Polyhydroxyalkanoate Polymers Research Articles

Insight on relationship between crystallinity and band gap energies of polyhydroxyalkanoates polymers

This study explores the electronic properties of polyhydroxyalkanoates (PHAs), a class of biodegradable polymers. The focus lies in examining the relationship between crystallinity and band gap energies in PHAs. A notable discovery is the identification of a band gap plateau, suggesting a threshold in electronic properties with increasing polymer chain length. DFT calculations were employed to model the complexities of PHA polymers, with the conductor-like polarizable continuum model (CPCM) offering insights into solvent effects. The results demonstrate a strong negative correlation between crystallinity and band gap in both vacuum and CPCM environments. This study underscores the significance of structural order in shaping the electronic properties of PHAs, paving the way for the development of sustainable polymeric materials for various applications.

A genetic toolbox to empower Paracoccus pantotrophus DSM 2944 as a metabolically versatile SynBio chassis

BackgroundTo contribute to the discovery of new microbial strains with metabolic and physiological robustness and develop them into successful chasses, Paracoccus pantotrophus DSM 2944, a Gram-negative bacterium from the phylum Alphaproteobacteria and the family Rhodobacteraceae, was chosen. The strain possesses an innate ability to tolerate high salt concentrations. It utilizes diverse substrates, including cheap and renewable feedstocks, such as C1 and C2 compounds. Also, it can consume short-chain alkanes, predominately found in hydrocarbon-rich environments, making it a potential bioremediation agent. The demonstrated metabolic versatility, coupled with the synthesis of the biodegradable polymer polyhydroxyalkanoate, positions this microbial strain as a noteworthy candidate for advancing the principles of a circular bioeconomy.ResultsThe study aims to follow the chassis roadmap, as depicted by Calero and Nikel, and de Lorenzo, to transform wild-type P. pantotrophus DSM 2944 into a proficient SynBio (Synthetic Biology) chassis. The initial findings highlight the antibiotic resistance profile of this prospective SynBio chassis. Subsequently, the best origin of replication (ori) was identified as RK2. In contrast, the non-replicative ori R6K was selected for the development of a suicide plasmid necessary for genome integration or gene deletion. Moreover, when assessing the most effective method for gene transfer, it was observed that conjugation had superior efficiency compared to electroporation, while transformation by heat shock was ineffective. Robust host fitness was demonstrated by stable plasmid maintenance, while standardized gene expression using an array of synthetic promoters could be shown. pEMG-based scarless gene deletion was successfully adapted, allowing gene deletion and integration. The successful integration of a gene cassette for terephthalic acid degradation is showcased. The resulting strain can grow on both monomers of polyethylene terephthalate (PET), with an increased growth rate achieved through adaptive laboratory evolution.ConclusionThe chassis roadmap for the development of P. pantotrophus DSM 2944 into a proficient SynBio chassis was implemented. The presented genetic toolkit allows genome editing and therewith the possibility to exploit Paracoccus for a myriad of applications.

Polyhydroxyalkanoates for Sustainable Aquaculture: A Review of Recent Advancements, Challenges, and Future Directions.

Polyhydroxyalkanoates (PHA) are biodegradable biopolymers produced by prokaryotic microbes, which, at the same time, can be applied as single-cell proteins (SCPs), growing on renewable waste-derived substrates. These PHA polymers have gained increasing attention as a sustainable alternative to conventional plastics. One promising application of PHA and PHA-rich SCPs lies within the aquaculture food industry, where they hold potential as feed additives, biocontrol agents against diseases, and immunostimulants. Nevertheless, the cost of PHA production and application remains high, partly due to expensive substrates for cultivating PHA-accumulating SCPs, costly sterilization, energy-intensive SCPs harvesting techniques, and toxic PHA extraction and purification processes. This review summarizes the current state of PHA production and its application in aquaculture. The structure and classification of PHA, microbial sources, cultivation substrates, biosynthesis pathways, and the production challenges and solutions are discussed. Next, the potential of PHA application in aquaculture is explored, focusing on aquaculture challenges, common and innovative PHA-integrated farming practices, and PHA mechanisms in inhibiting pathogens, enhancing the immune system, and improving growth and gut health of various aquatic species. Finally, challenges and future research needs for PHA production and application in aquaculture are identified. Overall, this review paper provides a comprehensive overview of the potential of PHA in aquaculture and highlights the need for further research in this area.

