Advances in Polyhydroxyalkanoate (PHA) Production, Volume 4

A special issue of Bioengineering (ISSN 2306-5354). This special issue belongs to the section "Biochemical Engineering".

Deadline for manuscript submissions: 30 June 2024 | Viewed by 8423

Special Issue Editor

Office of Research Management and Service, c/o Institute of Chemistry, University of Graz, 8010 Graz, Austria
Interests: polyhydroxyalkanoates (PHA); biopolymers; fermentation technology; downstream processing; sustainable process development
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Special Issue Information

Dear Colleagues,

Especially during the last couple of months, humankind became tremendously aware of the threats committed by a shortage of and insecure supply chains for fossil resources needed for the generation of energy carriers and goods like heavily utilized plastics. Together with the climate catastrophe that is becoming more and more apparent, soaring amounts of plastic waste, and ever more profound knowledge about the mechanisms of formation and effects of micro- and nanoplastics, this leads to intensified efforts in science, research and industry to focus on alternatives. In the field of plastics, such alternatives are biodegradable materials with versatile plastic-like characteristics. Such alternatives shall be intrinsically circular: biobased—originating from renewable carbon feedstock; biodegradable—amenable to degradability under aerobic and anaerobic conditions by biological factors, in both terrestrial and aquatic habitats; compostable both in industrial composting facilities and the compost heap in the garden; biocompatible—such materials do not exert any harm to the biosphere.

You, as an expert, are familiar with the fact that microbial polyhydroxyalkanoate (PHA) biopolyesters are the group of choice of alternative materials fulfilling these requirements. Produced predominately by prokaryotes as reserve- and stress-protectant materials, these versatile biopolymers have been demonstrated to mimic the properties and processability of various well-established petroplastics. Indeed, switching from limited fossil resources to PHA for plastic production excellently matches today´s initiatives to reach the global Climate Goals, and, if accomplished in an appropriate manner, even fits into the patterns of the 17 United Nations Sustainable Development Goals (SDGs), e.g., by saving food resources, fostering industrial innovation, sustainable consumption and production, and by protecting the oceans and land. Novel inexpensive feedstocks, advanced process engineering, optimized and robust microbial production strains, and smart processing with different compatible (nano)materials to high-tech products are currently lifting PHA to industrial maturity, as witnessed by “a new wave of industrialization of PHA biopolyesters”, which is currently pending worldwide. Indeed, an increasing number of companies of different sizes are already considering PHA as the way to go toward a circular bioeconomy!

However, the end of the road for these seminal materials has by no means been reached. Discovery and development of even more powerful production strains, optimized cultivation regimes, next-generation production strategies, finetuning of the nano-, micro- and macrostructure of PHA and follow-up products, truly sustainable protocols for PHA recovery, sound integration of PHA production into diverse biorefinery schemes, etc., are the directions that still need to be pursued in order not only to be able to produce PHA cost-effectively but also to adapt their properties to constantly increasing consumer expectations. This is exactly where your profound expertise is requested: Present Bioengineering Special Issue on “Polyhydroxyalkanoates: Production, Recent Developments and Applications”, already the fourth edition of this PHA series which I have the honor to guest-edit, is envisioned to invite contributions from all relevant fields of PHA research, encompassing microbiology, synthetic biology, genome editing, bioreactor technology, process design, tapping new raw material sources, mathematic modelling of diverse complexity, novel approaches for product recovery, PHA processing and modification, end of life and post-use options for PHA and follow-up materials, life cycle and sustainability considerations, and holistic circularity aspects.

We are very much looking forward to the participation of both emerging and long-established research teams active in the field of biopolymers. Moreover, we are confident that this Special Issue will provide similar seminal inspiration to the scientific community as the first three issues:

Volume 1 (15 papers): https://www.mdpi.com/journal/bioengineering/special_issues/PHA

Volume 2 (12 papers): https://www.mdpi.com/journal/bioengineering/special_issues/PHA2

Volume 3 (16 papers): https://www.mdpi.com/journal/bioengineering/special_issues/PHA3

Dr. Martin Koller
Guest Editor

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Published Papers (5 papers)

