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Non-recyclable fiber rejects from paper mills, particularly those from recycled linerboard mills, contain high levels of structural carbohydrates but are currently landfilled, causing financial and environmental burdens. The aim of this study was to develop efficient and sustainable bioprocess to upcycle these rejects into polyhydroxybutyrate (PHB), a biodegradable alternative to degradation-resistant petroleum-based plastics. To achieve high yields of PHB per unit biomass, the specific objective of the study was to investigate various approaches to enhance the hydrolysis yields of fiber rejects to maximize sugar recovery and evaluate the fermentation performance of these sugars using Escherichia coli LSBJ. The investigated approaches included size reduction, surfactant addition, and a chemical-free hydrothermal pretreatment process. A two-step hydrothermal pretreatment, involving a hot water pretreatment (150 °C and 15% solid loading for 10 min) followed by three cycles of disk refining, was found to be highly effective and resulted in an 83% cellulose conversion during hydrolysis. The hydrolysate obtained from pretreated biomass normally requires a detoxification step to enhance fermentation efficiency. However, the hydrolysate obtained from the pretreated biomass contained minimal to no inhibitory compounds, as indicated by the efficient sugar fermentation and high PHB yields, which were comparable to those from fermenting raw biomass hydrolysate. The structural and thermal properties of the extracted PHB were analyzed using various techniques and consistent with standard PHB. [ABSTRACT FROM AUTHOR]

The capture and reduction of atmospheric dinitrogen gas to ammonium can be accomplished through the enzyme nitrogenase in a process known as biological nitrogen fixation (BNF), by a class of microbes known as diazotrophs. The diazotroph Azotobacter vinelandii is a model organism for the study of aerobic nitrogen fixation, and in recent years has been promoted as a potential producer of biofertilizers. Prior reports have demonstrated the potential to partially deregulate BNF in A. vinelandii, resulting in accumulation and extracellular release of ammonium. In many cases, deregulation requires the introduction of transgenic genes or elements to yield the desired phenotype, and the long‐term stability of these strains has been reported to be somewhat problematic. In this work, we constructed two strains of A. vinelandii where regulation can be precisely controlled without the addition of any foreign genes or genetic markers. Regulation is maintained through native promoters found in A. vinelandii that can be induced through the addition of extraneous galactose. These strains result in varied degrees of regulation of BNF, and as a result, the release of extracellular ammonium is controlled in a precise, and galactose concentration‐dependent manner. In addition, these strains yield high biomass levels, similar to the wild‐type A. vinelandii strain and are further able to produce high percentages of the bioplastic polyhydroxybutyrate. [ABSTRACT FROM AUTHOR]

Biobased and biodegradable plastics have emerged as promising alternatives to conventional plastics offering the potential to reduce environmental impacts while promoting sustainability. This study focuses on the production of multilayer blown films with enhanced functional properties suitable for food packaging applications. Films were developed through co-extrusion in a three-layer film configuration, with Polybutylene Succinate (PBS) and Polybutylene Succinate Adipate (PBSA) as the external and internal layers, respectively. The functional layer consisted of Polyhydroxybutyrate (PHB) enhanced with nanoclays Cloisite® 30B at varying weight ratios. Films were also processed by manipulating the extruder screw speed of the functional layer to investigate its impact on the functional properties. Rheology, mechanical strength, and barrier performance were characterised to establish correlations between processing conditions and functional layer blends (Cloisite® 30B/PHB) on the properties of the resultant films. Rheological test results indicated that the system with 5% Cloisite® had the best polymer/nanofiller matrix dispersion. Mechanical and permeability tests showed that by varying the process conditions (the alteration of the thickness of the functionalized layer) resulted in an improvement in mechanical and barrier properties. Furthermore, the addition of the nanofiller resulted in a stiffening of the film with a subsequent decrease in permeability to oxygen and water vapour. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHA) are a promising bio-based alternative to traditional plastics derived from petroleum. Cyanobacteria are photosynthetic organisms that produce PHA from CO2 and sunlight, which can potentially reduce production costs and environmental footprint in comparison to heterotrophic bacteria cultures because (1) they utilize inorganic carbon sources for growth and (2) they do not require intensive aeration for oxygenation. Moreover, supplementing precursors such as propionate, acetate, valerate, etc., can be used to obtain various copolymers with plastic customizable properties in comparison to the classical homopolymers, such as polyhydroxybutyrate, PHB. This critical review covers the latest advances in PHA production, including recent discoveries in the metabolism interplay between PHA and glycogen production, and new insights into cultivation strategies that enhance PHA accumulation, and purification processes. This review also addresses the challenges and suggests potential solutions for a viable industrial PHAs production process. [ABSTRACT FROM AUTHOR]

The research on bioplastics (both biobased and biodegradable) is steadily growing and discovering environmentally friendly substitutes for conventional plastic. This review highlights the significance of bioplastics, analyzing, for the first time, the state of the art concerning the use of agri-food waste as an alternative substrate for biopolymer generation using Haloferax mediterranei. H. mediterranei is a highly researched strain able to produce polyhydroxybutyrate (PHB) since it can grow and produce bioplastic in high-salinity environments without requiring sterilization. Extensive research has been conducted on the genes and pathways responsible for PHB production using H. mediterranei to find out how fermentation parameters can be regulated to enhance cell growth and increase PHB accumulation. This review focuses on the current advancements in utilizing food waste as a substitute for costly substrates to reduce feedstock expenses. Specifically, it examines the production of biomass and the recovery of PHB from agri-food waste. Furthermore, it emphasizes the characterization of PHB and the significance of hydroxyvalerate (HV) abundance in the formation of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymer. The downstream processing options are described, and the crucial factors associated with industrial scale-up are assessed, including substrates, bioreactors, process parameters, and bioplastic extraction and purification. Additionally, the economic implications of various options are discussed. [ABSTRACT FROM AUTHOR]

In this study, we investigated the influence of γ-irradiation (0, 50, and 100 kGy) doses on the chemical and mechanical properties of biodegradable poly(hydroxybutyrate-valerate)/poly(caprolactone) (PHBV/PCL) polymer blends rich in low-molar-mass PCL, which were prepared using a co-rotating twin-screw extruder. In parallel, the density functional theory (DFT) and the time-dependent DFT (TD-DFT) methods were used together with a model containing four monomer units to provide an insight into the electronic structure, chemical bonds, and spectroscopic (such as Nuclear Magnetic Resonance (NMR) and Ultraviolet-visible (UV-vis)) properties of PHBV and PCL blend phases, which are critical for predicting and designing new materials with desired properties. We found that an increase in γ-irradiation doses caused splitting instead of crosslinks in the polymer chains, which led to evident deformation and an increase in tensile strength at break of 2.0 to 5.7 MPa for the PHBV/PCL blend. Further, this led to a decrease in crystallinity and proved the occurrence of a more favorable interaction between the blend phases. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB) is known for wide applications, biocompatibility, and degradability; however, it cannot be commercialized due to conventional recovery using solvents. The present study employed mechanical cell-disruption methods, such as Pestle and mortar, sonication, and glass bead vortexing, for solvent-free extraction of PHA from Bacillus sp. Different time intervals were set for grinding (5, 10, 15 min), sonicating (1, 3 and 5 min), and vortexing (2, 5 and 8 g glass beads with 5, 10 and 15 min each) hence studying their effect on cell lysis to release PHA. Tris buffer containing phenylmethyl sulfonyl fluoride (PMSF) (20 mM Tris–HCl, pH 8.0, 1 mM PMSF) was employed as a lysis buffer to study its action over Bacillus cells. Its presence was checked with the above methods in cell lysis. Sonicating cells for 5 min in the presence of lysis buffer achieved a maximum PHA yield of 45%. Cell lysis using lysis buffer yielded 35% PHA when vortexing with 5 g glass beads for 15 min. Grinding cells for 15 min showed a maximum yield of 34% but lacked a lysis buffer. The overall results indicated that the action of lysis buffer and physical extraction methods improved PHA yield by %. Therefore, the study sought to evaluate the feasibility of applying laboratory methods for cell disruption. These methods can showcase possible opportunities in large-scale applications. The polymer yield results were compared with standard sodium hypochlorite extraction. Confirmation of obtained polymers as polyhydroxy butyrate (PHB) was made through FTIR and 1HNMR characterization. [ABSTRACT FROM AUTHOR]

