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Polyhydroxyalkanoates (PHAs) are promising biopolymers as an alternative to traditional synthetic polymers due to their biodegradability and biocompatibility. The PHA market is blooming in response to the growing demand for biodegradable and environmentally friendly plastics. These biopolyesters are produced and degraded by a variety of microorganisms, making them environmentally friendly, while offering benefits such as biocompatibility (when adequately processed) and biodegradability. Their versatility extends to various areas, from biomedicine to agriculture and composite materials, where they pave the way for significative innovations. In the field of regenerative medicine, some PHAs have key applications, namely in vascular grafts, oral tissue regeneration, and development of self-healing polymers. In addition, PHAs have the potential to be used in the creation of dental implant materials and dental medical devices. PHAs can also be used to encapsulate hydrophobic drugs, providing an approach for more targeted and effective treatments. To summarize, PHAs open new perspectives in the field of medicine by improving drug delivery and offering ecologically biocompatible solutions for medical devices. The aim of this review is to present the medical and dental applications of PHA, their advantages, disadvantages, and indications. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoate (PHA), specifically poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P(3HB-co-3HHx), PHBHHx) with physical properties governed by the 3-hydroxyhexanoate (3HHx) mole fraction, is a promising bioplastic. Although engineered strains used to produce P(3HB-co-3HHx) with various 3HHx mole contents and fermentation techniques have been studied, mass production with specific 3HHx fractions and monomers depends on the batch, supply of substrates, and strains, resulting in the time-consuming development of strains and complex culture conditions for P(3HB-co-3HHx). To overcome these limitations, we blended poly(3-hydroxybutyrate) [(P(3HB), produced from C. necator H16] and P(3HB-co-20 mol%3HHx) [from C. necator 2668/pCB81] to prepare films with various 3HHx contents. We evaluated the molecular weight and physical, thermal, and mechanical properties of these films and confirmed the influence of the 3HHx monomer content on the mechanical and thermal properties as well as degradability of the blended P(3HB-co-3HHx) films containing various 3HHx mole fractions, similar to that of original microbial-based P(3HB-co-3HHx). Moreover, the degradation rate analyzed via Microbulbifer sp. was >76% at all blending ratios within 2 days, whereas a weaker effect of the 3HHx mole fraction of the blended polymer on degradation was observed. P(3HB-co-3HHx) could be produced via simple blending using abundantly produced P(3HB) and P(3HB-co-20 mol%HHx), and the resulting copolymer is applicable as a biodegradable plastic. [ABSTRACT FROM AUTHOR]

A pink-pigmented, ovoid-rod-shaped, Gram-negative bacterial strain ML10T was previously isolated in a study of a meromictic lake in British Columbia, Canada. It produces bacteriochlorophyll a, which is incorporated into the reaction center and light harvesting I complexes. This alongside no anaerobic or photoautotrophic growth supports the designation of the strain as an aerobic anoxygenic phototroph. The cells produce wavy polar flagellum and accumulate clear, refractive granules, presumed to be polyhydroxyalkanoate. Sequence of the 16S rRNA gene identified close relatedness to Salinarimonas rosea (97.85%), Salinarimonas ramus (97.92%) and Saliniramus fredricksonii (94.61%). The DNA G + C content was 72.06 mol %. Differences in cellular fatty acids and some physiological tests compared to Salinarimonadaceae members, as well as average nucleotide identity and digital DNA-DNA hybridization, define the strain as a new species in Salinarimonas. Therefore, we propose that ML10T (=NCIMB 15586T = DSM 118510T) be classified as the type strain of a new species in the genus with the name Salinarimonas chemoclinalis sp. nov. [ABSTRACT FROM AUTHOR]

Equations were derived for the biodegradative erosion of the surfaces of arbitrarily-sized circular and square objects, i.e., the decrease in volume caused by the catalytic activity of enzymes secreted by microorganisms attached to the object surfaces. Surface erosion is the primary mode of biodegradation for polyhydroxyalkanoate (PHA) objects resting on the ocean floor. Although the derivations were motivated by a need to assess the time-varying biodegradation and ultimate disintegration of PHA tubes and straws in the benthic environment, generality was maintained during the mathematical development such that the resulting equations are also applicable to other circular and square objects, including cylindrical rings, discs, and solid rods, and square plates, cubes, and prisms. Moreover, the equations are applicable to abiotic degradation via physical erosion, not just to biotic degradation caused by microbes. Surface erosion is expressed in terms of the ratio of the instantaneous mass to the initial mass, which is generally nonlinear with respect to time. The value of this ratio and the relative dimensions of the object establish a surface erosion function and its evolution over the lifetime of the object. Hence, the rate of degradation is not constant in the theory, but rather is prescribed by the irregular mass loss and the original geometry of the 3D object. [ABSTRACT FROM AUTHOR]

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Terephthalic acid (TPA) is an endocrine disruptor widely used as a plasticizer and as a monomer in the manufacturing of PET bottles. However, because of various harmful effects on humans and the environment, it is now recognized as a priority pollutant whose environmental level needs to be controlled. In the present work, the TPA biodegradation efficacy of the bacterium Rhodococcus erythropolis (MTCC 3951) was studied in mineral salt media with TPA as the sole carbon and energy source. R. erythropolis was observed to degrade 5 mM and 120 mM TPA within 10 h and 84 h of incubation, respectively. The degradation efficiency was further optimized by varying the culture conditions, and the following optimum conditions were obtained: inoculum size- 5% (v/v), temperature- 30 °C, agitation speed- 200 rpm, and pH- 8.0. The bacterium was found to use an ortho-cleavage pathway for TPA degradation determined based on enzymatic and GC–MS studies. Moreover, during the degradation of TPA, the bacterium was observed to produce polyhydroxyalkanoate (PHA)—a biopolymer. Biodegradation of 120 mM TPA resulted in an accumulation of PHA. The PHA granules were visualized using fluorescence and transmission electron microscopy and were later characterized using FTIR spectroscopy. Furthermore, the robustness of the bacterium was demonstrated by its ability to degrade TPA in real industrial wastewater. Overall, R. erythropolis (MTCC 3951) hold the potential for controlling TPA pollution in the environment and vis-à-vis the production of PHA biopolymer. [ABSTRACT FROM AUTHOR]