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Research

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13 pages, 1854 KiB  
Article
Characterization of Poly(3-hydroxybutyrate) (P3HB) from Alternative, Scalable (Waste) Feedstocks
by Rogerio Ramos de Sousa Junior, Fabiano Eduardo Marques Cezario, Leonardo Dalseno Antonino, Demetrio Jackson dos Santos and Maximilian Lackner
Bioengineering 2023, 10(12), 1382; https://doi.org/10.3390/bioengineering10121382 - 30 Nov 2023
Viewed by 740
Abstract
Bioplastics hold significant promise in replacing conventional plastic materials, linked to various serious issues such as fossil resource consumption, microplastic formation, non-degradability, and limited end-of-life options. Among bioplastics, polyhydroxyalkanoates (PHA) emerge as an intriguing class, with poly(3-hydroxybutyrate) (P3HB) being the most utilized. The [...] Read more.
Bioplastics hold significant promise in replacing conventional plastic materials, linked to various serious issues such as fossil resource consumption, microplastic formation, non-degradability, and limited end-of-life options. Among bioplastics, polyhydroxyalkanoates (PHA) emerge as an intriguing class, with poly(3-hydroxybutyrate) (P3HB) being the most utilized. The extensive application of P3HB encounters a challenge due to its high production costs, prompting the investigation of sustainable alternatives, including the utilization of waste and new production routes involving CO2 and CH4. This study provides a valuable comparison of two P3HBs synthesized through distinct routes: one via cyanobacteria (Synechocystis sp. PCC 6714) for photoautotrophic production and the other via methanotrophic bacteria (Methylocystis sp. GB 25) for chemoautotrophic growth. This research evaluates the thermal and mechanical properties, including the aging effect over 21 days, demonstrating that both P3HBs are comparable, exhibiting physical properties similar to standard P3HBs. The results highlight the promising potential of P3HBs obtained through alternative routes as biomaterials, thereby contributing to the transition toward more sustainable alternatives to fossil polymers. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production, Volume 4)
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12 pages, 2546 KiB  
Article
Production of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from CO2 via pH-Stat Jar Cultivation of an Engineered Hydrogen-Oxidizing Bacterium Cupriavidus necator
by Kenji Tanaka, Izumi Orita and Toshiaki Fukui
Bioengineering 2023, 10(11), 1304; https://doi.org/10.3390/bioengineering10111304 - 10 Nov 2023
Cited by 2 | Viewed by 906
Abstract
The copolyester of 3-hydroxybutyrate (3HB) and 3-hydoxyhexanoate (3HHx), PHBHHx, is a biodegradable plastic characterized by high flexibility, softness, a wide process window, and marine biodegradability. PHBHHx is usually produced from structurally related carbon sources, such as vegetable oils or fatty acids, but not [...] Read more.
The copolyester of 3-hydroxybutyrate (3HB) and 3-hydoxyhexanoate (3HHx), PHBHHx, is a biodegradable plastic characterized by high flexibility, softness, a wide process window, and marine biodegradability. PHBHHx is usually produced from structurally related carbon sources, such as vegetable oils or fatty acids, but not from inexpensive carbon sources such as sugars. In previous studies, we demonstrated that engineered strains of a hydrogen-oxidizing bacterium, Cupriavidus necator, synthesized PHBHHx with a high cellular content not only from sugars but also from CO2 as the sole carbon source in the flask culture. In this study, the highly efficient production of PHBHHx from CO2 was investigated via pH-stat jar cultivation of recombinant C. necator strains while feeding the substrate gas mixture (H2/O2/CO2 = 80:10:10 v/v%) to a complete mineral medium in a recycled-gas, closed-circuit culture system. As a result, the dry cell mass and PHBHHx concentration with the strain MF01/pBPP-ccrMeJAc-emd reached up to 59.62 ± 3.18 g·L−1 and 49.31 ± 3.14 g·L−1, respectively, after 216 h of jar cultivation with limited addition of ammonia and phosphate solutions. The 3HHx composition was close to 10 mol%, which is suitable for practical applications. It is expected that the autotrophic cultivation of the recombinant C. necator can be feasible for the mass production of PHBHHx from CO2. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production, Volume 4)
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12 pages, 1528 KiB  
Article
Co-Production of Poly(3-hydroxybutyrate) and Gluconic Acid from Glucose by Halomonas elongata
by Tânia Leandro, M. Conceição Oliveira, M. Manuela R. da Fonseca and M. Teresa Cesário
Bioengineering 2023, 10(6), 643; https://doi.org/10.3390/bioengineering10060643 - 25 May 2023
Cited by 2 | Viewed by 1152
Abstract
Polyhydroxyalkanoates (PHA) are biopolyesters regarded as an attractive alternative to petroleum-derived plastics. Nitrogen limitation and phosphate limitation in glucose cultivations were evaluated for poly(3-hydroxybutyrate) (P(3HB)) production by Halomonas elongata 1H9T, a moderate halophilic strain. Co-production of P(3HB) and gluconic acid was [...] Read more.
Polyhydroxyalkanoates (PHA) are biopolyesters regarded as an attractive alternative to petroleum-derived plastics. Nitrogen limitation and phosphate limitation in glucose cultivations were evaluated for poly(3-hydroxybutyrate) (P(3HB)) production by Halomonas elongata 1H9T, a moderate halophilic strain. Co-production of P(3HB) and gluconic acid was observed in fed-batch glucose cultivations under nitrogen limiting conditions. A maximum P(3HB) accumulation of 53.0% (w/w) and a maximum co-production of 133 g/L of gluconic acid were attained. Fed-batch glucose cultivation under phosphate limiting conditions resulted in a P(3HB) accumulation of only 33.3% (w/w) and no gluconic acid production. As gluconic acid is a valuable organic acid with extensive applications in several industries, this work presents an interesting approach for the future development of an industrial process aiming at the co-production of an intracellular biopolymer, P(3HB), and a value-added extracellular product, gluconic acid. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production, Volume 4)
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11 pages, 1596 KiB  
Article
Quantification of the Monomer Compositions of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Poly(3-hydroxyvalerate) by Alkaline Hydrolysis and Using High-Performance Liquid Chromatography
by Kyo Saito, M. Venkateswar Reddy, Omprakash Sarkar, A. Naresh Kumar, DuBok Choi and Young-Cheol Chang
Bioengineering 2023, 10(5), 618; https://doi.org/10.3390/bioengineering10050618 - 20 May 2023
Cited by 2 | Viewed by 1567
Abstract
With the growing interest in bioplastics, there is an urgent need to develop rapid analysis methods linked to production technology development. This study focused on the production of a commercially non-available homopolymer, poly(3-hydroxyvalerate) (P(3HV)), and a commercially available copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)), [...] Read more.
With the growing interest in bioplastics, there is an urgent need to develop rapid analysis methods linked to production technology development. This study focused on the production of a commercially non-available homopolymer, poly(3-hydroxyvalerate) (P(3HV)), and a commercially available copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)), through fermentation using two different bacterial strains. The bacteria Chromobacterium violaceum and Bacillus sp. CYR1 were used to produce P(3HV) and P(3HB-co-3HV), respectively. The bacterium Bacillus sp. CYR1 produced 415 mg/L of P(3HB-co-3HV) when incubated with acetic acid and valeric acid as the carbon sources, whereas the bacterium C. violaceum produced 0.198 g of P(3HV)/g dry biomass when incubated with sodium valerate as the carbon source. Additionally, we developed a fast, simple, and inexpensive method to quantify P(3HV) and P(3HB-co-3HV) using high-performance liquid chromatography (HPLC). As the alkaline decomposition of P(3HB-co-3HV) releases 2-butenoic acid (2BE) and 2-pentenoic acid (2PE), we were able to determine the concentration using HPLC. Moreover, calibration curves were prepared using standard 2BE and 2PE, along with sample 2BE and 2PE produced by the alkaline decomposition of poly(3-hydroxybutyrate) and P(3HV), respectively. Finally, the HPLC results obtained by our new method were compared using gas chromatography (GC) analysis. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production, Volume 4)
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Review

