Polyhydroxyalkanoates are a class of biodegradable homopolymers and copolymers whose material properties can rival those of conventional plastics. Microorganisms including bacteria, archaea and algae synthesize them as intracellular carbon and energy storage compounds, packaging the polymer into granules known as carbonosomes, which typically measure between 0.2 and 0.5 micrometers across. These inclusions are built from sugars, waste materials, lipids, or even greenhouse gases such as methane and carbon dioxide. The biosynthetic pathway hinges on three key enzymes: β-ketothiolase (PhaA), NADP-dependent acetoacetyl-CoA reductase (PhaB), and above all the PHA synthase PhaC, the central polymerization enzyme whose substrate specificity determines which R-hydroxyacyl-CoA monomers are threaded into the growing chain. Because managing plastic waste is becoming ever harder and the natural resources needed for conventional plastic production are being depleted, the search for organisms that can make PHAs efficiently, and cheaply, has taken on real urgency.

The ocean has long been viewed as a promising but underexplored hunting ground for such organisms. Marine microbes are exposed to dynamic swings in temperature, salinity and nutrient availability, including transient nutrient surges during algal blooms, conditions that favor the conversion of surplus carbon into storage compounds like PHA. Stress conditions in general tend to boost PHA accumulation, and halophiles isolated from marine settings have been reported to produce significant quantities of the polymers. Yet the logistical and technical challenges of sampling and cultivating ocean microorganisms have left much of this diversity hidden. Metagenomics sidesteps that problem entirely: by sequencing the collective genetic material of an entire environmental community, researchers can access the metabolic potential of organisms that have never been grown in a laboratory dish.

For this study, the team did not collect the water themselves. Instead, they retrieved a publicly available shotgun metagenomic dataset from the NCBI Sequence Read Archive under accession number SRR31715427, originally generated by the China University of Geosciences in Wuhan as part of a project on marine metagenome genome sequencing and assembly. The sample came from the deep chlorophyll maximum of the Western Pacific Ocean at coordinates 129.9996883°E, 13.9995375°N. The choice of the DCM layer was deliberate. Because this subsurface zone hosts elevated carbon sequestration and biogeochemical cycling alongside high biomass, the researchers reasoned that it should support specialized microbial communities, including organisms capable of synthesizing unusual biopolymers.

The computational pipeline behind the analysis was rigorous and multi-stage. Raw paired-end Illumina reads were first assessed with FastQC and trimmed using Trimmomatic, with only reads retaining Phred quality scores above 30, corresponding to 99.9 percent base-call accuracy, kept for assembly; reads shorter than 50 base pairs were discarded. The filtered reads were then assembled with MEGAHIT, a de Bruijn graph-based assembler optimized for complex metagenomic data, which adaptively selected k-mer sizes from 21 to 141 to maximize contiguity. From 57,552 assembled contigs, the team used MaxBin2, an expectation-maximization algorithm that clusters contigs into metagenome-assembled genomes, or MAGs, based on tetranucleotide frequencies, GC content and read coverage. Only bins meeting a completeness threshold of at least 70 percent and contamination below 10 percent, as assessed by CheckM, were carried forward, ultimately yielding 29 high-quality MAGs for detailed annotation.

Functional annotation proceeded through several complementary tools. Prokka and RASTtk identified coding sequences and assigned genes to metabolic pathways, while DRAM, the Distilled and Refined Annotation of Metabolism tool, performed in-depth metabolic reconstruction by drawing on databases including KEGG Orthology, Pfam, TIGRFAMs and UniRef90. PHA-related genes were verified using Hidden Markov Models against Pfam and TIGRFAMs, with only protein domain hits showing E-values below 1e-10 and alignment coverage greater than 70 percent counted as significant. Taxonomic identities were assigned with GTDB-Tk, which aligns conserved marker genes against the curated Genome Taxonomy Database, and a phylogenomic tree was built from 120 bacterial and 122 archaeal single-copy marker genes using FastTree, with bootstrap support values above 70 percent considered reliable.

The results were striking in both scale and breadth. Across the high-quality MAGs, the team identified a total of 34 putative PHA-related genes, spanning Class I through Class III PHA synthases, depolymerases encoded by phaZ, and accessory proteins such as phaP, the granule-associated phasin, and phaJ, an enoyl-CoA hydratase. Of the 58 assembled bins, 18 contained organisms with putative genes for PHA metabolism, and taxonomic classification showed that 83 percent of these were bacteria while 17 percent were archaea. Among the bacteria, the phylum Pseudomonadota dominated, accounting for roughly 60 percent of PHA gene contributors, with the Alphaproteobacteria subgroup alone representing 28 percent, followed by Gammaproteobacteria. Other notable bacterial phyla included Planctomycetota, Verrucomicrobiota, Chloroflexota, Acidobacteriota and Myxococcota.

