Utilization of waste fish oil and glycerol as carbon sources for polyhydroxyalkanoate production by Salinivibrio sp. M318

Enhanced production, functionalization, and applications of polyhydroxyalkanoates from organic waste: A review

Polyhydroxyalkanoates (PHAs) represent a promising class of biodegradable polyesters synthesized by various microorganisms as energy storage compounds. Their versatility and environmental friendliness make them potential candidates for replacing conventional plastics across numerous applications. However, challenges such as limited mechanical properties, high production costs, and thermal instability have hindered their widespread adoption. This paper explores innovative approaches to enhance the production, functionalization, and application of PHAs, particularly through the utilization of organic waste as a substrate, including chitosan, lignin, and cellulose derivatives. By incorporating various additives and blending with other biodegradable materials like chitosan, lignin, and cellulose derivatives, the functional properties of PHAs can be significantly improved. This study also delves into the impact of surface modifications on the thermal stability of PHAs, offering insights into their potential applications in fields such as biomedical implants, packaging, and sustainable materials. These advancements in PHA research not only address current material limitations but also contribute to a more sustainable and circular bioeconomy by valorizing organic waste streams into high-value biopolymers.

Exploiting latent microbial potentials for producing polyhydroxyalkanoates: A holistic approach

Plastics are versatile, however, nonbiodegradable polymers that are primarily derived from fossil fuels and pose notable environmental challenges. However, biopolymers, such as polyhydroxyalkanoates (PHAs), poly(lactic acid), starch, and cellulose have emerged as sustainable alternatives to conventional plastics. Among these, PHAs stand out as strong contenders as they are completely bio-based and biodegradable and are synthesized by microbes as an energy reserve under stress conditions. Despite their limitations, including low mechanical strength, susceptibility to degradation, a restricted scope of application, and high production costs, biopolymers have promising potential. This review explores strategies for enhancing PHA production to address these challenges, emphasizing the need for sustainable PHA production. These strategies include selecting robust microbial strains and feedstock combinations, optimizing cell biomass and biopolymer yields, genetically engineering biosynthetic pathways, and improving downstream processing techniques. Additives such as plasticizers, thermal stabilizers, and antioxidants are crucial for modifying PHA characteristics, and its processing for achieving the desired balance between processability and end-use performance. By overcoming these complications, biopolymers have become more viable, versatile, and eco-friendly alternatives to conventional plastics, offering hope for a more sustainable future.

Production of polyhydroxyalkanoate from new isolated bacteria of Acidovorax diaphorobacter ZCH-15 using orange peel and its underlying metabolic mechanisms

Polyhydroxyalkanoate (PHA) is considered a sustainable alternative to traditional petroleum-based plastics due to its biodegradability and biocompatibility. In this study, Acidovorax diaphorobacter ZCH-15, an efficient PHA-producing strain, was isolated from activated sludge. Using food waste-derived orange peel as a substrate, the strain initially achieved a PHA concentration of 0.39 g/L. Under optimal fermentation conditions (30℃, pH 8, 2 % inoculum concentration, and 30 g/L carbon source), the PHA concentration increased by 138 % to reach a maximum of 0.93 g/L. Proton nuclear magnetic resonance spectroscopy and gas chromatography analyses identified the PHA composition as poly(3-hydroxybutyrate-co-3-hydroxyvalerate), which exhibited high crystallinity and structural stability. Metabolomic analysis indicated that the tricarboxylic acid cycle and pentose phosphate pathway were involved in producing succinyl-CoA, a precursor required for PHA synthesis. This study demonstrates the potential for cost-effective industrial PHA production while enabling the high-value utilization of food waste.

Advances in polyhydroxyalkanoate (PHA) production from renewable waste materials using halophilic microorganisms: A comprehensive review

Polyhydroxyalkanoates (PHAs) are biodegradable and biocompatible polymers that can replace conventional plastics in different sectors. However, PHA commercialization is hampered due to their high production cost resulting from the use of high purity substrates, their low conversion into PHAs by using conventional microbial chassis and the high downstream processing cost. Taking these challenges into account, researchers are focusing on the use of waste by-products as alternative low-cost feedstocks for fast-growing and contamination-resistant halophilic microorganisms (Bacteria, Archaea…). This is of great importance since these extremophiles can use low-cost substrates, produce high PHA content of copolymers or different PHA monomer compositions. They can present high potential for reducing the costs of PHA fermentation and recovery processes, making their use in commercial applications easier. However, little is known about the potential of halophiles in advancing the PHA production from renewable waste materials at lab-scale and their successful implementation at industrial-scale. This review presents actual advances in PHA production by halophilic pure/engineered species (e.g. Haloferax mediterranei, Halomonas spp.) and mixed microbial consortia (MMC) using organic waste streams. The development of optimal PHA production process involves robust genetic engineering strategies, advanced fermentation processes using mixed microbial consortia versus pure/engineered strains as well as algal biomass as feedstocks.

Innovations in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and nanocomposites for sustainable food packaging via biochemical biorefinery platforms: A comprehensive review

The substantial build-up of non-biodegradable plastic waste from packaging sector not only poses severe environmental threats but also hastens the depletion of natural petroleum-based resources. Presently, poly (3-hydroxybutyrate-co-3-hydroxy valerate) (PHBV), received enormous attention as ideal alternatives for such traditional petroleum-derived plastics based on their biocompatibility and superior mechanical properties. However, high cost of such copolymer, due to expensive nature of feedstock, inefficient microbial processes and unfavorable downstream processing strategies restricts its large-scale commercial feasibility in the packaging sector. This review explores merits and challenges associated with using potent agricultural and industrial waste biomasses as sustainable feedstocks alongside improved fermentation and downstream processing strategies for the biopolymer in terms of biorefinery concept. Despite PHBV's attractive properties, its inherent shortcomings like weak thermal stability, poor mechanical properties, processability difficulty, substantial hydrophobicity and comparatively higher water vapor permeability (WVP) demand the development of its composites based on the application. Based on this fact, the review assessed properties and potential applications of PHBV-based composite materials having natural raw materials, nanomaterials and synthetic biodegradable polymers. Besides, the review also enlightens sustainability, future prospects, and challenges associated with PHBV-based composites in the field of food packaging while considering insights about economic evaluation and life cycle assessment.

