Search

Mathematical modelling of microbial polyhydroxyalkanoates (PHAs) production is essential to develop optimal bioprocess design. Though the use of mathematical models in PHA production has increased over the years, the selection of kinetics and model identification strategies from experimental data remains largely heuristic. In this study, PHA production from Cupriavidus necator utilizing sucrose and urea was modelled using a parametric discretization approach. Product formation kinetics and relevant parameters were established from urea-free experimental sets, followed by the selection of growth models from a batch containing both sucrose and urea. Logistic growth and Luedeking-Piret model for PHA production was selected based on regression coefficient (R 2 : 0.941), adjusted R 2 (0.930) and AICc values (-42.764). Model fitness was further assessed through cross-validation, confidence interval and sensitivity analysis of the parameters. Model-based optimal batch startup policy, incorporating multi-objective desirability, suggests an accumulation of 2.030 g l -1 of PHA at the end of 120 h. The modelling framework applied in this study can be used not only to avoid over-parameterization and identifiability issues but can also be adopted to design optimal batch startup policies., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The rate and extent of microbial polyhydroxyalkanoates (PHAs) production rely on the availability of substrates, growth of microbial biomass, and intracellular accumulation of polymer under nitrogen-limited conditions. The dynamics of PHAs production captured through various structured or unstructured models can be extended to design an optimal feeding strategy for process intensification. Large variability in process assumptions, choices of kinetics, and model complexity is expected depending on substrate(s), microbial metabolism, and discretization of the process under consideration. This communication attempts to review the estimation of stoichiometric yield coefficients, metabolic modelling, and choices of unstructured kinetics in microbial PHA production. Implementational irregularities in parameter estimation and quality check in modelling exercises have also been reviewed. It is observed that the scope of the majority of the "modelling" studies is confined to the estimation of stoichiometric parameters with limited utility. In dynamic models, microbial growth is often described using either Monod or logistic variants, while PHAs production adopts a Luedeking-Piret expression with or without substrate inhibition. Though model selection, regression with experimental data, parameter estimation, and model validation are integral parts of the exercise, very few provide sufficient coverage on all those aspects. Application of the model to control or optimize the bioprocess has rarely been attempted., (© 2022 Wiley Periodicals LLC.)

Background: Microbial polyhydroxyalkanoates (PHAs) produced using renewable resources could be the best alternative for conventional plastics. Despite their incredible potential, commercial production of PHAs remains very low. Nevertheless, sincere attempts have been made by researchers to improve the yield and economic viability of PHA production by utilizing low-cost agricultural or industrial wastes. In this context, the use of efficient microbial culture or consortia, adoption of experimental design to trace ideal growth conditions, nutritional requirements, and intervention of metabolic engineering tools have gained significant attention., Purpose and Scope: This review has been structured to highlight the important microbial sources for PHA production, use of conventional and non-conventional substrates, product optimization using experimental design, metabolic engineering strategies, and global players in the commercialization of PHA in the past two decades. The challenges about PHA recovery and analysis have also been discussed which possess indirect hurdle while expanding the horizon of PHA-based bioplastics., Summary: Selection of appropriate microorganism and substrate plays a vital role in improving the productivity and characteristics of PHAs. Experimental design-based bioprocess, use of metabolic engineering tools, and optimal product recovery techniques are invaluable in this dimension., Conclusion: Optimization strategies, which are being explored in isolation, need to be logically integrated for the successful commercialization of microbial PHAs., (© 2021 Wiley-VCH GmbH.)