Abstract Background Polyhydroxyalkanoates (PHAs) are optimal potential materials for industrial and medical uses, characterized by exceptional sustainability, biodegradability, and biocompatibility. These are primarily from various bacteria and archaea. Bacterial strains with effective PHA formation capabilities and minimal production cost form the foundation for PHA production. Detailed genomic analysis of these PHA-generating bacteria is vital to understand their PHA production pathways and enhance their synthesis capability. Results ZZQ-149, a halophilic, PHA-producing bacterium, was isolated from the sediment of China’s Qinghai Lake. Here, we decoded the full genome of ZZQ-149 using Single Molecule Real Time (SMRT) technology based on PacBio RS II platform, coupled with Illumina sequencing platforms. Physiological, chemotaxonomic traits, and phylogenetic analysis based on 16 S rRNA gene and single copy core genes of ninety-nine Halomonas type strains identified ZZQ-149 as the type strain of Halomonas qinghailakensis. Furthermore, a low average nucleotide identity (ANI,

Abstract Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight in rice. Polyhydroxyalkanoates (PHAs) consitute a diverse group of biopolyesters synthesized by bacteria under nutrient-limited conditions. The phaC gene is important for PHA polymerization. We investigated the effects of phaC gene mutagensis in Xoo strain PXO99A. The phaC gene knock-out mutant exhibited reduced swarming ability relative to that of the wild-type. Under conditions where glucose was the sole sugar source, extracellular polysaccharide (EPS) production by ΔphaC declined by 44.8%. ΔphaC showed weak hypersensitive response (HR) induction in the leaves of non-host Nicotiana tabacum, concomitant with downregulation of hpa1 gene expression. When inoculated in rice leaves by the leaf-clipping method, ΔphaC displayed reduced virulence in terms of lesion length compared with the wild-type strain. The complemented strain showed no significant difference from the wild-type strain, suggesting that the deletion of phaC in Xoo induces significant alterations in various physiological and biological processes. These include bacterial swarming ability, EPS production, transcription of hrp genes, and glucose metabolism. These changes are intricately linked to the energy utilization and virulence of Xoo during plant infection. These findings revealed involvement of phaC in Xoo is in the maintaining carbon metabolism by functioning in the PHA metabolic pathway.

Background: Polyhydroxyalkanoates (PHAs) are optimal potential materials for industrial and medical uses, characterized by exceptional sustainability, biodegradability, and biocompatibility. These are primarily from various bacteria and archaea. Bacterial strains with effective PHA formation capabilities and minimal production cost form the foundation for PHA production. Detailed genomic analysis of these PHA-generating bacteria is vital to understand their PHA production pathways and enhance their synthesis capability. Results: ZZQ-149, a halophilic, PHA-producing bacterium, was isolated from the sediment of China's Qinghai Lake. Here, we decoded the full genome of ZZQ-149 using Single Molecule Real Time (SMRT) technology based on PacBio RS II platform, coupled with Illumina sequencing platforms. Physiological, chemotaxonomic traits, and phylogenetic analysis based on 16 S rRNA gene and single copy core genes of ninety-nine Halomonas type strains identified ZZQ-149 as the type strain of Halomonas qinghailakensis. Furthermore, a low average nucleotide identity (ANI, < 95%) delineated the genetic differences between ZZQ-149 and other Halomonas species. The ZZQ-149 genome, with a DNA G + C content of 52%, comprises a chromosome (3, 798, 069 bps) and a plasmid (6, 107 bps). The latter encodes the toxin-antitoxin system, BrnT/BrnA. Through comprehensive genome sequencing and analysis, we identified multiple PHA-synthesizing enzymes and an unprecedented combination of eight PHA-synthesizing pathways in ZZQ-149. Conclusions: Being a halophilic, PHA-producing bacterium, ZZQ-149 exhibits potential as a high PHA producer for engineered bacteria via genome editing while ensuring low-cost PHA production through continuous, unsterilized fermentation. [ABSTRACT FROM AUTHOR]

With the rising demand for sustainable renewable resources, microorganisms capable of producing bioproducts such as bioplastics are attractive. While many bioproduction systems are well-studied in model organisms, investigating non-model organisms is essential to expand the field and utilize metabolically versatile strains. This investigation centers on Rhodopseudomonas palustris TIE-1, a purple non-sulfur bacterium capable of producing bioplastics. To increase bioplastic production, genes encoding the putative regulatory protein PhaR and the depolymerase PhaZ of the polyhydroxyalkanoate (PHA) biosynthesis pathway were deleted. Genes associated with pathways that might compete with PHA production, specifically those linked to glycogen production and nitrogen fixation, were deleted. Additionally, RuBisCO form I and II genes were integrated into TIE-1's genome by a phage integration system, developed in this study. Our results show that deletion of phaR increases PHA production when TIE-1 is grown photoheterotrophically with butyrate and ammonium chloride (NH4Cl). Mutants unable to produce glycogen or fix nitrogen show increased PHA production under photoautotrophic growth with hydrogen and NH4Cl. The most significant increase in PHA production was observed when RuBisCO form I and form I & II genes were overexpressed, five times under photoheterotrophy with butyrate, two times with hydrogen and NH4Cl, and two times under photoelectrotrophic growth with N2. In summary, inserting copies of RuBisCO genes into the TIE-1 genome is a more effective strategy than deleting competing pathways to increase PHA production in TIE-1. The successful use of the phage integration system opens numerous opportunities for synthetic biology in TIE-1. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are promising biodegradable polymers known for their biodegradability and eco-friendly properties. Recent studies indicate that PHAs can reduce the environmental impact by up to 50% compared to petroleum-based plastics. This comprehensive review evaluates the application of PHAs in sustainable food packaging, covering over 100 studies published between 2018 and 2023. The review highlights advancements in PHA production, with a focus on submerged and solid-state fermentation methods, achieving up to a 60% improvement in production efficiency through optimized culture selection. Sustainable extraction and purification methods have been identified, reducing energy consumption by 30%. Blending PHAs with other biodegradable polymers like polylactic acid, starch, and cellulose enhances material performance, with up to a 40% improvement in mechanical properties. The incorporation of antimicrobial agents and essential oils has been shown to extend the shelf life by 25% while maintaining food safety standards. This review underscores the potential of active PHA-based packaging in improving the barrier properties by 35% when combined with coatings, positioning PHA as a key material for the future of environmentally responsible and safe food packaging. [ABSTRACT FROM AUTHOR]

