Special Issue "Advances in Polyhydroxyalkanoate (PHA) Production"

A special issue of Bioengineering (ISSN 2306-5354).

Deadline for manuscript submissions: closed (30 April 2017)

Special Issue Editor

Guest Editor
Dr. Martin Koller

Office of Research Management and Service, c/o Institute of Chemistry, University of Graz, Austria
Website | E-Mail
Interests: Polyhydroxyalkanoates (PHA); Biopolymers; Fermentation technology; Downstream processing; Sustainable process development

Special Issue Information

Dear Colleagues,

Nowadays, we are witnessing highly dynamic research activities related to the intriguing field of biodegradable materials with plastic-like properties. These activities are provoked by a strengthened public awareness of prevailing ecological issues connected to growing piles of plastic waste and increasing greenhouse gas emissions; this goes hand-in-hand with the ongoing depletion of fossil feedstocks, which are traditionally used to produce full carbon backbone polymers. To a steadily increasing extend, polyhydroxyalkanoate (PHA) biopolyesters, a family of plastic-like materials with versatile material properties, are considered a future-oriented solution for diminishing these concerns. PHA production is based on renewable resources, and occurs in a bio-mediated fashion by the action of living organisms. If accomplished in an optimized way, PHA production and the entire PHA lifecycle are embedded into nature´s closed cycles of carbon.

You as a highly recognized expert in this field are aware of the fact that sustainable and efficient PHA production requires the understanding and improvement of all individual process steps. Holistic improvement of PHA production, applicable on an industrially relevant scale, calls for inter alia: consolidated knowledge about the enzymatic and genetic particularities of PHA accumulating organisms, in-depth understanding of the kinetics of the bioprocess, the selection of appropriate inexpensive fermentation feedstocks, tailoring the composition of PHA on the level of the monomeric constituents, optimized biotechnological engineering, and novel strategies for PHA recovery from biomass characterized by minor energy and chemical requirement.

In order to provide a comprehensive compilation of articles addressing all these individual aspects, we are contacting globally recognized experts like you. We are convinced that a contribution based on your special expertise in the PHA arena will be of major benefit to make this Special Issue even more attractive to the scientific community.

Dr. Martin Koller
Guest Editor

Manuscript Submission Information

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Keywords

•    Polyhydroxyalkanoate (PHA),
•    Biopolyesters,
•    Bioprocess Design,
•    Sustainable Development

Published Papers (14 papers)