Biopolymers have gained popularity as an alternative product to traditional plastics due to environmental concerns. Polyhydroxyalkanoates (PHAs), one of the most well‐known forms of biopolymers, are among the many that have been discovered so far. PHA has a wide range of applications, is biodegradable and compatible with living things, but its expensive extraction and production make it difficult to compete with traditional plastics. Solvents are the most popular extraction technique but have serious economic and environmental downsides. The "green method of extraction" has become a cutting‐edge remedy for addressing the shortcomings of downstream processing. However, developing the extraction technique for affordable and environmentally friendly biopolymer production is a difficult study topic. To make it easier to choose green recovery techniques for future study, this review combines the benefits and drawbacks of the numerous PHA recovery methods that are already in use. Also, advanced green downstream methods are scrutinized that undoubtedly makes PHA replace conventional plastics and reach a market globally promoting sustainability. [ABSTRACT FROM AUTHOR]

The study aimed at the production and characterization of biopolymer polyhydroxyalkanoate (PHA) by Bacillus endophyticus. The usage of refined (sucrose 2–4%) and inexpensive unrefined (sugar cane molasses 2–4%) carbon source was evaluated by varying the media components via shake flask method and batch cultivation in bioreactor. The optimal PHA production of 10.7 g/L of PHA from 15.37 g/L of cell density was obtained using 4% sugarcane molasses (SCM) at 250 rpm using optimized medium obtained through statistical experimental design. Batch cultivation with increased agitation rate and addition of feeding nutrients provided by SCM significantly lead to enhanced PHA production by the test organism by increasing the overall cell density. According to the statistical model, the increase in the sugar concentration (> 4%) by SCM had a negative effect on PHA production. Characterization by FTIR and 1H NMR was performed to confirm the biopolymer that has been produced by Bacillus spp. [ABSTRACT FROM AUTHOR]

Global concern about plastic pollution is forcing new policies and modifications of human consumption as well as promoting new research lines aiming at the replacement of non-degradable plastics with other polymers more environmentally friendly. Addressing food waste and promoting circular economy strategies, among other approaches, are crucial in reducing environmental impacts and fostering sustainability in several sectors like the agri-food industry. The European Union’s Circular Economy Action Plan is a significant initiative in this direction. Biotechnological processes, especially the valorisation of agri-food waste to produce highly marketed biomolecules like poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) using microorganisms as cellular factories, offer promising avenues for achieving these goals. PHBV is a biodegradable polymer firstly characterised as an isolated biopolymer from bacterial biomass. This biopolymer shows interesting physicochemical properties making possible immense potential in various applications due to its biocompatibility and sustainability, thus revealing it as a good candidate to replace plastics produced by chemical synthesis from petroleum (which are highly recalcitrant and consequently pollutants). This review critically analyses the PHBV synthesis and end-of-life scenarios from their synthesis using chemical and biological pathways, through the forms of biotechnological operation and production, to the forms described until the moment of recycling. [ABSTRACT FROM AUTHOR]

Hydroxalkanoate polymers, or polyhydroxyalkanoates (PHAs) are a diverse group of prokaryotic carbon and energy storage reserves. Since, PHAs have many of the same material characteristics as traditional plastics, they have been the subject of much interest as biodegradable alternatives to traditional fossil fuel based plastic polymers. Lately, much attention has been focused on establishing methods for the cost-effective manufacturing of PHAs. The isolation, qualitative and quantitative analysis and chemical characterisation of polyhydroxyalkanoates (PHAs) play a crucial role in the establishment of any kind of procedure. Various methodologies are required to initially identify potent microorganisms capable of synthesising polyhydroxyalkanoates (PHA), subsequently to ascertain unique building units of PHA polymer and last, to comprehend the structural and conformational chemistry of PHA at the intramolecular scale. This work aims to consolidate the existing methodologies for the identification, quantitative measurement and characterization of polyhydroxyalkanoates (PHAs), while also examining their respective merits and drawbacks. [ABSTRACT FROM AUTHOR]