Life cycle assessment of experimental Al-ion batteries for energy storage applications

In this work, the analysis of environmental performance and its coherence with circular economy priorities of different variants of Al-ion battery construction was performed. Al-ion-based batteries can be considered as one of the future alternatives for currently used Li-ion-based cells when the shortage of lithium or cobalt becomes a challenge.All tested batteries were constructed with Al anodes, polypropylene foil separator, polyvinylidene fluoride + N-Methyl-2-pyrrolidone (PVDF+NMP) binder, Al collector and laminated Al foil pouch cell. WO3, Norit and carbon from potato starch (CPS) were used as a cathode material. Saturated solutions of AlCl3 dissolved in diethylene glycol dimethyl ether (DEG) and deep eutectic solvents (DES) originating from bacterial polymer polyhydroxyalkanoate were used as electrolytes.The ReCiPe impact assessment method was used in this analysis. The indicator in this study was ReCiPe Endpoint (H) V1.07 referring to Europe. SimaPro 9.4 software with Ecoinvent 3.8 inventory database were used for all calculations. The analysis included experimental production and assembly of batteries and their end-of-life processing.Based on the performed analysis it was found that the overall weighted impact of each single construction variant of an Al-ion battery is dominated by the use of electricity, no matter which variant is considered since it is related to the electricity mix in Poland and its high dependence on fossil fuels. Overall environmental impact is the smallest for CPS DEG battery, while Norit DEG and CPS DEG variants have slightly higher impacts. The share of end-of-life processing in overall environmental impacts of all analysed variants was found low compared to the Li-ion batteries. This observation indicates the Al-ion batteries as a promising direction of alternative electrochemical devices for energy storage systems while end-of-life processing and circular solution are concerned.

Recent Challenges and Trends of Polyhydroxyalkanoate Production by Extremophilic Bacteria Using Renewable Feedstocks.

Polyhydroxyalkanoates (PHAs) are biodegradable polymers with immense potential in addressing the global plastic pollution crisis and advancing sustainable bioplastics production. Among the various microbes known for PHA production, extremophilic bacteria possess unique capabilities to thrive under extreme conditions, making them attractive candidates for PHA synthesis. Furthermore, the utilization of renewable feedstocks for PHA production aligns with the growing demand for sustainable bioplastic alternatives. A diverse range of extremophilic bacteria, especially halophiles and thermophiles, has provided cost-competitive platforms for producing customized PHA polymers. Extremophilic bacteria offer unique advantages over mesophiles due to their contamination resistance, high cell density growth, and unique culture conditions. The current status of Halomonas spp. as a chassis further allows exploration of metabolic engineering approaches to overcome the challenges associated with current industrial biotechnology. This article especially focuses on extremophilic bacteria and explores recent advances in utilizing renewable feedstocks such as lignocellulosic biomass, agro-industrial residues, and waste streams for PHA production. The integration of biorefinery concepts and circular economy principles in PHA manufacturing is also examined. This review is an attempt to provide an understanding of renewable substrates as feedstocks and emerging trends in PHA production by extremophilic bacteria. It underscores the pivotal role of extremophiles and sustainable feedstock sources in advancing the feasibility and eco-friendliness of PHAs as a promising biopolymer alternative.

Integrating the latest biological advances in the key steps of a food packaging life cycle.

