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Transmission electron micrograph of P. putida CA-3 cells containing PHA granules accumulated from styrene. The arrow indicates a PHA granule.
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Pseudomonas putida CA-3 is capable of converting the aromatic hydrocarbon styrene, its metabolite phenylacetic acid, and glucose into polyhydroxyalkanoate (PHA) when a limiting concentration of nitrogen (as sodium ammonium phosphate) is supplied to the growth medium. PHA accumulation occurs to a low level when the nitrogen concentration drops below...
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Pseudomonas putida KT2442 is a natural producer of polyhydroxyalkanoates (PHAs), which can substitute petroleum-based non-renewable plastics and form the basis for the production of tailor-made biopolymers. However, despite the substantial body of work on PHA production by P. putida strains, it is not yet clear how the bacterium re-arranges its who...
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... Such a narrow window of C/N ratio with high PHA accumulation is well-known and has been widely reported. For example, in another styrene-degrading and PHA-producing bacterium P. putida CA-3 (NCIMB 41162), little to no PHA production was observed until the C/N ratio exceeded 14:1 with peak PHA production occurring at the C/N ratio 28:1 22 . Similar observations were also made for other aromatic and non-aromatic substrates in pure and mixed cultures 23,24 . ...
Polyhydroxyalkanoates (PHAs) could be used to make sustainable, biodegradable plastics. However, the precise and accurate mechanistic modeling of PHA biosynthesis, especially medium-chain-length PHA (mcl-PHA), for yield improvement remains a challenge to biology. PHA biosynthesis is typically triggered by nitrogen limitation and tends to peak at an optimal carbon-to-nitrogen (C/N) ratio. Specifically, simulation of the underlying dynamic regulation mechanisms for PHA bioprocess is a bottleneck owing to surfeit model complexity and current modeling philosophies for uncertainty. To address this issue, we proposed a quantum-like decision-making model to encode gene expression and regulation events as hidden layers by the general transformation of a density matrix, which uses the interference of probability amplitudes to provide an empirical-level description for PHA biosynthesis. We implemented our framework modeling the biosynthesis of mcl-PHA in Pseudomonas putida with respect to external C/N ratios, showing its optimization production at maximum PHA production of 13.81% cell dry mass (CDM) at the C/N ratio of 40:1. The results also suggest the degree of P. putida’s preference in channeling carbon towards PHA production as part of the bacterium’s adaptative behavior to nutrient stress using quantum formalism. Generic parameters (kD, kN and theta θ) obtained based on such quantum formulation, representing P. putida’s PHA biosynthesis with respect to external C/N ratios, was discussed. This work offers a new perspective on the use of quantum theory for PHA production, demonstrating its application potential for other bioprocesses.
... Mealworms can also consume PS. 26,27 Two groups have shown that Pseudomonas putida can convert styrene to biodegradable polyhydroxyalkanoates (PHAs). 28,29 Recently, one group has shown that mixed plastics, including PS, can be oxidatively degraded and upgraded by an engineered strain of P. putida to β-ketoadipate or PHAs. 30 We recently reported an oxidative catalytic method to degrade post-consumer polyethylenes rapidly into distributions of carboxylic diacids. ...
Polystyrene (PS) is one of the most used yet infrequently recycled plastics. Although manufactured on the scale of 300 million tons per year globally, current approaches toward PS degradation are energy- and carbon-inefficient, slow, and/or limited in the value that they reclaim. We recently reported a scalable process to degrade post-consumer polyethylene-containing waste streams into carboxylic diacids. Engineered fungal strains then upgrade these diacids biosynthetically to synthesize pharmacologically active secondary metabolites. Herein, we apply a similar reaction to rapidly convert PS to benzoic acid in high yield. Engineered strains of the filamentous fungus Aspergillus nidulans then biosynthetically upgrade PS-derived crude benzoic acid to the structurally diverse secondary metabolites ergothioneine, pleuromutilin, and mutilin. Further, we expand the catalog of plastic-derived products to include spores of the industrially relevant biocontrol agent Aspergillus flavus Af36 from crude PS-derived benzoic acid.
... A large number of plastic degrading microbial species have been isolated from variety of environments including landfills, sewage sludge, marine water, crude oil contaminated Microbial bioprocesses in remediation of contaminated environments and resource recovery soil, and mulch films. Ward et al. (2005) reported microbial conversion of aromatic hydrocarbon styrene and its metabolites into PHA by Pseudomonas putida CA-3 in nitrogenlimiting growth medium. Further, Kenny et al. (2012) in their study recycled sodium terephthalate (TA), a by-product of PET pyrolysis and waste glycerol (WG) from biodiesel manufacture into PHA, in fed-batch bioreactor inoculated with Pseudomonas putida GO16. ...
... A large number of plastic degrading microbial species have been isolated from variety of environments including landfills, sewage sludge, marine water, crude oil contaminated Microbial bioprocesses in remediation of contaminated environments and resource recovery soil, and mulch films. Ward et al. (2005) reported microbial conversion of aromatic hydrocarbon styrene and its metabolites into PHA by Pseudomonas putida CA-3 in nitrogenlimiting growth medium. Further, Kenny et al. (2012) in their study recycled sodium terephthalate (TA), a by-product of PET pyrolysis and waste glycerol (WG) from biodiesel manufacture into PHA, in fed-batch bioreactor inoculated with Pseudomonas putida GO16. ...