Energy can be extracted from waste by chemical and biological means. There are many pathways involved in the conversion of complex carbon sources to industrially valuable products. Exploring valorization with the concept of green chemistry, focusing on transforming waste with a more environmentally compassionate product has become the new ideology. Especially efficient utilization of industrial discard as renewable feedstocks in the production of eco-friendly products are upcoming technology. The production of one such eco-friendly material, bioplastics polyhydroxyalkanoates (PHA) is discussed in this review. PHAs are naturally occurring polymers amongst various organisms and are produced intracellularly by bacterial fermentation. PHAs belong to a polyester family and, hence potentially replace hydrocarbon-based conventional polymers. Bacteria for PHA production can be grown on various renewable waste feedstocks. This process not only eliminates the waste it adds value to it. This review provides insight into the production of PHA from the feedstocks. With the possibility of synthesis of other value-added products. This can be waste-to-energy technology (WTE). [ABSTRACT FROM AUTHOR]

Wide applications of conventional plastics across the world have made its production inevitable. To avoid the ecocide occurring due to conventional plastics, studies on the production and extraction of renowned biopolymers like polyhydroxyalkanoates (PHAs) are explored. PHA is a family of polyesters naturally produced by bacterial fermentation with the potential to replace conventional hydrocarbon-based polymers. The efficient utilization of industrial discard as renewable feedstocks in the production of eco-friendly products such as bioplastics has been studied. This study focuses on the production of PHA using cashew industry wastewater (CIW). Since cashew industry wastewater (CIW) is rich in phenolic compounds and other sources, this study explores the possibility of eliminating the toxic phenol compounds from the waste by the production of PHA using cashew industry wastewater as a secondary source of carbon by paving the way to eco-friendly process. In this context, PHA-producing bacterium was isolated from wastewater samples collected from cashew industries. The morphological, microscopic, and biochemical characterization revealed that the isolated strain CFM1 is Bacillus sp. The strain CFM1 that gave maximum (30%) PHA in control medium was taken up for further studies with wastewater. The concentration of sucrose in the control production media was replaced with cashew industry wastewater. Wastewater was introduced to the medium at different concentrations (10–100%). As CIW concentration was increased, the sucrose concentration was decreased in the medium accordingly. CFM1 isolates produced 34% PHA with 20% wastewater. The biopolymer produced was characterized by FTIR and NMR. [ABSTRACT FROM AUTHOR]

The production of biodegradable plastic from microorganisms has great potential as a substitute for conventional plastic. This study aims to isolate bacterial strains capable of polyhydroxyalkanoates (PHAs) production from the Kampung Jawa landfill land (KJLL) and characterize biopolymers. The bacterial strains were able to produce PHA using a mineral salt medium (MSM) with glucose as a carbon source. The qualitative screening of PHA-producing bacteria was conducted by Sudan Black and Nile Red. Of the 64 bacteria strains, only 41 were able to accumulate PHA in Sudan Black and Nile Red. The results showed that one bacterium the Coccobacillus strain had the highest color intensity for further characterization of PHA. The characterization of PHA by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) showed a melting temperature (Tm) of 101.54 °C. X-ray diffraction (XRD) analysis revealed a crystalline structure with an index crystallinity (ICr) value of 15.82% for PHA. The results of the analysis proved that PHA was produced by bacteria isolate. This study suggests that this is the first report of the bacteria from the Kampung Jawa landfill producing PHA with good characteristics and potential biotechnology applications. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHA) envisage a potential biomaterial alternative to replacing synthetic polymers for their biodegradability and biocompatibility. Modification approaches exploit the attributes and adjust the intrinsic hydrophobic properties, such as blending to produce a new polymer mix with novel properties. Functionalization of PHA, especially chemical grafting, perform to introduce additional compounds covalently to PHA. As these methods address PHA potential and enable extensive utilization as a responsive material, reports are readily available in academia as confirmation. There are also substantial responsive PHA-based material applications in the biomedical area and agriculture materials, packaging materials, and nanocomposite materials. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are intracellularly synthesized by bacteria as carbonosomes that exhibit biodegradable thermoplastics and elastomeric properties. The use of cheaper edible oils as a source of carbon assists in the reduction of the production cost of such biopolyesters. In this work, different edible oils, such as groundnut oil (GNO), mustard oil, sesame oil, and soybean oil (SBO) were used to check their effect on PHA production from Pseudomonas aeruginosa EO1 (MK049902). Pseudomonas aeruginosa EO1 was used in a two-stage production system. In the first stage, bacterial growth was favored and, in the second, PHA was synthesized. GNO was found as the best carbon source for PHA production. The use of 2% (v/v) GNO, rich in saturated fatty acids, allowed PHA content of 58.41% and dry cell weight (DCW) of 10.5g/L at pH7 and temperature 35°C for 72h. Groundnut has a high potential for oil production and for the diversification of co-products with some potential of value aggregation. Such a perennial and sustainable species will almost certainly meet the criteria for becoming a significant commercial oilseed crop. Fourier transform infrared spectroscopy (FTIR) spectra showed strong characteristic bands at 1,282, 1,725, 2,935, 2,999, and 3,137cm−1 for the PHA polymer. Gas chromatography-mass spectrometry (GC-MS) detects the presence of PHA copolymers. [ABSTRACT FROM AUTHOR]

