Polyhydroxyalkanoates (PHAs) are natural polyesters consisting of various chains of hydroxyalkanoates (HAs) produced by microorganisms; this polyestres has attention due environmentally friendly compounds from renewable sources as a substitute to conventional petroleum-based plastics. The objective of this study consisted in evaluating the Genotypic characterization and production of polimer of a halobacterium isolated from hypersaline ponds located at Las Coloradas (Yucatan, Mexico). Characterization of polymer produced by this strain was also performed. We concluded that, the analyzes obtained from this work demonstrated that the JCCOL25.2 strain has a 99% similarity with Halomonas gomseomensis, and is capable of using different carbon sources to synthesize PHAs. The physicochemical analyzes allowed the identification of the biopolymer produced and classifying it as polyhydroxybutyrate (PHB), because the characteristics of this biopolymer have been reported for similar polymers. PHB has various applications in the pharmaceutical, medical, food and agronomy areas. Likewise, PHB has interesting properties for use in food packaging, due to its characteristics such as biodegradability, optical activity and good barrier properties. Finally, the significance and impact of our study, there is only one study published on the biosynthesis of PHA’s by H. gomseomensis strains, although the characterization of the obtained polymer was not report.

Global pollution from fossil plastics is one of the top environmental threats of our times. The end-of-life scenarios of fossil plastic, including recycling, incineration and disposal result in mi-croplastic formation, elevated atmospheric CO2 levels, and littering of terrestrial and aquatic environments by plastic waste. Currently thought-out regulations centered around banning plastics production and use and only recycling on a regional, national and global level are impeding efforts to rapidly replace fossil plastics through the use of natural alternatives. In particular, this review demonstrates how mi-crobial polyhydroxyalkanoates (PHA), a class of intrinsically natural polymers, can easily remedy for the fossil and persistent plastic dilemma. PHA are bio-based, bio-synthesized, bio-compatible, bio-degradable, and home- and industrially compostable. Therefore, they are one of the perfect replacements for our fossil plastics pollution dilemma, providing us with the benefits of fossil plastics and meeting all requirements of a truly circular economy. PHA biopolyesters are natural and green materials in all aspects of their life cycle. The review elaborates in detail how PHA’s production, consumption, and end-of-life profile are perfectly embedded in the current topical 12 Principles of Green Chemistry, which constitute the basis for sustainable product manufacturing. It is shown that it is time for a paradigm shift in plastics manufacturing, use and disposal. Hu-mankind needs alternatives to fossil plastics, which, as recalcitrant xenobiotics, contribute to the increasing deterioration of our planet. Natural PHA biopolyesters represent that paradigm shift!

Due to the growing interest in biopolymers, biosynthesizable and biodegradable polymers currently occupy a special place. Unfortunately, the properties of native biopolymers are not satisfactory, which explain that attempts are being made to modify them. The work attempts to improve the properties of poly(3-hydroxybutyrate) (P3HB) using linear aliphatic polyurethane (PU) based on 1,4-butanediol and hexamethylene 1,6-diisocyanate. The conducted studies on the effect of the amount of PU used (5, 10, 15 and 20 wt.%) showed an improvement in the thermal properties of the prepared polymer blends. There was an increase in the degradation temperature of the ob-tained blends in relation to the native P3HB by 12-57C, and the difference between the melting point and the degradation point was above 100°C for most of the obtained blends. As part of the tested mechanical properties of the new polymer blends, we noted the desired increase in the tensile strength, in the relative elongation at break and in the impact strength with a decrease in hardness, in particular with the presence of 5 wt.% PU. Therefore, for further improvement, hybrid nanobiocomposites with 5 wt.% PU and organically modified montmorillonite (MMT – Cloisite 30B) were produced. The nanoadditive was used in typical amount of 1-3 wt.%. The nanostructure of the biocomposites produced by extrusion was examined by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), the morphology by scanning electron microscopy (SEM), and compatibility by infrared spectroscopy (FT IR). In addition, selected mechanical properties were determined and thermal properties were tested by the thermogravimetric analysis (TGA) and the standard differential scanning calorimetry (DSC). The polyester and polyurethane chains penetrated into the interlayer spaces of organically modi-fied nanoclay – Cloisite30B and the complete delamination occurred during direct mixing in the extrusion process. FT IR spectral analysis showed the compatibility of the polymer biocomposite components by the coexistence of intermolecular interactions in the form of hydrogen bonds. The morphology studies of the produced hybrid nanobiocomposites showed an interaction of the bi-opolymer matrix with PU and Cloisite30B and the formation of easily migrating polyester-polyurethane-montmorillonite adducts, which resulted in improved mechanical properties com-pared to the properties of the native P3HB and P3HB-PU compositions. The influence of the presence of a nanofiller on the properties of the prepared nanobiocomposites was tested and it was found that, as expected, the smallest amount of nanofiller provides the best results.It was found that the obtained nanobiocomposites containing the smallest amount of nano-fillers, i.e. 1 wt.% Cloisite30B exhibited the best mechanical and thermal properties. The desired decrease in hardness by 15% and a higher value of impact strength by 15%, an increase in elonga-tion at break by 60% and an increase in thermal stability of the newly produced biocomposites compared to to the native P3HB were observed. The prepared nanobiocomposites combined the best features caused by the elasticizing effect of polyurethane and the formation of P3HB-PU-MMT adducts.