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Research

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Open AccessArticle The Molecular Level Characterization of Biodegradable Polymers Originated from Polyethylene Using Non-Oxygenated Polyethylene Wax as a Carbon Source for Polyhydroxyalkanoate Production
Bioengineering 2017, 4(3), 73; doi:10.3390/bioengineering4030073
Received: 2 August 2017 / Revised: 18 August 2017 / Accepted: 24 August 2017 / Published: 28 August 2017
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Abstract
There is an increasing demand for bio-based polymers that are developed from recycled materials. The production of biodegradable polymers can include bio-technological (utilizing microorganisms or enzymes) or chemical synthesis procedures. This report demonstrates the corroboration of the molecular structure of polyhydroxyalkanoates (PHAs) obtained
[...] Read more.
There is an increasing demand for bio-based polymers that are developed from recycled materials. The production of biodegradable polymers can include bio-technological (utilizing microorganisms or enzymes) or chemical synthesis procedures. This report demonstrates the corroboration of the molecular structure of polyhydroxyalkanoates (PHAs) obtained by the conversion of waste polyethylene (PE) via non-oxygenated PE wax (N-PEW) as an additional carbon source for a bacterial species. The N-PEW, obtained from a PE pyrolysis reaction, has been found to be a beneficial carbon source for PHA production with Cupriavidus necator H16. The production of the N-PEW is an alternative to oxidized polyethylene wax (O-PEW) (that has been used as a carbon source previously) as it is less time consuming to manufacture and offers fewer industrial applications. A range of molecular structural analytical techniques were performed on the PHAs obtained; which included nuclear magnetic resonance (NMR) and electrospray ionisation tandem mass spectrometry (ESI-MS/MS). Our study showed that the PHA formed from N-PEW contained 3-hydroxybutyrate (HB) with 11 mol% of 3-hydroxyvalerate (HV) units. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessArticle Biosynthesis of Polyhydroxyalkanoate from Steamed Soybean Wastewater by a Recombinant Strain of Pseudomonas sp. 61-3
Bioengineering 2017, 4(3), 68; doi:10.3390/bioengineering4030068
Received: 12 May 2017 / Revised: 3 August 2017 / Accepted: 4 August 2017 / Published: 8 August 2017
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Abstract
Pseudomonas sp. 61-3 accumulates a blend of poly(3-hydroxybutyrate) [P(3HB)] homopolymer and a random copolymer, poly(3-hydroxybutyrate-co-3-hydroxyalkanoate) [P(3HB-co-3HA)], consisting of 3HA units of 4–12 carbon atoms. Pseudomonas sp. 61-3 possesses two types of PHA synthases, PHB synthase (PhbC) and PHA synthases
[...] Read more.
Pseudomonas sp. 61-3 accumulates a blend of poly(3-hydroxybutyrate) [P(3HB)] homopolymer and a random copolymer, poly(3-hydroxybutyrate-co-3-hydroxyalkanoate) [P(3HB-co-3HA)], consisting of 3HA units of 4–12 carbon atoms. Pseudomonas sp. 61-3 possesses two types of PHA synthases, PHB synthase (PhbC) and PHA synthases (PhaC1 and PhaC2), encoded by the phb and pha loci, respectively. The P(94 mol% 3HB-co-6 mol% 3HA) copolymer synthesized by the recombinant strain of Pseudomonas sp. 61-3 (phbC::tet) harboring additional copies of phaC1 gene is known to have desirable physical properties and to be a flexible material with moderate toughness, similar to low-density polyethylene. In this study, we focused on the production of the P(3HB-co-3HA) copolymer using steamed soybean wastewater, a by-product in brewing miso, which is a traditional Japanese seasoning. The steamed soybean wastewater was spray-dried to produce a powder (SWP) and used as the sole nitrogen source for the synthesis of P(3HB-co-3HA) by the Pseudomonas sp. 61-3 recombinant strain. Hydrolyzed SWP (HSWP) was also used as a carbon and nitrogen source. P(3HB-co-3HA)s with relatively high 3HB fractions could be synthesized by a recombinant strain of Pseudomonas sp. 61-3 (phbC::tet) harboring additional copies of the phaC1 gene in the presence of 2% glucose and 10–20 g/L SWP as the sole nitrogen source, producing a PHA concentration of 1.0–1.4 g/L. When HSWP was added to a nitrogen- and carbon-free medium, the recombinant strain could synthesize PHA without glucose as a carbon source. The recombinant strain accumulated 32 wt% P(3HB-co-3HA) containing 80 mol% 3HB and 20 mol% medium-chain-length 3HA with a PHA concentration of 1.0 g/L when 50 g/L of HSWP was used. The PHA production yield was estimated as 20 mg-PHA/g-HSWP, which equates to approximately 1.0 g-PHA per liter of soybean wastewater. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
Open AccessArticle Prospecting for Marine Bacteria for Polyhydroxyalkanoate Production on Low-Cost Substrates
Bioengineering 2017, 4(3), 60; doi:10.3390/bioengineering4030060
Received: 5 May 2017 / Revised: 17 June 2017 / Accepted: 17 June 2017 / Published: 23 June 2017
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Abstract
Polyhydroxyalkanoates (PHAs) are a class of biopolymers with numerous applications, but the high cost of production has prevented their use. To reduce this cost, there is a prospect for strains with a high PHA production and the ability to grow in low-cost by-products.