This literature review provides a focus on the potential of integrating the latest scientific and technological advances in the biological field to improve the status of the key steps of a food packaging life cycle: production, usage, post-usage, and long-term fate. A case study of such multi-biological food packaging is demonstrated based on the use of PHAs (polyhydroxyalkanoates) polymer, a microbiologically produced polymer from non-food renewable resources, activated by the use of bioactive components to enhance its usage benefits by reducing food loss and waste, displaying potential for reusability, compostability as post-usage, and finally, being ultimately biodegradable in most common natural conditions to considerably reduce the negative impact that persistent plastics have on the environment. We discuss how designing safe and efficient multi "bio" food packaging implies finding a compromise between sometimes contradictory functional properties. For example, active antimicrobials help preserve food but can hamper the ultimate biodegradation rate of the polymer. This review presents such antagonisms as well as techniques (e.g., coatings, nanoencapsulation) and tools (e.g., release kinetic) that can help design optimized, safe, and efficient active food packaging.

Impact of Naproxen on Wastewater Biological Treatment: Focus on Reactor Performance and Mechanisms

Pharmaceutical contamination has emerged as a significant environmental concern; yet, the impact and underlying mechanisms of widely detected naproxen (NPX) on wastewater biological treatment remain poorly understood. To address this knowledge gap, this study investigates the influence of NPX on biological nutrient removal in wastewater treatment under mesophilic conditions, and elucidates the associated mechanisms. The results demonstrate that NPX concentrations below 0.05 mg/L have no significant effect on the removal of pollutants and nutrients in wastewater, whereas the concentrations exceeding 0.5 mg/L hinder the removal of both chemical oxygen demand (COD) and nutrients, with a more pronounced inhibitory effect observed at higher NPX doses. When the concentration of NPX was 2.0 mg/L, the removal efficiency of COD, NH4+-N and phosphate decreased to 81.2~83.6%, 82.5~84.2% and 80.2~82.6%, respectively, which was much lower than that of the blank. Furthermore, NPX leads to a decrease in activated sludge concentration and organic matter content within the sludge. Additionally, NPX promotes the secretion of extracellular polymeric substances (EPS). Periodic investigations reveal that NPX inhibits the biosynthesis of intracellular polymer polyhydroxyalkanoate (PHA), thereby reducing energy production during later stages of degradation. Enzyme activity analysis indicates that high NPX concentrations suppress the activity of key enzymes associated with biological nitrogen and phosphorus removal. These findings provide theoretical insights for the treatment of NPX-containing wastewater using activated sludge processes.

Business Roundup

BUSINESS Business Roundup ShareShare onFacebookTwitterWechatLinked InRedditEmail C&EN, 2023, 101 (13), p 17April 24, 2023Cite this:C&EN 101, 13, 17AbstractDSM has agreed to acquire Adare Biome, a French maker of postbiotics, for about $300 million. Postbiotics are inanimate microorganisms thought to deliver health benefits to humans and animals. Celanese will supply VitalDose, its ethylene vinyl acetate–based drug delivery technology, for use in Glaukos’s intraocular implant. The implant, which is not yet approved, delivers the glaucoma treatment travoprost. RWDC Industries has signed an agreement with Lummus Technology to market technology to make the biodegradable polymer polyhydroxyalkanoate. RWDC has a process to make the PHAs from plant based oils. Evonik Industries and Siemens Energy are collaborating on a green hydrogen pilot program in Herne, Germany. Siemens will provide an 8 MW electrolyzer, which will make both H 2 and oxygen for Evonik’s production of isophorone diamine. Chemours and TC Energy plan to collaborate on electrolytic hydrogen production in West Virginia. The firms plan to use proton exchange membranes from Chemours inView: PDF | Full Text HTML

Biodegradation Studies of Polyhydroxybutyrate and Polyhydroxybutyrate-co-Polyhydroxyvalerate Films in Soil.

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.

Biopolymers Produced by Lactic Acid Bacteria: Characterization and Food Application.