The archaeal findings may be the most intriguing part of the study. Within the archaeal fraction, the phylum Thermoplasmatota accounted for about 67 percent of PHA gene-harboring bins, followed by Thermoproteota. These archaea harbored Class III-type phaC genes and accessory elements, suggesting a role in PHA granule formation under marine conditions. While PHA biosynthesis is well characterized in bacteria, its presence in archaea points to broader evolutionary conservation and a reservoir of underexplored enzymatic diversity. The observation complements experimental work on haloarchaea such as Haloferax mediterranei, where homologous overexpression of PHA synthase genes has been shown to significantly increase PHBV yield and 3-hydroxyvalerate content, underscoring the industrial potential of extremophilic production systems.

Equally significant was the functional picture that emerged. DRAM-based annotation confirmed complete PHA biosynthetic pathways in many MAGs, including the full complement of core enzymes needed to convert precursors such as acetyl-CoA and propionyl-CoA into polymerizable hydroxyalkanoate monomers. The Pseudomonadota MAGs encoded both Class I synthases, which polymerize short-chain-length substrates of 3 to 5 carbons, and Class II synthases, which handle medium-chain-length monomers of 6 to 14 carbons, alongside regulatory proteins hinting at dynamic control of synthesis in response to environmental conditions. Crucially, many MAGs also encoded phaZ depolymerases, and the co-occurrence of biosynthesis and degradation genes suggests these microbes can perform dynamic PHA metabolism, likely a survival strategy in nutrient-limited waters. The phylogenetic tree showed PHA-producer genomes dispersed across multiple lineages, some clustering near known producers such as Shewanella and others belonging to novel or uncultured clades, a pattern consistent with convergent evolution of PHA gene clusters.

The authors are careful to note the limits of the approach. The presence of PHA-associated genes is a strong indicator of metabolic potential, but it does not conclusively demonstrate active synthesis or degradation under natural conditions. Future work will need to isolate and cultivate these organisms, validate enzymatic activity experimentally, and characterize the enzymes structurally through crystallography or cryo-electron microscopy, while integrating meta-transcriptomic and proteomic data to reveal how PHA metabolism is regulated in situ. Even so, the implications are considerable. Marine PHA producers with innate stress tolerance could be harnessed for non-sterile, open-system fermentations, cutting process costs and improving economic feasibility, and the identified depolymerases, with their notable stability and substrate specificity, could support PHA circularity and biodegradation applications. The study, its authors conclude, expands the genomic landscape of PHA-producing microorganisms in oceanic environments and reinforces the marine microbiome as a valuable yet underutilized reservoir for the bio-based materials industry.

Subject of Research: Metagenomic discovery of polyhydroxyalkanoate biosynthetic genes in marine microorganisms from the Western Pacific Ocean

Article Title: Metagenomic mining of microorganisms for polyhydroxyalkanoate (PHA) biosynthetic genes from marine sample of the Western Pacific Ocean

Article References: Tiwari, K. N., Ezhava, S. R., & Rodge, S. P. (2026). Metagenomic mining of microorganisms for polyhydroxyalkanoate (PHA) biosynthetic genes from marine sample of the Western Pacific Ocean. Discover Oceans, 3(1), Article 13. https://doi.org/10.1007/s44289-026-00132-6

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00132-6

Keywords: polyhydroxyalkanoates, metagenomics, marine microbiology, bioplastics, Western Pacific Ocean, metagenome-assembled genomes, PHA synthase, Thermoplasmatota, Pseudomonadota, biodegradable polymers, deep chlorophyll maximum, microbial biotechnology

The scale of the challenge is enormous. Population growth and rapid economic development have intensified global water shortages, while wastewater streams from domestic, municipal, industrial, agricultural and aquaculture activities carry nitrogen, phosphorus, heavy metals and high chemical oxygen demand into the environment. Conventional treatment processes, while useful, come with significant drawbacks, including greenhouse gas emissions, high energy requirements and nutrient-rich discharges. The review emphasizes that to build a sustainable future and support the circular economy, waste should be converted into valuable resources for recycling and reuse rather than simply discarded. Microalgae, with their ability to fix carbon dioxide and strip pollutants from water, offer an elegant biological solution that produces something useful in the process.

Among the many genera studied, Chlorella species stand out for their versatility in treating municipal wastewater at multiple stages, from pre-settling to post-activated sludge. But the review highlights that the real magic often happens in partnership. Many microalgae form symbiotic relationships with aerobic and anaerobic bacteria and fungi, and these consortia can dramatically improve treatment outcomes. In one striking example, bacteria coexisting with Chlorella pyrenoidosa in soybean processing wastewater enhanced the biodegradation of glucose, nitrogen, phosphorus and chemical oxygen demand. Bacterial partners synthesize antibiotics, growth stimulants, micronutrients, siderophores and vitamin B12 that support algal growth while protecting the algae from pathogens. In poultry wastewater, bacteria reduced nitrogen and organic matter while releasing carbon dioxide that the algae consumed, with the algae reciprocating with dissolved oxygen.