Microbial production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), from lab to the shelf: A review

Polyhydroxyalkanoates (PHAs) are natural biopolyesters produced by microorganisms that represent one of the most promising candidates for the replacement of conventional plastics due to their complete biodegradability and advantageous material properties which can be modulated by varying their monomer composition. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] has received particular research attention because it can be synthesized based on the same microbial platform developed for poly(3-hydroxybutyrate) [P(3HB)] without much modification, with as high productivity as P(3HB). It also offers more useful mechanical and thermal properties than P(3HB), which broaden its application as a biocompatible and biodegradable polyester. However, a significant commercial disadvantage of P(3HB-co-3HV) is its rather high production cost, thus many studies have investigated the economical synthesis of P(3HB-co-3HV) from structurally related and unrelated carbon sources in both wild-type and recombinant microbial strains. A large number of metabolic engineering strategies have also been proposed to tune the monomer composition of P(3HB-co-3HV) and thus its material properties. In this review, recent metabolic engineering strategies designed for enhanced production of P(3HB-co-3HV) are discussed, along with their current status, limitations, and future perspectives.

Valorization of food waste: A comprehensive review of individual technologies for producing bio-based products

BACKGROUND

The escalating global concerns about food waste and the imperative need for sustainable practices have fuelled a burgeoning interest in the valorization of food waste. This comprehensive review delves into various technologies employed for converting food waste into valuable bio-based products. The article surveys individual technologies, ranging from traditional to cutting-edge methods, highlighting their respective mechanisms, advantages, and challenges.

SCOPE AND APPROACH

The exploration encompasses enzymatic processes, microbial fermentation, anaerobic digestion, and emerging technologies such as pyrolysis and hydrothermal processing. Each technology's efficacy in transforming food waste into bio-based products such as biofuels, enzymes, organic acids, prebiotics, and biopolymers is critically assessed. The review also considers the environmental and economic implications of these technologies, shedding light on their sustainability and scalability. The article discusses the role of technological integration and synergies in creating holistic approaches for maximizing the valorization potential of food waste. Key finding and conclusion: This review consolidates current knowledge on the valorization of food waste, offering a comprehensive understanding of individual technologies and their contributions to the sustainable production of bio-based products. The synthesis of information presented here aims to guide researchers, policymakers, and industry stakeholders in making informed decisions to address the global challenge of food waste while fostering a circular and eco-friendly economy.

Biosynthesis of Polyhydroxyalkanoates in Cupriavidus necator B-10646 on Saturated Fatty Acids

It has been established that the wild-type Cupriavidus necator B-10646 strain uses saturated fatty acids (SFAs) for growth and polyhydroxyalkanoate (PHA) synthesis. It uses lauric (12:0), myristic (14:0), palmitic (16:0) and stearic (18:0) acids as carbon sources; moreover, the elongation of the C-chain negatively affects the biomass and PHA yields. When bacteria grow on C12 and C14 fatty acids, the total biomass and PHA yields are comparable up to 7.5 g/L and 75%, respectively, which twice exceed the values that occur on longer C16 and C18 acids. Regardless of the type of SFAs, bacteria synthesize poly(3-hydroxybutyrate), which have a reduced crystallinity (Cx from 40 to 57%) and a molecular weight typical for poly(3-hydroxybutyrate) (P(3HB)) (Mw from 289 to 465 kDa), and obtained polymer samples demonstrate melting and degradation temperatures with a gap of about 100 °C. The ability of bacteria to assimilate SFAs opens up the possibility of attracting the synthesis of PHAs on complex fat-containing substrates, including waste.

Organic waste-to-bioplastics: Conversion with eco-friendly technologies and approaches for sustainable environment

Petrochemical-based synthetic plastics poses a threat to humans, wildlife, marine life and the environment. Given the magnitude of eventual depletion of petrochemical sources and global environmental pollution caused by the manufacturing of synthetic plastics such as polyethylene (PET) and polypropylene (PP), it is essential to develop and adopt biopolymers as an environment friendly and cost-effective alternative to synthetic plastics. Research into bioplastics has been gaining traction as a way to create a more sustainable and eco-friendlier environment with a reduced environmental impact. Biodegradable bioplastics can have the same characteristics as traditional plastics while also offering additional benefits due to their low carbon footprint. Therefore, using organic waste from biological origin for bioplastic production not only reduces our reliance on edible feedstock but can also effectively assist with solid waste management. This review aims at providing an in-depth overview on recent developments in bioplastic-producing microorganisms, production procedures from various organic wastes using either pure or mixed microbial cultures (MMCs), microalgae, and chemical extraction methods. Low production yield and production costs are still the major bottlenecks to their deployment at industrial and commercial scale. However, their production and commercialization pose a significant challenge despite such potential. The major constraints are their production in small quantity, poor mechanical strength, lack of facilities and costly feed for industrial-scale production. This review further explores several methods for producing bioplastics with the aim of encouraging researchers and investors to explore ways to utilize these renewable resources in order to commercialize degradable bioplastics. Challenges, future prospects and Life cycle assessment of bioplastics are also highlighted. Utilizing a variety of bioplastics obtained from renewable and cost-effective sources (e.g., organic waste, agro-industrial waste, or microalgae) and determining the pertinent end-of-life option (e.g., composting or anaerobic digestion) may lead towards the right direction that assures the sustainable production of bioplastics.

Bio-conversion of organic wastes towards polyhydroxyalkanoates

The bio-manufacturing of products with substantial commercial value, particularly polyhydroxyalkanoates (PHA), using cost-effective carbon sources through microorganisms, has garnered heightened attention from both the scientific community and industry over the past few decades. Opting for industrial PHA production from various organic wastes, spanning industrial, agricultural, municipal, and food-based sources, emerges as a wiser choice. This strategy not only eases the burden of recycling organic waste and curbs environmental pollution but also trims down PHA production costs, rendering these materials more competitive in commercial markets. In addition, PHAs are a family of renewable, environmentally friendly, fully biodegradable and biocompatible polyesters with a multitude of applications. This review provides an overview of recent developments in PHA production from organic wastes. It covers the optimization of diverse metabolic pathways for producing various types of PHA from organic waste sources, pre-treatment and downstream processing for PHA using unrelated organic wastes, and challenges in industrial production of PHA using unrelated organic waste feedstocks and the challenges faced in industrial PHA production from organic wastes, along with potential solutions. Lastly, this study suggests underlying research endeavors aimed at further enhancing of the feasibility of industrial PHA production from organic wastes as an alternative to current petroleum-based plastics in the near future.