Novel model of biodegradable PHA copolymer films preparation was applied to evaluate biodegradability of various PHA copolymers and discuss its biomedical applicability. In this study, we illustrate the potential biomaterial degradation rate affectability by manipulation of monomer composition via controlling biosynthetic strategies. Within the experimental investigation, we have prepared two different copolymers of 3-hydroxybutyrate and 4-hydroxybutyrate – P(3HB-co-36 mol.% 4HB) and P(3HB-co-66 mol.% 4HB), by cultivating thermophilic bacterial strain Aneurinibacillus sp. H1 and further investigated its degradability in simulated body fluids (SBFs). Both copolymers revealed faster weight reduction in synthetic gastric juice (SGJ) and artificial colonic fluid (ACF) than simple homopolymer P3HB. In addition, degradation mechanisms differed across tested polymers, according to SEM micrographs. While incubated in SGJ, samples were fragmented due to fast hydrolysis sourcing from substantially low pH, which suggest abiotic degradation as the major degradation mechanism. On the contrary, ACF incubation indicated obvious enzymatic hydrolysis. Further, no cytotoxicity of the waste fluids was observed on CaCO-2 cell line. Based on these results in combination with high production flexibility, we suggest P(3HB-co-4HB) copolymers produced by Aneurinibacillus sp. H1 as very auspicious polymers for intestinal in vivo treatments.

Polyhydroxyalkanotes (PHA) are bio-based microbial biopolyesters with stiffness, elasticity, crystallinity and degradability tunable by the monomeric composition, bio-production strategy and post-synthetic processing; they display biological alternatives for diverse technomers of petrochemical origin. This, together with the fact that their monomeric and oligomeric in vivo degradation products do not exert any toxic or elsewhere negative effect to living cells or tissue of humans or animals, makes them highly stimulating for various applications in the medical field. The article provides an overview of PHA application in the therapeutic, surgical and tissue engineering area, and reviews strategies to produce PHA at purity levels high enough to be used in vivo. Tested applications of differently composed PHA and advanced follow-up products as carrier materials for controlled in vivo release of anti-cancer drugs or antibiotics, as scaffolds for tissue engineering, as guidance conduits for nerve repair or as enhanced sutures, implants or meshes are discussed from both a biotechnological and a material-scientific perspective. Particular attention is devoted to the adaptation of traditional polymer processing techniques for production of medicine-related devices based on PHA, such as melt-spinning, melt extrusion, or solvent evaporation, and to emerging processing techniques like 3D-printing, computer-aided wet-spinning, laser perforation, or electrospinning.

