Search Results (300)

(1) Background: Bio-based plastics are an alternative for commonly used petroleum-based plastics, and their production will increase in the coming decades. In this work, two innovative bio-based plastics, i.e., polylactide-based (PLA-based) and polyhydroxybutyrate-based (PHBV-based), were studied with regard to their effect on the growth of higher plants (Sorghum saccharatum, Sinapsis alba) in the soil environment. (2) Methods: The experiments were conducted in pots filled with the Organisation for Economic Co-operation and Development (OECD) reference soil with or without one of the bioplastics at concentrations from 0.1% w/w to 12.5% w/w. This study is one of few works in which soil instead of another medium (e.g., deionised water) was used for the evaluation of the impact of microplastics on plant growth. (3) Results: Mustard (Sinapsis alba) was more sensitive to the presence of microplastics in the soil than sorghum (Sorghum saccharatum). The length of mustard shoots exposed to PLA-based plastic were shorter from 25% to about 56% than those in the control tests, while in the case of PHBV-based plastic, the decrease of mustard shoot length varied from 6% to 26%. The presence of the bioplastics studied, in particular the PLA-based one, at the levels of 2.5% w/w and higher contributed to reduced germination and shoot length and to the decrease in the relative chlorophyll content. (4) Conclusions: These three endpoints occurred to be more sensitive than the dry weight or elemental composition of plant biomass. They are recommended to be used in the evaluation of phytotoxicity of microbioplastics to study how to maintain the sustainability of the soil environment. Full article

Electrospinning and electrospraying nanotechnologies were used to valorise agro-industrial residues into biohybrid controlled-release polyphenol (CRP) scaffolds. Four polyhydroxybutyrate ± polycaprolactone (PHB±PCL) architectures were fabricated that differed in polymer phase, Klason lignin from hazelnut shell (HS-KL) presence vs. absence, and co-location with grape-pomace polyphenols (GP-PPs), as well as in distribution between fibres and bead-like depots. Scaffolds were characterised using optical microscopy/stereomicroscopy/SEM, FTIR, UV–Vis spectroscopy, and dynamic water contact angle (absorption). GP-PP release was monitored for 14 days at ~25 °C and 37 °C, the latter representing shallow-soil hot-spell conditions in Mediterranean zones. All matrices exhibited multimodal release, with modest initial bursts and three phases (burst, mid, and late tail), analogous to controlled-release fertiliser profiles. At ~25 °C, the PHB/PCL matrix with HS-KL confined to PHB fibres and GP-PP in large PCL beads showed the highest total GP-PP release, whereas the architecture with HS-KL and GP-PP co-located in both PHB and PCL fibres and in PCL depots combined high total release with a smoother, well-metered late phase. At 37 °C, this HS-KL-GP-PP co-located scaffold was the most robust, retaining the highest total and late tail release. These results identify HS-KL-GP-PP co-located PHB/PCL architectures as promising carriers for temperature-resilient delivery of bioactive polyphenols in Mediterranean agrosystems. Full article

Halophilic proteases are valuable in industrial applications due to their resistance to harsh conditions. HtrA2 serine protease is widely distributed and conserved among eukaryotes and prokaryotes. However, HtrA2 proteases from archaea have been poorly characterized. In this study, htrA2 from haloarcheon Haloarcula sp. TG1 was cloned and corresponding nucleotide and amino acid sequences were analyzed. Recombinant HtrA2 was produced in Escherichia coli, and biochemical properties of purified HtrA2 were characterized. HtrA2 was immobilized for the first time using polyhydroxybutyrate (PHB) nanoparticles. Additionally, potential of HtrA2 as a detergent additive was evaluated by its bloodstain removal activity. Recombinant HtrA2 showed its optimum activity at 50 °C, pH 7.0, and 3.0 M NaCl. HtrA2 activity was highly retained over wide temperature (40 to 60 °C) and pH ranges (pH 5.0 to 11.0). Moreover, various organic solvents, inhibitors and metal ions were well tolerated by the enzyme. Acetone and Fe²⁺ significantly increased HtrA2 activity, while it was not inhibited by phenylmethylsulfonyl fluoride and sodium dodecyl sulfate. Also, immobilization of HtrA2 onto PHB nanoparticles improved its reusability. Furthermore, HtrA2 successfully removed the bloodstain from cotton fabric. This comprehensive characterization of HtrA2 demonstrates that recombinant HtrA2 obtained from Haloarcula sp. TG1 is promising for industrial applications. Full article