Microalgae are renewable and sustainable green biofactories that generate a huge repertoire of bioprospective products and bioenergy materials. In past decades huge advancements have been made to study the microalgal genome, transcriptome, and proteome, which have led to the generation of enormous data sets of the genome-wide transcriptome, proteome, and their interactions like protein–protein interactions in different microalgae. Such tremendous advancements are due to the development of various types of transformation, genetic manipulation strategies, and technological improvements in other fields like data analysis and machine learning, which have been applied to different microalgae. Owing to such technological advancements complemented by colossal price reduction in genome sequencing technologies, many algal genomes are sequenced now or are being sequenced. This chapter discusses the importance and recent advancements which have been made in studying the genomics of microalgae and highlights the shortcomings and benefits of different functional genomic approaches.
... Industries can also use PE for the synthesis of PHA by treating paraffin (depolymerized product of PE after pyrolysis) with the strain Pseudomonas aeruginosa PAO-1, resulting in a good yield ( Johnston et al., 2019;Ward et al., 2006). Some beneficial fatty acids can also be synthesized by treating hydrocarbons (extracted from depolymerized products of PE) with R. eutropha H16, producing 62 mg of PHA/g of styrene (( Johnston et al., 2017), whereas treatment of styrene (depolymerized products of PS) performed with P. putida CA-3 will give 0.1 g of PHA/g carbon (Ward, de Roo, & O'Connor, 2005). Ethylene glycol (EG) is the depolymerized product of PET, and treatment of EG and P. putida KT2440 provides a yield of 0.06 g of PHA/gram EG (Franden et al., 2018). ...
... A large number of plastic degrading microbial species have been isolated from variety of environments including landfills, sewage sludge, marine water, crude oil contaminated Microbial bioprocesses in remediation of contaminated environments and resource recovery soil, and mulch films. Ward et al. (2005) reported microbial conversion of aromatic hydrocarbon styrene and its metabolites into PHA by Pseudomonas putida CA-3 in nitrogenlimiting growth medium. Further, Kenny et al. (2012) in their study recycled sodium terephthalate (TA), a by-product of PET pyrolysis and waste glycerol (WG) from biodiesel manufacture into PHA, in fed-batch bioreactor inoculated with Pseudomonas putida GO16. ...
... Ward et al. [162] demonstrated that P. putida CA-3 is able to convert styrene into PHA if grown under nutrient-limited conditions. This finding establishes the metabolic link between styrene degradation and PHA [163,164]. ...
The use of fossil-based plastics has become unsustainable because of the polluting production processes, difficulties for waste management sectors, and high environmental impact. Polyhy-droxyalkanoates (PHA) are bio-based biodegradable polymers derived from renewable resources and synthesized by bacteria as intracellular energy and carbon storage materials under nutrients or oxygen limitation and through the optimization of cultivation conditions with both pure and mixed culture systems. The PHA properties are affected by the same principles of oil-derived polyolefins, with a broad range of compositions, due to the incorporation of different monomers into the polymer matrix. As a consequence, the properties of such materials are represented by a broad range depend-ing on tunable PHA composition. Producing waste-derived PHA is technically feasible with mixed microbial cultures (MMC), since no sterilization is required; this technology may represent a solution for waste treatment and valorization, and it has recently been developed at the pilot scale level with different process configurations where aerobic microorganisms are usually subjected to a dynamic feeding regime for their selection and to a high organic load for the intracellular accumulation of PHA. In this review, we report on studies on terrestrial and marine bacteria PHA-producers. The available knowledge on PHA production from the use of different kinds of organic wastes, and otherwise, petroleum-polluted natural matrices coupling bioremediation treatment has been explored. The advancements in these areas have been significant; they generally concern the terrestrial environment, where pilot and industrial processes are already established. Recently, marine bacteria have also offered interesting perspectives due to their advantageous effects on production practices, which they can relieve several constraints. Studies on the use of hydrocarbons as carbon sources offer evidence for the feasibility of the bioconversion of fossil-derived plastics into bioplastics.
... The intrinsic harmful nature of these chemicals makes it challenging to derive PHAs from aromatics. Bacteria of the genus Rhodococcus, Cupriavidus, Pseudomonas, and Burkholderia, Achromobacter are specialized aromatic degraders along with the ability to form PHA under nutrient imbalance from styrene (Ward et al., 2005), benzene-toluene-ethylbenzene-p-xylene (BTEX) (Nikodinovic et al., 2008), toluene (Hori et al., 2009), furfural (Pan et al., 2012), 4-hydroxybenzoic acid, vanillic acid (Tomizawa et al., 2014), and phenol (Zhang et al., 2018), but to limited amounts -less than 0.5 g L −1 of the polyester. Nevertheless, in a fed-batch process, one of the highest mcl-PHA titre (3.4 g L −1 ) was obtained from styrene in P. putida CA-3 (Nikodinovic-Runic et al., 2011). ...