[...] Read more.
Polyhydroxyalkanoates (PHAs) are a class of biopolymers with numerous applications, but the high cost of production has prevented their use. To reduce this cost, there is a prospect for strains with a high PHA production and the ability to grow in low-cost by-products. In this context, the objective of this work was to evaluate marine bacteria capable of producing PHA. Using Nile red, 30 organisms among 155 were identified as PHA producers in the medium containing starch, and 27, 33, 22 and 10 strains were found to be positive in media supplemented with carboxymethyl cellulose, glycerol, glucose and Tween 80, respectively. Among the organisms studied, two isolates, LAMA 677 and LAMA 685, showed strong potential to produce PHA with the use of glycerol as the carbon source, and were selected for further studies. In the experiment used to characterize the growth kinetics, LAMA 677 presented a higher maximum specific growth rate (µmax = 0.087 h−1) than LAMA 685 (µmax = 0.049 h−1). LAMA 677 also reached a D-3-hydroxybutyrate (P(3HB)) content of 78.63% (dry biomass), which was 3.5 times higher than that of LAMA 685. In the assay of the production of P(3HB) from low-cost substrates (seawater and biodiesel waste glycerol), LAMA 677 reached a polymer content of 31.7%, while LAMA 685 reached 53.6%. Therefore, it is possible to conclude that the selected marine strains have the potential to produce PHA, and seawater and waste glycerol may be alternative substrates for the production of this polymer. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessArticle The Bistable Behaviour of Pseudomonas putida KT2440 during PHA Depolymerization under Carbon Limitation
Bioengineering 2017, 4(2), 58; doi:10.3390/bioengineering4020058
Received: 14 May 2017 / Revised: 12 June 2017 / Accepted: 13 June 2017 / Published: 19 June 2017
Cited by 1 | PDF Full-text (2423 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Poly(hydroxyalkanoates) (PHAs) are bacterial polyesters offering a biodegradable alternative to petrochemical plastics. The intracellular formation and degradation of PHAs is a dynamic process that strongly depends on the availability of carbon and other nutrients. Carbon excess and nitrogen limitation are considered to favor
[...] Read more.
Poly(hydroxyalkanoates) (PHAs) are bacterial polyesters offering a biodegradable alternative to petrochemical plastics. The intracellular formation and degradation of PHAs is a dynamic process that strongly depends on the availability of carbon and other nutrients. Carbon excess and nitrogen limitation are considered to favor PHA accumulation, whereas carbon limitation triggers PHA depolymerization when all other essential nutrients are present in excess. We studied the population dynamics of Pseudomonas putida KT2440 at the single cell level during different physiological conditions, favoring first PHA polymerization during growth on octanoic acid, and then PHA depolymerization during carbon limitation. PHAs accumulate intracellularly in granules, and were proposed to separate preferentially together with nucleic acids, leading to two daughter cells containing approximately equal amounts of PHA. However, we could show that such P. putida KT2440 cells show bistable behavior when exposed to carbon limitation, and separate into two subpopulations: one with high and one with low PHA. This suggests an asymmetric PHA distribution during cell division under carbon limitation, which has a significant influence on our understanding of PHA mobilization. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessArticle Polyhydroxyalkanoate Production on Waste Water Treatment Plants: Process Scheme, Operating Conditions and Potential Analysis for German and European Municipal Waste Water Treatment Plants
Bioengineering 2017, 4(2), 54; doi:10.3390/bioengineering4020054
Received: 28 April 2017 / Revised: 2 June 2017 / Accepted: 3 June 2017 / Published: 6 June 2017
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Abstract
This work describes the production of polyhydroxyalkanoates (PHA) as a side stream process on a municipal waste water treatment plant (WWTP) and a subsequent analysis of the production potential in Germany and the European Union (EU). Therefore, tests with different types of sludge
[...] Read more.
This work describes the production of polyhydroxyalkanoates (PHA) as a side stream process on a municipal waste water treatment plant (WWTP) and a subsequent analysis of the production potential in Germany and the European Union (EU). Therefore, tests with different types of sludge from a WWTP were investigated regarding their volatile fatty acids (VFA) production-potential. Afterwards, primary sludge was used as substrate to test a series of operating conditions (temperature, pH, retention time (RT) and withdrawal (WD)) in order to find suitable settings for a high and stable VFA production. In a second step, various tests regarding a high PHA production and stable PHA composition to determine the influence of substrate concentration, temperature, pH and cycle time of an installed feast/famine-regime were conducted. Experiments with