Investigating mechanical properties of 3D printed polylactic acid / poly-3-hydroxybutyrate composites. Compressive and fatigue performance.

The 3D printing technique known as Material Extrusion (MEX) was initially employed for prototyping, but it has evolved to fit applications in mechanical and biomedical industries. Polylactic acid (PLA) stands out as a commonly used polymer for manufacture pieces by MEX, due to its good properties and organic origins. Pursuing renewable and biodegradable thermoplastics has led to the development materials such as composite of PLA with wood fibers and blends with poly-3-hydroxybutyrate (PHB). This study aims to characterize the effect of the most relevant printing parameters on the mechanical properties of a PLA/PHB blend, motivated by the interest to facilitate the use of this type of materials in industrial applications. To achieve it, compressive and fatigue tests were carried out, comparing the results with those obtained in previous studies for pure PLA and PLA-wood composite. Results show that the compressive behavior of PLA/PHB is influenced by the layer height, nozzle diameter and fill density. Its fatigue behavior is mainly determined by the nozzle diameter and the fill density. Moreover, the mechanical performance of PLA/PHB (Young's Modulus of 1.67 GPa, yield Strength of 33.8 MPa and maximum fatigue life of 9711 cycles) is inferior compared to pure PLA and PLA-wood composite. Despite the increase in the biodegradability that PHB introduces into PLA, the findings of this study reveal that there is statistically evidence that it can also hinder the mechanical performance of the base material.

Effect of Amorphous Halomonas-PHB on Growth, Body Composition, Immune-Related Gene Expression and Vibrio anguillarum Resistance of Hybrid Grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatu ♂) Juveniles.

Poly-ß-hydroxybutyrate (PHB) is a bacterial metabolite produced by bacteria such as Halomonas sp. that serves as a carbon and energy storage compound for bacteria under nutrient-limited conditions. Two experiments were conducted to investigate the effects of dietary supplementation with Halomonas-PHB on hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatu ♂). In experiment I, juvenile groupers were fed basal diets supplemented with 3% Halomonas-PHB (3% HM-PHB) containing 1.4% PHB and 3% Halomonas (3% HM) without PHB, as well as a control diet, for seven weeks. The results showed no significant difference in survival rate, weight gain, and crude fat content between the 3% HM-PHB group and the control group; however, the crude protein of the 3% HM-PHB group was significantly lower than that of the control group. Furthermore, supplementation with 3% HM-PHB increased the fatty acids content in fish muscles, including long-chain unsaturated fatty acids C18:1n9, EPA, and DHA. In experiment II, groupers were fed a basal diet supplemented with 6.5% Halomonas-PHB (6.5% HM-PHB) containing 3% PHB and 6.5% Halomonas (6.5% HM) containing no PHB, as well as a basal diet (Control). After seven weeks of rearing, the fish were challenged with Vibrio anguillarum for 48 h. Although no significant difference in survival rate and growth was observed among different groups, the dietary supplement of 6.5% Halomonas-PHB improved the survival rate of V. anguillarum challenged grouper and significantly increased the gene expressions of catalase (CAT) and superoxide dismutase (SOD) in blood, interleukin 1 (IL1) and interleukin 10 (IL10) in the liver, spleen, head kidney, and blood (p < 0.05). In conclusion, dietary supplementation of Halomonas-PHB had no significantly positive effect on fish growth performance but increased the content of fatty acids, including long-chain unsaturated fatty acids C18:1n9, EPA, and DHA in fish muscle; it also improved the V. anguillarum resistance, possibly through increasing immune-related gene expression in different tissues and organs. Our findings offer compelling evidence that Halomonas-PHB can be utilized as a feed additive in intensive grouper farming to enhance the groupers' resistance to Vibrio.

Thermoplastic PHB-Reinforced Chitosan Piezoelectric Films for Biodegradable Pressure Sensors.