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight in rice. Polyhydroxyalkanoates (PHAs) consitute a diverse group of biopolyesters synthesized by bacteria under nutrient-limited conditions. The phaC gene is important for PHA polymerization. We investigated the effects of phaC gene mutagensis in Xoo strain PXO99A. The phaC gene knock-out mutant exhibited reduced swarming ability relative to that of the wild-type. Under conditions where glucose was the sole sugar source, extracellular polysaccharide (EPS) production by ΔphaC declined by 44.8%. ΔphaC showed weak hypersensitive response (HR) induction in the leaves of non-host Nicotiana tabacum, concomitant with downregulation of hpa1 gene expression. When inoculated in rice leaves by the leaf-clipping method, ΔphaC displayed reduced virulence in terms of lesion length compared with the wild-type strain. The complemented strain showed no significant difference from the wild-type strain, suggesting that the deletion of phaC in Xoo induces significant alterations in various physiological and biological processes. These include bacterial swarming ability, EPS production, transcription of hrp genes, and glucose metabolism. These changes are intricately linked to the energy utilization and virulence of Xoo during plant infection. These findings revealed involvement of phaC in Xoo is in the maintaining carbon metabolism by functioning in the PHA metabolic pathway. [ABSTRACT FROM AUTHOR]

Waste cooking oil (WCO) from various sources were evaluated as low-cost carbon feedstock to produce poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] [P(3HB-co-3HHx)] copolymer, which is a type of polyhydroxyalkanoate (PHA). Different Cupriavidus necator transformants harbouring phaCBP−M−CPF4 were employed as PHA-producing organisms in one-stage cultivation in shake flasks. Biological and chemical recovery of PHA were evaluated. C. necator Re2058/pHT1-CBP−M−CPF4 was able to achieve a cell dry weight (CDW) of 8.5 g/L, PHA content of 75.5 wt% and PHA concentration of 6.4 g/L from 1% (v/v) WCO. The weight-average molecular weight (Mw) of the synthesized PHA obtained from the same strain was 1440 kDa. The CDW, PHA content and concentration acquired using WCO are comparable to those using fresh oils as carbon substrates. The copolymer produced from distinct sources of WCO and different extraction methods did not have significant differences in molecular weights and thermal properties. Mealworms can perform biological recovery of PHA from cells fed with WCO from distinct sources. This study suggests that WCO from any source can be used as carbon source for bacteria to produce PHA. WCO can be a sustainable alternative for the more expensive fresh oils, and the synthesized PHA can be biologically recovered by mealworms. A combination approach of utilising low-cost substrate such as WCO, high-performance PHA producer including C. necator transformants and biological recovery to extract PHA is beneficial in biosynthesis of PHA copolymer, since this can make PHA production more economical and can improve the ability of PHA to compete with conventional petrochemical plastics. [ABSTRACT FROM AUTHOR]

Poly(3-hydroxybutyrate) (P(3HB)) is an attractive biodegradable plastic alternative to petroleum-based plastic. However, the cost of microbial-based bioplastic production mainly lies in the cultivation medium. In this study, we screened the isolates capable of synthesizing P(3HB) using sugarcane bagasse (SCB) waste as a carbon source from 79 Bacillus isolates that had previously shown P(3HB) production using a commercial medium. The results revealed that isolate S356, identified as Bacillus cereus using 16S rDNA and gyrB gene analysis, had the highest P(3HB) accumulation. The highest P(3HB) yield (5.16 g/L, 85.3% of dry cell weight) was achieved by cultivating B. cereus S356 in an optimal medium with 1.5% total reducing sugar with SCB hydrolysate as the carbon source and 0.25% yeast extract as the nitrogen source. Transmission electron microscopy analysis showed the accumulation of approximately 3–5 P(3HB) granules in each B. cereus S356 cell. Proton nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy analyses confirmed that the polymer extracted from B. cereus S356 was P(3HB). Notably, during cultivation for P(3HB) plastic production, B. cereus S356 also secreted bacteriocin, which had high antibacterial activity against the same species (Bacillus cereus). Overall, this work demonstrated the possibility of co-producing eco-friendly biodegradable plastic P(3HB) and bacteriocin from renewable resources using the potential of B. cereus S356. [ABSTRACT FROM AUTHOR]

Introduction: Corneal regenerative medicine is a contemporary approach involving the use of biomaterials, biological factors and stem cells to reduce dependence on native tissue supply for transplantation. This study aims to investigate cellularized polyhydroxyalkanoate (PHA) scaffold with human telomerase-immortalized cornea epithelial cells (HTCEC) in combination with Wharton Jelly-Mesenchymal stem cells (MSC) or its conditioned media (CM) for ocular surface regeneration. Materials and methods: The PHA employed in this investigation, P(3HB-co-4HB-co-5HV-co-3HHx), was biosynthesized from Cupriavidus necator. The water contact angle as a measure of scaffold wettability was determined, and in vitro PHA biodegradation by lipase enzyme was conducted. The effects of MSC on the focal adhesion proteins were determined by immunofluorescence and immune regulatory proteins were studied. Common corneal genes' expression was evaluated using qPCR. Results: There was a significant loss of PHA dry weight due to lipase biodegradation. MSC-conditioned media (CM) significantly improved HTCEC viability (121%) as compared to control (100%), p < 0.005. The effect of HTCEC/MSC co-culture on focal adhesion protein expression was significantly higher as compared to HTCEC single culture (p < 0.05). MSC co-culture with HTCEC showed increased secretion of IL-1β and TGF-β1 more than single HTCEC culture in a pro-inflammatory stimulated HTCEC model. Gene expressions for common corneal markers ITGB1, ABCG2, ABCB5, CK3, CK12, CX43, and ΔNP63 were upregulated in the presence of CM p < 0.05. Conclusion: Cellularized PHA scaffold used in combination with MSC is a novel regenerative medicine approach which has a huge potential for anterior ocular surface diseases. [ABSTRACT FROM AUTHOR]

