• Biopolymers
• Food waste-derived substrates
• Operating condition analysis

• PHAs
• biosynthesis
• degradable polyhydroxyalkanoates
• fatty acid mixture
• fatty acids
• properties

• 23-64-10007 Russian Science Foundation

• Humans
• Polymers/pharmacology
• Solvents
• Biofouling/prevention & control
• Biocompatible Materials/pharmacology
• Proteins
• Surface Properties

• applications
• bacteria
• feedstock
• metabolism
• polyhydroxyalkanoate
• sustainability

• Humans
• Pandemics
• COVID-19
• Plastics
• Biopolymers
• Polyhydroxyalkanoates
• Biodiversity

• biocomposites
• biopolymers
• renewable sources
• waste valorization
• wood waste

Polyhydroxyalkanoates (PHAs) are bio-based polymers produced in bacterial cells to replace some petrochemical plastics. It has always been a challenge to commercialise PHA due in part to the costly recovery processes of the PHA granules from the bacterial cells. The biological approach of using mealworms, Tenebrio molitor, for the recovery of PHA from the bacterial cells is a newly established method that is at the scale-up stage. On the other hand, the aquaculture feed industry needs a low-cost mealworm meal as a protein source. We aimed at studying the nutritional value of the mealworms (which are by-products) used for the poly(3-hydroxybutyrate) (PHB) (the most common type of PHA) recovery from the bacterial and examining the effect of the mealworms on the growth performance, and feed utilization efficiency of red hybrid tilapia (Oreochromis sp.). The cells were fed to the mealworms to digest the proteinaceous cellular materials and excrete the PHB granules in the form of fecal pellets. The resulting mealworms were used as fishmeal replacement to formulate five isonitrogenous (35% crude protein) and isolipidic (8% lipid) diets at mealworm meal (MwM) inclusion levels of 0% (MwM0/control diet), 25% (MwM25), 50% (MwM50), 75% (MwM75) or 100% (MwM100). The results showed good nutritive value mealworms [high protein (75%), low-lipid (10%)] and up to 75% MwM inclusion diet was good in supplying satisfactory nutrients and energy to the red hybrid tilapia. This approach is beneficial in a way that minimal cost was involved in recovering kilograms of PHB and the proteins, lipids, and minerals from the bacterial cells do not end up as wastes but in turn, are used as nutrition by the larvae.

Cyanobacteria are a promising source for the sustainable production of biodegradable bioplastics such as poly(3-hydroxybutyrate) (PHB). The auto-phototrophic biomass formation is based on light and CO₂, which is an advantage compared to heterotrophic PHB-producing systems. So far, only a handful of cyanobacterial species suitable for the high-yield synthesis of PHB have been reported. In the present study, the PHB formation, biomass, and elemental composition of Leptolyngbya sp. NIVA-CYA 255 were investigated. Therefore, a three-stage cultivation process was applied, consisting of a growth stage; an N-, P-, and NP-depleted phototrophic stage; and a subsequent mixotrophic deficiency stage, initiated by sodium acetate supplementation. The extracted cyanobacterial PHB was confirmed by FTIR- and GC-MS analyses. Furthermore, the fluorescent dyes LipidGreen2 and Nile red were used for fluorescence-based monitoring and the visualization of PHB. LipidGreen2 was well suited for PHB quantification, while the application of Nile red was limited by fluorescence emission crosstalk with phycocyanin. The highest PHB yields were detected in NP- (325 mg g⁻¹) and N-deficiency (213 mg g⁻¹). The glycogen pool was reduced in all cultures during mixotrophy, while lipid composition was not affected. The highest glycogen yield was formed under N-deficiency (217 mg g⁻¹). Due to the high carbon storage capacity and PHB formation, Leptolyngbya sp. NIVA-CYA 255 is a promising candidate for PHB production. Further work will focus on upscaling to a technical scale and monitoring the formation by LipidGreen2-based fluorometry.