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

Poly-β-hydroxybutyrate (PHB) is a potential source of biodegradable plastics that are environmentally friendly due to their complete degradation to water and carbon dioxide. This study aimed to investigate PHB production in the cyanobacterium Synechocystis sp. PCC6714 MT_a24 in an outdoor bioreactor using urban wastewater as a sole nutrient source. The culture was grown in a thin-layer raceway pond with a working volume of 100 L, reaching a biomass density of up to 3.5 g L−1 of cell dry weight (CDW). The maximum PHB content was found under nutrient-limiting conditions in the late stationary phase, reaching 23.7 ± 2.2% PHB per CDW. These data are one of the highest reported for photosynthetic production of PHB by cyanobacteria, moreover using urban wastewater in pilot-scale cultivation which multiplies the potential of sustainable cultivation approaches. Contamination by grazers (Poterioochromonas malhamensis) was managed by culturing Synechocystis in a highly alkaline environment (pH about 10.5) which did not significantly affect the culture growth. Furthermore, the strain MT_a24 showed significant wastewater nutrient remediation removing about 72% of nitrogen and 67% of phosphorus. These trials demonstrate that the photosynthetic production of PHB by Synechocystis sp. PCC6714 MT_a24 in the outdoor thin-layer bioreactor using urban wastewater and ambient carbon dioxide. It shows a promising approach for the cost-effective and sustainable production of biodegradable carbon-negative plastics. Key points: • High PHB production by cyanobacteria in outdoor raceway pond • Urban wastewater used as a sole source of nutrients for phototrophic growth • Potential for cost-effective and sustainable production of biodegradable plastics [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHA), due to their remarkable biodegradability, biocompatibility, and favorable physical and chemical properties, are tested for applications in the agricultural, industrial, and medical fields in place of conventional plastic. Sustainable microbial PHA production is a challenge because of the economic aspects accrued due to the cost-effective substrates and downstream processing. Different approaches are adopted to circumvent the high economic price of PHA production by co-production, employing recombinant strain, mixed cultures, and low-cost feedstock. The review focuses on the co-production of intracellular microbial PHA with an extracellular value-added product. The present review highlights the feasibility of other bio-based products from the feedstock to offset the cost of PHA production with emphasis on another viable option. The paper discusses the recent progress in the simultaneous production of PHA with exopolysaccharides, pigments, enzymes, bio-surfactants, biofuels which primarily fulfill the criteria of higher yield of PHA, and another high-value product that can be achieved. This approach not only maximizes resource utilization but also provides opportunities for the development of a wide range of sustainable bio-based products to improve the overall feasibility of the process. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB), a sustainable biodegradable polymer with various industrial and medical applications, produced by microorganisms is a good replacement of conventional plastics, a major environmental contaminant. The aim of this study is to isolate and evaluate the PHB producing ability of the microorganisms isolated from various soil sources. By employing different staining methods such as Sudan black B, Nile red and Nile blue A, the primary screening of PHB producers was performed. Among the 104 soil isolates, four strains (SNA1, SNA2, SNA3 and SNA4) exhibited positive results for all the staining tests. On further studies, among these the strain SNA2 produced highest level of PHB (64%) from its whole cell dry weight, while glucose (20 g/L) and urea (2 g/L) were used as the carbon and nitrogen sources respectively at pH 7, 30 °C after 48 h of incubation. The Fourier transform infrared spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance (1H NMR) results confirmed that the polymer produced was PHB. The 16S rRNA sequencing revealed results that the strain SNA2 was Klebsiella pneumonia. The production ability of the novel Klebsiella pneumonia SNA2 was further enhanced by optimizing various process parameters such as carbon and nitrogen sources, pH, temperature and incubation period. The process optimization resulted in enhanced PHB synthesis (up to 75%) with Xylose as carbon source and urea as the nitrogen source with pH 7.5 at 35 °C after 36 h. In addition, an attempt to produce a biofilm from the extracted polymer was also successful. Thus, the novel bacterial isolate Klebsiella pneumonia SNA2 was proved to be a challenging host for the synthesis of PHB and the scale up studies are under progress. Whole genome sequencing, identification of pathway genes and metabolic engineering strategies were believed to enhance the PHB synthesis further to the industrial scale. [ABSTRACT FROM AUTHOR]

Summary: Plant‐based co‐production of polyhydroxyalkanoates (PHAs) and seed oil has the potential to create a viable domestic source of feedstocks for renewable fuels and plastics. PHAs, a class of biodegradable polyesters, can replace conventional plastics in many applications while providing full degradation in all biologically active environments. Here we report the production of the PHA poly[(R)‐3‐hydroxybutyrate] (PHB) in the seed cytosol of the emerging bioenergy crop Camelina sativa engineered with a bacterial PHB biosynthetic pathway. Two approaches were used: cytosolic localization of all three enzymes of the PHB pathway in the seed, or localization of the first two enzymes of the pathway in the cytosol and anchoring of the third enzyme required for polymerization to the cytosolic face of the endoplasmic reticulum (ER). The ER‐targeted approach was found to provide more stable polymer production with PHB levels up to 10.2% of the mature seed weight achieved in seeds with good viability. These results mark a significant step forward towards engineering lines for commercial use. Plant‐based PHA production would enable a direct link between low‐cost large‐scale agricultural production of biodegradable polymers and seed oil with the global plastics and renewable fuels markets. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrates (PHBs) are produced by microorganisms. PHBs are chosen as biodegradable plastic alternatives due to their rapid degradability under natural circumstances. In this study, the isolation and identification of PHB‐producing organisms by Sudan black, fermentation, solvent extraction, and characterization of purified PHB are all discussed in detail. Serratia sp. was employed to produce PHB biopolymer from lignocellulose waste coconut coir and a response surface software tool was used to optimize it. PHB characterization, FTIR (1730 cm−1 C = O stretch), TGA (268.53°C), and DTA (276.67°C) results. Sudan Black B stain was employed for the pre‐screening of these vital bacteria that produced intracellular granules of PHB. The best optimized parameters are used during the fermentation process, including 20 g/L coconut coir hydrolysate, pH 7, 30°C temperature, 1.5 g/L peptone, and 48 h. The optimization of the response surface methodology yields a high biomass output of 9.34 g/L, PHB yield of 5.48 g/L, and dry cell weight of 58.67%. The ANOVA findings, F and R2 value of biomass (10.04 and 0.9036) and PHB (23.33 and 0.9561). The results show that employing coconut coir as a feedstock allows for the enhanced production of PHB. [ABSTRACT FROM AUTHOR]