Flexible and wearable pressure sensors have attracted significant attention in the fields of smart medicine and human health monitoring. Nevertheless, the design and fabrication of degradable disposable pressure sensors still face urgent challenges. Herein, we fabricated poly(3-hydroxybutyrate) (PHB)-reinforced chitosan (CS) piezoelectric films for intelligent sensors through a simple, low-cost, and environmentally friendly roll-forming method. The results show that PHB doping successfully increased the effective piezoelectric coefficient of the chitosan-based film from 40.12 to 49.38 pm/V (a 23% increase). Simultaneously, the pressure sensor based on the CS/PHB film exhibited excellent response sensitivity (484 mV/kPa) and a wide linear response range (0-130 kPa), which could be used as haptic sensors and motion monitoring sensors for the fast response to human motion signals. Additionally, the CS/PHB film could be completely degraded within 18 days in a natural soil environment, demonstrating outstanding degradability. Therefore, chitosan-based piezoelectric films with excellent biodegradability and piezoelectric characteristics have been successfully fabricated in this work, which will promote the innovative development of green chitosan-based electronic devices and disposable pressure sensors.

Engineered Halomonas for production of gamma-Aminobutyric acid and 2-Pyrrolidone.

Gamma-Aminobutyric acid (GABA) is a derivative of L-glutamate, also a precursor for the synthesis of 2-pyrrolidone, which is a monomer of nylon-4. This study achieved a one-step biosynthesis of GABA and 2-pyrrolidone by Halomonas bluephagenesis overexpressing key genes involved in GABA and 2-pyrrolidone synthesis and deleting GABA degradation genes combined with reducing the degradation of 2-pyrrolidone precursor. The resulting H. bluephagenesis strain WLp07 was employed in whole-cell catalysis, producing 357 g/L of GABA and 72 wt% of PHA. Furthermore, a self-flocculating H. bluephagenesis allowed rapid, convenient recycling of the cells, achieving 880 g/L of GABA over three cycles. Shake flask studies showed that engineered H. bluephagenesis harboring ß-alanine CoA transferase was able to synthesized 2-pyrrolidone from GABA. H. bluephagenesis as a chassis of next generation industrial biotechnology (NGIB), demonstrated its diverse ability to produce GABA and 2-pyrrolidone in addition to intracellular PHA.

Production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by Haloferax mediterranei Using Candy Industry Waste as Raw Materials.

The haloarchaeon Haloferax mediterranei synthesizes poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) under unfavorable nutritional conditions without the addition of any precursor to the culture, which is an advantage compared to other microbial counterparts able to synthesize polyhydroxyalkanoates (PHA). PHBV is a biodegradable polymer showing physiochemical properties of biotechnological and biomedical interest and can be used as an alternative to plastics made from chemical synthesis (which are not environmentally friendly). The versatile metabolism of H. mediterranei makes the use of waste as a carbon source for cellular growth and PHA synthesis possible. In this work, cellular growth and the production and characterization of PHBV using two different types of confectionery waste were analyzed and compared with cellular growth and PHBV synthesis in a standard culture media with glucose of analytical grade as a carbon source. The PHBV granules produced were analyzed by TEM and the biopolymer was isolated and characterized by GC-MS, FTIR NMR, and DSC. The results reveal that H. mediterranei can use these two residues (R1 and R2) for pure PHBV production, achieving 0.256 and 0.983 g PHBV/L, respectively, which are among the highest yields so far described using for the first-time waste from the candy industry. Thus, a circular economy-based process has been designed to optimize the upscaling of PHBV production by using haloarchaea as cell factories and valorizing confectionery waste.

Bioplastic production by harnessing cyanobacteria-rich microbiomes for long-term synthesis.

Departing from the conventional axenic and heterotrophic cultures, our research ventures into unexplored territory by investigating the potential of photosynthetic microbiomes for polyhydroxybutyrate (PHB) synthesis, a biodegradable polyester that presents a sustainable alternative to conventional plastics. Our investigation focused on a cyanobacteria-enriched microbiome, dominated by Synechocystis sp. and Synechococcus sp., cultivated in a 3 L photobioreactor under non-sterile conditions, achieving significant PHB production-up to 28 % dry cell weight (dcw) over a span of 108 days through alternating cycles of biomass growth and PHB accumulation. Nile Blue staining and Transmission Electron Microscope visualization allowed to successfully confirm the presence of PHB granules within cyanobacteria cells. Furthermore, the overexpression of PHA synthase during the accumulation phase directly correlated with the increased PHB production. Also, gene expression changes revealed glycogen as the primary storage compound, but under prolonged macronutrient stress, there was a shift of the carbon flux towards favoring PHB synthesis. Finally, analysis through Raman, Fourier- transform infrared spectroscopy and proton Nuclear Magnetic Resonance further validated the extracted polymer as PHB. Overall, it was demonstrated for the first time the feasibility of using phototrophic microbiomes to continuous production of PHB in a non-sterile system. This study also offers valuable insights into the metabolic pathways involved.