a semi-continuous reactor operation showed that a short RT of 4 days and a small WD of 25% at pH = 6 and around 30 °C is preferable for a high VFA production rate (PR) of 1913 mgVFA/(L×d) and a stable VFA composition. A high PHA production up to 28.4% of cell dry weight (CDW) was reached at lower substrate concentration, 20 °C, neutral pH-value and a 24 h cycle time. A final step a potential analysis, based on the results and detailed data from German waste water treatment plants, showed that the theoretically possible production of biopolymers in Germany amounts to more than 19% of the 2016 worldwide biopolymer production. In addition, a profound estimation regarding the EU showed that in theory about 120% of the worldwide biopolymer production (in 2016) could be produced on European waste water treatment plants. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessArticle Production of Polyhydroxyalkanoates Using Hydrolyzates of Spruce Sawdust: Comparison of Hydrolyzates Detoxification by Application of Overliming, Active Carbon, and Lignite
Bioengineering 2017, 4(2), 53; doi:10.3390/bioengineering4020053
Received: 28 April 2017 / Revised: 24 May 2017 / Accepted: 25 May 2017 / Published: 28 May 2017
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Abstract
Polyhydroxyalkanoates (PHAs) are bacterial polyesters which are considered biodegradable alternatives to petrochemical plastics. PHAs have a wide range of potential applications, however, the production cost of this bioplastic is several times higher. A major percentage of the final cost is represented by the
[...] Read more.
Polyhydroxyalkanoates (PHAs) are bacterial polyesters which are considered biodegradable alternatives to petrochemical plastics. PHAs have a wide range of potential applications, however, the production cost of this bioplastic is several times higher. A major percentage of the final cost is represented by the price of the carbon source used in the fermentation. Burkholderia cepacia and Burkholderia sacchari are generally considered promising candidates for PHA production from lignocellulosic hydrolyzates. The wood waste biomass has been subjected to hydrolysis. The resulting hydrolyzate contained a sufficient amount of fermentable sugars. Growth experiments indicated a strong inhibition by the wood hydrolyzate. Over-liming and activated carbon as an adsorbent of inhibitors were employed for detoxification. All methods of detoxification had a positive influence on the growth of biomass and PHB production. Furthermore, lignite was identified as a promising alternative sorbent which can be used for detoxification of lignocellulose hydrolyzates. Detoxification using lignite instead of activated carbon had lower inhibitor removal efficiency, but greater positive impact on growth of the bacterial culture and overall PHA productivity. Moreover, lignite is a significantly less expensive adsorbent in comparison with activated charcoal and; moreover, used lignite can be simply utilized as a fuel to, at least partially, cover heat and energetic demands of fermentation, which should improve the economic feasibility of the process. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessArticle Utilization of Sugarcane Bagasse by Halogeometricum borinquense Strain E3 for Biosynthesis of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)
Bioengineering 2017, 4(2), 50; doi:10.3390/bioengineering4020050
Received: 29 March 2017 / Revised: 17 May 2017 / Accepted: 22 May 2017 / Published: 25 May 2017
Cited by 1 | PDF Full-text (2879 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Sugarcane bagasse (SCB), one of the major lignocellulosic agro-industrial waste products, was used as a substrate for biosynthesis of polyhydroxyalkanoates (PHA) by halophilic archaea. Among the various wild-type halophilic archaeal strains screened, Halogeometricum borinquense strain E3 showed better growth and PHA accumulation as
[...] Read more.
Sugarcane bagasse (SCB), one of the major lignocellulosic agro-industrial waste products, was used as a substrate for biosynthesis of polyhydroxyalkanoates (PHA) by halophilic archaea. Among the various wild-type halophilic archaeal strains screened, Halogeometricum borinquense strain E3 showed better growth and PHA accumulation as compared to Haloferaxvolcanii strain BBK2, Haloarcula japonica strain BS2, and Halococcus salifodinae strain BK6. Growth kinetics and bioprocess parameters revealed the maximum PHA accumulated by strain E3 to be 50.4 ± 0.1 and 45.7 ± 0.19 (%) with specific productivity (qp) of 3.0 and 2.7 (mg/g/h) using NaCl synthetic medium supplemented with 25% and 50% SCB hydrolysate, respectively. PHAs synthesized by strain E3 were recovered in chloroform using a Soxhlet apparatus. Characterization of the polymer using crotonic acid assay, X-ray diffraction (XRD), differential scanning calorimeter (DSC), Fourier transform infrared (FT-IR), and proton nuclear magnetic resonance (1H-NMR) spectroscopy analysis revealed the polymer obtained from SCB hydrolysate to be a co-polymer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] comprising of 13.29 mol % 3HV units. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessArticle Molecular Diagnostic for Prospecting Polyhydroxyalkanoate-Producing Bacteria