Biobased plastics have the potential to be sustainable, but to explore their circularity further, current end-of-life options need to be broadened. Mechanical recycling is one of the most accepted methods to bring back plastics into the loop. Polyhydroxybutyrates (PHBs) are biobased and biodegradable in nature with promising properties and varied applications in the market. This study focuses on their potential for mechanical recycling by multiple extrusion cycles (E1–E5) and multi-faceted characterization of the virgin (V) and reprocessed materials from E1 to E5. The behavior is compared to polypropylene (PP) as a reference with a similar property profile, which has also been reprocessed five times. The thermal properties of both series showed a stable melting point and thermal decomposition temperature from thermal analyses (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)). However, a steady increase in the degree of crystallinity was observed which could counterbalance the decrease in molecular weight due to repeated extrusion measured by gel permeation chromatography and resulted in similar values of tensile strength across the cycles. The strain at break was impacted after the first extrusion, but no significant change was observed thereafter; the same was observed for impact strength. Even in scanning electron microscopy (SEM) images, virgin and E5 samples appeared similar, showing the stability of morphological characteristics. Fourier transform infrared spectroscopy (FTIR) results revealed that no new groups are being formed even on repeated processing. The deviation between the PHB and PP series was more predominant in the melt mass flow rate (MFR) and rheology studies. There was a drastic drop in the MFR values in PHB from virgin to E5, whereas not much difference was observed for PP throughout the cycles. This observation was corroborated by frequency sweeps conducted with the parallel plate method. The viscosity dropped from virgin to E1 and E2, but from E3 to E5 it presented similar values. This was in contrast to PP, where all the samples from virgin to E5 had the same values of viscosity. This paper highlights the possibilities of mechanical recycling of PHB and explains why future work with the addition of virgin material and other additives is an area to be explored. [ABSTRACT FROM AUTHOR]

In light of the growing concern for environmental protection and the alarming amount of waste produced due to hygiene regulations, this study suggests a biodegradable and eco-friendly solution that could make a significant contribution to the preservation of our planet. The developed solution was based on a polyhydroxybutyrate/polyhydroxyvalerate biopolymer, which has been tested regarding its physicochemical parameters and possible use in printed electrically conductive structures. Graphene nanoplatelets have been used as the conductive functional phase, due to literature reports of their potential use in biomedical applications and due to the potential of providing cytocompatibility in electrical structures by carbon nanomaterials. Prepared composites have been spray-coated onto PET film and paper substrates and then subjected to electrical, adhesion and optical measurements. In order to establish the conductivity of the developed composite, its resistance, layer thickness and surface topography were measured. Optical parameters have been specified using scanning electron microscopy (SEM) imaging and spectrophotometry. The conducted research opens a wide path for the use of the polyhydroxybutyrate/polyhydroxyvalerate biopolymer with graphene nanoplatelets in biomedical applications, ensuring good conductivity, biocompatibility and stability. [ABSTRACT FROM AUTHOR]

Background: Bioplastics are attracting considerable attention, owing to the increase in non-degradable waste. Using microorganisms to degrade bioplastics is a promising strategy for reducing non-degradable plastic waste. However, maintaining bacterial viability and activity during culture and storage remains challenging. With the use of conventional methods, cell viability and activity was lost; therefore, these conditions need to be optimized for the practical application of microorganisms in bioplastic degradation. Therefore, we aimed to optimize the feasibility of the lyophilization method for convenient storage and direct use. In addition, we incoporated protective reagents to increase the viability and activity of lyophilized microorganisms. By selecting and applying the best protective reagents for the lyophilization process and the effects of additives on the growth and PHB-degrading activity of strains were analyzed after lyophilization. For developing the lyophilization method for protecting degradation activity, it may promote practical applications of bioplastic-degrading bacteria. Results: In this study, the polyhydroxybutyrate (PHB)-degrading strain, Bacillus sp. JY14 was lyophilized with the use of various sugars as protective reagents. Among the carbon sources tested, raffinose was associated with the highest cell survival rate (12.1%). Moreover, 7% of raffionose showed the highest PHB degradation yield (92.1%). Therefore, raffinose was selected as the most effective protective reagent. Also, bacterial activity was successfully maintained, with raffinose, under different storage temperatures and period. Conclusions: This study highlights lyophilization as an efficient microorganism storage method to enhance the applicability of bioplastic-degrading bacterial strains. The approach developed herein can be further studied and used to promote the application of microorganisms in bioplastic degradation. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are bioplastics that can serve as substitutes for petroleum-based plastics with the advantages of being biodegradable, biocompatible, and biobased. The microbial production of polyhydroxyalkanoates is generally conducted in the presence of sugar mixes rich in monosaccharides. In this study, molecular and cultural approaches based on forest soils enriched with hydrocarbon complexes led to the identification and isolation of microbial strains affiliated with Paraburkholderia sp. that dominated the microbial communities that are recognized among the top polyhydroxyalkanoates producers. The genome sequencing of those isolated affiliated strains showed that compared to the reference type strain of their species, they harbored more gene copies of the enzymes involved in PHB synthesis. The microbial conversion of sugar mixes for the newly isolated strains showed a higher PHB production (g/L) and content (%) than was exhibited by the reference strain type of that genus Paraburkholderia for PHB production (P. sacchari LMG 19450T). [ABSTRACT FROM AUTHOR]

Background: Polyhydroxybutyrate (PHB) is currently the most common polymer produced by natural bacteria and alternative to conventional petrochemical-based plastics due to its similar material properties and biodegradability. Massilia sp. UMI-21, a newly found bacterium, could produce PHB from starch, maltotriose, or maltose, etc. and could serve as a candidate for seaweed-degrading bioplastic producers. However, the genes involved in PHB metabolism in Massilia sp. UMI-21 are still unclear. Results: In the present study, we assembled and annotated the genome of Massilia sp. UMI-21, identified genes related to the metabolism of PHB, and successfully constructed recombinant Escherichia coli harboring PHB-related genes (phaA2, phaB1 and phaC1) of Massilia sp. UMI-21, which showed up to 139.41% more product. Also, the vgb gene (encoding Vitreoscilla hemoglobin) was introduced into the genetically engineered E. coli and gained up to 117.42% more cell dry weight, 213.30% more PHB-like production and 44.09% more product content. Fermentation products extracted from recombinant E. coli harboring pETDuet1-phaA2phaB1-phaC1 and pETDuet1-phaA2phaB1-phaC1-vgb were identified as PHB by Fourier Transform Infrared and Proton nuclear magnetic resonance spectroscopy analysis. Furthermore, the decomposition temperature at 10% weight loss of PHB extracted from Massilia sp. UMI-21, recombinant E. coli DH5α-pETDuet1-phaA2phaB1-phaC1 and DH5α-pETDuet1-phaA2phaB1-phaC1-vgb was 276.5, 278.7 and 286.3 °C, respectively, showing good thermal stability. Conclusions: Herein, we presented the whole genome information of PHB-producing Massilia sp. UMI-21 and constructed novel recombinant strains using key genes in PHB synthesis of strain UMI-21 and the vgb gene. This genetically engineered E. coli strain can serve as an effective novel candidate in E. coli cell factory for PHB production by the rapid cell growth and high PHB production. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrates (PHBs) are macromolecules synthesized by bacteria. PHBs are the most promising type of bioplastic; they are nontoxic, biodegradable and biocompatible and have properties similar to those of conventional plastics. In the present study, an attempt was made to screen of different bacterial isolates accumulating PHB from soil samples collected from Istanbul, Turkey. A total of 86 different bacterial isolates were isolated from soil samples and a total of 32 isolates were suggested to be PHB producer when stained with Sudan Black B, a preliminary screening agent for lipophilic compounds. 13 bacterial isolates were selected as PHB producing isolates by using the Nile blue A dying technique. 16S rRNA gene sequences analysis showed that PHB producing 13 isolates belonged to Pseudomonas, Arthrobacter and Bacillus genera. The PHB from the isolates was extracted using the dispersion method of the hypochlorite and chloroform method. The highest PHB production and percentage productivity were obtained from Pseudomonas plecoglossicida M9 (0.94 PHB g/L; 78.8% PHB) and Pseudomonas baetica Y6 (0.81 PHB g/L; 74.3% PHB) respectively. [ABSTRACT FROM AUTHOR]