Dried okara (DOK), a lignocellulosic byproduct from tofu production, was evaluated as both a carbon source and culture medium to enable cost-effective polyhydroxybutyrate (PHB) production. Hydrolysis with either HCl or H₂SO₄ generated 48–51 g/L reducing sugars with peak values reaching 60.2 g/L using 3% acid at 121 °C. Analysis of monosaccharides indicated pentoses, especially xylose, as the main sugars present. A novel strain, Burkholderia sp. EP10 exhibited direct growth and PHB accumulation in DOK hydrolysate without requiring detoxification, tolerating inhibitory compounds such as furfural and 5-hydroxymethylfurfural. In shake flask experiments, the strain achieved 6.9 g/L biomass and 26.3 wt% PHB, while in fermentor studies, biomass reached 10.9 g/L and PHB content was 29.3 wt% at a C/N ratio of 5.7. Notably, these outcomes were achieved without pH control, constituting a key benefit for operational simplification and cost minimization. The biopolymer was verified as PHB using gas chromatography, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance spectroscopy. The PHB displayed melting transitions at 163.5 and 172.4 °C, a degradation onset at 268 °C, and high molecular weight (4.66 × 10⁵ Da). Burkholderia sp. EP10 for sustainable PHB production via direct bioconversion of lignocellulosic hydrolysates, without the need for pH adjustment, detoxification, or complex medium development. Full article

Polyhydroxybutyrate (PHB) is a biodegradable polyester considered a sustainable alternative to petroleum-based plastics. However, its biodegradation in the presence of plasticizers remains poorly defined. This study investigated the impact of phthalate ester- and glycol-based plasticizers on PHB degradation by Ralstonia sp. C1. Real Time -Polymerase Chain Reaction(RT-PCR) analysis showed that expression of the PHB depolymerase gene phaZa1 remained unchanged in all additive-treated cultures, indicating no transcriptional interference. Liquid-medium degradation assays quantified by HPLC revealed rapid PHB utilization, with more than 50% degraded within 24 h and over 98% degraded within 48 h, with no significant differences relative to the control. Growth-inhibition assays further demonstrated that none of the plasticizers impaired bacterial viability, as OD₆₀₀ profiles were comparable to untreated cultures. Soil degradation experiments confirmed that PHB films containing additives decomposed at rates similar to additive-free films, reaching approximately 80% degradation within 10 weeks. Overall, the tested plasticizers did not affect enzyme expression, microbial activity, or PHB biodegradation, highlighting the suitability of plasticized PHB materials for environmentally sustainable applications and supporting their scalable use as biodegradable alternatives to conventional plastics. Full article

Biodegradable polymers based on poly(lactic acid) (PLA) and polyhydroxybutyrate (PHB) are widely investigated for biomedical engineering applications, particularly for temporary implants and tissue scaffolds fabricated by additive manufacturing. However, their degradation behavior is influenced not only by material composition, but also by manufacturing-related parameters, geometric design, and environmental conditions. This study investigates the in vitro degradation behavior of PLA/PHB structures fabricated using fused filament fabrication (FFF). Degradation was evaluated under two model environmental conditions over a 45 day period. Changes in specimen mass and the evolution of degradation medium pH were monitored as a function of exposure time, specimen geometry, and infill density. The results revealed a progressive degradation process, with pH values decreasing to approximately 2.7–4.1 in physiological saline solution and increasing to 8.9–9.7 in urea solution, depending on specimen geometry and infill density. After 45 days of exposure, the relative mass loss reached approximately 25–32% for type A specimens and 29–41% for type B specimens. The results revealed distinct differences between degradation environments and specimen geometries, while differences related to infill density partially overlapped within the investigated range. The findings indicate that the degradation behavior of additively manufactured PLA/PHB structures cannot be interpreted solely based on material composition, but should be considered in the context of manufacturing strategy and structural design. These results provide useful insights for the design of biodegradable polymer components with more predictable degradation behavior. Full article