Bioengineering 2017, 4(2), 52; doi:10.3390/bioengineering4020052
Received: 24 April 2017 / Revised: 12 May 2017 / Accepted: 19 May 2017 / Published: 25 May 2017
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Abstract
The use of molecular diagnostic techniques for bioprospecting and microbial diversity study purposes has gained more attention thanks to their functionality, low cost and quick results. In this context, ten degenerate primers were designed for the amplification of polyhydroxyalkanoate synthase (phaC)
[...] Read more.
The use of molecular diagnostic techniques for bioprospecting and microbial diversity study purposes has gained more attention thanks to their functionality, low cost and quick results. In this context, ten degenerate primers were designed for the amplification of polyhydroxyalkanoate synthase (phaC) gene, which is involved in the production of polyhydroxyalkanoate (PHA)—a biodegradable, renewable biopolymer. Primers were designed based on multiple alignments of phaC gene sequences from 218 species that have their genomes already analyzed and deposited at Biocyc databank. The combination of oligos phaCF3/phaCR1 allowed the amplification of the expected product (PHA synthases families types I and IV) from reference organisms used as positive control (PHA producer). The method was also tested in a multiplex system with two combinations of initiators, using 16 colonies of marine bacteria (pre-characterized for PHA production) as a DNA template. All amplicon positive organisms (n = 9) were also PHA producers, thus no false positives were observed. Amplified DNA was sequenced (n = 4), allowing for the confirmation of the phaC gene identity as well its diversity among marine bacteria. Primers were also tested for screening purposes using 37 colonies from six different environments. Almost 30% of the organisms presented the target amplicon. Thus, the proposed primers are an efficient tool for screening bacteria with potential for the production of PHA as well to study PHA genetic diversity. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessArticle Additive Manufacturing of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/poly(ε-caprolactone) Blend Scaffolds for Tissue Engineering
Bioengineering 2017, 4(2), 49; doi:10.3390/bioengineering4020049
Received: 27 April 2017 / Revised: 19 May 2017 / Accepted: 21 May 2017 / Published: 24 May 2017
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Abstract
Additive manufacturing of scaffolds made of a polyhydroxyalkanoate blended with another biocompatible polymer represents a cost-effective strategy for combining the advantages of the two blend components in order to develop tailored tissue engineering approaches. The aim of this study was the development of
[...] Read more.
Additive manufacturing of scaffolds made of a polyhydroxyalkanoate blended with another biocompatible polymer represents a cost-effective strategy for combining the advantages of the two blend components in order to develop tailored tissue engineering approaches. The aim of this study was the development of novel poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/ poly(ε-caprolactone) (PHBHHx/PCL) blend scaffolds for tissue engineering by means of computer-aided wet-spinning, a hybrid additive manufacturing technique suitable for processing polyhydroxyalkanoates dissolved in organic solvents. The experimental conditions for processing tetrahydrofuran solutions containing the two polymers at different concentrations (PHBHHx/PCL weight ratio of 3:1, 2:1 or 1:1) were optimized in order to manufacture scaffolds with predefined geometry and internal porous architecture. PHBHHx/PCL scaffolds with a 3D interconnected network of macropores and a local microporosity of the polymeric matrix, as a consequence of the phase inversion process governing material solidification, were successfully fabricated. As shown by scanning electron microscopy, thermogravimetric, differential scanning calorimetric and uniaxial compressive analyses, blend composition significantly influenced the scaffold morphological, thermal and mechanical properties. In vitro biological characterization showed that the developed scaffolds were able to sustain the adhesion and proliferation of MC3T3-E1 murine preosteoblast cells. The additive manufacturing approach developed in this study, based on a polymeric solution processing method avoiding possible material degradation related to thermal treatments, could represent a powerful tool for the development of customized PHBHHx-based blend scaffolds for tissue engineering. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessArticle Fed-Batch Synthesis of Poly(3-Hydroxybutyrate) and Poly(3-Hydroxybutyrate-co-4-Hydroxybutyrate) from Sucrose and 4-Hydroxybutyrate Precursors by Burkholderia sacchari Strain DSM 17165
Bioengineering 2017, 4(2), 36; doi:10.3390/bioengineering4020036
Received: 4 April 2017 / Revised: 13 April 2017 / Accepted: 19 April 2017 / Published: 20 April 2017
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Abstract