Exploring Microorganisms from Plastic-Polluted Sites: Unveiling Plastic Degradation and PHA Production Potential

The exposure of microorganisms to conventional plastics is a relatively recent occurrence, affording limited time for evolutionary adaptation. As part of the EU-funded project BioICEP, this study delves into the plastic degradation potential of microorganisms isolated from sites with prolonged plastic pollution, such as plastic-polluted forests, biopolymer-contaminated soil, oil-contaminated soil, municipal landfill, but also a distinctive soil sample with plastic pieces buried three decades ago. Additionally, samples from Arthropoda species were investigated. In total, 150 strains were isolated and screened for the ability to use plastic-related substrates (Impranil dispersions, polyethylene terephthalate, terephthalic acid, and bis(2-hydroxyethyl) terephthalate). Twenty isolates selected based on their ability to grow on various substrates were identified as Streptomyces, Bacillus, Enterococcus, and Pseudomonas spp. Morphological features were recorded, and the 16S rRNA sequence was employed to construct a phylogenetic tree. Subsequent assessments unveiled that 5 out of the 20 strains displayed the capability to produce polyhydroxyalkanoates, utilizing pre-treated post-consumer PET samples. With Priestia sp. DG69 and Neobacillus sp. DG40 emerging as the most successful producers (4.14% and 3.34% of PHA, respectively), these strains are poised for further utilization in upcycling purposes, laying the foundation for the development of sustainable strategies for plastic waste management.

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.

Properties of Degradable Polyhydroxyalkanoates Synthesized from New Waste Fish Oils (WFOs)

The synthesis of PHA was first investigated using WFOs obtained from smoked-sprat heads, substandard fresh sprats, and fresh mackerel heads and backbones. All the WFOs ensured the growth of the wild-type strain Cupriavidus necator B-10646 and the synthesis of PHA, regardless of the degree of lipid saturation (from 0.52 to 0.65) and the set and ratio of fatty acids (FA), which was represented by acids with chain lengths from C14 to C24. The bacterial biomass concentration and PHA synthesis were comparable (4.1-4.6 g/L and about 70%) when using WFO obtained from smoked-sprat heads and fresh mackerel, and it was twice as high as the bacterial biomass concentration from the fresh sprat waste. This depended on the type of WFO, the bacteria synthesized P(3HB) homopolymer or P(3HB-co-3HV-co-3HHx) copolymer, which had a lower degree of crystallinity (Cx 71%) and a lower molecular weight (Mn 134 kDa) compared to the P(3HB) (Mn 175-209 kDa and Cx 74-78%) at comparable temperatures (Tmelt and Tdegr of 158-168 °C and 261-284 °C, respectively). The new types of WFO, studied for the first time, are suitable as a carbon substrates for PHA synthesis. The WFOs obtained in the production of canned Baltic sprat and Baltic mackerel can be considered a promising and renewable substrate for PHA biosynthesis.

Valorization of organic wastes using bioreactors for polyhydroxyalkanoate production: Recent advancement, sustainable approaches, challenges, and future perspectives

Microbial polyhydroxyalkanoates (PHA) are encouraging biodegradable polymers, which may ease the environmental problems caused by petroleum-derived plastics. However, there is a growing waste removal problem and the high price of pure feedstocks for PHA biosynthesis. This has directed to the forthcoming requirement to upgrade waste streams from various industries as feedstocks for PHA production. This review covers the state-of-the-art progress in utilizing low-cost carbon substrates, effective upstream and downstream processes, and waste stream recycling to sustain entire process circularity. This review also enlightens the use of various batch, fed-batch, continuous, and semi-continuous bioreactor systems with flexible results to enhance the productivity and simultaneously cost reduction. The life-cycle and techno-economic analyses, advanced tools and strategies for microbial PHA biosynthesis, and numerous factors affecting PHA commercialization were also covered. The review includes the ongoing and upcoming strategies viz. metabolic engineering, synthetic biology, morphology engineering, and automation to expand PHA diversity, diminish production costs, and improve PHA production with an objective of "zero-waste" and "circular bioeconomy" for a sustainable future.

Production of polyhydroxyalkanoates from renewable resources: a review on prospects, challenges and applications

Bioplastics replace synthetic plastics of petrochemical origin, which contributes challenge to both polymer quality and economics. Novel polyhydroxyalkanoates (PHA)-composite materials, with desirable product quality, could be developed, thus targeting the global plastics market, in the coming years. It is possible that PHA can be a greener substitute for their petroleum-based competitors since they are simply decomposed, which may lessen the pressure on municipal and industrial waste management systems. PHA production has proven to be the bottleneck in industrial application and commercialization because of the high price of carbon substrates and downstream processes required to achieve reliability. Bacterial PHA production by these municipal and industrial wastes, which act as a cheap, renewable carbon substrate, eliminates waste management hassles and acts as an efficient substitute for synthetic plastics. In the present review, challenges and opportunities related to the commercialization of polyhydroxyalkanoates are discussed and presented. Moreover, it discusses critical steps of their production process, feedstock evaluation, optimization strategies, and downstream processes. This information may provide us the complete utilization of bacterial PHA during possible applications in packaging, nutrition, medicine, and pharmaceuticals.