• 3-Hydroxybutyric Acid
• Cyanobacteria
• Glycogen
• Hydroxybutyrates
• Polyesters

The ever-increasing use of plastics, their fossil origin, and especially their persistence in nature have started a wave of new innovations in materials that are renewable, offer the functionalities of plastics, and are biodegradable. One such class of biopolymers, polyhydroxyalkanoates (PHAs), are biosynthesized by numerous microorganisms through the conversion of carbon-rich renewable resources. PHA homo- and heteropolyesters are intracellular products of secondary microbial metabolism. When isolated from microbial biomass, PHA biopolymers mimic the functionalities of many of the top-selling plastics of petrochemical origin, but biodegrade in soil, freshwater, and marine environments, and are both industrial- and home-compostable. Only a handful of PHA biopolymers have been studied in-depth, and five of these reliably match the desired material properties of established fossil plastics. Realizing the positive attributes of PHA biopolymers, several established chemical companies and numerous start-ups, brand owners, and converters have begun to produce and use PHA in a variety of industrial and consumer applications, in what can be described as the emergence of the “PHA industry”. While this positive industrial and commercial relevance of PHA can hardly be described as the first wave in its commercial development, it is nonetheless a very serious one with over 25 companies and start-ups and 30+ brand owners announcing partnerships in PHA production and use. The combined product portfolio of the producing companies is restricted to five types of PHA, namely poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), even though PHAs as a class of polymers offer the potential to generate almost limitless combinations of polymers beneficial to humankind. To date, by varying the co-monomer type and content in these PHA biopolymers, their properties emulate those of the seven top-selling fossil plastics, representing 230 million t of annual plastics production. Capacity expansions of 1.5 million t over the next 5 years have been announced. Policymakers worldwide have taken notice and are encouraging industry to adopt biodegradable and compostable material solutions. This wave of commercialization of PHAs in single-use and in durable applications holds the potential to make the decisive quantum leap in reducing plastic pollution, the depletion of fossil resources, and the emission of greenhouse gases and thus fighting climate change. This review presents setbacks and success stories of the past 40 years and the current commercialization wave of PHA biopolymers, their properties, and their fields of application.

Volatile fatty acids obtained from the fermentation of the organic fraction of municipal solid waste can be used as raw materials for non-toxic ethyl ester (EE) synthesis as well as feedstock for the production of polyhydroxyalkanoates (PHAs). Taking advantage of the concept of an integrated process of a bio-refinery, in the present paper, a systematic investigation on the extraction of intracellular poly(3-hydroxybutyrate-co-3-hydroxyvalerate), produced by mixed microbial culture by using EEs was reported. Among the tested EEs, ethyl acetate (EA) was the best solvent, dissolving the copolymer at the lowest temperature. Then, extraction experiments were carried out by EA at different temperatures on two biomass samples containing PHAs with different average molecular weights. The parallel characterization of the extracted and non-extracted PHAs evidenced that at the lower temperature (100 °C) EA solubilizes preferentially the polymer fractions richer in 3HV comonomers and with the lower molecular weight. By increasing the extraction temperature from 100 °C to 125 °C, an increase of recovery from about 50 to 80 wt% and a molecular weight reduction from 48% to 65% was observed. The results highlighted that the extracted polymer purity is always above 90 wt% and that it is possible to choose the proper extraction condition to maximize the recovery yield at the expense of polymer fractionation and degradation at high temperatures or use milder conditions to maintain the original properties of a polymer.

• PHA extraction
• downstream processing
• ethyl esters
• mixed microbial culture
• molecular weight
• polyhydroxyalkanoates

• PHA
• Polyhydroxyalkanoate
• downstream processing
• high cell density cultivations
• production
• productivity

• Biomedical devices
• Drug delivery
• Exopolysaccharides
• Polyhydroxyalkanoates

• Animals
• Biopolymers/chemistry
• Humans
• Hydroxybutyrates/chemistry
• Polyesters/chemistry
• Polyhydroxyalkanoates/chemistry
• Polysaccharides/chemistry

• Bioplastic
• Environmental assessment
• LCA
• LCC
• Urban biowaste

• Biofuels
• Food
• Polyhydroxyalkanoates
• Refuse Disposal
• Sewage

• Contaminants control
• Lipids
• Mixed microbial cultures
• Nitrogen starvation
• PHA
• Uncoupled nutrients

• Bacteria/metabolism
• Biofuels
• Biomass
• Industrial Microbiology
• Lipids
• Microalgae/metabolism
• Nitrogen/metabolism
• Polysaccharides
• Yeasts/metabolism

• Contamination control
• Feast-famine
• Mixed microbial cultures
• Polyhydroxyalkanoates
• Starvation
• Storage compound accumulation
• Strain selection
• Triacylglycerols
• Uncoupled C/N feeding
• Wastewater treatment