The increase in environmental consciousness has promoted the use of renewable resources. A tremendous spike has been observed in the use of products that decompose into environment-friendly constituents, which leads to the protection of the environment. Such environment-centric thinking has reduced the volume of solid waste generated by consumers every year, together with reuse and recycling. However, the environmentally friendly initiatives and regulations face a setback when the cost is high. Often the quality of such products is compromised in comparison with synthetically derived products for consumer usage. Plastic is a ubiquitous pollutant with potentially harmful effects on living beings. The increasing population and a steady increase in petrochemical plastics' demand hamper global plastic waste management. The use of bioplastics has helped us to overcome these issues. Poly(hydroxybutyrate) (PHB) is commonly known, first synthesized bioplastic, which has strong potential in replacing conventional plastics. This review focuses on the PHB biopolymer's significant properties over plastic, its application in different fields, i.e., medical science, agriculture, construction, packaging, energy, etc. It also covers PHB biosynthesis using different waste products as a substrate to minimize the production process cost, degradation, and different analytical methods to characterize the PHB. Along with these, we have also discussed about the other polysaccharide based biodegradable polymers. [ABSTRACT FROM AUTHOR]

The increasing use of synthetic polymers and their disposal has raised concern due to their adverse effects on the environment. Thus, other sustainable alternatives to synthetic plastics have been sought, such as polyhydroxyalkanoates (PHAs), which are promising microbial polyesters, mainly due to their compostable nature, biocompatibility, thermostability, and resilience, making this biopolymer acceptable in several applications in the global market. The large-scale production of PHAs by microorganisms is still limited by the high cost of production compared to conventional plastics. This review reports some strategies mentioned in the literature aimed at production and recovery, paving the way for the bio-based economy. For this, some aspects of PHAs are addressed, such as synthesis, production systems, process control using by-products from industries, and advances and challenges in the downstream. The bioplastics properties made them a prime candidate for food, pharmaceutical, and chemical industrial applications. With this paper, it is possible to see that biodegradable polymers are promising materials, mainly for reducing the pollution produced by polymers derived from petroleum. [ABSTRACT FROM AUTHOR]

The immense use of conventional plastic is becoming the major cause of environmental issues. To solve these problems, bioplastic is a promising alternative of conventional plastic. The polyhydroxybutyrate (PHB) is a common biodegradable bioplastic naturally synthesized in various microorganisms. The main limitation with bacterial fermentation-based PHB bioplastic is its high production cost. This study aimed to screen, optimize, and selection of cyanobacteria, the oxygenic photosynthetic prokaryotes, for PHB production. Ten cyanobacterial morphotypes isolated from Garhwal Himalaya. The highest PHB content 1.38% was noted in Leptolyngbya sp. and lowest 0.24% in Cylinderospermum sp. Similarly, in case of biomass yield, highest 6.16 (g/L) biomass observed in Leptolyngbya sp. and lowest 0.986 (g/L) biomass noted in Cylinderospermum sp. Based on the current findings, Leptolyngbya sp. might be the promising candidate for PHB production. [ABSTRACT FROM AUTHOR]

Global sustainable development has intensified the demand for switching to a renewable economy with a reduced carbon footprint. Here, we report a hybrid system, coupling a chemical process for CO2 reduction with hydrogen, and a biological process for polyhydroxybutyrate (PHB) synthesis, capable of converting CO2 into bioplastics with a theoretical carbon yield of 100%. The synthetic pathway from CO2 to PHB was modularly optimized by improving the catalytic efficiency of key enzymes, avoiding the kinetic trap of metabolic flux and optimizing the whole catalytic process, resulting in 5.96 g L−1 PHB with a productivity of 1.19 g L−1 h−1 and a molar CO2 utilization efficiency of 71.8%. These results represent a promising closed-loop production process from CO2 to biodegradable plastics. [ABSTRACT FROM AUTHOR]

Due to increased environmental pressures, significant research has focused on finding suitable biodegradable plastics to replace ubiquitous petrochemical-derived polymers. Polyhydroxyalkanoates (PHAs) are a class of polymers that can be synthesized by microorganisms and are biodegradable, making them suitable candidates. The present study looks at the degradation properties of two PHA polymers: polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-polyhydroxyvalerate (PHBV; 8 wt.% valerate), in two different soil conditions: soil fully saturated with water (100% relative humidity, RH) and soil with 40% RH. The degradation was evaluated by observing the changes in appearance, chemical signatures, mechanical properties, and molecular weight of samples. Both PHB and PHBV were degraded completely after two weeks in 100% RH soil conditions and showed significant reductions in mechanical properties after just three days. The samples in 40% RH soil, however, showed minimal changes in mechanical properties, melting temperatures/crystallinity, and molecular weight over six weeks. By observing the degradation behavior for different soil conditions, these results can pave the way for identifying situations where the current use of plastics can be replaced with biodegradable alternatives. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB) is considered a potential substitute for conventional, non-biodegradable petroleum-based plastics. However, high production cost has been a major drawback to the commercialization of PHB. The use of low-cost lignocellulosic agricultural residues such as corn stover, together with an effective pretreatment method, can reduce production costs. In this study, optimization of pretreatment methods for corn stover - namely, steam explosion and sequential steam explosion-dilute acid pretreatment - was done to maximize the concentration of reducing sugars in the hydrolysate obtained after enzymatic saccharification. Response surface methodology (RSM)-designed experiments showed that steam explosion temperature had the highest impact on reducing sugar production for both pretreatment methods. Optimum conditions for steam explosion pretreatment were 220.9 °C steam explosion temperature and 11.2 min residence time, yielding a hydrolysate with 9.67 g/L (64.50% yield) of reducing sugars after saccharification. For the sequential pretreatment, 9.14 g/L of reducing sugars (60.93% yield) was produced from the optimum conditions of 224.8 °C steam explosion temperature, 144.2 °C dilute acid temperature, 43.8 min reaction time, and 5% w/v acid concentration. Dilute acid pretreatment significantly decreased the reducing sugar yield after the steam explosion by 5.5%, probably due to the degradation of reducing sugars, making steam explosion sufficient in the pretreatment of corn stover. More importantly, PHB was produced using the hydrolysate from steam-exploded corn stover, with a maximum concentration of 1.81 g/L after 24 h of bacterial fermentation. Therefore, the steam explosion was proven effective in producing sugar-rich hydrolysates from corn stover for PHB production. [ABSTRACT FROM AUTHOR]