The Role of Bacterial Polyhydroalkanoate (PHA) in a Sustainable Future: A Review on the Biological Diversity

Environmental challenges related to the mismanagement of plastic waste became even more evident during the COVID-19 pandemic. The need for new solutions regarding the use of plastics came to the forefront again. Polyhydroxyalkanoates (PHA) have demonstrated their ability to replace conventional plastics, especially in packaging. Its biodegradability and biocompatibility makes this material a sustainable solution. The cost of PHA production and some weak physical properties compared to synthetic polymers remain as the main barriers to its implementation in the industry. The scientific community has been trying to solve these disadvantages associated with PHA. This review seeks to frame the role of PHA and bioplastics as substitutes for conventional plastics for a more sustainable future. It is focused on the bacterial production of PHA, highlighting the current limitations of the production process and, consequently, its implementation in the industry, as well as reviewing the alternatives to turn the production of bioplastics into a sustainable and circular economy.

Production of polyhydroxyalkanoates containing monomers conferring amorphous and elastomeric properties from renewable resources: Current status and future perspectives

Petrochemical-based plastics cause environmental pollution and threaten humans and ecosystems. Polyhydroxyalkanoate (PHA) is considered a promising alternative to nondegradable plastics since it is eco-friendly and biodegradable polymer having similar properties to conventional plastics. PHA's material properties are generally determined by composition and type of monomers in PHA. PHA can be designed in tailor-made manner for their suitable application areas. Among many monomers in PHAs, ω-hydroxalkanoates such as 3-hydroxypropionate (3HP), 4-hydroxybutyrate (4HB), 5-hydroxyvalerate (5HV), and 6-hydroxyhexanoate (6HHx) and medium-chain-length 3-hydroxyalkanoate such as 3-hydroxyhexanoate (3HHx) and 4-hydroxyvalerate (4HV), have been examined as potential monomers able to confer amorphous and elastomer properties when these are incorporated as comonomer in poly(3-hydroxybutyrate) copolymer that has 3HB as main monomer along with comonomers in different monomer fraction. Herein, recent advances in production of PHAs designed to have amorphous and elastomeric properties from renewable sources such as lignocellulose, levulinic acid, crude glycerol, and waste oil are discussed.

Revealing the Phenotypic and Genomic Background for PHA Production from Rapeseed-Biodiesel Crude Glycerol Using Photobacterium ganghwense C2.2

Polyhydroxyalkanoates (PHA) are promising biodegradable and biocompatible bioplastics, and extensive knowledge of the employed bacterial strain's metabolic capabilities is necessary in choosing economically feasible production conditions. This study aimed to create an in-depth view of the utilization of Photobacterium ganghwense C2.2 for PHA production by linking a wide array of characterization methods: metabolic pathway annotation from the strain's complete genome, high-throughput phenotypic tests, and biomass analyses through plate-based assays and flask and bioreactor cultivations. We confirmed, in PHA production conditions, urea catabolization, fatty acid degradation and synthesis, and high pH variation and osmotic stress tolerance. With urea as a nitrogen source, pure and rapeseed-biodiesel crude glycerol were analyzed comparatively as carbon sources for fermentation at 20 °C. Flask cultivations yielded 2.2 g/L and 2 g/L PHA at 120 h, respectively, with molecular weights of 428,629 g/mol and 81,515 g/mol. Bioreactor batch cultivation doubled biomass accumulation (10 g/L and 13.2 g/L) in 48 h, with a PHA productivity of 0.133 g/(L·h) and 0.05 g/(L·h). Thus, phenotypic and genomic analyses determined the successful use of Photobacterium ganghwense C2.2 for PHA production using urea and crude glycerol and 20 g/L NaCl, without pH adjustment, providing the basis for a viable fermentation process.

Production of biopolymers from food waste: Constrains and perspectives

Food is an essential commodity for the survival of any form of life on earth. Yet generation of plethora of food waste has significantly elevated the global concern for food scarcity, human and environment deterioration. Also, increasing use of polymers derived from petroleum hydrocarbons has elevated the concerns towards the depletion of this non-renewable resource. In this review, the use of waste food for the production of bio-polymers and their associated challenges has been thoroughly investigated using scientometric analysis. Various categories of food waste including fruit, vegetable, and oily waste can be employed for the production of different biopolymers including polyhydroxyalkanoates, starch, cellulose, collagen and others. The advances in the production of biopolymers through chemical, microbial or enzymatic process that increases the acceptability of these biopolymers has been reviewed. The comprehensive compiled information may assist researchers for addressing and solving the issues pertaining to food wastage and fossil fuel depletion.

Efficient production of poly-3-hydroxybutyrate from acetate and butyrate by halophilic bacteria Salinivibrio spp. TGB4 and TGB19

Volatile fatty acids (VFAs) derived from biomass are considered to be economical and environmentally friendly feedstocks for microbial fermentation. Converting VFAs to polyhydroxyalkanoate (PHA) could reduce the substrate cost and provide an economically viable route for the commercialization of PHA. The halophilic bacteria Salinivibrio spp. TGB4 and TGB19, newly isolated from salt fields, were found to accumulate poly-3-hydroxybutyrate (PHB) using acetate or butyrate as the substrate. Both strains exhibited considerable cell growth (OD₆₀₀ of ~8) even at acetate concentration of 100 g/L. In shake flask cultures, TGB4 produced PHB titers of 0.90 and 1.34 g/L, while TGB19 produced PHB titers of 0.25 and 2.53 g/L with acetate and butyrate, respectively. When acetate and butyrate were both applied, PHB production was significantly increased, and the PHB titer of TGB4 and TGB19 reached 6.14 and 6.84 g/L, respectively. After optimizing the culture medium, TGB19 produced 8.42 g/L PHB, corresponding to 88.55 wt% of cell dry weight. During fed-batch cultivation, TGB19 produced a PHB titer of 53.23 g/L. This is the highest reported PHB titer using acetate and butyrate by pure microbial cultures and would provide promising hosts for the industrial production of PHA from VFAs.

Advances and trends in microbial production of polyhydroxyalkanoates and their building blocks

With the rapid development of synthetic biology, a variety of biopolymers can be obtained by recombinant microorganisms. Polyhydroxyalkanoates (PHA) is one of the most popular one with promising material properties, such as biodegradability and biocompatibility against the petrol-based plastics. This study reviews the recent studies focusing on the microbial synthesis of PHA, including chassis engineering, pathways engineering for various substrates utilization and PHA monomer synthesis, and PHA synthase modification. In particular, advances in metabolic engineering of dominant workhorses, for example Halomonas, Ralstonia eutropha, Escherichia coli and Pseudomonas, with outstanding PHA accumulation capability, were summarized and discussed, providing a full landscape of diverse PHA biosynthesis. Meanwhile, we also introduced the recent efforts focusing on structural analysis and mutagenesis of PHA synthase, which significantly determines the polymerization activity of varied monomer structures and PHA molecular weight. Besides, perspectives and solutions were thus proposed for achieving scale-up PHA of low cost with customized material property in the coming future.