The feasibility of using acrylic acid-grafted poly(hydroxyalkanoate) and a treated (cross-linked) natural product (treated marine algae powder) as a bacteria-encapsulated film capsule material was evaluated for the controlled release of an encapsulated bacterium. For the purposes of comparison and accurate characterization, a poly(hydroxyalkanoate) or acrylic acid-grafted poly(hydroxyalkanoate) and its composite film capsules were also assessed. The water resistance of acrylic acid-grafted poly(hydroxyalkanoate)/treated marine algae powder was greater than that of poly(hydroxyalkanoate)/marine algae powder, although the weight loss of composites buried inAzospirillum brasilensecompost indicated that both were biodegradable, especially at high levels of marine algae powder or treated marine algae powder substitution. After 120 days, the weight loss of the acrylic acid-grafted poly(hydroxyalkanoate)/treated marine algae powder (20 wt%) composite was greater than 50%. Poly(hydroxyalkanoate)/marine algae powder exhibited a weight loss of approximately 3–12 wt% more than acrylic acid-grafted poly(hydroxyalkanoate)/treated marine algae powder. The bacterium completely degraded both the poly(hydroxyalkanoate) and acrylic acid-grafted poly(hydroxyalkanoate) and their composite film capsules, resulting in cell release. Based on the results of this work, the controlled release of bacteria-encapsulated film capsules for fertilizer utilization promotion appears achievable. [ABSTRACT FROM PUBLISHER]

ABSTRACT One of the most significant limitations to widespread industrial implementation of emerging bioplastics such as poly(lactic acid) and poly(hydroxyalkanoate) (PHA) is that they do not match the flexibility and impact resistance of petroleum-based plastics like poly(propylene) or high-density poly(ethylene). The basic goal of this research is to identify alternative, affordable, sustainable, biodegradable materials that can replace petroleum-based polymers in a wide range of industrial applications, with an emphasis on providing a solution for increasing the flexibility of PHA to a level that makes it a superior material for bioplastic nursery-crop containers. A series of bio-based PHA/poly(amide) (PA) blends with different concentrations were mechanically melt processed using a twin-screw extruder and evaluated for physical characteristics. The effects of blending on viscoelastic properties were investigated using small-amplitude oscillatory shear flow experiments to model the physical character as a function of blend composition and angular frequency. The mechanical, thermal, and morphological properties of the blends were investigated using dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and tensile tests. The complex viscosity of the blends increased significantly with increasing concentration of PHA and reached a maximum value for 80 wt % PHA blend. In addition, the tensile strength of the blends increased markedly as the content of PHA increased. For blends containing PA at >50 wt %, samples failed only after a very large elongation (up to 465%) without significant decrease in tensile strength. The particle size significantly increased and the blends became more brittle with increasing concentration of PHA. In addition, the concentration of the PA had a substantial effect on the glass relaxation temperature of the resulting blends. Our results demonstrate that the thermomechanical and rheological properties of PHA/PA blends can be tailored for specific applications, and that blends of PHA/PA can fulfill the mechanical properties required for flexible, impact-resistant bio-based nursery-crop containers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42209. [ABSTRACT FROM AUTHOR]