The technical details of cultivation matter enormously to the economics. Microalgae are grown in open raceway ponds or closed photobioreactors, using water, atmospheric carbon dioxide and nutrient-rich media. Because water itself contributes heavily to operational costs, substituting wastewater as the growth medium is a major economic lever. Yet raw wastewater can be too harsh for sensitive strains, so pretreatment or dilution is often essential. Studies cited in the review show that titanium oxide plus intense pulse light pretreatment of swine wastewater boosted growth of Tribonema and Synechocystis species, while diluting textile wastewater to 50 percent increased Chlorella vulgaris biomass suitable for biofuel production. Under tropical conditions, Arthrospira achieved 84 to 96 percent removal of ammoniacal nitrogen and 72 to 87 percent phosphorus removal in outdoor raceway ponds, and olive oil mill wastewater treated with microalgae yielded 73 percent chemical oxygen demand removal along with complete elimination of phenols, phosphorus and nitrates.

What makes this approach commercially compelling is the sheer value of what the algae produce. Countries including China, Germany, Japan and Taiwan collectively yield roughly 19,000 tonnes of dehydrated microalgal biomass annually, generating a turnover of 5.7 billion US dollars through derived high-value products. The biomass contains lipids, proteins, pigments, carbohydrates, vitamins and minerals that can be converted into biofuels such as biogas, biodiesel, bio-hydrogen, bioethanol and biobutanol through thermochemical and biological routes. Third-generation biofuels from microalgae avoid the food-versus-fuel conflicts of earlier generations, and when combined with co-product extraction, the economics improve substantially. The review notes that pyrolysis of microalgae also yields astaxanthin, carotenoids, phycocyanin, fatty acids, lectins and polysaccharides, creating multiple revenue streams from a single feedstock.

Pigments represent some of the most lucrative products in the microalgal portfolio. Phycocyanin, the brilliant blue water-soluble protein extracted mainly from red algae and cyanobacteria, is projected to reach a global market value of 245.5 million dollars by 2027. Spirulina, or Arthrospira platensis, remains the primary industrial source, supplying powder and aqueous formulations for cosmetics, food and analytical applications. Beyond its role as a natural colorant replacing synthetic dyes with their adverse effects, phycocyanin exhibits immunomodulating, antioxidant, anti-nephrolith and anti-cancer activities, and its fluorescence properties have inspired phycofluor probes for immunodiagnostics and biosensors capable of detecting heavy metals like mercury at low concentrations. Phycoerythrin, a 263-kilodalton phycobiliprotein from Porphyridium species, has been produced in quantity from microalgae grown in slaughterhouse wastewater, demonstrating that even the most challenging effluents can support premium product formation.

Carotenoids form another pillar of the value proposition. Astaxanthin, a naturally occurring keto-carotenoid, boasts antioxidant power approximately 1,000 times greater than vitamin E and ten times greater than other microalgal carotenoids. Its annual market value has surpassed 550 million US dollars, with Haematococcus pluvialis and Chlorella zofingiensis serving as the main producers. Researchers have grown these species in palm oil mill effluent, achieving phycoremediation and astaxanthin production simultaneously, and two-stage LED lighting strategies have further enhanced yields. Fucoxanthin, a xanthophyll from brown algae and diatoms, commands prices between 40,000 and 80,000 US dollars per kilogram for pure material, with a global market estimated at roughly 600 million dollars in 2020. The diatom Phaeodactylum tricornutum, grown in diluted swine wastewater, produced high fucoxanthin yields while removing toxic nutrients, and the Israeli firm Algatechnologies launched the first commercial microalgal fucoxanthin product, Fucovital, in 2018 using closed tubular photobioreactors.

Beyond pigments, the biochemical versatility of wastewater-grown microalgae extends into nutrition and materials science. Under stress conditions, microalgae can accumulate up to 60 percent triacylglycerols, providing viable biodiesel feedstock, with wastewater-derived biodiesel reaching 0.40 to 0.78 tonnes per hectare per year. Polyunsaturated fatty acids such as omega-3, EPA and DHA, produced by species like Nannochloropsis oceanica cultivated in industrial effluents, can replace fish oil in aquaculture feeds. Spirulina strains contain gamma-linolenic acid at levels rivaling the best plant sources, and Arthrospira biomass is roughly 70 percent protein by dry weight with digestibility of 83 to 90 percent. Microalgae also synthesize polyhydroxyalkanoates, biodegradable biopolyesters with thermoplastic and elastomeric qualities that promise alternatives to conventional plastics, and their biomass serves as biofertilizer, with field trials in Indian paddy systems showing doubled chlorophyll and carbohydrate content in algal mats and significantly enriched iron, magnesium and calcium in rice grains.