Plants, animals, bacteria, and food waste are subjects of intensive research, as they are biological sources for the production of biopolymers. The topic links to global challenges related to the extended life cycle of products, and circular economy objectives. A severe and well-known threat to the environment, the non-biodegradability of plastics obliges different stakeholders to find legislative and technical solutions for producing valuable polymers which are biodegradable and also exhibit better characteristics for packaging products. Microorganisms are recognized nowadays as exciting sources for the production of biopolymers with applications in the food industry, package production, and several other fields. Ubiquitous organisms, lactic acid bacteria (LAB) are well studied for the production of exopolysaccharides (EPS), but much less as producers of polylactic acid (PLA) and polyhydroxyalkanoates (PHAs). Based on their good biodegradability feature, as well as the possibility to be obtained from cheap biomass, PLA and PHAs polymers currently receive increased attention from both research and industry. The present review aims to provide an overview of LAB strains' characteristics that render them candidates for the biosynthesis of EPS, PLA, and PHAs, respectively. Further, the biopolymers' features are described in correlation with their application in different food industry fields and for food packaging. Having in view that the production costs of the polymers constitute their major drawback, alternative solutions of biosynthesis in economic terms are discussed.

Modification of Polyhydroxyalkanoates Polymer Films Surface of Various Compositions by Laser Processing.

The results of surface modification of solvent casting films made from polyhydroxyalkanoates (PHAs) of various compositions are presented: homopolymer poly-3-hydroxybutyrate P(3HB) and copolymers comprising various combinations of 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), 4-hydroxybutyrate(4HB), and 3-hydroxyhexanoate (3HHx) monomers treated with a CO2 laser in continuous and quasi-pulsed radiation modes. The effects of PHAs film surface modification, depending on the composition and ratio of monomers according to the results of the study of SEM and AFM, contact angles of wetting with water, adhesion and growth of fibroblasts have been revealed for the laser radiation regime used. Under continuous irradiation with vector lines, melted regions in the form of grooves are formed on the surface of the films, in which most of the samples have increased values of the contact angle and a decrease in roughness. The quasi-pulse mode by the raster method causes the formation of holes without pronounced melted zones, the total area of which is lower by 20% compared to the area of melted grooves. The number of viable fibroblasts NIH 3T3 on the films after the quasi-pulse mode is 1.5-2.0 times higher compared to the continuous mode, and depends to a greater extent on the laser treatment mode than on the PHAs' composition. The use of various modes of laser modification on the surface of PHAs with different compositions makes it possible to influence the morphology and properties of polymer films in a targeted manner. The results that have been obtained contribute to solving the critical issue of functional biodegradable polymeric materials.

From Agri-Food Wastes to Polyhydroxyalkanoates through a Sustainable Process

The biologically-derived polymers polyhydroxyalkanoates (PHAs) are biodegradable and can be considered a valuable alternative to conventional fossil-based plastics. However, upstream and downstream processes for PHA production are characterized by high energy and chemical consumption and are not economically competitive with petroleum-based polymers. Aiming to improve both the environmental and economical sustainability of PHAs production, in this work, corn straw was used as raw material to obtain a mixture of fermentable sugars after microwave-assisted flash hydrolysis (2 min, 0.01 g/L, 50.7% yield). A mixed microbial culture enriched from dairy industry waste was used for fermentation in a shake flask, allowing us to achieve good poly(hydroxy-butyrate-co-hydroxy-valerate) yields (41.4%, after 72 h of fermentation). A scale-up in a stirred tank bioreactor (3 L) gave higher yields (76.3%, after 96 h), allowing in both cases to achieve a concentration of 0.42 g/L in the fermentation medium. The possibility of producing PHAs from agricultural waste using a mixed microbial culture from the food industry with enabling technologies could make the production of biopolymers more competitive.

Polyhydroxyalkanoate (PHA) Biopolymer Synthesis by Marine Bacteria of the Malaysian Coral Triangle Region and Mining for PHA Synthase Genes.