Nowadays, the search for new materials with a sustainable character to reduce the production of residues is under continuous research. In this sense, fully biodegradable composites based on polyhydroxybutyrate and different pretreated fibres coming from barley straw have been fabricated, and their resistance to environmental controlled conditions have been characterized. The materials were already compounded in a kinetic mixer and injection-moulded as specimens for tensile assay to be aged in a Xenotest chamber so as to simulate environmental conditioning. The samples, after accelerated aging, were characterized thus: mechanical characterization (tensile assay), water uptake (immersion and contact angle), and surface observation (optical and SEM microscopy). The incorporation of the fibres helps the composite to keep its structure for a longer time. On the other hand, the presence of the fibres increases the water uptake capacity to allow water permeation in the composite, which allows final degradation, characterised by a significant drop in properties after one month of exposure to simulated environmental conditions. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB) is a biodegradable bio-based polymer synthesized by microorganisms under unfavorable conditions from agro-industrial residues as a source of carbon. These aspects make the bio-based polymer attractive for the mass production of biodegradable plastics, and a definitive replacement for petroleum-based plastics. The aim of this work was to characterize the putative PHB-producing bacterium 1B isolated from the argan soil, to identify the polymer produced, and quantify the PHB production using argan seeds waste. DNA extraction, PCR, and Sanger sequencing were conducted for the molecular identification of strain 1B; the residual biomass and the PHB quantification were measured and compared in the presence of simple sugars and pretreated argan seeds waste. The 1B growth and PHB synthesis were optimized by selecting physical and nutritional parameters: temperature, incubation time, pH, NaCl concentration, and nitrogen sources concentrations. A preliminary characterization of the bio-based polymer extracted was conducted by UV-Visible spectrophotometry and FTIR analysis. The strain 1B was identified as belonging to the genus Sphingomonas. The PHB final yield was higher in a growth culture enriched with argan waste (3.06%) than with simple sugars. The selected conditions for the bacterial optimal growth incremented the PHB final yield to 6.13%, while the increase in the argan residue concentration from 1 to 3% in a larger culture volume led to the PHB final yield of 8.16%. UV-Visible spectrophotometry of the extracted sample reported a remarkable peak at 248 nm, as well as FTIR spectra analysis, showed peaks at 1728 and 1282 wavenumber/cm. Both preliminary characterizations demonstrated that the extracted sample is the bio-based polymer polyhydroxybutyrate. The results reported in this work reveal how the costless available argan seeds can be used for polyhydroxybutyrate production using a novel Sphingomonas species. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB) is a biodegradable bioplastic with potential applications as an alternative to petroleum-based plastics. However, efficient PHB production remains difficult. The main cost of PHB production is attributed to carbon sources; hence, finding inexpensive sources is important. Galactose is a possible substrate for polyhydroxyalkanoate production as it is abundant in marine environments. Marine bacteria that produce PHB from galactose could be an effective resource that can be used for efficient PHB production. In this study, to identify a galactose utilizing PHB producer, we examined 16 Halomonas strains. We demonstrated that Halomonas cerina (Halomonas sp. YK44) has the highest growth and PHB production using a culture media containing 2% galactose, final 4% NaCl, and 0.1% yeast extract. These culture conditions yielded 8.98 g/L PHB (78.1% PHB content (w/w)). When galactose-containing red algae (Eucheuma spinosum) hydrolysates were used as a carbon source, 5.2 g/L PHB was produced with 1.425% galactose after treatment with activated carbon. Since high salt conditions can be used to avoid sterilization, we examined whether Halomonas sp. YK44 could produce PHB in non-sterilized conditions. Culture media in these conditions yielded 72.41% PHB content. Thus, Halomonas sp. YK44 is robust against contamination, allowing for long-term culture and economical PHB production. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB) is a sustainable polymer that is a promising candidate for replacing petroleum‐based plastics in food packaging. Fillers are used to improve the mechanical properties of PHB composites, simultaneously changing the crystallinity of the polymer matrix. However, it is not well understood how fillers affect crystallisation and microstructure, and thus the resulting mechanical properties of the composite. This review summarises simulation work on polymer nucleation and crystallisation and how nucleation is influenced by different types of polymer–filler interfaces. Experimental studies of PHB composites with a wide variety of fillers are reviewed to find trends between the filler type, crystallinity and mechanical properties. It is clear that fillers act as nucleants that increase the number of spherulites while reducing spherulite size. This behaviour is apparent for almost all fillers regardless of filler chemistry or topology. However, the data obtained from the literature do not seem to produce strong conclusions about the effect of the degree of crystallinity on the tensile properties of PHB–filler composites, although there are some weak trends that indicate the importance of microstructure. In order to enable prediction and control of PHB composite properties, further systematic studies are required to elucidate the effect of specific filler types and the connection between crystallinity, microstructure and mechanical properties. © 2022 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

To date, hundreds of millions tons of plastics has been produced worldwide. Their production and disposal are associated with high pollution and carbon release into the atmosphere. A more environmentally friendly alternative is bioplastics, and the most popular is polyhydroxybutyrate (PHB) polymer. Large amounts of PHB can be obtained from activated sludge where used cooking oil or other industrial waste can be used as potential substrates. In this work, efficient bioplastic production strategies are studied, and the considered substrate is a mixture of oil and peptone. Pseudomonas fluorescens bacteria are used to accumulate PHB, and the cultivation of microorganisms is carried out in batch and continuous-flow bioreactors. Microscopic observations and laboratory essays are performed to confirm presence of PHB and other key parameters. The obtained results allow us to determine the optimal feeding strategy. [ABSTRACT FROM AUTHOR]

This work aims to characterize the haloarchaeal diversity of unexplored environmental salty samples from a hypersaline environment on the southern coast of Jeddah, Saudi Arabia, looking for new isolates able to produce polyhydroxyalkanoates (PHAs). Thus, the list of PHA producers has been extended by describing two species of Halolamina; Halolamina sediminis sp. strain NRS_35 and unclassified Halolamina sp. strain NRS_38. The growth and PHA-production were investigated in the presence of different carbon sources, (glucose, sucrose, starch, carboxymethyl cellulose (CMC), and glycerol), pH values, (5–9), temperature ranges (4–65 °C), and NaCl concentrations (100–350 g L−1). Fourier-transform infra-red analysis (FT-IR) and Liquid chromatography–mass spectrometry (LC-MS) were used for qualitative identification of the biopolymer. The highest yield of PHB was 33.4% and 27.29% by NRS_35 and NRS_38, respectively, using starch as a carbon source at 37 °C, pH 7, and 25% NaCl (w/v). The FT-IR pattern indicated sharp peaks formed around 1628.98 and 1629.28 cm−1, which confirmed the presence of the carbonyl group (C=O) on amides and related to proteins, which is typical of PHB. LC-MS/MS analysis displayed peaks at retention times of 5.2, 7.3, and 8.1. This peak range indicates the occurrence of PHB and its synthetic products: Acetoacetyl-CoA and PHB synthase (PhaC). In summary, the two newly isolated Halolamina species showed a high capacity to produce PHB using different sources of carbon. Further research using other low-cost feedstocks is needed to improve both the quality and quantity of PHB production. With these results, the use of haloarchaea as cell factories to produce PHAs is reinforced, and light is shed on the global concern about replacing plastics with biodegradable polymers. [ABSTRACT FROM AUTHOR]

Background: Polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-hydroxyvalerate (PHBV) are the most common polyhydroxyalkanoates (PHAs). They are important candidates for biodegradable plastics that accumulate in the cytoplasm in the form of intracellular granules under unbalanced growth conditions. The present study focused on the production and optimization of PHAs from Paraburkholderia sp. PFN29 for the first time under submerged fermentation. Results: Two hundred bacterial isolates were collected from soil samples in Thailand, six of which were found to accumulate PHB using the Nile red staining method. Six isolates were identified by 16S rDNA gene sequencing and were shown to be closely related to the genera Azotobacter, Sphingobium and Paraburkholderia. The best strain, Paraburkholderia sp. PFN29, showed the highest PHB concentration (5 ± 0.17 g/L). Optimization of PHB accumulation was achieved in modified medium containing 3% (w/v) glucose, and 0.1% (w/v) (NH4)2Fe(SO4) with incubation at pH 7.0 and 35°C for 96 h with shaking at 200 rpm. In preliminary PHBV synthesis, PFN29 was utilized to synthesize PHBV from glucose and organic acids (levulinic acid and propionic acid). 1H nuclear magnetic resonance (1H NMR) spectroscopy and gas chromatography-mass spectrometry (GC/MS) analyses confirmed the extracted PHAs compared to standard PHB and PHBV. Conclusions: PFN29 can be used for feasible PHB production with a PHB content of up to 97.3% of 5.14 ± 0.17 g/L CDW. The PHBV concentration can be further improved by optimizing the production parameters as cosubstrates. The present study provides useful data on PHA production by Paraburkholderia, which may be used as a candidate species for commercial PHA production. How to cite: Sriyapai T, Chuarung T, Kimbara K, et al. Production and optimization of polyhydroxyalkanoates (PHAs) from Paraburkholderia sp. PFN 29 under submerged fermentation. Electron J Biotechnol 2022;56. https://doi.org/10.1016/j.ejbt.2021.12.003