Dynamics of PHA-Accumulating Bacterial Communities Fed with Lipid-Rich Liquid Effluents from Fish-Canning Industries

The biosynthesis of polyhydroxyalkanoates (PHAs) from industrial wastes by mixed microbial cultures (MMCs) enriched in PHA-accumulating bacteria is a promising technology to replace petroleum-based plastics. However, the populations' dynamics in the PHA-accumulating MMCs are not well known. Therefore, the main objective of this study was to address the shifts in the size and structure of the bacterial communities in two lab-scale sequencing batch reactors (SBRs) fed with fish-canning effluents and operated under non-saline (SBR-N, 0.5 g NaCl/L) or saline (SBR-S, 10 g NaCl/L) conditions, by using a combination of quantitative PCR and Illumina sequencing of bacterial 16S rRNA genes. A double growth limitation (DGL) strategy, in which nitrogen availability was limited and uncoupled to carbon addition, strongly modulated the relative abundances of the PHA-accumulating bacteria, leading to an increase in the accumulation of PHAs, independently of the saline conditions (average 9.04 wt% and 11.69 wt%, maximum yields 22.03 wt% and 26.33% SBR-N and SBR-S, respectively). On the other hand, no correlations were found among the PHAs accumulation yields and the absolute abundances of total Bacteria, which decreased through time in the SBR-N and did not present statistical differences in the SBR-S. Acinetobacter, Calothrix, Dyella, Flavobacterium, Novosphingobium, Qipengyuania, and Tsukamurella were key PHA-accumulating genera in both SBRs under the DGL strategy, which was revealed as a successful tool to obtain a PHA-enriched MMC using fish-canning effluents.

A fermentation process for the production of poly(3-hydroxybutyrate) using waste cooking oil or waste fish oil as inexpensive carbon substrate

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Both WCO and WFO can be used as promising substrates for PHA production.

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First report of a fed-batch fermentation process using WFO as sole carbon source for PHA production.

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High PHB yields of 0.8 g/g and 0.92 g/g were produced from WCO and WFO, respectively.

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Highest PHB productivity (1.73 g/L/h) was achieved when using waste oil as carbon source.

The utilization of waste cooking oil (WCO) or waste fish oil (WFO) as inexpensive carbon substrate for the production of poly(3-hydroxybutyrate) (PHB) by Cupriavidus necator H16 was investigated. Fed-batch cultivation mode in bioreactor was applied in this study. High cell dry weight (CDW) of 135.1 g/L, PHB content of 76.9 wt%, PHB productivity of 1.73 g/L/h, and PHB yield of 0.8 g/g were obtained from WCO. In the case of WFO, the CDW, PHB content, PHB productivity, and PHB yield were 114.8 g/L, 72.5 wt%, 1.73 g/L/h, and 0.92 g/g, respectively. The PHB productivity and yield obtained in the current study from WCO or WFO are among the highest reported so far for PHA production using oils as sole carbon substrate, suggesting that both WCO and WFO can be used as inexpensive carbon substrates for the production of PHA on an industrial scale.

Production of polyhydroxyalkanoates by three novel species of Marinobacterium

Several species of novel marine bacteria from the genus Marinobacterium, including M. nitratireducens, M. sediminicola, and M. zhoushanense were found to be capable of producing polyhydroxyalkanoates (PHA) using sugars and volatile fatty acids (VFAs) as the carbon source. M. zhoushanense produced poly-3-hydroxybutytate (PHB) from sucrose, achieving a product titer and PHB content of 2.89 g/L and 64.05 wt%, respectively. By contrast, M. nitratireducens accumulated 3.38 g/L PHB and 66.80 wt% polymer content using butyrate as the substrate. A third species, M. sediminicola showed favorable tolerance to propionate, butyrate, and valerate. The use of 10 g/L valerate yielded 3.37 g/L poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), with a 3-hydroxyvalerate (3 HV) monomer content of 94.75 mol%. Moreover, M. sediminicola could be manipulated to produce PHBV with changeable polymer compositions by feeding different mixtures of VFAs. Our results indicate that M. sediminicola is a promising halophilic bacterium for the production of PHA.

A review on polyhydroxyalkanoate production from agricultural waste Biomass: Development, Advances, circular Approach, and challenges

Polyhydroxyalkanoates are biopolymers produced by microbial fermentation. They have excellent biodegradability and biocompatibility, which are regarded as promising substitutes for traditional plastics in various production and application fields. This review details the research progress in PHA production from lignocellulosic crop residues, lipid-type agricultural wastes, and other agro-industrial wastes such as molasses and whey. The effective use of agricultural waste can further reduce the cost of PHA production while avoiding competition between industrial production and food. The latest information on fermentation parameter optimization, fermentation strategies, kinetic studies, and circular approach has also been discussed. This review aims to analyze the crucial process of the PHA production from agricultural wastes to provide support and reference for further scale-up and industrial production.

Production of Polyhydroxyalkanoates (PHAs) by Vibrio alginolyticus Strains Isolated from Salt Fields

Vibrio alginolyticus is a halophilic organism usually found in marine environments. It has attracted attention as an opportunistic pathogen of aquatic animals and humans, but there are very few reports on polyhydroxyalkanoate (PHA) production using V. alginolyticus as the host. In this study, two V. alginolyticus strains, LHF01 and LHF02, isolated from water samples collected from salt fields were found to produce poly(3-hydroxybutyrate) (PHB) from a variety of sugars and organic acids. Glycerol was the best carbon source and yielded the highest PHB titer in both strains. Further optimization of the NaCl concentration and culture temperature improved the PHB titer from 1.87 to 5.08 g/L in V. alginolyticus LHF01. In addition, the use of propionate as a secondary carbon source resulted in the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). V. alginolyticus LHF01 may be a promising host for PHA production using cheap waste glycerol from biodiesel refining.