Prohibitin 2 confers NADPH oxidase 1-mediated cytosolic oxidative signaling to promote gastric cancer progression by ERK activation.

Oxidative signaling plays a dual role in tumor initiation and progression to malignancy; however, the regulatory mechanisms of oxidative stress in gastric cancer remain to be explored. In this study, we discovered that Prohibitin 2 (PHB2) specifically regulates cytosolic reactive oxygen species production in gastric cancer and facilitates its malignant progression. Previously, we found that PHB2 is upregulated in gastric cancer, correlating with increased tumorigenicity of gastric cancer cells and poor patient prognosis. Here, we discovered that PHB2 expression correlates with the activation of the ERK/MAPK cascade, positively regulating the top gene NADPH oxidase 1 (NOX1) within this pathway. Further mechanistic investigation reveals that PHB2 enhances NOX1 transcription by interacting with the transcription factor C/EBP-beta and promoting its translocation into the nucleus, resulting in elevated intracellular oxidative signaling driven by NOX1, which subsequently activates ERK. Therefore, we propose that targeting PHB2-C/EBP-beta-NOX1-mediated cytosolic oxidative stress could offer a promising therapeutic avenue for combating gastric cancer malignant progression.

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.

Quantitative Analysis of Rhodobacter sphaeroides Storage Organelles via Cryo-Electron Tomography and Light Microscopy.

Bacterial cytoplasmic organelles are diverse and serve many varied purposes. Here, we employed Rhodobacter sphaeroides to investigate the accumulation of carbon and inorganic phosphate in the storage organelles, polyhydroxybutyrate (PHB) and polyphosphate (PP), respectively. Using cryo-electron tomography (cryo-ET), these organelles were observed to increase in size and abundance when growth was arrested by chloramphenicol treatment. The accumulation of PHB and PP was quantified from three-dimensional (3D) segmentations in cryo-tomograms and the analysis of these 3D models. The quantification of PHB using both segmentation analysis and liquid chromatography and mass spectrometry (LCMS) each demonstrated an over 10- to 20-fold accumulation of PHB. The cytoplasmic location of PHB in cells was assessed with fluorescence light microscopy using a PhaP-mNeonGreen fusion-protein construct. The subcellular location and enumeration of these organelles were correlated by comparing the cryo-ET and fluorescence microscopy data. A potential link between PHB and PP localization and possible explanations for co-localization are discussed. Finally, the study of PHB and PP granules, and their accumulation, is discussed in the context of advancing fundamental knowledge about bacterial stress response, the study of renewable sources of bioplastics, and highly energetic compounds.

Blockade of the lncRNA-PART1-PHB2 axis confers resistance to PARP inhibitor and promotes cellular senescence in ovarian cancer.

PARPi is currently the most important breakthrough in the treatment of ovarian cancer in decades, and it has been integrated into the initial maintenance therapy for ovarian cancer. However, the mechanism leading to PARPi resistance remains unelucidated. Our study aims to screen novel targets to better predict and reverse resistance to PARPi and explore the potential mechanism. Here, we conducted a comparative analysis of differentially expressed genes between platinum-sensitive and platinum-resistant groups within the TCGA ovarian cancer cohort. The analysis indicated that lncRNA PART1 was significantly highly expressed in platinum-sensitive patients compared to platinum-resistant individuals in TCGA-OV cohort and further validated in the GEO dataset and Qilu hospital cohort. Moreover, the upregulation of PART1 was positively correlated with a favorable prognosis in ovarian cancer. Furthermore, in vitro and in vivo experiments showed that inhibition of PART1 conferred resistance to both cisplatin and PARP inhibitor and promoted cellular senescence. Senescent cells are more resistant to chemotherapeutics. RNA antisense purification and RNA immunoprecipitation assays revealed an interaction between PART1 and PHB2, a crucial mitophagy receptor. Knockdown of PART1 could promote the degradation of PHB2, impairing mitophagy and leading to cellular senescence. Rescue assays indicated that overexpression of PHB2 remarkably diminished the resistance to PARPi and cellular senescence caused by PART1 knockdown. PDX models were utilized to further confirm the findings. Altogether, our study demonstrated that lncRNA PART1 has the potential to serve as a novel promising target to reverse resistance to PARPi and improve prognosis in ovarian cancer.