This study systematically optimised extrusion-printing parameters for polyhydroxybutyrate (PHB) using a Design of Experiment (DoE) approach to improve printability and construct fidelity. A five-factor DoE was conducted to evaluate the individual and interactive effects of printhead temperature, printing pressure, printing speed, bed temperature, and cartridge heating time on the dimensional accuracy of printed constructs. The resulting regression model enabled the identification of statistically significant main and interaction effects among processing variables. An optimised parameter set (printhead temperature 145 °C, pressure 150 kPa, speed 15 mm s⁻¹, bed temperature 25 °C, and cartridge heating time 120 s) enabled the fabrication of PHB scaffolds with substantially improved shape fidelity, which was experimentally validated using verification prints. These results demonstrate that a DoE-based optimisation strategy provides a robust and efficient route for rationally tuning PHB extrusion-printing conditions, thereby enhancing process reliability for scaffold fabrication in regenerative medicine applications. Full article

From 1950 to the present, plastic production and use have increased mainly because plastics possess qualities like stability, light weight, versatility, and decreasing production costs. However, most plastics are not biodegradable, and only a small portion is recycled worldwide. Bioplastics serve as an alternative if they are biodegradable and derived from residual materials, promoting a circular economy. PHB is a polymer with characteristics similar to some commercial plastics. It was discovered in the 1920s and has been examined by researchers and engineers since then due to its potential as a biodegradable bioplastic. Some microorganisms can produce PHB under controlled conditions. In this work, PHB production was analyzed using two strains, Bacillus subtilis and Bacillus megaterium, and two byproducts—whey and glycerol—as substrates and varying the culture media compositions. Both byproducts and both strains are suitable for PHB production; the absence of nitrogen and trace element sources enhances PHB yield. Additionally, bacterial growth, substrate uptake, and PHB production were modeled using logistic growth and the Luedeking–Piret models. Full article

This study investigated a phototrophic approach to close nutrient loops by using landfill leachate as a culture medium to produce biomass and polyhydroxybutyrate (PHB) from a thermotolerant strain of Potamosiphon sp. A multi-cycle reuse scheme in which post-culture leachate was partially replenished with fresh leachate and reused in successive cultivation rounds to increase the biomass concentration (g/L) and the intracellular PHB content (% w/w) was tested. Three operational variables were optimized (leachate replenishment percentage, number of reuse cycles, and sanitation method (autoclaving, UV irradiation, or no treatment)) via the Box–Behnken response surface method. Both response variables were modeled with high predictive accuracy (R² = 0.98 for biomass and R² = 1.00 for PHB content). According to the experimental data, leachate replenishment emerged as the key factor influencing nutrient availability—particularly nitrogen and phosphorus—and thus PHB accumulation. The optimized conditions (2.17% v/v fresh leachate, three reuse cycles, and UV sanitation) yielded predicted values of 0.29 g/L biomass and 3.48% w/w PHB. These results demonstrate the feasibility of a controlled multicycle reuse process that integrates effluent treatment and biopolymer synthesis, offering a low-input, circular biotechnological approach for sustainable leachate valorization. Full article