The review also points to genetic engineering as the next frontier. Advances in CRISPR gene editing and omics technologies have opened unprecedented prospects for creating modified microalgal strains with elevated pigment production and tailored metabolic pathways. Promoters, gene vectors, selection markers and gene editors are now available for rewiring microalgal metabolism, potentially enabling fourth-generation energy feedstocks and enhanced secondary metabolite output. Yet the authors caution that commercialization remains hindered by high cultivation costs, and that most products derive from only a handful of genera. Poor productivity, slow growth rates, lack of robustness and continued reliance on conventional technology explain why only around fifteen strains are cultivated at industrial scale despite tens of thousands of known species. Optimized upstream and downstream processing, combined with symbiotic co-cultivation systems and strategic wastewater pretreatment, will be crucial to closing the gap between laboratory promise and full-scale operation.

The vision that emerges from this synthesis is one of integrated biorefineries where wastewater treatment, carbon dioxide fixation and high-value product generation happen in a single loop. Combining pigment extraction with biogas production from residual biomass, for instance, yields an estimated 5 to 10 percent additional energy recovery while advancing circular economy goals. The authors argue that collaborative efforts among researchers, industries and policymakers will be decisive in scaling microalgae-based wastewater treatment, and that sustained investment in research and development can unlock the full potential of these organisms. If the technical and economic barriers fall, the humble microalga could become a cornerstone of sustainable resource management, simultaneously delivering cleaner water, renewable fuels, nutritious foods, natural colorants and biodegradable materials from streams we currently flush away.

Subject of Research: Microalgae-based wastewater treatment and biorefinery production of high-value products

Article Title: Microalgae cultivation and value-based products from wastewater: insights and applications

Article References: Microalgae cultivation and value-based products from wastewater: insights and applications. (n.d.). https://doi.org/10.1186/s44315-024-00019-1

Image Credits: AI Generated

DOI: 10.1186/s44315-024-00019-1

Keywords: microalgae, wastewater treatment, phycoremediation, biorefinery, phycocyanin, astaxanthin, fucoxanthin, biodiesel, circular economy, nutraceuticals, polyhydroxyalkanoates, biofertilizers

The research team focused on third-instar Drosophila melanogaster larvae, the maggot-like stage of one of biology’s most intensively studied model organisms. Larvae were exposed for 96 hours through their diet to 5-micrometer PHA particles at three concentrations: 0.25, 2.5, and 7.5 milligrams per liter. These doses were deliberately sublethal, meaning the larvae survived the exposure. The question was not whether the particles killed the animals, but whether they changed how the animals behaved, a subtler class of toxicity that ecologists increasingly recognize as critically important for survival in the wild.

To capture those behavioral changes with precision, the researchers turned to SLEAP, a deep-learning system for multi-animal pose tracking originally developed by computational biologists and published in Nature Methods. Rather than relying on human observers to eyeball crawling larvae, the system uses neural networks to track body positions frame by frame, converting hours of video into quantitative trajectories. From these trajectories, the team extracted speed and angular-speed interval distributions along with nine spatial features, including total distance travelled, displacement, path straightness, convex-hull perimeter and area, and radius of gyration, a measure of how far an animal roams from the center of its activity.

The results were striking at the highest dose. Compared with unexposed control larvae, animals exposed to 7.5 milligrams per liter of PHA particles crawled 37.8 percent more slowly on average and covered 40.7 percent less distance. The distribution of speeds shifted in a telling way: larvae spent more time in the low-speed category and less time in the medium- and high-speed categories. In other words, exposed larvae were not simply moving at a uniformly reduced pace; they were spending a larger fraction of their time nearly stationary, a pattern consistent with impaired or disorganized locomotor function.

The spatial features told a complementary story. Exposed larvae showed reduced displacement, meaning they ended up farther from where their normal trajectories would have carried them, and reduced path straightness, indicating more meandering, less directed movement. Their convex-hull perimeter and area, which describe the spatial footprint of their wandering, shrank, as did their radius of gyration. Together these measures paint a picture of larvae confined to smaller, less purposeful territories, exploring less of their environment than their unexposed counterparts.

Intriguingly, angular speed behaved differently from linear speed. The occupancy of angular-speed categories shifted from the low category toward the medium and high categories, suggesting exposed larvae made more frequent or sharper turns, yet the mean angular speed itself did not differ significantly among the treatment groups. This dissociation between linear and rotational movement is exactly the kind of nuance that only high-resolution, machine-learning-based tracking can reveal, and it hints that PHA particles may affect the neural or muscular control of crawling in ways that a simple speed measurement would miss entirely.

Perhaps most concerning from an environmental standpoint, the study detected effects even at the lowest concentration tested. Changes in the proportion of time spent at low speeds and low angular speeds were evident at 0.25 milligrams per liter, the mildest exposure in the experiment. While the broadest and most severe response occurred at 7.5 milligrams per liter, the fact that subtle alterations appeared at the low end of the dose range suggests that the behavioral effects of biodegradable microplastics may begin at concentrations lower than those typically flagged as hazardous in conventional toxicity testing.