Assessment of Antibiofilm Potencies of Nervonic and Oleic Acid against Acinetobacter baumannii Using In Vitro and Computational Approaches

Acinetobacter baumannii is a nosocomial pathogen, and its biofilms are tolerant to desiccation, nutrient starvation, and antimicrobial treatment on biotic and abiotic surfaces, tissues, and medical devices. Biofilm formation by A. baumannii is triggered by a quorum sensing cascade, and we hypothesized that fatty acids might inhibit its biofilm formation by interfering with quorum sensing. Initially, we investigated the antibiofilm activities of 24 fatty acids against A. baumannii ATCC 17978 and two clinical isolates. Among these fatty acids, two unsaturated fatty acids, nervonic and oleic acid, at 20 μg/mL significantly inhibited A. baumannii biofilm formation without affecting its planktonic cell growth (MICs were >500 μg/mL) and markedly decreased the motility of A. baumannii but had no toxic effect on the nematode Caenorhabditis elegans. Interestingly, molecular dynamic simulations showed that both fatty acids bind to the quorum sensing acyl homoserine lactone synthase (AbaI), and decent conformational stabilities of interactions between the fatty acids and AbaI were exhibited. Our results demonstrate that nervonic and oleic acid inhibit biofilm formation by A. baumannii strains and may be used as lead molecules for the control of persistent A. baumannii infections.

Comparison of Water-Removal Efficiency of Molecular Sieves Vibrating by Rotary Shaking and Electromagnetic Stirring from Feedstock Oil for Biofuel Production

Adequate water-removal techniques are requisite to remain superior biofuel quality. The effects of vibrating types and operating time on the water-removal efficiency of molecular sieves were experimentally studied. Molecular sieves of 3 Å pore size own excellent hydrophilic characteristics and hardly absorb molecules other than water. Molecular sieves of 3 Å accompanied by two different vibrating types, rotary shaking and electromagnetic stirring, were used to remove initial water from the reactant mixture of feedstock oil in order to prevent excessive growth or breeding of microorganisms in the biofuel product. The physical structure of about 66% molecular sieves was significantly damaged due to shattered collision between the magnetic bar and molecular sieves during electromagnetic stirring for 1 h. The molecular sieves vibrated by the rotary shaker appeared to have relatively higher water-removal efficiency than those by the electromagnetic stirrer and by keeping the reactant mixture motionless by 6 and 5 wt.%, respectively. The structure of the molecular sieves vibrated by an electromagnetic stirrer and thereafter being dehydrated appeared much more irregular and damaged, and the weight loss accounted for as high as 19 wt.%. In contrast, the structure of the molecular sieves vibrated by a rotary shaker almost remained original ball-shaped, and the weight loss was much less after regenerative treatment for those molecular sieves. As a consequence, the water-removal process using molecular sieves vibrated by the rotary shaker is considered a competitive method during the biofuel production reaction to achieve a superior quality of biofuels.

Biosynthesis of polyhydroxyalkanoate from food waste oil by Pseudomonas alcaligenes with simultaneous energy recovery from fermentation wastewater

Bioconversion of food waste oil (FWO) into biodegradable plastic is a promising method for converting waste into high-value products. In this study, a strain (Pseudomonas sp. H3) was isolated for polyhydroxyalkanoate (PHA) synthesis from FWO. After 72 h of cultivation with 20 g/L of FWO, the high cell dry weight (CDW) of 3.6 g/L, PHA yield of 2.4 g/L, and PHA content of 65 wt% were obtained under the optimal temperature (25 °C) and inoculum amount (6% (v/v)). Fed-batch fermentation was conducted in a 5 L bioreactor with a maximum CDW of 16 g/L, PHA content of 54 wt%, and PHA productivity of 0.23 g/(L·h) after 36 h. The PHA had a molecular weight of 54 782 Da and a low polydispersity index of 1.41 with glass transition, melting, and degradation temperatures of -20 °C, 34 °C, and 210 °C, respectively. To further utilize the wastewater after PHA production, anaerobic digestion was employed for CH₄ production, and the CH₄ yield was 284 mL/g volatile solids. Microbial community analysis showed that the abundance of acetate-oxidizing bacteria and Methanobacterium significantly increased during anaerobic digestion. This study describes a new strain for the economical synthesis of biodegradable plastics and presents a novel framework for fully utilizing FWO with the production of PHA and CH₄.

Production of polyhydroxyalkanoates by a moderately halophilic bacterium of Salinivibrio sp. TGB10

A moderately halophilic bacterium isolated from the water samples collected from a salt field, Salinivibrio sp. TGB10 was found capable of producing poly-3-hydroxybutytate (PHB) from various sugars. Cell dry weight (CDW) of 8.82 g/L and PHB titer of 6.84 g/L were obtained using glucose as the carbon source after 24 h of cultivation in shake flasks. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was synthesized when propionate was provided as secondary carbon source. Salinivibrio sp. TGB10 exhibited favorable tolerance to propionate. The use of 8 g/L propionate and 20 g/L glucose as combinational substrates yielded 1.45 g/L PHBV with a 3-hydroxyvalerate monomer content of 72.02 mol% in flask cultures. In bioreactor study, CDW of 33.45 g/L and PHBV titer of 27.36 g/L were obtained after 108 h of fed-batch cultivation. The results indicated that Salinivibrio sp. TGB10 is a promising halophilic bacterium for the production of PHBV with various polymer compositions.