The increased production of bio-based plastics, such as polyhydroxybutyrate (PHB), raises the need for a thorough understanding of the fate of these materials in natural and controlled disposal environments, such as landfills. However, there is a paucity of knowledge regarding PHB biodegradation at alkaline landfill sites containing incineration ash. This study aimed to investigate the biodegradability of PHB films in alkaline landfill soil (pH 9.7) and campus soil (pH 7). PHB biodegradation was much faster in campus soil (100%) than in alkaline landfill soil (65.2%) after 63 days. Bioaugmentation with Ralstonia insidiosa C1 (Ralstonia sp. C1) enhanced the PHB biodegradability from 13.6% to 35% in landfill soil and from 26.6% to 79.8% in campus soil. Landfill soil had a bacterial CFU of (2.1 × 10⁶) and fungal CFU of (7.3 × 10³), which is significantly lower than the bacterial CFU (4.4 × 10⁸) and fungal CFU (1.1 × 10⁷) in campus soil, thereby limiting the biomass required for effective PHB decomposition. Next-generation sequencing revealed that landfill soil lacks key PHB-degrading microbial genera that are normally found in soil, such as Ralstonia, Enterobacter, and Comamonas. In conclusion, PHB biodegradability is strongly affected by alkaline landfill soil, the control of which is the key to ensuring effective in situ bioplastic waste management. Full article

Cupriavidus necator is a well-studied microorganism with potential application in bioregenerative life support systems for single-cell protein and bioplastic production. Most studies have been carried out in autotrophy or heterotrophy, requiring O₂ as the final electron acceptor. In the context of inhabited missions, access to O₂ will primarily be limited to the crew. In this study, we investigated the capacity of C. necator to carry out nitrate respiration as a strategy to limit oxygen supply to the cultures by providing nitrate from another compartment of the Bioregenerative Life Support System (BLSS). Batch bioreactor experiments were carried out to determine the best conditions for nitrate utilization in terms of pH and aeration. Continuous cultures were then performed under two carbon sources (glucose vs. acetic acid) and two substrate limitations (nitrate vs. carbon). The optimal conditions were found to be pH 7.5 under anaerobiosis. They were applied in chemostats, where three steady-states were obtained at a low dilution rate. In all cases, the biomass consisted of a mixture of protein (from 29 ± 1% Cell Dry Weight (CDW) to 39 ± 2% CDW) and polyhydroxybutyrate (from 45 ± 2% CDW to 57 ± 3% CDW), which was found to be a key component for nitrate respiration metabolism. Microaerobic conditions were also tested in batch culture, reporting for the first time aerobic nitrate respiration in C. necator. Under these conditions, growth parameters improved during the nitrate phase; however, the specific growth rate during the nitrite phase was lower than that observed under strictly anaerobic conditions. Full article

Delivering net-zero CO₂ emissions by 2050 requires rapid, large-scale carbon sequestration. Global photosynthesis, driven by cyanobacteria, microalgae, and higher plants, captures CO₂ and constitutes the dominant natural carbon sink (biomass). The built environment represents a second major sink. Large-scale microalgal cultivation and the integration of its bioproducts into building materials offers a pathway to capture and store CO₂ in built infrastructure. Colourful sustainably produced biopolymers offer one such route for carbon sequestration. Although pigments have a minor direct contribution, their coloration potential can accelerate the adoption of C-containing materials to increase architectural carbon sequestration. Here, we blended (individually and in combination) a range of structurally different pigments; the carotenoids—lutein (yellow) and astaxanthin (red), a water-soluble chlorophyll derivative—sodium copper chlorophyllin (green), and a water-soluble protein (phycocyanin, blue) into two biopolymers, polyhydroxybutyrate-hydroxyhexanoate and polycaprolactone with melting points of 135 °C and 60 °C, respectively. Six blending processes were evaluated for homogeneous coloured biopolymer production. UV resistance of coloured biopolymers was evaluated and enhanced by the application of a UV-protective coating. The best of the coloured biopolymer samples were integrated into a small-scale curved architectural structure to gain insight into the use and performance of the translucent materials produced for exhibition. Full article