Why does larval crawling matter? Locomotion is not a luxury for a fruit fly larva; it is the engine of survival. Larvae rely on crawling to find food, occupy suitable habitats, disperse across their environment, and escape predators and other threats. A larva that moves nearly 40 percent less distance and wanders less effectively is a larva that feeds less efficiently, disperses less successfully, and may be more vulnerable to predation. The authors argue that these coordinated changes constitute an ecologically relevant effect, one that could translate into real consequences for insect populations even when no individual animal dies. Behavioral ecotoxicology has increasingly emphasized that sublethal effects on movement, foraging, and escape responses can ripple through food webs in ways that lethality assays never capture.

The study arrives at a moment of rapid growth for the bioplastics industry. European Bioplastics market updates report continued expansion in biodegradable polymer production, and PHAs in particular have been celebrated as the greenest plastics so far, because bacteria synthesize them naturally and soil microbes can break them down. But the new findings join a growing body of evidence that biodegradable does not mean harmless. Previous work has documented that incomplete degradation can leave PHA-derived particles in soil and water, that secondary nanoplastics released from biodegradable microplastics can severely impact freshwater environments, and that poly-3-hydroxybutyrate, a common PHA, can exert acute, chronic, and multigenerational effects on the water flea Daphnia magna. Related studies have shown hazardous effects of polylactic acid nanoplastics in Drosophila, another widely used bioplastic.

The broader lesson is that the environmental fate of biodegradable plastics deserves the same scrutiny applied to conventional polymers. Degradation is a process, not an instant, and during the window between release and full breakdown, bioplastic particles behave much like any other microplastic: small, persistent, and available for ingestion by organisms at every trophic level. Feng and Shen’s findings show that biodegradable-polymer particles can elicit sublethal effects in terrestrial insects, a group that has received far less attention than aquatic organisms in microplastics research, and the authors argue that such particles warrant inclusion in ecological hazard assessment. As bioplastics flood into packaging, agriculture, and consumer products, the study serves as a timely reminder that solving the plastic problem requires not just swapping materials, but rigorously testing what those new materials do once they fragment into the environment, one crawling larva at a time.

Subject of Research: Sublethal behavioral toxicity of biodegradable polyhydroxyalkanoate microplastics in Drosophila melanogaster larvae

Article Title: Behavioral toxicity of polyhydroxyalkanoate microplastics in Drosophila melanogaster larvae revealed by deep-learning pose estimation

Article References: Feng, F., & Shen, J. (2026). Behavioral toxicity of polyhydroxyalkanoate microplastics in Drosophila melanogaster larvae revealed by deep-learning pose estimation. Ecotoxicology, 35(8), Article 179. https://doi.org/10.1007/s10646-026-03162-0

Image Credits: AI Generated

DOI: 10.1007/s10646-026-03162-0

Keywords: polyhydroxyalkanoates, biodegradable plastics, microplastics, Drosophila melanogaster, locomotor behavior, SLEAP, deep learning, pose estimation, ecotoxicology, sublethal effects, behavioral toxicity, terrestrial insects

The scale of the problem the authors address is staggering. Since the 1950s, humanity has produced billions of tonnes of plastic, the vast majority of which has never been recycled and instead accumulates in landfills, rivers, and oceans. Microplastics and nanoplastics are now documented in marine and terrestrial ecosystems, in the guts of animals ranging from whales to earthworms, and even in the human digestive tract, where recent studies have identified PET-degrading enzyme candidates in the gut microbiome. Beyond the physical contamination, the plastic lifecycle contributes substantially to greenhouse gas emissions, linking the pollution crisis directly to climate change. Conventional mechanical recycling degrades polymer quality with each cycle, and chemical recycling often demands intense heat and petrochemical inputs, which is precisely why biological routes have attracted such intense scientific attention.

The turning point in plastic biodegradation came in 2016, when Japanese researchers described Ideonella sakaiensis, a bacterium capable of degrading and assimilating polyethylene terephthalate, the ubiquitous plastic known as PET. The bacterium deploys two enzymes in sequence: PETase, which hydrolyzes the polymer into mono-(2-hydroxyethyl) terephthalate (MHET) and related intermediates, and MHETase, which cleaves those intermediates into the monomers terephthalic acid and ethylene glycol. That discovery ignited a global hunt for plastic-degrading enzymes, and subsequent surveys have found PETase-like enzymes with functional motifs distributed across the world’s oceans, in glaciers, in deep-sea sediments, and among uncultured marine microorganisms. Machine learning and multi-omics databases such as PAZy and PlasticEnz are now accelerating the discovery of previously hidden candidate enzymes, dramatically expanding the known catalytic repertoire.