Phosphoglycerate mutase 5 exacerbates alcoholic cardiomyopathy in male mice by inducing prohibitin-2 dephosphorylation and impairing mitochondrial quality control.

BACKGROUND: The induction of mitochondrial quality control (MQC) mechanisms is essential for the re-establishment of mitochondrial homeostasis and cellular bioenergetics during periods of stress. Although MQC activation has cardioprotective effects in various cardiovascular diseases, its precise role and regulatory mechanisms in alcoholic cardiomyopathy (ACM) remain incompletely understood. METHODS: We explored whether two mitochondria-related proteins, phosphoglycerate mutase 5 (Pgam5) and prohibitin 2 (Phb2), influence MQC in male mice during ACM. RESULTS: Myocardial Pgam5 expression was upregulated in a male mouse model of ACM. Notably, following ACM induction, heart dysfunction was markedly reversed in male cardiomyocyte-specific Pgam5 knockout (Pgam5cKO) mice. Meanwhile, in alcohol-treated male mouse-derived neonatal cardiomyocytes, Pgam5 depletion preserved cell survival and restored mitochondrial dynamics, mitophagy, mitochondrial biogenesis and the mitochondrial unfolded protein response (mtUPR). We further found that in alcohol-treated cardiomyocyte, Pgam5 binds Phb2 and induces its dephosphorylation at Ser91. Alternative transduction of phospho-mimetic (Phb2S91D) and phospho-defective (Phb2S9A) Phb2 mutants attenuated and enhanced, respectively, alcohol-related mitochondrial dysfunction in cardiomyocytes. Moreover, transgenic male mice expressing Phb2S91D were resistant to alcohol-induced heart dysfunction. CONCLUSIONS: We conclude that ACM-induced Pgam5 upregulation results in Pgam5-dependent Phb2S91 dephosphorylation, leading to MQC destabilisation and mitochondrial dysfunction in heart. Therefore, modulating the Pgam5/Phb2 interaction could potentially offer a novel therapeutic strategy for ACM in male mice. HIGHLIGHTS: Pgam5 knockout attenuates alcohol-induced cardiac histopathology and heart dysfunction in male mice. Pgam5 KO reduces alcohol-induced myocardial inflammation, lipid peroxidation and metabolic dysfunction in male mice. Pgam5 depletion protects mitochondrial function in alcohol-exposed male mouse cardiomyocytes. Pgam5 depletion normalises MQC in ACM. EtOH impairs MQC through inducing Phb2 dephosphorylation at Ser91. Pgam5 interacts with Phb2 and induces Phb2 dephosphorylation. Transgenic mice expressing a Ser91 phospho-mimetic Phb2 mutant are resistant to ACM.

Bioinformatic and functional analysis of a PHB polymerase (PhbC) from Azospirillum baldaniorum.