This research assesses a triphasic extraction technique for the sequential retrieval of C-phycocyanin (C-PC) and polyhydroxybutyrate (PHB) from a thermotolerant Potamosiphon sp. strain. A two-stage design-of-experiments methodology was employed (Minimum Run Resolution V factorial design involving six variables, followed by a central composite design (CCD)) to optimize the chosen region. In the factorial stage, PHB ranged from 109.396 to 168.995 mg/g, and the model was significant (F = 22.63, p < 0.0001). Freeze-milling and vortexing were identified as critical elements, underscoring the importance of the t-butanol × (NH₄)₂SO₄ interaction for phase selectivity. The CCD concentrating on freeze-milling and vortex cycles yielded a robust quadratic model (F = 78.18, p < 0.0001), forecasting a peak PHB yield of 191.82 mg/g at six freeze-milling cycles and three vortex cycles (desirability 0.921), while maintaining t-butanol at 19.9 mL, t-butanol concentration at 94.7% (v/v), (NH₄)₂SO₄ at 49.9% (w/v), and vortex duration at 1.2 min. Ten separate trials validated the model’s accuracy, yielding an observed PHB of 191.5 mg/g, which closely matched the model’s prediction. The platform facilitates an integrated downstream process in which C-PC is recovered under moderate conditions before triphasic partitioning. This enables the simultaneous valorization of pigment, lipophilic fraction, and biopolymer inside a unified cyanobacterial biorefinery process. Full article

Thermoplastic starch (TPS) blended with biodegradable polyesters such as polyhydroxybutyrate (PHB), polylactic acid (PLA), polybutylene succinate (PBS), and polycaprolactone (PCL) represents a promising route toward sustainable alternatives to petroleum-based plastics. TPS offers advantages related to abundance, low cost, and biodegradability, while polyesters provide improved mechanical strength, thermal stability, and barrier performance. However, the intrinsic incompatibility between hydrophilic TPS and hydrophobic polyesters typically leads to immiscible systems with poor interfacial adhesion and limited performance. This review critically examines recent advances in the development of TPS/polyester blends, with emphasis on compatibilization strategies based on chemical modification, natural and synthetic compatibilizers, bio-based additives, and reinforcing agents. Particular attention is given to the role of organic acids, essential oils, phenolic compounds, nanofillers, and natural reinforcements in controlling morphology, crystallinity, interfacial interactions, and thermal–mechanical behavior. In addition, the contribution of bioactive additives to antimicrobial and antioxidant functionality is discussed as an emerging multifunctional feature of some TPS/polyester systems. Finally, current limitations related to long-term stability, scalability, and life cycle assessment are highlighted, identifying key challenges and future research directions for the development of advanced biodegradable materials with tailored properties. Full article

Infectious pathogens pose serious threats to public health, necessitating the development of more antimicrobials. In this study, oligohydroxybutyrates were obtained through the catalyzed polymerization of β-butyrolactone using N, N-dimethyl-4-aminopyridine (DMAP) and aluminum isopropoxide [Al(OiPr)₃] and applied as sustainable antimicrobial agents. The poly3-hydroxybutyrate (PHB) oligomers exhibited broad-spectrum antibacterial activities against both Gram-negative (E. coli) and Gram-positive (S. aureus) model bacteria. Additionally, PHB oligomers displayed robust (inhibiting rate: >95%) and rapid (action time: <20 min) antiviral activity against three notorious single-stranded RNA viruses, that is, influenza A virus (H1N1 and H3N2) and coronavirus (SARS-CoV-2). In particular, a comprehensive set of advanced experimental characterizations, including FT-IR, ¹H- and ¹³C-NMR, and H-ESI-MS/MS, was applied to analyze their chemical structures. The results confirmed the loss of terminal hydroxyl groups in the PHB intermediate and end products associated with theoretical calculations. These findings will also help provide deep insight into the major chain growth mechanism during the synthesis of PHB. The structural variations, which were treated as unwanted side reactions, were identified as a pivotal factor by deactivating the terminal hydroxy during chain growth. Their effective sterilization properties and degradability endowed the as-prepared PHB oligomers with a promising biomedical potential, including for use as disinfectants, sanitizers, and antiseptics. Full article