Microbial production of biopolymers derived from renewable substrates and waste streams reduces our heavy reliance on petrochemical plastics. One of the most important biodegradable polymers is the family of polyhydroxyalkanoates (PHAs), naturally occurring intracellular polyoxoesters produced for decades by bacterial fermentation of sugars and fatty acids at the industrial scale. Despite the advances, PHA production still suffers from heavy costs associated with carbon substrates and downstream processing to recover the intracellular product, thus restricting market positioning. In recent years, model‐aided metabolic engineering and novel synthetic biology approaches have spurred our understanding of carbon flux partitioning through competing pathways and cellular resource allocation during PHA synthesis, enabling the rational design of superior biopolymer producers and programmable cellular lytic systems. This review describes these attempts to rationally engineering the cellular operation of several microbes to elevate PHA production on specific substrates and waste products. We also delve into genome reduction, morphology, and redox cofactor engineering to boost PHA biosynthesis. Besides, we critically evaluate engineered bacterial strains in various fermentation modes in terms of PHA productivity and the period required for product recovery.
... Phenylacetic acid is converted to phenylacetyl coenzyme A, that forms acetyl-CoA after β-oxidation, which then enters in the TCA cycle (Tischler et al., 2009;Tischler, 2015;Danso et al., 2019;Jacquin et al., 2019). P. putida and Rhodococcus zopfii convert polystyrene (thermally transformed into styrene oil) into polyhydroxyalkanoate, a value-added biodegradable polymer (O'Leary et al., 2005;Ward et al., 2005, Ward et al., 2006. Curiously, the larvae of Tenebrio molitor and other mealworms, dark mealworms (Tenebrio obscurus), and superworms (Zophobas atratus) eat and degrade PS, which seems to be assisted by the gut microbiota in some extent (Yang et al., 2015b(Yang et al., ,c, 2018Brandon et al., 2018). ...
Anthropogenic activities have extensively transformed the biosphere by extracting and disposing of resources, crossing boundaries of planetary threat while causing a global crisis of waste overload. Despite fundamental differences regarding structure and recalcitrance, lignocellulose and plastic polymers share physical-chemical properties to some extent, that include carbon skeletons with similar chemical bonds, hydrophobic properties, amorphous and crystalline regions. Microbial strategies for metabolizing recalcitrant polymers have been selected and optimized through evolution, thus understanding natural processes for lignocellulose modification could aid the challenge of dealing with the recalcitrant human-made polymers spread worldwide. We propose to look for inspiration in the charismatic fungal-growing insects to understand multipartite degradation of plant polymers. Independently evolved in diverse insect lineages, fungiculture embraces passive or active fungal cultivation for food, protection, and structural purposes. We consider there is much to learn from these symbioses, in special from the community-level degradation of recalcitrant biomass and defensive metabolites. Microbial plant-degrading systems at the core of insect fungicultures could be promising candidates for degrading synthetic plastics. Here, we first compare the degradation of lignocellulose and plastic polymers, with emphasis in the overlapping microbial players and enzymatic activities between these processes. Second, we review the literature on diverse insect fungiculture systems, focusing on features that, while supporting insects' ecology and evolution, could also be applied in biotechnological processes. Third, taking lessons from these microbial communities, we suggest multidisciplinary strategies to identify microbial degraders, degrading enzymes and pathways, as well as microbial interactions and interdependencies. Spanning from multiomics to spectroscopy, microscopy, stable isotopes probing, enrichment microcosmos, and synthetic communities, these strategies would allow for a systemic understanding of the fungiculture ecology, driving to application possibilities. Detailing how the metabolic landscape is entangled to achieve ecological success could inspire sustainable efforts for mitigating the current environmental crisis.
... Styrene or phenylacetate as substrate for PHA production was presented by the group of O'Connor (Ward et al., 2005). They went on and used PS pyrolysis oil to convert 64 g of plastic waste into 6.4 g of PHA (Ward et al., 2006), which could be enhanced even further (Goff et al., 2007;Nikodinovic-Runic et al., 2011). ...
The plastic crisis requires drastic measures, especially for the plastics’ end-of-life. Mixed plastic fractions are currently difficult to recycle, but microbial metabolism might open new pathways. With new technologies for degradation of plastics to oligo- and monomers, these carbon sources can be used in biotechnology for the upcycling of plastic waste to valuable products, such as bioplastics and biosurfactants. We briefly summarize well-known monomer degradation pathways and computed their theoretical yields for industrially interesting products. With this information in hand, we calculated replacement scenarios of existing fossil-based synthesis routes for the same products. Thereby, we highlight fossil-based products for which plastic monomers might be attractive alternative carbon sources. Notably, not the highest yield of product on substrate of the biochemical route, but rather the (in-)efficiency of the petrochemical routes (i.e., carbon, energy use) determines the potential of biochemical plastic upcycling. Our results might serve as a guide for future metabolic engineering efforts towards a sustainable plastic economy.