Polyhydroxyalkanoate (PHA), a biodegradable and plastic-like biopolymer, has been receiving research and industrial attention due to severe plastic pollution, resource depletion, and global waste issues. This has spurred the isolation and characterisation of novel PHA-producing strains through cultivation and non-cultivation approaches, with a particular interest in genes encoding PHA synthesis pathways. Since sea sponges and sediment are marine benthic habitats known to be rich in microbial diversity, sponge tissues (Xestospongia muta and Aaptos aaptos) and sediment samples were collected in this study from Redang and Bidong islands located in the Malaysian Coral Triangle region. PHA synthase (phaC) genes were identified from sediment-associated bacterial strains using a cultivation approach and from sponge-associated bacterial metagenomes using a non-cultivation approach. In addition, phylogenetic diversity profiling was performed for the sponge-associated bacterial community using 16S ribosomal ribonucleic acid (16S rRNA) amplicon sequencing to screen for the potential presence of PHA-producer taxa. A total of three phaC genes from the bacterial metagenome of Aaptos and three phaC genes from sediment isolates (Sphingobacterium mizutaii UMTKB-6, Alcaligenes faecalis UMTKB-7, Acinetobacter calcoaceticus UMTKB-8) were identified. Produced PHA polymers were shown to be composed of 5C to nC monomers, with previously unreported PHA-producing ability of the S. mizutaii strain, as well as a 3-hydroxyvalerate-synthesising ability without precursor addition by the A. calcoaceticus strain.

Polyhydroxyalkanoate recovery from newly screened Bacillus sp. LPPI-18 using various methods of extraction from Loktak Lake sediment sample

BackgroundNowadays, the conventional plastic wastes are very challenging to environments and its production cost also creates an economic crisis due to petrochemical-based plastic. In order to solve this problem, the current studies were aimed at screening and characterizing these polyhydroxyalkanoate (PHA)-producing isolates and evaluating the suitability of some carbon source for newly screened PHA-producing isolates. Material and methodsSome carbon sources such as D-fructose, glucose, molasses, D-ribose and sucrose were evaluated for PHA production. Data were analyzed using SPSS version 20. The 16SrRNA gene sequence of these isolates was performed. These newly isolated taxa were related to Bacillus species. It was designated as Bacillus sp. LPPI-18 and affiliated Bacillus cereus ATCC 14577T (AE01687) (99.10%). Paenibacillus sp. 172 (AF273740.1) was used as an outgroup. ResultsBacillus sp. LPPI-18 is a gram-positive, rod-shaped, endospore former, and citrate test positive. This isolate showed positive for amylase, catalase, pectinase, and protease test. They produced intracellular PHA granules when this isolate was stained with Sudan Black B (SBB) and Nile blue A (NBA) preliminary and specific staining dyes, respectively. Both temperature and pH used to affect polyhydroxyalkanoates (PHA) productivity. Bacteria are able to reserve PHA in the form of granules during stress conditions. This isolate produces only when supplied with carbon sources. More PHA contents (PCs) were obtained from glucose, molasses, and D-fructose. In this regard, the maximum mean value of PC was obtained from glucose (40.55±0.7%) and the minimum was obtained from D-ribose (12.4±1.4%). Great variations (P≤0.05) of PCs were observed among glucose and sucrose, molasses and sucrose, and D-fructose and sucrose carbon sources for PHA productivity (PP) of cell dry weight (CDW) g/L. After extraction, PHA film was produced for this typical isolate using glucose as a sole carbon source. Fourier transform infrared spectrum was performed for this isolate and showed the feature of polyester at 1719.64 to 1721.16 wavelengths for these extracted samples. The peak of fingerprinting (band of carboxylic acid group) at this wavelength is a characteristic feature of polyhydroxybutyrate (PHB) and corresponds to the ester functional group (C=O). ConclusionIn this study, newly identified Bacillus sp. LPPI-18 is found to be producing biodegradable polymers that are used to replace highly pollutant conventional plastic polymers. This isolate is also used to employ certain cost-effective carbon sources for the production of PHA polymers. Graphical Abstract▪

Scale-Up Studies for Polyhydroxyalkanoate and Halocin Production by <i>Halomonas</i> Sp. as Potential Biomedical Materials