• cell lysis
• extraction methods
• green solvents
• mixed microbial cultures
• polyhydroxyalkanoates
• single microbial strains
• surfactants

• biopolymer
• biorefinery
• circular economy
• cyanobacteria
• polyhydroxyalkanoate
• waste

• Biotechnology
• Cyanobacteria/metabolism
• Green Chemistry Technology/methods
• Plastics/chemistry
• Plastics/metabolism
• Polyhydroxyalkanoates/biosynthesis
• Polyhydroxyalkanoates/chemistry

• 88882.445488/2019-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

• P(HB-co-HHx)
• Ralstonia eutropha
• medium chain length PHA
• molecular weight
• multi-stage extraction
• non-halogenated solvents
• polyhydroxyalkanoate
• recovery

• Carotenoids
• Hydrogen
• Nutrient recovery
• Polyhydroxyalkanoates
• Purple non‑sulfur bacteria
• Purple sulfur bacteria
• Single-cell protein
• Waste
• Wastewater

Poly-β-hydroxybutyrate (PHB) in cyanobacteria, which accumulates as energy and carbon sources through the action of photosynthesis, is expected to substitute for petroleum-based plastics. This study first demonstrated that PHB accumulation was induced, with the appearance of lipid droplets, in sulfur (S)-starved cells of a cyanobacterium, Synechocystis sp. PCC 6803, however, to a lower level than in nitrogen (N)- or phosphorus (P)-starved cells. Concomitantly found was repression of the accumulation of total cellular proteins in the S-starved cells to a similar level to that in N-starved cells, and a severer level than in P-starved cells. Intriguingly, PHB accumulation was induced in Synechocystis even under nutrient-replete conditions, upon repression of the accumulation of total cellular proteins through treatment of the wild type cells with a protein synthesis inhibitor, chloramphenicol, or through disruption of the argD gene for Arg synthesis. Meanwhile, the expression of the genes for PHB synthesis was hardly induced in S-starved cells, in contrast to their definite up-regulation in N- or P-starved cells. It therefore seemed that PHB accumulation in S-starved cells is achieved through severe repression of protein synthesis, but is smaller than in N- or P-starved cells, owing to little induction of the expression of PHB synthesis genes.

The negative effects of petrochemical-derived plastics on the global environment and depletion of global fossil fuel supplies have paved the way for exploring new technologies for the production of bioplastics. Polyhydroxyalkanoates (PHAs) are considered an alternative for synthetic polymers because of their biodegradability, biocompatibility, and non-toxicity. Many bacteria have been reported to have the ability to synthesize PHAs. Among them, the Aeromonas species seem to be ideal hosts for the industrial production of these biopolyesters due to their robust growth, simple growth requirements, their ability for the synthesis of homopolymers, co-polymers, and terpolymers with unique material properties. Some Aeromonas strains were able to produce PHAs in satisfactory amounts from simple carbon sources. Efforts have been made to use genetically modified Aeromonas strains for enhanced PHAs and to obtain bacteria with modified compositions and improved properties. This review discusses the current state of knowledge of polyhydroxyalkanoates synthesized by Aeromonas species, with a special focus on their potential, challenges, and progress in PHA synthesis.

• Aeromonas spp.
• biodegradable polymers
• biopolymers
• polyhydroxyalkanoates

• Bacillus megaterium Ti3
• Enzyme based extraction
• Lytic assay
• P3HB
• PHA recovery
• Streptomyces albus Tia1

Microbial polyhydroxyalkanoates (PHAs) are promising biodegradable polymers that may alleviate some of the environmental burden of petroleum-derived polymers. The requirements for carbon substrates and energy for bioreactor operations are major factors contributing to the high production costs and environmental impact of PHAs. Improving the process productivity is an important aspect of cost reduction, which has been attempted using a variety of fed-batch, continuous, and semi-continuous bioreactor systems, with variable results. The purpose of this review is to summarize the bioreactor operations targeting high PHA productivity using pure cultures. The highest volumetric PHA productivity was reported more than 20 years ago for poly(3-hydroxybutryate) (PHB) production from sucrose (5.1 g L⁻¹ h⁻¹). In the time since, similar results have not been achieved on a scale of more than 100 L. More recently, a number fed-batch and semi-continuous (cyclic) bioreactor operation strategies have reported reasonably high productivities (1 g L⁻¹ h⁻¹ to 2 g L⁻¹ h⁻¹) under more realistic conditions for pilot or industrial-scale production, including the utilization of lower-cost waste carbon substrates and atmospheric air as the aeration medium, as well as cultivation under non-sterile conditions. Little development has occurred in the area of fully continuously fed bioreactor systems over the last eight years.