Wild-type enzymes, however, are far too slow for industrial use, and this is where enzyme engineering has transformed the field. Directed evolution campaigns have produced thermostable PET depolymerases that operate at temperatures approaching the glass transition of PET, where the polymer chains become more mobile and accessible. Computational redesign strategies, including the GRAPE approach and machine learning-aided hydrolase engineering published in Nature, have yielded variants capable of nearly complete PET depolymerization at industrially relevant high-solids loading. Researchers have also engineered the expression side of the equation, optimizing signal peptides such as pelB and SPamy to boost secretion of PETase from Escherichia coli and Bacillus subtilis, and displaying engineered PETase and MHETase on bacterial cell surfaces to create efficient dual-enzyme cascade systems. Multi-enzyme cascade strategies and self-assembled complexes now push degradation rates further, and PET enzymatic recycling has reached pilot scale, marking a genuine milestone on the road to commercialization.

PET is not the only target. Polyurethanes, found in foams, adhesives, and coatings, are attacked by enzymes including urethanases, esterases, and lipases, with recent multi-omics studies revealing how marine fungi degrade these polymers. Polyethylene, the most produced plastic and chemically the most recalcitrant, is far harder: its carbon-carbon backbone resists hydrolysis, and degradation typically requires oxidative enzymes such as alkane hydroxylases and, more recently, small laccases, including one discovered in Acinetobacter dijkshoorniae that shows potential for polyethylene depolymerization and bio-upcycling. Polystyrene degradation has been documented in bacteria such as Exiguobacterium, with evidence for atypical oxygenase-mediated pathways, and multi-omic analyses of plastic-associated microbial communities continue to reveal novel enzymes, dubbed plastizymes, with unexplored biotransformation potential. Pretreatment technologies, including UV irradiation, plasma, and thermal conditioning, are increasingly recognized as key enablers that make polymers vulnerable to enzymatic attack.

Degrading plastic is only half of the circular equation; the other half is turning the resulting monomers and renewable carbon into new materials. Here the review highlights polyhydroxyalkanoates (PHAs), a family of microbially synthesized polyesters that behave like conventional plastics yet biodegrade readily in soil and marine environments, and that already show promise in biomedical applications such as wound treatment and food packaging. Metabolic engineering has been decisive in making PHA production economically viable. Researchers have knocked out competing fermentation pathways in E. coli to channel carbon into PHB, disrupted PHA depolymerase genes in Rhodobacter sphaeroides to prevent the polymer from being consumed, and overexpressed biosynthetic gene clusters to raise yields. In halophilic chassis such as Halomonas bluephagenesis, scientists have even manipulated the size of intracellular PHA granules, which influences polymer processing properties, while fine-tuning monomer composition to tune material performance from rigid to elastic.

Perhaps the most exciting frontier is the direct coupling of the two halves of the cycle: converting plastic waste itself into new bioplastic. Pseudomonas putida KT2440 has emerged as the leading chassis for this kind of plastic upcycling, engineered to metabolize both terephthalic acid and ethylene glycol, the two monomers released from PET, and to funnel them into value-added products including PHAs and beta-ketoadipic acid. Tandem chemical deconstruction followed by biological upcycling has been demonstrated for PET, and engineered strains have been built for concurrent PET monomer metabolism and hydrolase expression, effectively creating synthetic PETrophy. Even more striking, I. sakaiensis itself has been shown to directly convert PET into PHA fermentatively, and co-cultivation strategies pair a PET-degrading strain with a PHB-producing strain to achieve one-step degradation and biosynthesis. Similar logic applies to polyurethane monomers, which defined microbial mixed cultures can convert into bioplastic, and to mixed microbial communities that produce PHA from terephthalic acid.

Synthetic consortium design adds another layer of sophistication. Engineered microbial division of labor, in which different strains specialize in depolymerization, monomer transport, and product synthesis, has been shown to improve plastic upcycling beyond what single strains achieve. Artificial consortia have also been used to convert inexpensive feedstocks such as inulin and glucose-xylose mixtures into medium-chain-length PHAs, and photoheterotrophic communities can co-produce biohydrogen alongside PHA. These systems mirror the modular logic of industrial chemistry but operate at ambient temperature and pressure in water, offering a potentially far lower energy footprint than thermochemical recycling routes such as pyrolysis, which nonetheless remain part of the broader circular economy toolkit.

The authors are candid about the bottlenecks that remain. Enzyme stability and catalytic efficiency still fall short of the throughput needed for bulk waste streams, particularly for polyolefins like polyethylene and polypropylene, where degradation rates remain orders of magnitude below those for PET. Process economics, downstream separation, feedstock logistics, and the cost of engineered strains all weigh against bioplastic prices that must compete with commodity petroplastics. The review also notes that some researchers caution microbial enzymes will offer limited solutions to the global pollution crisis on their own, underscoring that biology must be integrated with policy, sorting infrastructure, and system-level design rather than seen as a silver bullet. The authors call for interdisciplinary collaboration spanning strain engineering, protein design, bioprocess innovation, and environmental systems analysis to overcome these barriers.