Polyhydroxyalkanoates (PHA) are the biomaterials isolated naturally from bacterial strains. These are present in granules and accumulated intracellularly for storage and energy uptake in stressed conditions. This work was based on the extraction of polyhydroxyalkanoates from haloarchaeal strains isolated from samples of a salt mine and Halocin activity screening of these isolates. For the screening of polyhydroxyalkanoates, Nile Blue and Sudan Black Staining were performed. After confirmation and theoretical determination, polyhydroxyalkanoates extraction was done by sodium hypochlorite digestion and solvent extraction by chloroform method in combination. Polyhydroxyalkanoates production was calculated along with the determination of biomass. Halocin activity of these strains was also screened at different intervals. Isolated strains were identified by 16S RNA gene sequencing. Polyhydroxyalkanoates polymer was produced in form of biofilms and brittle crystals. Halocin activity was exhibited by four strains, among which confirmed halocin activity was shown by strain K7. The remarkable results showed that polyhydroxyalkanoates can replace synthetic plastics which are not environment friendly as they cause environmental pollution – a major threat to Earth rising gradually. Therefore, by switching to the use of biodegradable bioplastics from the use of synthetic plastics, it would be beneficial to the ecosphere.

A unique class I polyhydroxyalkanoate synthase (PhaC) from Brevundimonas sp. KH11J01 exists as a functional trimer: A comparative study with PhaC from Cupriavidus necator H16

Polyhydroxyalkanoates (PHAs) are natural biodegradable polyesters that are produced by numerous prokaryotic microorganisms primarily as a carbon- and energy reserve. The PhaC enzyme catalyzes the last step in the PHA biosynthesis pathway and synthesizes PHA polymers from hydroxyalkanoic acids. A type I PhaC from a PHA-producing marine bacterium Brevundimonas sp. KH11J01 (BrPhaC) was identified, produced recombinantly and characterized. Its properties were compared with its homolog from C. necator H16 (RePhaC). Unlike other PhaCs, it was found that BrPhaC is a lag-phase free enzyme organized as a trimer, even without the presence of a substrate. The enzymatic reaction is initiated instantly irrespective of temperature, in contrast to RePhaC in which the duration of the lag-phase was highly affected by temperature. At 10 °C BrPhaC was 40% active whereas RePhaC was barely active. The significance of using marine microorganisms, harboring cold-active PHA biosynthesis enzymes, for energy efficient PHA production, is also discussed briefly. The unique trimeric organization of BrPhaC challenges our understanding of the PhaC reaction mechanisms, which is mainly based on the crystal structures of the inactive forms of the enzyme.

Biosynthesis of diverse α,ω-diol-derived polyhydroxyalkanoates by engineered Halomonas bluephagenesis

Polyhydroxyalkanoates (PHA) are a family of biodegradable and biocompatible plastics with potential to replace petroleum based plastics. Diversity of PHA monomer structures provides flexibility in material properties to suit more applications. In this study, 5-hydroxyvalerate (5HV) synthesis pathway was established based on intrinsic alcohol/aldehyde dehydrogenases. The PHA polymerase cloned from Cupriavidus necator functions to polymerize 5HV into its copolymers in ratios ranging from 8% to 32%. Elastic copolymer P(85% 3HB-co-15% 5HV) was generated with an elongation at break and a Young's modulus of 1283% and 73.1 MPa, respectively. The recombinant H. bluephagenesis was able to convert various diols including 1, 3-propanediol, 1, 4-butanediol and 1, 5-pentanediol into PHA, leading to 13 PHA polymers including transparent P(53% 3HB-co-20% 4HB-co-27% 5HV) and sticky P(3HB-co-3HP-co-4HB-co-5HV). The engineered H. bluephagenesis was successfully grown in a 7-L bioreactor to produce the highly elastic P(85% 3HB-co-15% 5HV) and the sticky P(3HB-co-3HP-co-4HB-co-5HV), demonstrating their potential for industrial scale-up.