BACKGROUND: Azospirillum baldaniorum Sp245 produces poly-ß-hydroxybutyrate, a biodegradable polymer with characteristics similar to synthetic thermoplastics, including polypropylene. In the synthesis pathway, the poly-ß-hydroxybutyrate synthase enzyme uses thioesters of 3-hydroxy butyryl-CoA as a substrate and catalyzes their polymerization with HS-CoA release. METHODS: A study was conducted using in silico analysis of the two phbC genes of A. baldaniorum Sp245. One was selected for amplification and cloning into the pEXP5- CT/TOPO® vector, which was analysed by restriction pattern, polymerase chain reaction, and sequencing. SDS-PAGE analysis determined the molecular weight of the PhbC1 protein from Azospirillum baldaniorum (AbPhbC1). The presence of the protein was confirmed by Western blotting using anti-polyhistidine monoclonal antibodies. The enzymatic activity in the crude extract of AbPhbC1 was determined by measuring the concentration of sulfhydryl groups using the Ellman method. A UV-Vis assay was performed. To confirm the presence of the poly-ß-hydroxybutyrate product, an NMR assay was performed. RESULTS: In silico analyses, it is revealed that AbPhbC1 and the PhbC2 protein from Azospirillum baldaniorum (AbPhbC2) retain the poly-ß-hydroxybutyrate polymerase and α/ß hydrolase domain. The Cys-His-Asp catalytic triad is highly conserved in all four polyß-hydroxyalkanoate synthases in the central subdomain, structurally similar to the reported crystallized proteins. The dimerization subdomain is different; in AbPhbC1, it is in the closed form; in AbPhbC2, it is in the open form; and in AbPhbC2, it lacks the EC region as class III and IV poly-ß-hydroxyalcanoate synthases. In vitro, the molecular weight of AbPhbC1 was 68 kDa. The polymerization of PHB by AbPhbC1 was detected by the release of HS-CoA from the quantification of SH. The UV-Vis scan showed a characteristic peak at 264 nm. A comparison of the NMR spectra of the bacterial and commercial poly-ß-hydroxybutyrate samples suggested their presence. CONCLUSION: In silico analyses suggested that AbPhbC1 and AbPhbC2 are structurally functional, except that AbPhbC2 might require the PhaR subunit for its activity; this strongly suggests that it could be a class IV poly-ß-hydroxyalcanoate synthase. UV-Vis scanning and NMR spectroscopy revealed the synthesis of poly-ß-hydroxybutyrate by the A. baldaniorum enzyme AbPhbC1, indicating that the enzyme is functional.

CRISPR-editing of the virus vector Aedes albopictus cell line C6/36, illustrated by prohibitin 2 gene knockout.

Aedes mosquitoes are important virus vectors. We provide a toolkit for CRISPR-Cas9-editing of difficult-to-knockdown gene previously shown to be refractory to siRNA silencing in mosquito cells, which is pivotal in understanding vector biology, vector competence, host-pathogen interactions and in gene annotations. Starting from database searches of Ae. albopictus and the C6/36 cell line whole genome shotgun sequences for the prohibitin 2 (PHB2) gene, primers were designed to confirm the gene sequence in our laboratory-passaged C6/36 cell line for the correct design and cloning of CRISPR RNA into an insect plasmid vector to create a single guide RNA for the PHB2 gene target. After transfection of this plasmid vector into the C6/36 cells, cell clones selected by puromycin and/or limiting dilution were analyzed for insertions and deletions (INDELs) using PCR, sequencing and computational sequence decomposition. From this, we have identified mono-allelic and bi-allelic knockout cell clones. Using a mono-allelic knockout cell clone as an example, we characterized its INDELs by molecular cloning and computational analysis. Importantly, mono-allelic knockout was sufficient to reduce >80 % of PHB2 expression, which led to phenotypic switching and the propensity to form foci but was insufficient to affect growth rate or to inhibit Zika virus infection.•We provide a toolkit for CRISPR-Cas9-editing of the virus vector, Aedes albopictus C6/36 cell line•We validate this using a difficult-to-knockdown gene prohibitin 2•This toolkit is pivotal in understanding vector biology, vector competence, host-pathogen interactions and in gene annotations.

Evaluating the osteogenic properties of polyhydroxybutyrate-zein/multiwalled carbon nanotubes (MWCNTs) electrospun composite scaffold for bone tissue engineering applications.