What emerges from the BRIN team’s synthesis is a coherent vision: microorganisms as the connective tissue of a circular plastics economy, digesting yesterday’s bottles and packaging and secreting tomorrow’s materials. With PET enzymatic recycling already demonstrated at pilot scale, PHA strains genetically fine-tuned for yield and composition, and upcycling routes from waste plastic to new bioplastic proven in the laboratory, the pieces of the puzzle are increasingly in place. The remaining challenge is less one of discovery than of integration and scale, of turning elegant metabolic pathways into robust industrial processes. If that integration succeeds, the microbes that evolved in a world saturated with plastic may become the very tool humanity uses to unsaturate it.

Subject of Research: Microbial metabolic engineering for plastic degradation and bioplastic synthesis in a circular plastics economy

Article Title: The role of microbial metabolic engineering for circular plastics economy

Article References: The role of microbial metabolic engineering for circular plastics economy. (n.d.). https://doi.org/10.1007/s13205-026-05050-0

Image Credits: AI Generated

DOI: 10.1007/s13205-026-05050-0

Keywords: metabolic engineering, plastic degradation, PETase, polyhydroxyalkanoates, bioplastics, circular economy, Ideonella sakaiensis, enzyme engineering, Pseudomonas putida, biodegradation, plastic recycling, microbial consortia

One of the most consequential shifts highlighted by the editorial concerns the way scientists fight infection. Conventional antibiotics and antifungals exert strong selective pressure by trying to eliminate pathogens outright, a strategy that inexorably breeds resistance. The emerging alternative is anti-virulence therapy: blocking the molecular machinery pathogens use to cause damage, leaving them alive but harmless. A study by Wang and colleagues illustrates the approach with unusual precision. The researchers identified alcohol dehydrogenase 1, or Adh1, as a previously unrecognized regulator of morphogenesis in Candida albicans, the opportunistic fungus responsible for serious hospital-acquired infections. Adh1 acts through modulation of SNF1 phosphorylation, a signalling step that governs the yeast-to-hypha transition. When the team applied 2-hydroxyanthraquinone, the compound inhibited hyphal formation and biofilm development by targeting this pathway. Because biofilms and invasive hyphae are central to C. albicans virulence, the work opens a route to next-generation antifungals that control pathogenicity rather than survival, easing the evolutionary pressure that drives drug resistance.

A second pillar of the new microbial biotechnology is the engineering of cell factories, the living production lines that manufacture high-value molecules. Here the editorial highlights two studies that push host engineering in different directions. In the first, Yan and colleagues transformed Trichoderma reesei, a filamentous fungus long prized for industrial enzyme production, into a secretory platform for insulin glargine, a mainstay therapeutic for diabetes. Producing therapeutic proteins extracellularly in fungi is notoriously difficult, because misfolded products trigger endoplasmic reticulum stress and degradation. By systematically optimizing secretion signals, fusion partners and the fungus’s ER stress responses, the authors substantially improved recombinant protein secretion, expanding the prospect of filamentous fungi as scalable hosts for pharmaceutical manufacturing. In the second study, Li and colleagues redesigned membrane trafficking pathways in the yeast Saccharomyces cerevisiae to enhance the production of extracellular vesicles. These nanoscale membrane particles are emerging as promising vehicles for drug delivery, and the work establishes generic approaches for their biomanufacture, suggesting a future in which therapeutic delivery systems are grown rather than synthesized.

Parallel to cell factory engineering, protein design is enlarging the catalytic repertoire of microbial enzymes, with direct consequences for sustainable chemistry. Fucosylated oligosaccharides, human milk components with applications in infant nutrition and glycobiology, are difficult to synthesize chemically. Vodičková and colleagues reprogrammed an α-L-fucosidase from the bacterium Paenibacillus thiaminolyticus into an efficient transfucosidase through rational mutagenesis, shifting the enzyme’s catalytic output from hydrolysis, which cleaves bonds, towards transglycosylation, which builds them. The redesigned catalyst enables selective synthesis of valuable fucosylated products and holds potential for biosensor development. In a complementary demonstration of how small changes yield large functional leaps, Kato and colleagues took CYP107J1, a previously uncharacterized cytochrome P450 from Bacillus subtilis, and converted it into a hydrogen peroxide-driven peroxygenase with just two amino acid substitutions. The redesigned enzyme displayed dramatically improved catalytic activity and broadened substrate specificity, including efficient synthesis of indigo, the dye behind classic blue denim. These results echo a broader trend of enzyme bioprospecting through metagenomics, in which unexplored microbial diversity supplies raw catalytic material that protein engineering then refines for industrial use.