As a way to reduce microplastics or nano-plastics in the ocean, it is of interest to develop biodegradable paper-based drinking straws to replace non-degradable plastic drinking straws. Primary questions to be addressed include how to design suitable coatings for paper drinking straws. Such coatings not only need to resist water. In addition, consumers have high expectations for the strength of a drinking straw. It is proposed here to replace non-biodegradable polypropylene, which is presently the main component of straws, with biodegradable and hydrophobic coating components via an entropy-driven approach. It is further proposed to develop colored paper-based drinking straws with cellulose nematic liquid crystal photonic pigments as a way to make the product stand out visibly, while at the same time mediating the usage of toxic chemical pigments. [ABSTRACT FROM AUTHOR]

In this study, polyethylene (PE) was used as the raw material, and polyhydroxyalkanoate (PHA), modified nano-CaCO3 and bagasse fiber(BF) were used as the composite fillers, and the nano-CaCO3/BF/PHA/PE composites were prepared by melt extrusion and injection molding. The effects of the optimal ratios of PHA, modified nano-CaCO3 and BF and their contents on the internal structure and properties of the composites were investigated by mechanical property tests, Fourier transform infrared spectroscopy (FTIR) analysis, thermogravimetric (TG) analysis, scanning electron microscopy (SEM) and other characterization methods. The results show that with 5% PHA, 5% BF, and 5% nano-CaCO3, the mechanical properties of the composites were optimal at 12.9 MPa, and the maximum thermal decomposition temperature of the nano-CaCO3/BF/PHA/PE composites reached 437 °C at this ratio, which was higher than the thermal decomposition temperature (453 °C) of the composites before modification. The study provides ideas for the green development of degradable polymer materials. [ABSTRACT FROM AUTHOR]

Production of medium chain length polyhydroxyalkanoate (mcl-PHA) was attempted using Pseudomonas gessardii NIBRBAC000509957, which was isolated from Sunchang, Jeollabuk-do, Republic of Korea (35°24′27.7"N, 127°09′13.0"E) and effectively utilized acetate and formate as carbon sources. We first evaluated the utilization of acetate as a carbon source, revealing optimal growth at 5 g/L acetate. Then, formate was supplied to the acetate minimal medium as a carbon source to enhance cell growth. After overexpressing the acetate and formate assimilation pathway enzymes, this strain grew at a significantly higher rate in the medium. As this strain naturally produces PHA, it was further engineered metabolically to enhance mcl-PHA production. The engineered strain produced 0.40 g/L of mcl-PHA with a biomass content of 30.43% in fed-batch fermentation. Overall, this strain can be further developed to convert acetate and formate into valuable products. [ABSTRACT FROM AUTHOR]

Microbial production of polyhydroxyalkanoate (PHA) is greatly restricted by high production cost arising from high‐temperature sterilization and expensive carbon sources. In this study, a low‐cost PHA production platform was established from Halomonas cupida J9. First, a marker‐less genome‐editing system was developed in H. cupida J9. Subsequently, H. cupida J9 was engineered to efficiently utilize xylose for PHA biosynthesis by introducing a new xylose metabolism module and blocking xylonate production. The engineered strain J9UΔxylD‐P8xylA has the highest PHA yield (2.81 g/L) obtained by Halomonas with xylose as the sole carbon source so far. This is the first report on the production of short‐ and medium‐chain‐length (SCL‐co‐MCL) PHA from xylose by Halomonas. Interestingly, J9UΔxylD‐P8xylA was capable of efficiently utilizing glucose and xylose as co‐carbon sources for PHA production. Furthermore, fed‐batch fermentation of J9UΔxylD‐P8xylA coupled to a glucose/xylose co‐feeding strategy reached up to 12.57 g/L PHA in a 5‐L bioreactor under open and unsterile condition. Utilization of corn straw hydrolysate as the carbon source by J9UΔxylD‐P8xylA reached 7.0 g/L cell dry weight (CDW) and 2.45 g/L PHA in an open fermentation. In summary, unsterile production in combination with inexpensive feedstock highlights the potential of the engineered strain for the low‐cost production of PHA from lignocellulose‐rich agriculture waste. [ABSTRACT FROM AUTHOR]

In this study, fully bio-based membranes were fabricated from polyhydroxyalkanoate (PHA) and cellulose filaments (CFs). The challenge in producing fiber-reinforced polymer composites lies in controlling the dispersion of fibers, which can deteriorate the mechanical and barrier properties of the materials. To address this, the natural reinforcement was modified with a commercial surfactant (Shwego-wett 6267) prior to blending it with PHA. The morphological analyses revealed a homogeneous dispersion of modified CFs within the polymer matrix. The tensile test results demonstrated that incorporating modified CFs into PHA enhanced the mechanical performance of the composites. Additionally, the water vapor barrier performance of developed membranes was evaluated under varying relative humidity conditions (35, 50, 70, and 85%). The results showed that composites reinforced with cellulose filaments exhibited a smart and responsive water vapor permeability, varying with humidity levels, thanks to the hygroscopic nature of fibers. The findings indicate that the developed bio-based composites provide an eco-friendly alternative to conventional petroleum-based membranes, potentially meeting industry standards for building envelope applications. [ABSTRACT FROM AUTHOR]

In the current study, bioelectricity and polyhydroxyalkanoate (PHA) production were integrated by a dual chamber microbial fuel cell (MFC) using Enterobacter sp. TS1L and textile wastewater (TW), and the method was evaluated. The highest open circuit voltage (OCV, 986.50 mV), current density (CD, 6.04 W/m3) and power density (PD, 0.32 W/m3) were observed when sterile TW was used as the substrate. Sterilization had no effect on electricity generation, while the OCV, CD and PD were not significantly different. The prolong MFC was operated by Enterobacter sp. TS1L using non-sterile TW for a period of 7 days. Throughout the 7-day operation, the experiment yielded a consistent CD output, ranging from 1.56 A/m3 to 2.31 A/m3. After MFC treatment, the quality of the effluent surpassed the Thailand water quality standard. A high percentage of decolorization (72.9%) was observed by Enterobacter sp. under TW-fed MFC. Thereafter, biomass was collected, then, PHA was extracted and characterized. The highest biomass (3.5 ± 0.6 g/L) and PHA (56.1 ± 1.5% cell dry mass, CDM) level were observed at 6 days of MFC operation. The isolated polymer from Enterobacter sp. TS1L was confirmed to be medium chain length-co-long chain length PHA (mcl-co-lcl PHA) containing 3-hydroxyhexadecanoate (3HD, C14) and 3-hydroxyoctadecanoate (3HOD, C18). [ABSTRACT FROM AUTHOR]