In this investigation, the electrospun nanocomposite scaffolds were developed utilizing poly-3-hydroxybutyrate (PHB), zein, and multiwalled carbon nanotubes (MWCNTs) at varying concentrations of MWCNTs including 0.5 and 1 wt%. Based on the SEM evaluations, the scaffold containing 1 wt% MWCNTs (PZ-1C) exhibited the lowest fiber diameter (384 ± 99 nm) alongside a suitable porosity percentage. The presence of zein and MWCNT in the chemical structure of the scaffold was evaluated by FTIR. Furthermore, TEM images revealed the alignment of MWCNTs with the fibers. Adding 1 % MWCNTs to the PHB-zein scaffold significantly enhanced tensile strength by about 69 % and reduced elongation by about 31 %. Hydrophilicity, surface roughness, crystallinity, and biomineralization were increased by incorporating 1 wt% MWCNTs, while weight loss after in vitro degradation was decreased. The MG-63 cells exhibited enhanced attachment, viability, ALP secretion, calcium deposition, and gene expression (COLI, RUNX2, and OCN) when cultivated on the scaffold containing MWCNTs compared to the scaffolds lacking MWCNTs. Moreover, the study found that MWCNTs significantly reduced platelet adhesion and hemolysis rates below 4 %, indicating their favorable anti-hemolysis properties. Regarding the aforementioned results, the PZ-1C electrospun composite scaffold is a promising scaffold with osteogenic properties for bone tissue engineering applications.

Cast Extruded Films Based on Polyhydroxyalkanoate/Poly(lactic acid) Blend with Herbal Extracts Hybridized with Zinc Oxide.

The aim of the presented work was to functionalize a blend based on polyhydroxyalkanoate (PHA): poly(hydroxybutyrate (PHB) with poly(lactic acid) (PLA) and a mixture of three selected herb extracts, namely, Hypericum L., Urtica L. and Chelidonium L., (E), zinc oxide (ZnO) and a combined system (EZnO), produced via extrusion. Before processing with bioresin, the natural modifiers were characterized using thermal analysis, FTIR and antimicrobial tests. The results revealed interactions between the extracts and the filler, leading to higher thermal stability in EZnO than when using E alone. Moreover, the mixture of extracts exhibited antimicrobial properties toward both Gram-negative (S. aureus) as well as Gram-positive bacteria (E. coli). Modified regranulates were transformed into films by cast extrusion. The influence of the additives on thermal (DSC, TGA and OIT), mechanical, barrier (WVTR and OTR), morphological (FTIR) and optical properties was investigated. The EZnO additive had the highest impact on the mechanical, barrier (OTR and WVTR) and optical properties of the bioresin. The microbial test results revealed that PHA-EZnO exhibited higher activity than PHA-ZnO and PHA-E and also reduced the number of S. aureus, E. coli and C. albicans cells. The findings confirmed the synergistic effect between the additive components. Modified polyester films did not eliminate the phi6 bacteriophage particles completely, but they did decrease their number, confirming moderate antiviral effectiveness.

Atmospheric Plasma Treatment to Improve PHB Coatings on 316L Stainless Steel.

In the present study, biopolymeric coatings of polyhydroxybutyrate (PHB) were deposited on 316L stainless steel substrates. The PHB coatings were developed using the spin coating method. To improve the adhesion of the PHB coating on the substrate, this method uses an atmospheric plasma treatment. Adhesion tests show a 156% increase in adhesion after 5 s of surface treatment. Raman spectroscopy analysis of the polymer shows the incorporation of functional groups and the formation of new hydrogen bonds, which can help us bind drugs and promote osteogenesis after plasma treatment. Additionally, the electrochemical behaviors in artificial body fluids (Hanks' solution) of the PHB coatings on the steel were evaluated with potentiodynamic tests, which revealed a decrease in the corrosion current and resistance to the transfer of the charge from the electrolyte to the 316L steel because of the PHB coating. All the PHB coatings were characterized using scanning electron microscopy and Raman spectroscopy after the electrochemical tests. This analysis confirmed the diffusion of electrolyte species toward the surface and the degradation of the polymer chain for the first 15 s of treatment with atmospheric plasma. These findings support the claim that plasma surface modification is a quick, environmentally friendly, and cost-effective method to enhance the performance of PHB coatings on 316L stainless steel for medical devices.

A Comparison of the Effects of Continuous Illumination and Day/Night Regimes on PHB Accumulation in Synechocystis Cells.