This review summarizes the state-of-the-art knowledge of the usage of poly(hydroxy alkanoate)s in medical and sanitary applications. Depending on the monomers incorporated into the polymers and copolymers, this class of polymers exhibits a broad range of (thermo-)plastic properties, enabling their processing by, e.g., solution casting or melt extrusion. In this review, strategies for the polymer analogous modification of these materials and their surfaces are highlighted and correlated with the potential applications of the corresponding materials and blends. While the commercial availability of purified PHAs is addressed in brief, special focus is put on the (bio-)degradability of these polymers and ways to influence the degradation mechanism and/or the duration of degradation. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are non-toxic, biocompatible, piezoelectric, and biodegradable thermoplastic. This study was designed to isolate the bacterial strains from trinitrotoluene (TNT)-contaminated soil capable of giving PHAs at high yields with tailor-made compositions. The isolated bacterial strain B. cereus FC11 gave PHA yield at 76.40 wt% using 500 mL Erlenmeyer flasks each containing 200 mL synthetic medium in the presence of glucose as a sole carbon source at pH value 7.0, 30°C and 150 rpm after 48 h of incubation under submerged fermentation. Furthermore, tailor-made PHA compositions were synthesized by B. cereus FC11 by adding different co-substrates along with glucose in the medium. High performance liquid chromatography analysis revealed that the retention time of crotonic acid (by-product) obtained from digested PHA was approximately 24.97 min which was similar to the retention time of crotonic acid (by-product) obtained from the digestion of commercially available poly-3-hydroxybutyrate and poly-3-hydroxybutyratc-co-3-hydroxyvalerate (Sigma-Aldrich). Fourier transform infrared spectrum showed the absorption bands at 1719, 1275 and 2932 cm'1, which were attributed to C=0, C-O stretching and C-H vibrations, respectively. The proton and carbon nuclear magnetic resonance analysis confirmed that this indigenously synthesized polymer was composed of 3-hydroxybutyrate (3-1 IB) and 3-hydroxyvaleratc (3-1IV) monomers. The number average molar mass (Mn) of copolymer was 37.98 kDa. [ABSTRACT FROM AUTHOR]

The purpose of this study was to enhance the production of polyhydroxyalkanoate (PHA) by sequential mutation of Bacillus licheniformis PHAs-007, using UV and N-methyl-N′-nitro-N-nitrosoguanidine (NTG). In addition, the effect of nutrient additions and environmental conditions were optimized to increase the production of PHA. Bacillus licheniformis PHAs-007 produced high amounts of PHA (64.09 ∼ 68.80% of DCW) under both synthetic and renewable substrates. After mutagenesis treatment, mutant M2-12 was selected from 380 strains, based on its high biomass and PHA concentration. The mutant M2-12 gave the highest value of specific growth rate (0.09/h), biomass (22.24 g/L) and PHA content (19.55 g/L) under optimal conditions, consisting of 3% palm oil mill effluent, with no additional trace elements, at 45oC and pH 7. The mutant strain showed higher resistance to substrate concentrations, as well as pH and temperature, than the wild type. The accumulation of PHA was increased by 3.18-fold compared to the wild type, and the production of PHA by the mutant M2-12 was constantly retained over 12 times of cultivation. The mutation and optimization strategy appear to be suitable for producing high density PHA, reducing the medium cost and consequently lowering the production cost. Interestingly, the mutant strain could synthesize the novel PHA copolymers such as 3-hydroxyvalerate and 3-hydroxyhexanoate, which were not produced by the wild type. [ABSTRACT FROM AUTHOR]