BACKGROUND: One significant component of new, rapid economic development is the creation of biodegradable polymers. One of these biopolymers is polyhydroxyalkanoate (PHA). This biodegradable, thermoplastic and water‐insoluble storage polymer can be generated from sustainable carbon sources. PHA may be effectively used for treating wastewaters by immobilizing enzymes. For eliminating micropollutants along with many phenolic compounds, laccase is considered as a potential enzyme. Hence, it has been known to be highly effective for water purification procedures. However, adequate immobilization is required for laccase to perform efficient catalysis. The immobilization procedure increases laccase stability with respect to reusability, temperature, pH and storage, making it superior to free laccase. RESULT: In the present study, laccase was partially purified from Beauveria pseudobassiana PHF4 by gel filtration chromatography and further immobilized on PHA microbeads. The crude extract displayed specific activity of 19.08 U mg−1 and PHA microbeads demonstrated immobilization efficiency of 77.44%. Characterization of PHA microbeads by scanning electron microscopy showed an increase in their size from 3–5 μm to 5–6 μm after the immobilization. Furthermore, catechol biodegradation by immobilized laccase was analyzed using UV–visible spectrophotometry (84.25% in 10 h), which was also confirmed by high‐performance liquid chromatography (83.65% in 24 h). CONCLUSION: Iimmobilizing laccase on PHA microbeads can help to address the pollution and environmental damage that catechol and similar chemicals cause also in an ecofriendly manner. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

An ideal wound dressing should create a healing environment that relieves pain, protects against infections, maintains moisture, removes debris, and speeds up wound closure and repair. However, conventional options like gauze often fall short in fulfilling these requirements, especially for chronic or nonhealing wounds. Hence there is a critical need for inventive formulations that offer efficient, cost‐effective, and eco‐friendly alternatives. This study focuses on assessing the innovative formulation based on a microbial‐derived copolymer known as poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate), P(3HB‐co‐4HB) bioactive glass and graphene particles, and exploring their biological response in vitro and in vivo—to find the best combination that promotes cell adhesion and enhances wound healing. The formulation optimized at concentration of bioactive glass (1 w/w%) and graphene (0.01 w/w%) showed accelerated degradation and enhanced blood vessel formation. Meanwhile biocompatibility was evaluated using murine osteoblasts, human dermal fibroblasts, and standard cell culture assays, demonstrating no adverse effects after 7 days of culture and well‐regulated inflammatory kinetics. Whole thickness skin defect using mice indicated the feasibility of the biocomposites for a faster wound closure and reduced inflammation. Overall, this biocomposite appears promising as an ideal wound dressing material and positively influencing wound healing rates. [ABSTRACT FROM AUTHOR]

The growing demand for sustainable food packaging and the increasing concerns regarding environmental pollution have driven interest in biodegradable materials. This paper presents an in-depth review of the production of Polyhydroxyalkanoates (PHA), a biodegradable polymer, from food waste. PHA-based bioplastics, particularly when derived from low-cost carbon sources such as volatile fatty acids (VFAs) and waste oils, offer a promising solution for reducing plastic waste and enhancing food packaging sustainability. Through optimization of microbial fermentation processes, PHA production can achieve significant efficiency improvements, with yields reaching up to 87 % PHA content under ideal conditions. This review highlights the technical advancements in using PHA for food packaging, emphasizing its biodegradability, biocompatibility, and potential to serve as a biodegradable alternative to petroleum-based plastics. However, challenges such as high production costs, mechanical limitations, and the need for scalability remain barriers to industrial adoption. The future of PHA in food packaging hinges on overcoming these challenges through further research and innovation in production techniques, material properties, and cost reduction strategies, along with necessary legislative support to promote widespread use.

Due to the rapid increase in the world's population, many developing countries are facing malnutrition problems, including famine and food insecurity. Particularly, the deficiency of protein sources becomes a serious problem for human and animal nutrition. In this context, Single Cell Proteins, could be exploited as an alternative source of unconventional proteins. The aim of the study was to investigate SCP production and composition by Cupriavidus necator under various environmental conditions, temperature and pH values. A mono-factorial approach was implemented using batch bioreactor cultures under well-controlled conditions. Results were compared in terms of bacterial growth and SCP composition (proteins, nucleic acids, amino acids and elemental formula). Complementary analyses were performed by flow cytometry to study cell morphology, membrane permeability and the presence of Poly(3-hydroxybutyrate) (PHB) production. Our data confirmed the ability of C. necator to produce high amount of proteins (69 % DW at 30 °C and pH7). The results showed that temperature and pH independently impact SCP production and composition. This impact was particularly observed at the highest temperature (40 °C) and also the lowest pH value (pH5) providing lower growth rates, cell elongation, changes in granularity and lower amounts of proteins (down to 44 % DW at pH5) and nucleic acids. These low percentages were related to the production of PHB production (up to 44 % DW at 40 °C) which is the first report of a PHB accumulation in C. necator under nutrient unlimited conditions. • Higher amount of Proteins (69 % DW) obtained at 30°C and pH7 • PHB accumulation under nutrient unlimited conditions at 40°C or pH5 • Cells morphology change at 40°C or pH5 [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) have gained interest recently due to their biodegradability and versatility. In particular, the chemical compositions of medium‐chain‐length (mcl)‐PHAs are highly diverse, comprising different monomers containing 6–14 carbon atoms. This review summarizes different feedstocks and fermentation strategies to enhance mcl‐PHA production and briefly discusses the downstream processing. This review also provides comprehensive details on analytical tools for determining the composition and properties of mcl‐PHA. Moreover, this study provides novel information by statistically analyzing the data collected from several reports on mcl‐PHA to determine the optimal fermentation parameters (specific growth rate, PHA productivity, and PHA yield from various structurally related and unrelated substrates), mcl‐PHA composition, molecular weight (MW), and thermal and mechanical properties, in addition to other relevant statistical values. The analysis revealed that the median PHA productivity observed in the fed‐batch feeding strategy was 0.4 g L−1 h−1, which is eight times higher than that obtained from batch feeding (0.05 g L−1 h−1). Furthermore, 3‐hydroxyoctanoate and ‐decanoate were the primary monomers incorporated into mcl‐PHA. The investigation also determined the median glass transition temperature (−43°C) and melting temperature (47°C), which indicated that mcl‐PHA is a flexible amorphous polymer at room temperature with a median MW of 104 kDa. However, information on the monomer composition or heterogeneity and the associated physical and mechanical data of mcl‐PHAs is inadequate. Based on their mechanical values, the mcl‐PHAs can be classified as semi‐crystalline polymers (median crystallinity 23%) with rubber‐like properties and a median elongation at break of 385%. However, due to the limited mechanical data available for mcl‐PHAs with known monomer composition, identifying suitable processing tools and applications to develop mcl‐PHAs further is challenging. [ABSTRACT FROM AUTHOR]