A Review on Biological Synthesis of the Biodegradable Polymers Polyhydroxyalkanoates and the Development of Multiple Applications

Polyhydroxyalkanoates, or PHAs, belong to a class of biopolyesters where the biodegradable PHA polymer is accumulated by microorganisms as intracellular granules known as carbonosomes. Microorganisms can accumulate PHA using a wide variety of substrates under specific inorganic nutrient limiting conditions, with many of the carbon-containing substrates coming from waste or low-value sources. PHAs are universally thermoplastic, with PHB and PHB copolymers having similar characteristics to conventional fossil-based polymers such as polypropylene. PHA properties are dependent on the composition of its monomers, meaning PHAs can have a diverse range of properties and, thus, functionalities within this biopolyester family. This diversity in functionality results in a wide array of applications in sectors such as food-packaging and biomedical industries. In order for PHAs to compete with the conventional plastic industry in terms of applications and economics, the scale of PHA production needs to grow from its current low base. Similar to all new polymers, PHAs need continuous technological developments in their production and material science developments to grow their market opportunities. The setup of end-of-life management (biodegradability, recyclability) system infrastructure is also critical to ensure that PHA and other biobased biodegradable polymers can be marketed with maximum benefits to society. The biobased nature and the biodegradability of PHAs mean they can be a key polymer in the materials sector of the future. The worldwide scale of plastic waste pollution demands a reformation of the current polymer industry, or humankind will face the consequences of having plastic in every step of the food chain and beyond. This review will discuss the aforementioned points in more detail, hoping to provide information that sheds light on how PHAs can be polymers of the future.

Antitumor bioactivity and gut microbiota modulation of polyhydroxybutyrate (PHB) in a rat animal model for colorectal cancer

Polyhydroxybutyrate (PHB) is a non-toxic polyhydroxyalkanoate polymer produced by several microorganisms, widely used as a biological substitute for plastics derived from fossil hydrocarbons. In this work, PHB polymer has been tested in an animal model for colorectal cancer. In the animal model, PHB has been able to reduce the number of polyps by 48,1%, and the tumoral extension area by 58,1%. Also, PHB induces a selective increase in beneficial gut bacterial taxons in this animal model, and a selective reduction in pro-inflammatory taxons, demonstrating its value as a nutraceutical compound. This antitumor effect is caused by gut production of 3-hydroxybutyrate and butyrate. In this animal model, 3-hydroxybutyrate is also observed in plasma and in brain tissue, after PHB consumption, making PHB supplementation interesting as a bioactive compound in other extraintestinal conditions, as 3-hydroxybutyrate has been reported to enhance brain and cognitive function, cardiac performance, appetite suppression and diabetes. Therefore, PHB could be postulated as an interesting non-polysaccharide antitumor prebiotic, paving the way towards its future use in functional foods.

Polyhydroxyalkanoates, the bioplastics of microbial origin: Properties, biochemical synthesis, and their applications

The rising plastic pollution deteriorates the environment significantly as these petroleum-based plastics are not biodegradable, and their production requires natural fuels (energy source) and other resources. Polyhydroxyalkanoates (PHAs) are bioplastic and a sustainable and eco-friendly alternative to synthetic plastics. PHAs can be entirely synthesized using various microorganisms such as bacteria, algae, and fungi. These value-added biopolymers show promising properties such as enhanced biodegradability, biocompatibility, and other chemo-mechanical properties. Further, it has been established that the properties of PHA polymers depend on the substrates and chemical composition (monomer unit) of these polymers. PHAs hold great potential as an alternative to petroleum-based polymers, and further research for economic production and utilization of these biopolymers is required. The review describes the synthesis mechanism and different properties of microbially synthesized PHAs for various applications. The classification of PHAs and the multiple techniques necessary for their detection and evaluation have been discussed. In addition, the synthesis mechanism involving the genetic regulation of these biopolymers in various microbial groups has been described. This review provides information on various commercially available PHAs and their application in multiple sectors. The industrial production of these microbially synthesized polymers and the different extraction methods have been reviewed in detail. Furthermore, the review provides an insight into the potential applications of this biopolymer in environmental, industrial, and biomedical applications.