Poly(3-hydroxybutyrate) (PHB) is a biobased and biodegradable polymer with properties comparable to polypropylene and therefore has the potential to replace conventional plastics. PHB is intracellularly accumulated by prokaryotic organisms. For the cells PHB functions manly as carbon and energy source, but all possible functions of PHB are still not known. Synechocystis (cyanobacteria) accumulates PHB using light as energy and CO2 as carbon source. The main trigger for PHB accumulation in cyanobacteria is nitrogen and phosphorous depletion with simultaneous surplus of carbon and energy. For the above reasons, obtaining knowledge about external factors influencing PHB accumulation is of highest interest. This study compares the effect of continuous light exposure and day/night (16/8 h) cycles on selected physiology parameters of three Synechocystis strains. We show that continuous illumination at moderate light intensities leads to an increased PHB accumulation in Synechocystis salina CCALA 192 (max. 14.2% CDW - cell dry weight) compared to day/night cycles (3.7% CDW). In addition to PHB content, glycogen and cell size increased, while cell density and cell viability decreased. The results offer new approaches for further studies to gain deeper insights into the role of PHB in cyanobacteria to obtain bioplastics in a more sustainable and environmentally friendly way.

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 ß 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.

Identification and characterization of a potential strain for the production of polyhydroxyalkanoate from glycerol.

While poly (3-hydroxybutyrate) (PHB) holds promise as a bioplastic, its commercial utilization has been hampered by the high cost of raw materials. However, glycerol emerges as a viable feedstock for PHB production, offering a sustainable production approach and substantial cost reduction potential. Glycerol stands out as a promising feedstock for PHB production, offering a pathway toward sustainable manufacturing and considerable cost savings. The identification and characterization of strains capable of converting glycerol into PHB represent a pivotal strategy in advancing PHB production research. In this study, we isolated a strain, Ralstonia sp. RRA (RRA). The strain exhibits remarkable proficiency in synthesizing PHB from glycerol. With glycerol as the carbon source, RRA achieved a specific growth rate of 0.19 h-1, attaining a PHB content of approximately 50% within 30 h. Through third-generation genome and transcriptome sequencing, we elucidated the genome composition and identified a total of eight genes (glpR, glpD, glpS, glpT, glpP, glpQ, glpV, and glpK) involved in the glycerol metabolism pathway. Leveraging these findings, the strain RRA demonstrates significant promise in producing PHB from low-cost renewable carbon sources.

Pyruvate kinase M2 sustains cardiac mitochondrial quality surveillance in septic cardiomyopathy by regulating prohibitin 2 abundance via S91 phosphorylation.

The endogenous mitochondrial quality control (MQC) system serves to protect mitochondria against cellular stressors. Although mitochondrial dysfunction contributes to cardiac damage during many pathological conditions, the regulatory signals influencing MQC disruption during septic cardiomyopathy (SC) remain unclear. This study aimed to investigate the involvement of pyruvate kinase M2 (PKM2) and prohibitin 2 (PHB2) interaction followed by MQC impairment in the pathogenesis of SC. We utilized LPS-induced SC models in PKM2 transgenic (PKM2TG) mice, PHB2S91D-knockin mice, and PKM2-overexpressing HL-1 cardiomyocytes. After LPS-induced SC, cardiac PKM2 expression was significantly downregulated in wild-type mice, whereas PKM2 overexpression in vivo sustained heart function, suppressed myocardial inflammation, and attenuated cardiomyocyte death. PKM2 overexpression relieved sepsis-related mitochondrial damage via MQC normalization, evidenced by balanced mitochondrial fission/fusion, activated mitophagy, restored mitochondrial biogenesis, and inhibited mitochondrial unfolded protein response. Docking simulations, co-IP, and domain deletion mutant protein transfection experiments showed that PKM2 phosphorylates PHB2 at Ser91, preventing LPS-mediated PHB2 degradation. Additionally, the A domain of PKM2 and the PHB domain of PHB2 are required for PKM2-PHB2 binding and PHB2 phosphorylation. After LPS exposure, expression of a phosphorylation-defective PHB2S91A mutant negated the protective effects of PKM2 overexpression. Moreover, knockin mice expressing a phosphorylation-mimetic PHB2S91D mutant showed improved heart function, reduced inflammation, and preserved mitochondrial function following sepsis induction. Abundant PKM2 expression is a prerequisite to sustain PKM2-PHB2 interaction which is a key element for preservation of PHB2 phosphorylation and MQC, presenting novel interventive targets for the treatment of septic cardiomyopathy.