Emergent Approaches to Efficient and Sustainable Polyhydroxyalkanoate Production

Petroleum-derived plastics dominate currently used plastic materials. These plastics are derived from finite fossil carbon sources and were not designed for recycling or biodegradation. With the ever-increasing quantities of plastic wastes entering landfills and polluting our environment, there is an urgent need for fundamental change. One component to that change is developing cost-effective plastics derived from readily renewable resources that offer chemical or biological recycling and can be designed to have properties that not only allow the replacement of current plastics but also offer new application opportunities. Polyhydroxyalkanoates (PHAs) remain a promising candidate for commodity bioplastic production, despite the many decades of efforts by academicians and industrial scientists that have not yet achieved that goal. This article focuses on defining obstacles and solutions to overcome cost-performance metrics that are not sufficiently competitive with current commodity thermoplastics. To that end, this review describes various process innovations that build on fed-batch and semi-continuous modes of operation as well as methods that lead to high cell density cultivations. Also, we discuss work to move from costly to lower cost substrates such as lignocellulose-derived hydrolysates, metabolic engineering of organisms that provide higher substrate conversion rates, the potential of halophiles to provide low-cost platforms in non-sterile environments for PHA formation, and work that uses mixed culture strategies to overcome obstacles of using waste substrates. We also describe historical problems and potential solutions to downstream processing for PHA isolation that, along with feedstock costs, have been an Achilles heel towards the realization of cost-efficient processes. Finally, future directions for efficient PHA production and relevant structural variations are discussed.

What Is New in the Field of Industrial Wastes Conversion into Polyhydroxyalkanoates by Bacteria?

The rising global consumption and industrialization has resulted in increased food processing demand. Food industry generates a tremendous amount of waste which causes serious environmental issues. These problems have forced us to create strategies that will help to reduce the volume of waste and the contamination to the environment. Waste from food industries has great potential as substrates for value-added bioproducts. Among them, polyhydroxyalkanaotes (PHAs) have received considerable attention in recent years due to their comparable characteristics to common plastics. These biodegradable polyesters are produced by microorganisms during fermentation processes utilizing various carbon sources. Scale-up of PHA production is limited due to the cost of the carbon source metabolized by the microorganisms. Therefore, there is a growing need for the development of novel microbial processes using inexpensive carbon sources. Such substrates could be waste generated by the food industry and food service. The use of industrial waste streams for PHAs biosynthesis could transform PHA production into cheaper and more environmentally friendly bioprocess. This review collates in detail recent developments in the biosynthesis of various types of PHAs produced using waste derived from agrofood industries. Challenges associated with this production bioprocess were described, and new ways to overcome them were proposed.

A novel strategy for triacylglycerides and polyhydroxyalkanoates production using waste lipids

Lipids are one of the main components of the organic matter present in the effluents of the food-processing industry. These waste streams can be biotransformed into valuable triacylglycerides (TAGs) and polyhydroxyalkanoates (PHAs), precursors of biofuels and biomaterials alternative to petroleum-based products. These compounds are yielded by mixed microbial cultures, and considering that both TAG and PHA accumulators may coexist within the community, it seems crucial to define those operational strategies that might control the selection of the dominant metabolic pathways (TAG or PHA accumulation). In this work, residual fish-canning oil was used as a carbon source in a two-stage process (culture selection and intracellular compounds accumulation) in which the substrate was simultaneously hydrolyzed in these two stages without the need for a previous fermentation unit. It was pretended to maximize preferential TAG or PHA storage in the accumulation reactor by the imposition of certain selective pressures in the enrichment one. Uncoupling C and N feedings and limiting nitrogen availability in the medium, allowed to maximize PHA production (82.3 wt% of PHAs, 0.80 Cmmol_PHA/Cmmol_S). Besides, when low pH in the famine phase was considered as additional selective pressure, it was possible to shift the ratio TAG:PHA from 4:96 obtaining 43.0 wt% of TAGs (0.67 Cmmol_TAG/Cmmol_S). Therefore, this novel and simplified process demonstrated versatility and efficiency in the storage of TAGs and PHAs from a unique residual feedstock and using an open culture proving that product selection can be harnessed if choosing the right operational conditions in the enrichment stage.

A comprehensive overview and recent advances on polyhydroxyalkanoates (PHA) production using various organic waste streams

Polyhydroxyalkanoates (PHA) are appealing as an important alternative to replace synthetic plastics owing to its comparable physicochemical properties to that of synthetic plastics, and biodegradable and biocompatible nature. This review gives an inclusive overview of the current research activities dealing with PHA production by utilizing different waste fluxes generated from food, milk and sugar processing industries. Valorization of these waste fluxes makes the process cost effective and practically applicable. Recent advances in the approaches adopted for waste treatment, fermentation strategies, and genetic engineering can give insights to the researchers for future direction of waste to bioplastics production. Lastly, synthesis and application of PHA-nanocomposites, research and development challenges, future perspectives for sustainable and cost-effective PHB production are also discussed. In addition, the review addresses the useful information about the opportunities and confines associated with the sustainable PHA production using different waste streams and their evaluation for commercial implementation within a biorefinery.

Biowaste-to-bioplastic (polyhydroxyalkanoates): Conversion technologies, strategies, challenges, and perspective

Biowaste management is a challenging job as it is high in nutrient content and its disposal in open may cause a serious environmental and health risk. Traditional technologies such as landfill, bio-composting, and incineration are used for biowaste management. To gain revenue from biowaste researchers around the world focusing on the integration of biowaste management with other commercial products such as volatile fatty acids (VFA), biohydrogen, and bioplastic (polyhydroxyalkanoates (PHA)), etc. PHA production from various biowastes such as lignocellulosic biomass, municipal waste, waste cooking oils, biodiesel industry waste, and syngas has been reported successfully. Various nutrient factors i.e., carbon and nitrogen source concentration and availability of dissolved oxygen are crucial factors for PHA production. This review is an attempt to summarize the recent advancements in PHA production from various biowaste, its downstream processing, and other challenges that need to overcome making bioplastic an alternate for synthetic plastic.

P(3HB-co-4HB) as high value polyhydroxyalkanoate: its development over recent decades and current advances

Polyhydroxyalkanoate (PHA) is a biogenic polymer that has the potential to substitute synthetic plastic in numerous applications. This is due to its unique attribute of being a biodegradable and biocompatible thermoplastic, achievable through microbial fermentation from a broad utilizable range of renewable resources. Among all the PHAs discovered, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] stands out as a next generation healthcare biomaterial for having high biopharmaceutical and medical value since it is highly compatible to mammalian tissue. This review provides a critical assessment and complete overview of the development and trend of P(3HB-co-4HB) research over the last few decades, highlighting aspects from the microbial strain discovery to metabolic engineering and bioprocess cultivation strategies. The article also outlines the relevance of P(3HB-co-4HB) as a material for high value-added products in numerous healthcare-related applications.