The large production of non-degradable petrol-based plastics has become a major global issue due to its environmental pollution. Biopolymers produced by microorganisms such as polyhydroxyalkanoates (PHAs) are gaining potential as a sustainable alternative, but the high cost associated to their industrial production has been a limiting factor. Post-transcriptional regulation is a key step to control gene expression in changing environments and has been reported to play a major role in numerous cellular processes. However, limited reports are available concerning the regulation of PHA accumulation in bacteria, and many essential regulatory factors still need to be identified. Here, we review studies where the synthesis of PHA has been reported to be regulated at the post-transcriptional level, and we analyze the RNA-mediated networks involved. Finally, we discuss the forthcoming research on riboregulation, synthetic and metabolic engineering which could lead to improved strategies for PHAs synthesis in industrial production, thereby reducing the costs currently associated with this procedure.

Valorization of excess sludge through the recovery of high-value products, such as biopolymers, could be a crucial step to implement circular economy principles in wastewater treatment plant (WWTP). In this frame, the present study was aimed at evaluating the simultaneous production of polyhydroxyalkanoates (PHA) and extracellular polymeric substances (EPS), obtainable from the treatment of an agro-industrial wastewater. Two biological systems, one implementing aerobic granular sludge (AGS) and the other a conventional activated sludge operating as a sequencing batch reactor (SBR) were operated for 204 and 186 days, respectively. Both the systems involved a three-stage process for mixed microbial culture enrichment and biopolymers accumulation. The maximum biopolymers accumulation capacity was close to 0.60 mg gVSS^-1 in the AGS when the enrichment reactor was operated at 3 kgCODm^-3d^-1, whereas in the SBR it was slightly more than half (0.35 mg gVSS^-1). Biopolymers extracted from the AGS were mainly constituted by EPS (>70%), which percentage increased with the organic loading rate applied in the enrichment reactor up to 95%. In contrast, SBR enabled to obtain a higher PHA production (50% of the biopolymers). Results suggested that organic carbon was mainly channeled toward metabolic pathways for extracellular storing in AGS, likely as a consequence of metabolic stressors (e.g., hydraulic selection pressure, shear forces) applied for promoting aerobic granulation.

The Bacillus megaterium LVN01 species native to Colombia has demonstrated the ability to metabolize different co-products or industrial waste (such as fique juice, cane molasses, residual glycerol) and accumulate polyhydroxybutyrate (PHB), giving it potential in the bioplastics industry. In this research, the potential of liquid digestate as a carbon source for the production of PHA in fermentation processes with this bacterial strain was evaluated. Favorably, it was found that B. megaterium utilizes the nutrients from this residual substrate to multiply appropriately and efficiently synthesize poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV). Bench scale aerobic batch fermentation, under the operational conditions of this research [Volume: 3L; Temperature: 30.8°C; Agitation: 400 rpm; pH: 7.0 ± 0.2; Disolved Oxygen: 100% saturation; Antifoam 10% (v/v)], generated maximum values of DCW (0.56 g cell L-1) at 60 h, while the maximum PHB yield (360 mg PHB L-1) occurred at 16 h, which is very favorable for sustainable degradable bioplastics production. Additionally, GC-MS and NMR analyses confirmed that the PHBV copolymer synthesized by B. megaterium is made up of the monomers 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV). Furthermore, the thermal properties determined by TGA (Tonset=283.1 ºC, Tendset= 296.98 ºC. Td =290.114 °C) and DSC (Tm= ºC155.7 °C, ΔHf= 19.80 J g-1, Xcr = 18.17%), indicate that it is a thermally stable biopolymer with low percentages of crystallinity, providing flexibility that facilitates molding, adaptation, and application in various industrial sectors.

Films prepared from poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymers produced by Aneurinibacillus sp. H1 using an automatic film applicator were homogeneous and had a defined thickness, which allowed a detailed study of physicochemical properties. Their properties were compared with a poly (3-hydroxybutyrate) homopolymer film prepared by the same procedure, which proved to be significantly more crystalline by DSC and XRD. Structural differences between samples had a major impact on their properties. With increasing 4-hydroxybutyrate content, the ductility and release rate of the model hydrophilic active ingredient increased significantly. Other observed properties, such as the release of the hydrophobic active substance, the contact angle with water and ethylene glycol, or the surface morphology and roughness, were also affected by the composition. The identified properties predetermine these copolymers for wide use in areas such as biomedicine or smart biodegradable packaging for food or cosmetics. The big advantage is the possibility of fine-tuning properties simply by changing the fermentation conditions.