Ralstonia eutropha strain H16 is a chemoautotrophic bacterium that oxidizes hydrogen and accumulates poly[(R)-3-hydroxybutyrate] [P(3HB)], a prominent polyhydroxyalkanoate (PHA), within its cell. R. eutropha utilizes fructose or CO2 as its sole carbon source for this process. A PHA-negative mutant of strain H16, known as R. eutropha strain PHB−4, cannot produce PHA. Strain 1F2, derived from strain PHB−4, is a leucine analog-resistant mutant. Remarkably, the recombinant 1F2 strain exhibits the capacity to synthesize 3HB-based PHA copolymers containing 3-hydroxyvalerate (3HV) and 3-hydroxy-4-methyvalerate (3H4MV) comonomer units from fructose or CO2. This ability is conferred by the expression of a broad substrate-specific PHA synthase and tolerance to feedback inhibition of branched amino acids. However, the total amount of comonomer units incorporated into PHA was up to around 5 mol%. In this study, strain 1F2 underwent genetic engineering to augment the comonomer supply incorporated into PHA. This enhancement involved several modifications, including the additional expression of the broad substrate-specific 3-ketothiolase gene (bktB), the heterologous expression of the 2-ketoacid decarboxylase gene (kivd), and the phenylacetaldehyde dehydrogenase gene (padA). Furthermore, the genome of strain 1F2 was altered through the deletion of the 3-hydroxyacyl-CoA dehydrogenase gene (hbdH). The introduction of bktB-kivd-padA resulted in increased 3HV incorporation, reaching 13.9 mol% from fructose and 6.4 mol% from CO2. Additionally, the hbdH deletion resulted in the production of PHA copolymers containing (S)-3-hydroxy-2-methylpropionate (3H2MP). Interestingly, hbdH deletion increased the weight-average molecular weight of the PHA to over 3.0 × 106 on fructose. Thus, it demonstrates the positive effects of hbdH deletion on the copolymer composition and molecular weight of PHA. [ABSTRACT FROM AUTHOR]

[Objectives]The present study aimed to investigate the effect of nitrification intensity on enhanced biological phosphorus removal(EBPR)process performance. [Methods]Acclimation of EBPR sludge was firstly carried out in an anaerobic-aerobic sequencing batch reactor(SBR). The influent ammonia concentration was raised to 48 mg·L-1 and a comparative study was conducted on the nitrification intensity and phosphorus removal efficiency of EBPR system with or without nitrification inhibitors addition for the purpose of further analyzing the effect of nitrification intensity on the operational performance of EBPR process. In each of those operational phases, cyclic changes of phosphate, ammonia, nitrate, nitrite concentrations in the mixed liquor, glycogen and polyhydroxyalkanoate(PHA)contents in EBPR sludge were determined to analyze the effect of nitrification intensity on the metabolism of polyphosphate accumulating organisms(PAOs). [Results]When the influent ammonia concentration raised to 48 mg·L-1 and with allylthiourea eliminated, the nitrification rate of EBPR system rose to 1.45-1.80 mg·h-1·g-1 after 17 days of operation, and an unexpected phenomenon of aerobic phosphorus release occurred, leading to a substantial decrease in the phosphorus removal efficiency of the system. Metabolic abnormality also occurred in PAOs as indicated by a significant increase in the amount of glycogen degradation and synthesis and a significant decrease in the amount of PHA synthesis and degradation. However, EBPR performance was restored to the normal level within 24 h following re-supplementation of allylthiourea to the influent. [Conclusions]EBPR process performance was closely related to the nitrification intensity and aerobic phosphorus release occurred as nitrification rate rose up to a certain degree, leading to a significant decline in phosphorus removal efficiency of EBPR process. [ABSTRACT FROM AUTHOR]

This study investigates the biodegradation behavior of a blend of poly(L-lactic acid) (PLLA) and amorphous polyhydroxyalkanoate (aPHA) (50:50 wt%) under seawater conditions for 12 weeks at 30 °C. The results revealed that the inclusion of aPHA in the blend enhanced the biodegradation of PLLA. The average molecular weight analysis indicated that the blend underwent homogeneous degradation primarily through exo-chain scission. Morphological changes observed via scanning electron microscopy demonstrated that aPHA first underwent decomposition in the blend, creating channels within PLLA that enhanced water and microorganism contact and promoted PLLA hydrolysis. The release of low-molecular-weight acids from the aPHA decomposition further facilitated PLLA hydrolysis. The graph depicts fluctuations in the weight-average molecular weight of PLLA, the PLLA/aPHA blend, and aPHA throughout the biodegradation period under seawater conditions. [ABSTRACT FROM AUTHOR]

Purpose: Herein, we examined C. necator for its production of bioplastic under mixotrophic fermentation. The mixotrophic process utilized dual carbon sources of mixed CO2 and glucose for the production of PHB. Methods: C. necator was optimized through adaptive laboratory evolution under a mixed carbon sources of CO2 and glucose. The isolated mutant was then studied for its ability to co-utilize glucose and CO2 carbon sources for growth and for PHB production. Experimental design based on central composition design was implemented to optimize PHB production under mixotrophic fermentation. Parameters effecting PHB accumulation including CO2 and glucose substrate ratio, cell dosage and aeration were studied. Results: Under optimized mixotrophic batch process, 0.22 g/L of PHB and 28% PHB content was reached from mixed carbon sources. Further CO2 and glucose co-feeding strategy optimization in mixotrophic fed-batch, PHB titer was elevated to 0.41 g/L. Conclusion: Overall, this study offered a promising alternative for CO2 valorization through the mixotrophic conversion of CO2 and glucose to PHB by C. necator, which could provide basis in future Bio-CCU technology development for climate change mitigation. [ABSTRACT FROM AUTHOR]