Based on direct sucrose conversion, the bacterium Burkholderia sacchari is an excellent producer of the microbial homopolyester poly(3-hydroxybutyrate) (PHB). Restrictions of the strain’s wild type in metabolizing structurally related 3-hydroxyvalerate (3HV) precursors towards 3HV-containing polyhydroxyalkanoate (PHA) copolyester calls for alternatives. We demonstrate the
[...] Read more.
Based on direct sucrose conversion, the bacterium Burkholderia sacchari is an excellent producer of the microbial homopolyester poly(3-hydroxybutyrate) (PHB). Restrictions of the strain’s wild type in metabolizing structurally related 3-hydroxyvalerate (3HV) precursors towards 3HV-containing polyhydroxyalkanoate (PHA) copolyester calls for alternatives. We demonstrate the highly productive biosynthesis of PHA copolyesters consisting of 3-hydroxybuytrate (3HB) and 4-hydroxybutyrate (4HB) monomers. Controlled bioreactor cultivations were carried out using saccharose from the Brazilian sugarcane industry as the main carbon source, with and without co-feeding with the 4HB-related precursor γ-butyrolactone (GBL). Without GBL co-feeding, the homopolyester PHB was produced at a volumetric productivity of 1.29 g/(L•h), a mass fraction of 0.52 g PHB per g biomass, and a final PHB concentration of 36.5 g/L; the maximum specific growth rate µmax amounted to 0.15 1/h. Adding GBL, we obtained 3HB and 4HB monomers in the polyester at a volumetric productivity of 1.87 g/(L•h), a mass fraction of 0.72 g PHA per g biomass, a final PHA concentration of 53.7 g/L, and a µmax of 0.18 1/h. Thermoanalysis revealed improved material properties of the second polyester in terms of reduced melting temperature Tm (161 °C vs. 178 °C) and decreased degree of crystallinity Xc (24% vs. 71%), indicating its enhanced suitability for polymer processing. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessArticle The Evolution of Polymer Composition during PHA Accumulation: The Significance of Reducing Equivalents
Bioengineering 2017, 4(1), 20; doi:10.3390/bioengineering4010020
Received: 6 January 2017 / Revised: 20 February 2017 / Accepted: 23 February 2017 / Published: 7 March 2017
Cited by 1 | PDF Full-text (2243 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper presents a systematic investigation into monomer development during mixed culture Polyhydroxyalkanoates (PHA) accumulation involving concurrent active biomass growth and polymer storage. A series of mixed culture PHA accumulation experiments, using several different substrate-feeding strategies, was carried out. The feedstock comprised volatile
[...] Read more.
This paper presents a systematic investigation into monomer development during mixed culture Polyhydroxyalkanoates (PHA) accumulation involving concurrent active biomass growth and polymer storage. A series of mixed culture PHA accumulation experiments, using several different substrate-feeding strategies, was carried out. The feedstock comprised volatile fatty acids, which were applied as single carbon sources, as mixtures, or in series, using a fed-batch feed-on-demand controlled bioprocess. A dynamic trend in active biomass growth as well as polymer composition was observed. The observations were consistent over replicate accumulations. Metabolic flux analysis (MFA) was used to investigate metabolic activity through time. It was concluded that carbon flux, and consequently copolymer composition, could be linked with how reducing equivalents are generated. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessArticle Biodegradable Polymeric Substances Produced by a Marine Bacterium from a Surplus Stream of the Biodiesel Industry
Bioengineering 2016, 3(4), 34; doi:10.3390/bioengineering3040034
Received: 13 September 2016 / Revised: 11 November 2016 / Accepted: 24 November 2016 / Published: 30 November 2016
Cited by 2 | PDF Full-text (2470 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Crude glycerol is generated as a by-product during transesterification process and during hydrolysis of fat in the soap-manufacturing process, and poses a problem for waste management. In the present approach, an efficient process was designed for simultaneous production of 0.2 g/L extracellular ε-polylysine
[...] Read more.
Crude glycerol is generated as a by-product during transesterification process and during hydrolysis of fat in the soap-manufacturing process, and poses a problem for waste management. In the present approach, an efficient process was designed for simultaneous production of 0.2 g/L extracellular ε-polylysine and 64.6% (w/w) intracellular polyhydroxyalkanoate (PHA) in the same fermentation broth (1 L shake flask) utilizing Jatropha biodiesel waste residues as carbon rich source by marine bacterial strain (Bacillus licheniformis PL26), isolated from west coast of India. The synthesized ε-polylysine and polyhydroxyalkanoate PHA by Bacillus licheniformis PL26 was characterized by thermogravimetric analysis (TGA), differential scanning colorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and 1H Nuclear magnetic resonance spectroscopy (NMR). The PHA produced by Bacillus licheniformis was found to be poly-3-hydroxybutyrate-co-3-hydroxyvalerate (P3HB-co-3HV). The developed process needs to be statistically optimized further for gaining still better yield of both the products in an efficient manner. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Review