• PHAs
• bioreactor
• continuous fermentation
• fed-batch fermentation
• polyhydroxyalkanoates
• productivity
• scale-up

• Burkholderia sacchari
• Levulinic acid
• Poly-3-hydroxybutyrate-block-3-hydroxyvalerate
• Xylose

• Burkholderia
• Hydroxybutyrates
• Levulinic Acids
• Polyesters
• Polyhydroxyalkanoates
• Tandem Mass Spectrometry
• Xylose

• Bacteria
• Biodiesel
• Biomaterial
• Carbon dioxide sequestration
• Microorganisms

• Bacteria
• Biocompatible Materials
• Biofuels
• Carbon
• Carbon Dioxide
• Greenhouse Effect
• Humans

• Bacteria/chemistry
• Bacteria/classification
• Bacteria/genetics
• Bacteria/metabolism
• Bacterial Proteins/chemistry
• Bacterial Proteins/genetics
• Bacterial Proteins/metabolism
• Phylogeny
• Plant Lectins/chemistry
• Plant Lectins/genetics
• Plant Lectins/metabolism
• Polyhydroxyalkanoates/metabolism

Phasins are unusual amphiphilic proteins that bind to microbial polyhydroxyalkanoate (PHA) granules in nature and show great potential for various applications in biotechnology and medicine. Despite their remarkable diversity, only the crystal structure of PhaP_Ah from Aeromonas hydrophila has been solved to date. Based on the structure of PhaP_Ah, homology models of PhaP_Az from Azotobacter sp. FA‐8 and PhaP_TD from Halomonas bluephagenesis TD were successfully established, allowing rational mutagenesis to be conducted to enhance the stability and surfactant properties of these proteins. PhaP_Az mutants, including PhaP_AzQ38L and PhaP_AzQ78L, as well as PhaP_TD mutants, including PhaP_TDQ38M and PhaP_TDQ72M, showed better emulsification properties and improved thermostability (6‐10°C higher melting temperatures) compared with their wild‐type homologues under the same conditions. Importantly, the established PhaP homology‐modelling approach, based on the high‐resolution structure of PhaP_Ah, can be generalized to facilitate the study of other PhaP members.

Polyhydroxyalkanoates (PHAs) are a group of bioplastics that have a wide range of applications. Extensive progress has been made in our understanding of PHAs’ biosynthesis, and currently, it is possible to engineer bacterial strains to produce PHAs with desired properties. The substrates for the fermentative production of PHAs are primarily derived from food-based carbon sources, raising concerns over the sustainability of their production in terms of their impact on food prices. This paper gives an overview of the current carbon sources used for PHA production and the methods used to transform these sources into fermentable forms. This allows us to identify the opportunities and restraints linked to future sustainable PHA production. Hemicellulose hydrolysates and crude glycerol are identified as two promising carbon sources for a sustainable production of PHAs. Hemicellulose hydrolysates and crude glycerol can be produced on a large scale during various second generation biofuels’ production. An integration of PHA production within a modern biorefinery is therefore proposed to produce biofuels and bioplastics simultaneously. This will create the potential to offset the production cost of biofuels and reduce the overall production cost of PHAs.

• biorefinery
• carbon sources
• microorganisms
• polyhydroxyalkanoates

• biodegradable scaffolds
• bone tissue regeneration
• osteoinductivity
• polyhydroxyacids
• tissue engineering

• Decanoic acid
• Fed-batch
• Fermentation
• MCL-PHA
• Medium-chain-length poly-3-hydroxyalkanoate
• Pseudomonas putida

• Activated sludge
• High-throughput sequencing
• PHBHHx
• Sodium laurate

• 3-Hydroxybutyric Acid/biosynthesis
• Aerobiosis/drug effects
• Bacteria/drug effects
• Bacteria/genetics
• Bacteria/metabolism
• Base Sequence
• Batch Cell Culture Techniques
• Biological Oxygen Demand Analysis
• Biotechnology/methods
• Caproates
• Carbon/pharmacology
• Genetic Variation
• Nitrogen/pharmacology
• Phosphorus/pharmacology
• RNA, Ribosomal, 16S/genetics
• Sewage/chemistry
• Sewage/microbiology
• Time Factors