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16 pages, 1005 KiB  
Review
Microbial PolyHydroxyAlkanoate (PHA) Biopolymers—Intrinsically Natural
by Anindya Mukherjee and Martin Koller
Bioengineering 2023, 10(7), 855; https://doi.org/10.3390/bioengineering10070855 - 19 Jul 2023
Cited by 8 | Viewed by 3477
Abstract
Global pollution from fossil plastics is one of the top environmental threats of our time. At their end-of-life phase, fossil plastics, through recycling, incineration, and disposal result in microplastic formation, elevated atmospheric CO2 levels, and the pollution of terrestrial and aquatic environments. [...] Read more.
Global pollution from fossil plastics is one of the top environmental threats of our time. At their end-of-life phase, fossil plastics, through recycling, incineration, and disposal result in microplastic formation, elevated atmospheric CO2 levels, and the pollution of terrestrial and aquatic environments. Current regional, national, and global regulations are centered around banning plastic production and use and/or increasing recycling while ignoring efforts to rapidly replace fossil plastics through the use of alternatives, including those that occur in nature. In particular, this review demonstrates how microbial polyhydroxyalkanoates (PHAs), a class of intrinsically natural polymers, can successfully remedy the fossil and persistent plastic dilemma. PHAs are bio-based, biosynthesized, biocompatible, and biodegradable, and thus, domestically and industrially compostable. Therefore, they are an ideal replacement for the fossil plastics pollution dilemma, providing us with the benefits of fossil plastics and meeting all the requirements of a truly circular economy. PHA biopolyesters are natural and green materials in all stages of their life cycle. This review elaborates how the production, consumption, and end-of-life profile of PHAs are embedded in the current and topical, 12 Principles of Green Chemistry, which constitute the basis for sustainable product manufacturing. The time is right for a paradigm shift in plastic manufacturing, use, and disposal. Humankind needs alternatives to fossil plastics, which, as recalcitrant xenobiotics, contribute to the increasing deterioration of our planet. Natural PHA biopolyesters represent that paradigm shift. Full article
(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production, Volume 4)
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