Poly-hydroxybutyrate (PHB) is an environmentally friendly alternative for conventional fossil fuel-based plastics that is produced by various microorganisms. Large-scale PHB production is challenging due to the comparatively higher biomanufacturing costs. A PHB overproducer is the haloalkaliphilic bacterium Halomonas campaniensis, which has low nutritional requirements and can grow in cultures with high salt concentrations, rendering it resistant to contamination. Despite its virtues, the metabolic capabilities of H. campaniensis as well as the limitations hindering higher PHB production remain poorly studied. To address this limitation, we present HaloGEM, the first high-quality genome-scale metabolic network reconstruction, which encompasses 888 genes, 1528 reactions (1257 gene-associated), and 1274 metabolites. HaloGEM not only displays excellent agreement with previous growth data and experiments from this study, but it also revealed nitrogen as a limiting nutrient when growing aerobically under high salt concentrations using glucose as carbon source. Among different nitrogen source mixtures for optimal growth, HaloGEM predicted glutamate and arginine as a promising mixture producing increases of 54.2% and 153.4% in the biomass yield and PHB titer, respectively. Furthermore, the model was used to predict genetic interventions for increasing PHB yield, which were consistent with the rationale of previously reported strategies. Overall, the presented reconstruction advances our understanding of the metabolic capabilities of H. campaniensis for rationally engineering this next-generation industrial biotechnology platform. Key points: A comprehensive genome-scale metabolic reconstruction of H. campaniensis was developed. Experiments and simulations predict N limitation in minimal media under aerobiosis. In silico media design increased experimental biomass yield and PHB titer. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoate (PHA) synthesised by microbial strains has properties (biocompatible, non-toxic, and biodegradable) that make it appropriate as an environment-friendly plastic component. This research evaluated the cheap carbon substrates (molasses, olive oil, and their mixture) of industrial waste as an alternative to costly ones for the manufacturing enhancement of mcl-PHA by C. necator. The strain was cultured in both nutrient and mineral media with and without nitrogen. mcl-PHA content was found to be 24.33%, 18.66%, and 40% with molasses, olive oil, and a mixture of both substrates, respectively. The chromatographic technique, GCMS, was utilized to confirm the types of PHA monomers (3HB and HHx). The maximum PHA content produced was 2.03 g/L using a combination of substrates compared to molasses (1.41 g/L) and olive oil (1.12 g/L). Morphology exhibits pseudo-spherical granules with comparatively consistent distribution by SEM. FTIR spectroscopy was used to detect PHA presence rapidly. In conclusion, C. necator DSM 428 cultivated on a mixture of substrates is proficient in manufacturing mcl-PHA along with scl-PHA; the type of PHA monomer depends upon the selection of substrate. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoate (PHA) has unique physicochemical and mechanical properties like conventional plastics; however, its high production cost makes it unsuitable for commercial use. Therefore, the purpose of the present study is to use low-cost and bioavailable raw materials such as agro-industrial waste of asparagus husk, as substrate for obtaining PHA by Bacillus thuringiensis. The proximal characteristics and structural carbohydrates of the waste were previously determined using HPLC. The pretreatment conditions were optimized using a Plackett-Burman design and response surface of the central compounds, evaluating temperature, %NaOH, time, % solid/liquid and solvent. Likewise, the enzymatic hydrolysates of the optimal conditions of the pretreatment were used, using an enzymatic solution with cellulase activity at 45°C at 100 rpm for 72 h. To produce PHA, a mineral-based medium, supplemented with enzymatic hydrolysate from the optimal pretreatment, was utilized. This study examined the effects of varying initial inoculum concentrations (0.25, 0.5, and 0.75 g/L) and percentages of enzymatic hydrolysate supplement (%, v/v). The process was conducted at 30°C and agitated at 125 rpm for 72 h. Maximum production of PHA was obtained with 0.138 g/L from an initial inoculum of 0.75 g/L of B. thuringiensis and a 47% supplement of the enzymatic hydrolysate. The PHA biopolymer was identified by its chemical characteristics by FTIR and correlated by HPLC with a standard. This study contributes to the use of agro-industrial waste to obtain biologically-based bioplastic through a low-cost process aligned with the circular economy strategy. [ABSTRACT FROM AUTHOR]

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A pink-pigmented, ovoid-rod-shaped, Gram-negative bacterial strain ML10T was previously isolated in a study of a meromictic lake in British Columbia, Canada. It produces bacteriochlorophyll a, which is incorporated into the reaction center and light harvesting I complexes. This alongside no anaerobic or photoautotrophic growth supports the designation of the strain as an aerobic anoxygenic phototroph. The cells produce wavy polar flagellum and accumulate clear, refractive granules, presumed to be polyhydroxyalkanoate. Sequence of the 16S rRNA gene identified close relatedness to Salinarimonas rosea (97.85%), Salinarimonas ramus (97.92%) and Saliniramus fredricksonii (94.61%). The DNA G + C content was 72.06 mol %. Differences in cellular fatty acids and some physiological tests compared to Salinarimonadaceae members, as well as average nucleotide identity and digital DNA-DNA hybridization, define the strain as a new species in Salinarimonas. Therefore, we propose that ML10T (=NCIMB 15586T = DSM 118510T) be classified as the type strain of a new species in the genus with the name Salinarimonas chemoclinalis sp. nov.