Sugarcane stillage is an abundant wastewater from ethanol production. It has drawn considerable interest as a potential feedstock for biotechnological processes aiming at the recovery of energy and value-added products. In this study we explored the use of stillage for the production of polyhydroxyalkanoates (PHA), which are microbial bioplastics with potential to replace conventional plastics in specific applications. As stillage is nutrient deficient, we investigated the impact of external nutrient supplementation on the selection of PHA-producing mixed cultures. Cultures selected under four different total-chemical-oxygen-demand-to-nitrogen ratios (COD.t/N) (15, 30, 40 and 80) were evaluated according to their PHA production performance and microbial composition. The experimental results demonstrated that the most favorable PHA production was achieved for the biomass selected under strict carbon-limiting conditions, with a COD.t/N ratio of 15. This resulted in an overall PHA volumetric productivity of 2.10 g PHA L−1 d−1, a maximum intracellular PHA content of 0.65 g PHA g VSS−1 and a PHA storage yield of 0.71 g COD PHA g COD H.Org −1. The resulting PHA was a copolymer of 3-hydroxybutyrate (73 %mol) and 3-hydroxyvalerate (27 %mol) monomers. The microbial consortium was enriched by members of the Brevundimonas genus, known PHA producers, with a relative abundance of 26.4 %. • Optimal biomass enrichment occurred under strict carbon-limiting conditions. • Nutrient supplementation increased volumetric PHA productivity by 4.5-fold. • Nutrient supplementation increased HV monomer content in the PHA. • The microbial consortium was enriched in Brevundimonas genus (26.4 % abundance). [ABSTRACT FROM AUTHOR]

• Anaerobic environment (DO < 0.2 mg/L) did not inhibit the growth of Pseudomonas sp. • PHB accumulation by Pseudomonas sp. in anaerobic environment is about 1.9 times higher than in aerobic environment. • A significant increase in the activity of key enzyme for PHB synthesis was found in anaerobic environment. Polyhydroxyalkanoates (PHAs) are biodegradable polyesters with great possibility to replace petroleum-based plastics, but the high costs of production associated with energy inputs have been an obstacle to their commercial application. The production of PHAs under anaerobic environments without aeration appears to be more attractive but has not been adequately investigated. A strain capable of accumulating poly(3-hydroxybutyrate) (PHB) under anaerobic conditions was isolated. The strain anaerobically accumulated PHB reached 38.7 % of cell dry weight (CDW), which was 1.9 times higher than under aerobic conditions. It was also found that the concentrations of key enzymes for PHB synthesis were higher under anaerobic conditions than under aerobic conditions. The highest PHB accumulation was 77.9 % obtained at oxygen-limited conditions and the highest PHB yield was 0.13 g PHB/g carbon obtained at anaerobic conditions. It suggests that the conditions should be well controlled according to the purpose of PHB production. This study offers a new alternative of PHAs formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nutrient stresses were applied to Cupriavidus necator growing on carbon dioxide. • Nitrogen starvation induced a PHB accumulation of 54% of total cell dry weight. • The carbon conversion yield into PHB reached a maximum of 85% under nitrogen stress. • Single-stage starvation was more effective than double-stages for PHB production. • Gas transfer enhancement in the fed-batch mode could improve the polymer yield. Cupriavidus necator is a facultative chemolithoautotrophic bacterium able to convert carbon dioxide into poly-3-hydroxybutyrate. This is highly promising as the conversion process allows the production of sustainable and biodegradable plastics. Poly-3-hydroxybutyrate accumulation is known to be induced by nutrient starvation, but information regarding the optimal stress conditions controlling the process is still heterogeneous and fragmentary. This study presents a comprehensive comparison of the effects of nutrient stress conditions, namely nitrogen, hydrogen, phosphorus, oxygen, and magnesium deprivation, on poly-3-hydroxybutyrate accumulation in C. necator DSM545. Nitrogen starvation exhibited the highest poly-3-hydroxybutyrate accumulation, achieving 54% of total cell dry weight after four days of nutrient stress, and a carbon conversion efficiency of 85%. The gas consumption patterns indicated flexible physiological mechanisms underlying polymer accumulation and depolymerization. These findings provide insights into strategies for efficient carbon conversion into bioplastics, and highlight the key role of C. necator for future industrial-scale applications. [ABSTRACT FROM AUTHOR]

In 2021, global petroleum-based plastic production reached over 400 million metric tons (Mt), and the accumulation of these non-biodegradable plastics in the environment is a worldwide concern. Polyhydroxybutyrate (PHB) offers many advantages over traditional petroleum-based plastics, being biobased, completely biodegradable, and non-toxic. However, its production and use are still challenging due to its low deformation capacity and narrow processing window. In this work, two linear-chain polyester oligomers were used as plasticizers to improve the processability and properties of PHB. Thermal analyses, XRD, and polarized optical microscopy were performed to evaluate the plasticizing effect on the PHB and the reflection on the mechanical behavior. Both oligomers acted as PHB plasticizers, with a reduction in Tg and Tm as a function of the plasticizer concentration, which can make it easier to handle the material in thermal processing and reduce the probability of thermal degradation. Plasticizer 2 proved to be the most promising between the two with an optimized condition of 20%, in which there was a decrease in elastic modulus of up to 72% and an increase in the maximum elongation of 467%. [ABSTRACT FROM AUTHOR]

In order to make bioplastics accessible for a wider spectrum of applications, ready-to-use plastic material formulations should be available with tailored properties. Ideally, these kinds of materials should also be "home-compostable" to simplify their organic recycling. Therefore, materials based on PLA (polylactid acid) and PHB (polyhydroxybutyrate) blends are presented which contain suitable additives, and some of them contain also thermoplastic starch as a filler, which decreases the price of the final compound. They are intended for various applications, as documented by products made out of them. The produced materials are fully biodegradable under industrial composting conditions. Surprisingly, some of the materials, even those which contain more PLA than PHB, are also fully biodegradable under home-composting conditions within a period of about six months. Experiments made under laboratory conditions were supported with data obtained from a kitchen waste pilot composter and from municipal composting plant experiments. Material properties, environmental conditions, and microbiology data were recorded during some of these experiments to document the biodegradation process and changes on the surface and inside the materials on a molecular level. [ABSTRACT FROM AUTHOR]