Jump to: Research

Open AccessReview Recent Advances and Challenges towards Sustainable Polyhydroxyalkanoate (PHA) Production
Bioengineering 2017, 4(2), 55; doi:10.3390/bioengineering4020055
Received: 30 April 2017 / Revised: 29 May 2017 / Accepted: 9 June 2017 / Published: 11 June 2017
Cited by 1 | PDF Full-text (1172 KB) | HTML Full-text | XML Full-text
Abstract
Sustainable biofuels, biomaterials, and fine chemicals production is a critical matter that research teams around the globe are focusing on nowadays. Polyhydroxyalkanoates represent one of the biomaterials of the future due to their physicochemical properties, biodegradability, and biocompatibility. Designing efficient and economic bioprocesses,
[...] Read more.
Sustainable biofuels, biomaterials, and fine chemicals production is a critical matter that research teams around the globe are focusing on nowadays. Polyhydroxyalkanoates represent one of the biomaterials of the future due to their physicochemical properties, biodegradability, and biocompatibility. Designing efficient and economic bioprocesses, combined with the respective social and environmental benefits, has brought together scientists from different backgrounds highlighting the multidisciplinary character of such a venture. In the current review, challenges and opportunities regarding polyhydroxyalkanoate production are presented and discussed, covering key steps of their overall production process by applying pure and mixed culture biotechnology, from raw bioprocess development to downstream processing. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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Open AccessReview Cyanobacterial PHA Production—Review of Recent Advances and a Summary of Three Years’ Working Experience Running a Pilot Plant
Bioengineering 2017, 4(2), 26; doi:10.3390/bioengineering4020026
Received: 7 March 2017 / Revised: 15 March 2017 / Accepted: 16 March 2017 / Published: 28 March 2017
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Abstract
Cyanobacteria, as photoautotrophic organisms, provide the opportunity to convert CO2 to biomass with light as the sole energy source. Like many other prokaryotes, especially under nutrient deprivation, most cyanobacteria are able to produce polyhydroxyalkanoates (PHAs) as intracellular energy and carbon storage compounds. In
[...] Read more.
Cyanobacteria, as photoautotrophic organisms, provide the opportunity to convert CO2 to biomass with light as the sole energy source. Like many other prokaryotes, especially under nutrient deprivation, most cyanobacteria are able to produce polyhydroxyalkanoates (PHAs) as intracellular energy and carbon storage compounds. In contrast to heterotrophic PHA producers, photoautotrophic cyanobacteria do not consume sugars and, therefore, do not depend on agricultural crops, which makes them a green alternative production system. This review summarizes the recent advances in cyanobacterial PHA production. Furthermore, this study reports the working experience with different strains and cultivating conditions in a 200 L pilot plant. The tubular photobioreactor was built at the coal power plant in Dürnrohr, Austria in 2013 for direct utilization of flue gases. The main challenges were the selection of robust production strains, process optimization, and automation, as well as the CO2 availability. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)
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