Polyhydroxyalkanoates (PHAs) are high-value biodegradable polyesters with thermoplastic properties used in the manufacturing of different products such as packaging films. PHAs have gained much attention from researchers and industry because of their biobased nature and appropriate features, similar to conventional synthetic plastics. This review aims to discuss some of the recent solutions to challenges associated with PHA production. The implementation of a cost-effective process is presented by following different strategies, such as the use of inexpensive carbon sources, the selection of high-producing microorganisms, and the functionalization of the final materials to make them suitable for food packaging applications, among others. Research efforts are needed to improve the economic viability of PHA production at a large scale. Haloferax mediterranei is a promising producer of PHAs due to its ability to grow in non-sterile conditions and the possibility of using seawater to prepare the growth medium. Additionally, downstream processing for PHA extraction can be simplified by treating the H. mediterranei cells with pure water. Further research should focus on the optimization of the recycling conditions for the effluents and on the economic viability of the side streams reutilization and desalinization as an integrated part of PHA biotechnological production. [ABSTRACT FROM AUTHOR]

With the world shifting towards renewable and sustainable resources, polyhydroxyalkanoates (PHAs) have attracted significant interest as an alternative to synthetic plastics. While possessing promising properties suitable for various applications, the production of PHAs has not yet reached a global commercial scale. The main reason is the high cost of production, which represents a major limitation. Sugarcane bagasse (SCB) is an abundant lignocellulosic waste around the world. Its use to produce PHA enhances the feasibility of producing PHAs at commercial scale. However, SCB requires pretreatment and hydrolysis steps to release the sugars prior to the microbial fermentation. The cost associated with these steps poses additional challenges for large-scale production. Another challenge is the release of inhibitors during the pretreatment process which can result in a low PHA yield. The development of a low cost, co-culture strategy for the bioconversion of SCB into PHAs, can represent a pivotal step towards the large-scale production of bioplastics. This review highlights the advancements made in recent years on the microbial production of PHA using SCB as potential feedstock, with a proposed biological strategy and circular economy model. [ABSTRACT FROM AUTHOR]

Bradyrhizobium diazoefficiens can live inside soybean root nodules and in free-living conditions. In both states, when oxygen levels decrease, cells adjust their protein pools by gene transcription modulation. PhaR is a transcription factor involved in polyhydroxyalkanoate (PHA) metabolism but also plays a role in the microaerobic network of this bacterium. To deeply uncover the function of PhaR, we applied a multipronged approach, including the expression profile of a phaR mutant at the transcriptional and protein levels under microaerobic conditions, and the identification of direct targets and of proteins associated with PHA granules. Our results confirmed a pleiotropic function of PhaR, affecting several phenotypes, in addition to PHA cycle control. These include growth deficiency, regulation of carbon and nitrogen allocation, and bacterial motility. Interestingly, PhaR may also modulate the microoxic-responsive regulatory network by activating the expression of fixK2 and repressing nifA, both encoding two transcription factors relevant for microaerobic regulation. At the molecular level, two PhaR-binding motifs were predicted and direct control mediated by PhaR determined by protein-interaction assays revealed seven new direct targets for PhaR. Finally, among the proteins associated with PHA granules, we found PhaR, phasins, and other proteins, confirming a dual function of PhaR in microoxia. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are biopolymers accumulated by a diversity of bacterial strains as carbon and energy reserve when grown under unbalanced nutritional conditions. Among the wide spectrum of applications for these biopolymers, the generation of nano and microparticles has drawn huge attention. PHA nanoparticles showed a high surface‐to‐volume ratio that makes them interesting for pharmaceutical uses. Bacteria from the Halomonas genus became interesting tools for biopolymer production in the last years, due to its metabolic plasticity that allows them to grow in a wide spectrum of compounds and salt concentrations. Halomonas titanicae KHS3 was previously isolated based on their ability to grow using aromatic hydrocarbons as the sole carbon source. In this work, the novelty lies in the evaluation of PHA accumulation by H. titanicae KHS3. Accumulation was successfully observed and thoroughly characterized on various carbon sources. Irrespective of the carbon source employed for growth, our experimental conditions consistently yielded PHB as the sole material identified. The truly intriguing aspect of this study is that PHB solutions in glacial acetic acid demonstrated exceptional suitability for electrospraying processing. This groundbreaking development led to the creation of nanoparticles with unique characteristics that hold immense promise for a wide range of applications. [ABSTRACT FROM AUTHOR]

Infections of agricultural crops caused by pathogen ic fungi are among the most widespread and harmful, as they not only reduce the quantity of the harvest but also significantly deteriorate its quality. This study aims to develop unique seed-coating formulations incorporating biopolymers (polyhydroxyalkanoate and pullulan) and beneficial microorganisms for plant protection against phytopathogens. A microbial association of biocompatible endophytic bacteria has been created, including Pseudomonas flavescens D5, Bacillus aerophilus A2, Serratia proteamaculans B5, and Pseudomonas putida D7. These strains exhibited agronomically valuable properties: synthesis of the phytohormone IAA (from 45.2 to 69.2 µg mL−1), antagonistic activity against Fusarium oxysporum and Fusarium solani (growth inhibition zones from 1.8 to 3.0 cm), halotolerance (5–15% NaCl), and PHA production (2.77–4.54 g L−1). A pullulan synthesized by Aureobasidium pullulans C7 showed a low viscosity rate (from 395 Pa·s to 598 Pa·s) depending on the concentration of polysaccharide solutions. Therefore, at 8.0%, w/v concentration, viscosity virtually remained unchanged with increasing shear rate, indicating that it exhibits Newtonian flow behavior. The effectiveness of various antifungal seed coating formulations has been demonstrated to enhance the tolerance of barley plants to phytopathogens. [ABSTRACT FROM AUTHOR]

Silicone materials are widely used in fouling release coatings, but developing eco-friendly protection via biosourced coatings, such as polyhydroxyalcanoates (PHA) presents a major challenge. Anti-bioadhesion properties of medium chain length PHA and short chain length PHA films are studied and compared with a reference Polydimethylsiloxane coating. The results highlight the best capability of the soft and low-roughness PHA-mcl films to resist bacteria or diatoms adsorption as compared to neat PDMS and PHBHV coatings. These parameters are insufficient to explain all the results and other properties related to PHA crystallinity are discussed. Moreover, the addition of a low amount of PEG copolymers within the coatings, to create amphiphilic coatings, boosts their anti-adhesive properties. This work reveals the importance of the physical or chemical ambiguity of surfaces in their anti-adhesive effectiveness and highlights the potential of PHA-mcl film to resist the primary adhesion of microorganisms. [ABSTRACT FROM AUTHOR]