Recently, there has been significant interest in bio-based degradable plastics owing to their potential as a green and sustainable alternative to synthetic plastics due to their biodegradable properties. Polyhydroxybutyrate (PHB) is a biodegradable polymer that is produced by bacteria and archaea as carbon and energy reserves. Due to its rapid degradation in natural environments, it can be considered a biodegradable plastic alternative. In the present study, a dye-based procedure was used to screen PHB-producing bacteria isolated from mangrove soil samples. Among the seven isolates, Agromyces indicus (A. indicus), identified by means of 16S rRNA analysis, accumulated the highest amount of PHB. The extracted polymer was characterized by a UV–Vis spectrophotometer, Fourier-transform infrared (FTIR) spectroscopy, and for the presence of the phbB gene, which confirmed the structure of the polymer as PHB. The maximum PHB production by A. indicus was achieved after 96 h of incubation at a pH of 8.0 and 35 °C in the presence of 2% NaCl, with glucose and peptone as the carbon and nitrogen sources, respectively. The strain was found to be capable of accumulating PHB when various cheap agricultural wastes, such as rice, barley, corn, and wheat bran, were used as the carbon sources. The response surface methodology (RSM) through the central composite design (CCD) for optimizing the PHB synthesis was found to be highly efficient at augmenting the polymer yields. As a result of the optimum conditions obtained from the RSM, this strain can increase the PHB content by approximately 1.4-fold when compared with an unoptimized medium, which would substantially lower the production cost. Therefore, the isolate A. indicus strain B2 may be regarded as one of the best candidates for the industrial production of PHB from agricultural wastes, and it can remove the environmental concerns associated with synthetic plastic. [ABSTRACT FROM AUTHOR]

As a biodegradable plastic, polyhydroxybutyrate (PHB) has relatively poor mechanical properties, preventing its wider use. Various plasticizers have been studied to improve the mechanical properties of PHB; however, due to the slow degradation speed in the soil environment and lack of evaluation methods, studies on the degradation of PHB with plasticizers are rarely reported. In this study, by applying Microbulbifer sp. SOL66, which is able to degrade PHB very quickly, a benign plasticizer was evaluated with good properties and good degradability, not inhibiting microbial activities. Eight different plasticizers were applied with PHB and Microbulbifer sp. SOL66, PHB film containing 10% and 20% tributyl citrate showed significant biodegradability of PHB. It was confirmed that tributyl citrate could increase the speed of PHB degradation by Microbulbifer sp. SOL66 by 88% at 1 day, although the degree of degradation was similar after 3 days with and without tributyl citrate. By the analysis of microbial degradation, physical, chemical, and mechanical properties, tributyl citrate was shown not only to improve physical, chemical, and mechanical properties but also the speed of microbial degradation. [ABSTRACT FROM AUTHOR]

Petroleum-based plastics have become a big problem in many countries because of their non-degradability and that they become microplastics in the environment. This study focused on the optimization of production medium and conditions of polyhydroxyalkanoates (PHAs), which are biodegradable bioplastics and are accumulated in microbial cells. Among 341 isolates from 40 composted soil samples, the best isolate was the HD34 strain, which was identified using morphological, molecular, and biochemical methods. The results showed that the strain was most closely related to Ensifer adhaerens LMG20216T, with 99.6% similarity. For optimization of production medium and conditions using response surface methodology, it exhibited an optimal medium containing 3.99% (w/v) of potato dextrose broth (PDB) and 1.54% (w/v) of D-glucose with an adjusted initial pH of 9.0. The optimum production was achieved under culture conditions of a temperature of 28 °C, inoculum size of 2.5% (v/v), and a shaking speed of 130 rpm for 5 days. The results showed the highest PHA content, total cell dry weight, and PHA yield as 72.96% (w/w) of cell dry weight, 9.30 g/L, and 6.78 g/L, respectively. The extracted PHA characterization was studied using gas chromatography, 1H NMR, FTIR, and XRD. The results found that the polymer was a polyhydroxybutyrate (PHB) with a melting temperature (Tm) and degradation temperature (Td) of 173.5 °C and 260.8 °C, respectively. [ABSTRACT FROM AUTHOR]

Background: Polyhydroxybutyrate (PHB) is a biopolymer formed by some microbes in response to excess carbon sources or essential nutrient depletion. PHBs are entirely biodegradable into CO2 and H2O under aerobic and anaerobic conditions. It has several applications in various fields such as medicine, pharmacy, agriculture, and food packaging due to its biocompatibility and nontoxicity nature. Result: In the present study, PHB-producing bacterium was isolated from the Dirout channel at Assiut Governorate. This isolate was characterized phenotypically and genetically as Bacillus cereus SH-02 (OM992297). According to one-way ANOVA test, the maximum PHB content was observed after 72 h of incubation at 35 °C using glucose and peptone as carbon and nitrogen source. Response surface methodology (RSM) was used to study the interactive effects of glucose concentration, peptone concentration, and pH on PHB production. This result proved that all variables have a significant effect on PHB production either independently or in the interaction with each other. The optimized medium conditions with the constraint to maximize PHB content and concentration were 22.315 g/L glucose, and 15.625 g/L peptone at pH 7.048. The maximum PHB content and concentration were 3100.799 mg/L and 28.799% which was close to the actual value (3051 mg/l and 28.7%). The polymer was identified as PHB using FTIR, NMR, and mass spectrometry. FT-IR analysis showed a strong band at 1724 cm− 1 which attributed to the ester group's carbonyl while NMR analysis has different peaks at 169.15, 67.6, 40.77, and 19.75 ppm that were corresponding to carbonyl, methine, methylene, and methyl resonance. Mass spectroscopy exhibited molecular weight for methyl 3- hydroxybutyric acid. Conclusion: PHB–producing strain was identified as Bacillus cereus SH-02 (OM992297). Under optimum conditions from RSM analysis, the maximum PHB content and concentration of this strain can reach (3100.799 mg/L and 28.799%); respectively. FTIR, NMR, and Mass spectrometry were used to confirm the polymer as PHB. Our results demonstrated that optimization using RSM is one of the strategies used for reducing the production cost. RSM can determine the optimal factors to produce the polymer in a better way and in a larger quantity without consuming time. [ABSTRACT FROM AUTHOR]

Bioplastics are contemplated as remarkable substitutes for conventional plastics to accommodate green technological advancements. However, their industrial production has not been fully implemented owing to the cost of carbon resources. From another perspective, valorizing different paper mill wastes has become a prominent research topic. These materials may serve as an affording sustainable feedstock for bioplastic production. Adjustment of cardboard waste hydrolysate as suitable fermentation media for production of bacterial polyhydroxyalkanoates (PHAs) has been investigated. Cardboard samples were defibered and dried before enzymatic hydrolysis. The enzymatic degradation of commercial cellulase was monitored over 15 days. Interestingly, 18.2 ± 0.2 g/L glucose yield was obtained from 50 g cardboard samples using a 1.5% (v/v) enzyme concentration. The samples exhibited maximum weight loss values of 69–73%. Meanwhile, five soil samples were collected from local sites in Lodz, Poland. A total of 31 bacterial isolates were screened and cultured on Nile blue plates. Analysis of the 16S rRNA gene sequence of the most potent producer revealed 100% similarity to Bacillus mycoides. Cardboard hydrolysates whole medium, modified MSM with cardboard hydrolysate and nitrogen depleted MSM with cardboard hydrolysate were utilized for PHA production, followed by PHA productivity and cell dry weight (CDW) estimation compared to glucose as a standard carbon source. An impressive PHA accumulation of 56% CDW was attained when the waste hydrolysate was used as a carbon source. FTIR and NMR analysis of the isolated PHA indicated that functional groups of the polymer were related to PHB (polyhydroxybutyrate). Thermal analysis demonstrates that PHB and PHB-CB (PHB produced from cardboard hydrolysate) have degradation temperatures of 380 and 369 °C, respectively, which reflect the high thermal stability and heat resistance compared to the same properties for a standard polymer. This is the first demonstration of full saccharification of corrugated cardboard paper waste for high-level production of PHA. In addition, the attained PHB productivity is one of the highest levels achieved from a real lignocellulosic waste. [ABSTRACT FROM AUTHOR]

