillus niacini GS1 Utilizing Corn Flour, Wheat Bran, and Peptone: A Sustainable Approach

Plastic pollution is a pressing environmental challenge, necessitating the development of biodegradable alternatives like polyhydroxybutyrate (PHB). This study focuses on optimizing PHB production by Neobacillus niacini GS1, a bacterium isolated from a municipal dumping site. By utilizing agricultural residues such as corn flour, wheat bran, and peptone as substrates, we aimed to establish an eco-friendly method for biopolymer production, contributing to sustainable agricultural residue management and bioplastic innovation. The bacterium was identified using morphological, biochemical, and molecular techniques. The optimization process involved adjusting variables such as inoculum age, inoculum size, incubation time, agitation rate, incubation temperature, pH of the medium, carbon sources, and nitrogen sources. Response surface methodology (RSM) was employed to identify optimal conditions, with the highest PHB yield of 61.1% achieved under specific conditions: 37 °C, pH 7, and an agitation rate of 150 rpm. These findings underscore the potential of Neobacillus niacini GS1 in converting agro-industrial residues into valuable biopolymers, promoting sustainable bioplastic production, and advancing agricultural residue valorization efforts through the use of eco-friendly materials.