Engineering ambition, the editorial argues, is now extending beyond genomes to the manufacturing process itself. Delvenne and colleagues introduced Segregostat, a real-time cell-machine interface that pairs automated flow cytometry with dynamic process control. The platform continuously monitors microbial population structure inside a bioreactor and adjusts operating conditions on the fly, maintaining stable physiological states even under industrially relevant perturbations such as nutrient fluctuations or scaling stresses. This matters because the gap between laboratory performance and industrial robustness remains one of biotechnology’s most persistent bottlenecks. By treating a living culture as a controllable system with real-time feedback, Segregostat points toward intelligent, automated biomanufacturing in which systems biology and digital process control converge to improve scalability and reproducibility.

Agriculture represents another frontier where microbial engineering is challenging chemical orthodoxy. Plant growth-promoting microorganisms and biocontrol agents are at the heart of efforts to replace synthetic fertilizers and pesticides, and the editorial spotlights work by Grace and colleagues who reported the first bacteriophages isolated against the bacteria associated with acute oak decline, a devastating syndrome of European oak trees. The phages effectively inhibited Brennera goodwinii and Gibbsiella quercinencis under laboratory conditions, yet performed only modestly in oak saplings. Far from being a failure, the authors argue, the discrepancy exposes the ecological complexity that any field-deployed biocontrol strategy must navigate, from sap chemistry to microbial community dynamics. The episode also marks the return of phage therapy, a practice pioneered more than a century ago and sidelined by the antibiotic era, now re-emerging as antimicrobial resistance erodes conventional treatments. With resistance crises mounting in both medicine and agriculture, phages may be poised to become stars of biological control, provided ecological understanding keeps pace with microbiological innovation.

Vaccine engineering, meanwhile, has been transformed by the COVID-19 era, which demonstrated that mRNA and recombinant platforms can be developed with unprecedented speed. Byun and colleagues contributed a showcase of converging nanobiotechnology and protein engineering: a recombinant nanoparticle vaccine against West Nile virus built on the cholera toxin B subunit displaying the viral envelope domain III antigen. The nanoparticles elicited strong neutralizing antibody responses while minimizing cross-reactivity with related flaviviruses, a critical safety consideration given the risk that imperfect antibodies can worsen disease in secondary flavivirus infections. The result supports the platform’s promise as a safe, scalable technology for responding to emerging infectious diseases, where rapid, specific and manufacturable vaccines are decisive.

Environmental sustainability remains perhaps the field’s defining challenge, and the editorial presents two complementary visions of microbial solutions. Phale and colleagues offered a systems-level perspective on bacterial biodegradation of aromatic pollutants, arguing that successful bioremediation depends not merely on metabolic pathways but on a coordinated arsenal of traits: environmental sensing, chemotaxis, stress tolerance, substrate transport, regulatory networks and microbial cooperation. Their framing recasts biodegradation as an emergent property of complex microbial communities rather than the work of any single enzyme, a view with practical consequences for designing or enriching cleanup consortia. Taking upcycling a step further, Molpeceres-García and colleagues integrated chemical depolymerization with synthetic biology to turn polyethylene terephthalate waste into biodegradable bioplastics. The process first converts PET into BHET by glycolysis, after which an engineered consortium of Comamonas testosteroni and Pseudomonas putida cooperatively metabolizes the PET-derived intermediates into polyhydroxyalkanoates, valuable biodegradable polymers. By coupling chemical recycling with microbial metabolism, the study sketches a credible route toward a circular plastics economy in which yesterday’s bottles become tomorrow’s compostable materials.

Taken together, these studies describe a discipline in the midst of a profound transformation. Whether the goal is an enzyme that builds rather than breaks, a fungus that secretes medicine, a phage that shields a forest, a nanoparticle vaccine against an emerging virus, or a bacterial duo that eats plastic, the common thread is the deliberate integration of mechanistic biological knowledge with engineering principles. Microbial biotechnology, the editorial concludes, is evolving into a truly engineering-driven science, one capable of delivering scalable solutions for healthcare, agriculture, industrial manufacturing and environmental sustainability. As followers of the field’s own reading habits suggest, the most exciting discoveries are no longer those that explain what microbes do, but those that decide what they will do next.

Subject of Research: Engineering microorganisms and enzymes as platforms for antimicrobial therapy, therapeutic protein production, biocatalysis, vaccines, agriculture and plastic upcycling

Article Title: Microbial Biotechnology at the Frontiers of Innovation: Engineering Solutions for Health, Industry and Sustainability

Article References: Bernal, P., & Ramos, J. L. (2026). Microbial Biotechnology at the Frontiers of Innovation: Engineering Solutions for Health, Industry and Sustainability. Microbial Biotechnology, 19(9), Article e70440. https://doi.org/10.1111/1751-7915.70440

Image Credits: AI Generated

DOI: 10.1111/1751-7915.70440

Keywords: microbial biotechnology, synthetic biology, anti-virulence therapy, Candida albicans, cell factories, protein engineering, biocatalysis, bacteriophage biocontrol, nanoparticle vaccines, bioremediation, PET upcycling, polyhydroxyalkanoates