Complete genome sequence of Photobacterium ganghwense C2.2: A new polyhydroxyalkanoate production candidate

Polyhydroxyalkanoates (PHAs) are biodegradable bioplastics that can be manufactured sustainably and represent a promising green alternative to petrochemical-based plastics. Here, we describe the complete genome of a new marine PHA-producing bacterium-Photobacterium ganghwense (strain C2.2), which we have isolated from the Black Sea seashore. This new isolate is psychrotolerant and accumulates PHA when glycerol is provided as the main carbon source. Transmission electron microscopy, specific staining with Nile Red visualized via epifluorescence microscopy and gas chromatography analysis confirmed the accumulation of PHA. This is the only PHA-producing Photobacterium for which we now have a complete genome sequence, allowing us to investigate the pathways for PHA production and other secondary metabolite synthesis pathways. The de novo assembly genome, obtained using open-source tools, comprises two chromosomes (3.5, 2 Mbp) and a megaplasmid (202 kbp). We identify the entire PHA synthesis gene cluster that encodes a class I PHA synthase, a phasin, a 3-ketothiolase, and an acetoacetyl-CoA reductase. No conventional PHA depolymerase was identified in strain C2.2, but a putative lipase with extracellular amorphous PHA depolymerase activity was annotated, suggesting that C2.2 is unable to degrade intracellular PHA. A complete pathway for the conversion of glycerol to acetyl-CoA was annotated, in accordance with its ability to convert glycerol to PHA. Several secondary metabolite biosynthetic gene clusters and a low number of genes involved in antibiotic resistance and virulence were also identified, indicating the strain's suitability for biotechnological applications.

Genome Mining Reveals the Biosynthetic Pathways of Polyhydroxyalkanoate and Ectoines of the Halophilic Strain Salinivibrio proteolyticus M318 Isolated from Fermented Shrimp Paste

Salinivibrio proteolyticus M318, a halophilic bacterium isolated from fermented shrimp paste, is able to produce polyhydroxyalkanoate (PHA) from different carbon sources. In this study, we report the whole-genome sequence of strain M138, which comprises 2 separated chromosomes and 2 plasmids, and the complete genome contains 3,605,935 bp with an average GC content of 49.9%. The genome of strain M318 contains 3341 genes, 98 tRNA genes, and 28 rRNA genes. The 16S rRNA gene sequence and average nucleotide identity analysis associated with morphological and biochemical tests showed that this strain has high homology to the reference strain Salinivibrio proteolyticus DSM 8285. The genes encoding key enzymes for PHA and ectoine synthesis were identified from the bacterial genome. In addition, the TeaABC transporter responsible for ectoine uptake from the environment and the operon doeABXCD responsible for the degradation of ectoine were also detected. Strain M318 was able to produce poly(3-hydroxybutyrate) [P(3HB)] from different carbon sources such as glycerol, maltose, glucose, fructose, and starch. The ability to produce ectoines at different NaCl concentrations was investigated. High ectoine content of 26.2% of cell dry weight was obtained by this strain at 18% NaCl. This report provides genetic information regarding adaptive mechanisms of strain M318 to stress conditions, as well as new knowledge to facilitate the application of this strain as a bacterial cell factory for the production of PHA and ectoine.

Utilization of food waste streams for the production of biopolymers

Uncontrolled decomposition of agro-industrial waste leads to extensive contamination of water, land, and air. There is a tremendous amount of waste from various sources which causes serious environmental problems. The concern in the disposal problems has stimulated research interest in the valorization of waste streams. Valorization of the wastes not only reduces the volume of waste but also reduces the contamination to the environment. Waste from food industries has great potential as primary or secondary feedstocks for biopolymer production by extraction or fermentation with pre-treatment or without pre-treatment by solid-state fermentation to obtain fermentable sugars. Various types of waste can be used as substrates for the production of biomaterials but recently more focus has been observed on the agro-industrial wastes which have a high rate of production worldwide. This review collates in detail the different food wastes used for biopolymer, technologies for the production and characterization of the biopolymers, and their economic/technical viability.

Cobetia sp. Bacteria, Which Are Capable of Utilizing Alginate or Waste Laminaria sp. for Poly(3-Hydroxybutyrate) Synthesis, Isolated From a Marine Environment

We isolated the Cobetia sp. strains IU 180733JP01 (5-11-6-3) and 190790JP01 (5-25-4-2) from seaweeds and showed that both strains accumulate poly(3-hydroxybutyrate) [P(3HB)] homopolymer in a nitrogen-limiting mineral salt medium containing alginate as a sole carbon source. Genome sequence analysis of the isolated strains showed that they have putative genes which encode enzymes relevant to alginate assimilation and P(3HB) synthesis, and the putative alginate-assimilating genes formed a cluster. Investigation of the optimum culture conditions for high accumulation of P(3HB) showed that when the 5-11-6-3 strain was cultured in a nitrogen-limiting mineral salt medium (pH 5.0) containing 6% NaCl and 3% (w/v) alginate as a sole carbon source for 2 days, the P(3HB) content and P(3HB) production reached 62.1 ± 3.4 wt% and 3.11 ± 0.16 g/L, respectively. When the 5-25-4-2 strain was cultured in a nitrogen-limiting mineral salt medium (pH 4.0) containing 5% NaCl and 3% (w/v) alginate for 2 days, the P(3HB) content and P(3HB) production reached 56.9 ± 2.1 wt% and 2.67 ± 0.11 g/L, respectively. Moreover, the 5-11-6-3 strain also produced P(3HB) in a nitrogen-limiting mineral salt medium (pH 5.0) containing 6% NaCl and freeze-dried and crushed waste Laminaria sp., which is classified into brown algae and contains alginate abundantly. The resulting P(3HB) content and P(3HB) productivity were 13.5 ± 0.13 wt% and 3.99 ± 0.15 mg/L/h, respectively. Thus, we demonstrated the potential application of the isolated strains to a simple P(3HB) production process from seaweeds without chemical hydrolysis and enzymatic saccharification.