Poly(3-hydroxybutyrate) (PHB) is a thermoplastic polyester that can be synthesised by many bacteria under unfavourable growth conditions. Among all its properties, biodegradability is the most attractive since it makes PHB a potential alternative to non-biodegradable plastics. However, the current market penetration of this polymer is limited by the high production costs, which accounts for approximately 40% of the total price, and the complexity in scaling-up the biological process. In this work, an innovative approach is presented, simulating the production of PHB through a double stage aerobic fermentation in which a Methylocystis strain grows and accumulates PHB granules. The effects of the reactor geometry on PHB yields were investigated in terms of aspect ratio (A), which was varied in the range 5-16 both at constant volume and variable volume: in the first case, the working volume was kept constant at 100 L and the diameter of the reactor was varied in the range 0.2-0.3 m; in the second case, the working volume was varied between 100 and 340L, keeping constant the diameter at 0.3 m. The effect of the geometry on transition parameters was evaluated as well. Results show that a maximum transition superficial gas velocity (Ut) of 0.05 ms-1 was obtained at A=16; while the productivity of PHB ranged between 0.12 and 0.25 kgm-3d-1 . [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB) is a potential substitute for plastics derived from fossil fuels, owing to its biodegradable and biocompatible properties. Lignocellulosic biomass could be used to reduce PHB production costs; however, the co-utilization of sugars, such as glucose and xylose, without catabolite repression is a difficult problem to be solved. Here, we selected a novel Loktanella sp. SM43 from a marine environment and optimized the conditions for PHB production. Loktanella sp. SM43 showed high PHB production (66.5% content) from glucose. When glucose and xylose were used together, this strain showed high utilization of both substrates compared to other high PHB-producers such as Halomonas sp. and Cupriavidus necator , which showed glucose preference. Loktanella sp. SM43 showed high growth and PHB production with lignocellulosic hydrolysates. When pine tree hydrolysates were used, PHB production was the highest at 3.66 ± 0.01 g/L, followed by Miscanthus (3.46 ± 0.09 g/L) and barley straw hydrolysate (3.36 ± 0.36 g/L). Overall, these results reveal the potential of Loktanella sp. SM43 to produce PHB using various lignocellulosic hydrolysates as feedstock and the first systematic study for PHB production with Loktanella sp. The approach of screening novel strains is a strategy to overcome co-utilization of sugars without genetic engineering. [ABSTRACT FROM AUTHOR]

The use of 3D printing is becoming more and more popular, and new applications in extrusion and photopolymerization are being discovered every day. Due to the unidirectional action of the materials used, it is necessary to develop polyfunctional composites that provide a complex of extrusion and photopolymerization processes for 3D printing technology. The current problem of 3D printing application is the availability of ineffective composite materials with deteriorated mechanical and damping properties, which makes it difficult to use existing composite materials for application in 3D printing technologies. Therefore, the aim of this study was to create a biodegradable composite material based on polylactic acid and poly(3‐hydroxybutyrate) reinforced with cellulose fibrils and plasticized with polyoxyethylene for possible application in extrusion, using the example of Maestro 3D printer. The study looked at mechanical, dynamic and thermal indicators. Except for the mechanical ones, all of the indicators tested out to be quite good. Thus, composite PLA: PHB (3:7) + 10% CFs demonstrated the highest glass transition temperature of 57°C. A 75% weight loss occurred at 373.58°C. In future, it is necessary to investigate alternative types of characteristics, modify the material's composition, or use it in applications where they are not critical. The scientific novelty of the work is the creation of a biodegradable composite material to study the properties of the composite material by extrusion for the purpose of application in 3D printing technologies. [ABSTRACT FROM AUTHOR]

Due to their excellent properties, polyhydroxyalkanoates are gaining increasing recognition in the biodegradable polymer market. These biogenic polyesters are characterized by high biodegradability in multiple environments, overcoming the limitation of composting plants only and their versatility in production. The most consolidated techniques in the literature or the reference legislation for the physical, chemical and mechanical characterisation of the final product are reported since its usability on the market is still linked to its quality, including the biodegradability certificate. This versatility makes polyhydroxyalkanoates a promising prospect with the potential to replace fossil-based thermoplastics sustainably. This review analyses and compares the physical, chemical and mechanical properties of poly-β-hydroxybutyrate and poly-β-hydroxybutyrate-co-β-hydroxyvalerate, indicating their current limitations and strengths. In particular, the copolymer is characterised by better performance in terms of crystallinity, hardness and workability. However, the knowledge in this area is still in its infancy, and the selling prices are too high (9–18 $ kg−1). An analysis of the main extraction techniques, established and in development, is also included. Solvent extraction is currently the most widely used method due to its efficiency and final product quality. In this context, the extraction phase of the biopolymer production process remains a major challenge due to its high costs and the need to use non-halogenated toxic solvents to improve the production of good-quality bioplastics. The review also discusses all fundamental parameters for optimising the process, such as solubility and temperature. [Display omitted] • PHB and PHBV characterization approaches have been reported. • PHB and PHBV properties have been compared to fossil-based plastics. • Biopolymer extraction processes have been discussed. [ABSTRACT FROM AUTHOR]

The aim of this work was to produce the biopolymer polyhydroxybutyrate (PHB) from industrial flue gas as CO 2 source and electrolysis originating hydrogen via microbial electrosynthesis. Besides the laboratory experiments, the experiments were carried out under industrial conditions directly on-site in a cogeneration plant. We were able to demonstrate that the use of flue gas as a CO 2 source has no detectable negative effect on bacterial growth and PHB production in comparison to a pure gas mixture. In an electrochemical H-cell 333 ± 44 mg L−1 PHB were obtained, which corresponds to a PHB content of 43 ± 3 % of the cell dry weight. By using flue gas for the production of the biopolymer PHB, not only CO 2 emissions are reduced, but also possible environmental pollution from non-biodegradable plastics. To the best of our knowledge, this is the first time that the production of PHB from flue gas has been demonstrated using Cupriavidus necator. • First-ever production of polyhydroxybutyrate from flue gas with Cupriavidus necator. • Microbial growth and product formation not affected by flue gas components. • Using CO 2 as a resource while reducing greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

Cyanobacteria are a promising source for the sustainable production of biodegradable bioplastics such as poly(3-hydroxybutyrate) (PHB). The auto-phototrophic biomass formation is based on light and CO2, which is an advantage compared to heterotrophic PHB-producing systems. So far, only a handful of cyanobacterial species suitable for the high-yield synthesis of PHB have been reported. In the present study, the PHB formation, biomass, and elemental composition of Leptolyngbya sp. NIVA-CYA 255 were investigated. Therefore, a three-stage cultivation process was applied, consisting of a growth stage; an N-, P-, and NP-depleted phototrophic stage; and a subsequent mixotrophic deficiency stage, initiated by sodium acetate supplementation. The extracted cyanobacterial PHB was confirmed by FTIR- and GC-MS analyses. Furthermore, the fluorescent dyes LipidGreen2 and Nile red were used for fluorescence-based monitoring and the visualization of PHB. LipidGreen2 was well suited for PHB quantification, while the application of Nile red was limited by fluorescence emission crosstalk with phycocyanin. The highest PHB yields were detected in NP- (325 mg g−1) and N-deficiency (213 mg g−1). The glycogen pool was reduced in all cultures during mixotrophy, while lipid composition was not affected. The highest glycogen yield was formed under N-deficiency (217 mg g−1). Due to the high carbon storage capacity and PHB formation, Leptolyngbya sp. NIVA-CYA 255 is a promising candidate for PHB production. Further work will focus on upscaling to a technical scale and monitoring the formation by LipidGreen2-based fluorometry. [ABSTRACT FROM AUTHOR]