Accumulation of non-degradable plastic waste in the environment might be prevented by the use of biodegradable polyhydroxyalkanoate (PHA). In this study, the thermophile Schlegelella thermodepolymerans produced up to 80 wt% PHA based on dry cell mass. The largest PHA granules were found in the cells within 48 h using 20 g/L xylose, a C/N ratio of 100, an initial pH of 7, at 50 °C. The substrate consumption, pH changes, and cell growth were monitored, revealing the time dependency of PHA production in S. thermodepolymerans. The metabolic pathways from xylose to PHA were identified based on proteomic analysis, revealing involvement of classic phaCAB, de novo fatty acid biosynthesis, and fatty acid β-oxidation. In addition, it was shown that S. thermodepolymerans degraded extracellular PHA with a high efficiency at 50 °C.
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For the future circular economy, renewable carbon feedstocks manifest considerable promise for synthesizing sustainable and biodegradable polyhydroxyalkanoate (PHA). In this study, 16 wt% and 30 wt% PHA (cell dry weight) are respectively produced by thermophilic Caldimonas thermodepolymerans from beechwood xylan and wheat arabinoxylan as the sole carbon source. Moreover, an in silico study of the potential xylan-degrading proteins was conducted using proteome sequencing and CAZyme specialized bioinformatic tools. This study demonstrates the feasibility of utilizing complex polysaccharide substrates for PHA biosynthesis, thereby potentially eliminate additional processing steps and reducing overall production costs for sustainable plastic.
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The transition to a biobased economy necessitates utilizing renewable resources as a sustainable alternative to traditional fossil fuels. Bioconversion is a way to produce many green chemicals from renewables, e.g., biopolymers like PHAs. However, fermentation and bioconversion processes mostly rely on expensive, and highly refined pure substrates. The utilization of crude fractions from biorefineries, especially herbaceous lignocellulosic feedstocks, could significantly reduce costs. This presentation shows the microbial production of PHA from such a crude stream by a wild-type thermophilic bacterium Schlegelella thermodepolymerans [1]. Specifically, it uses crude xylose-rich fractions derived from a newly developed biorefinery process for grassy biomasses (the ALACEN process). This new stepwise mild flow-through biorefinery approach for grassy lignocellulosic biomass allows the production of various fractions: a fraction containing esterified aromatics, a monomeric xylose-rich stream, a glucose fraction, and a native-like lignin residue [2]. The crude xylose-rich fraction was free of fermentation-inhibiting compounds meaning that the bacterium S.thermodepolymerans could effectively use it for the production of one type of PHA, polyhydroxybutyrate. Almost 90% of the xylose in the refined wheat straw fraction was metabolized with simultaneous production of PHA, matching 90% of the PHA production per gram of sugars, comparable to PHA yields from commercially available xylose. In addition to xylose, S. thermodepolymerans converted oligosaccharides with a xylose backbone (xylans) into fermentable xylose, and subsequently utilized the xylose as a source for PHA production. Since the xylose-rich hydrolysates from the ALACEN process also contain some oligomeric xylose and minor hemicellulose-derived sugars, optimal valorization of the C5-fractions derived from the refinery process can be obtained using S. thermodepolymerans. This opens the way for further exploration of PHA production from C5-fractions out of a variety of herbaceous lignocellulosic biomasses using the ALACEN process combined with S. thermodepolymerans. Overall, the innovative utilization of renewable resources in fermentation technology, as shown herein, makes a solid contribution to the transition to a biobased economy.[1] W. Zhou, D.I. Colpa, H. Permentier, R.A. Offringa, L. Rohrbach, G.J.W. Euverink, J. Krooneman. Insight into polyhydroxyalkanoate (PHA) production from xylose and extracellular PHA degradation by a thermophilic Schlegelella thermodepolymerans. Resources, Conservation and Recycling 194 (2023) 107006, ISSN 0921-3449, https://doi.org/10.1016/j.resconrec.2023.107006. [2] S. Bertran-Llorens, W.Zhou. M.A.Palazzo, D.I.Colpa, G.J.W.Euverink, J.Krooneman, P.J.Deuss. ALACEN: a holistic herbaceous biomass fractionation process attaining a xylose-rich stream for direct microbial conversion to bioplastics. Submitted 2023.
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Plastic is one of the biggest contributors to pollution of the planet. Due to the low recyclability of oil-based plastics, most plastic is being disposed into the environment. According to plastic oceans, 10 million tons of plastic are dumped into oceans annually. Currently, researchers are developing recycling methods for oil-based plastics and are looking for biobased alternatives. One of these alternatives are a class of polymers called polyhydroxyalkanoates (PHA’s). PHA’s differ from other biobased polymers, due to the process of fabrication. PHA’s are a natural polymer, acting as an energy and carbon storage for different strains of bacteria. Functioning as an energy storage, nature can break down PHA’s and PHA-based waste. (1) Different companies are working on PHA’s production, but a large deviations in physical properties were observed. This research aims to establish a relationship between the chemical and physical properties of the different PHA’s, using gel permeability chromatography (GPC), nuclear magnetic resonance (NMR) and gas chromatography-mass spectroscopy (GC-MS).
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Overusing non-degradable plastics causes a series of environmental issues, inferring a switch to biodegradable plastics. Polyhydroxyalkanoates (PHAs) are promising biodegradable plastics that can be produced by many microbes using various substrates from waste feedstock. However, the cost of PHAs production is higher compared to fossil-based plastics, impeding further industrial production and applications. To provide a guideline for reducing costs, the potential cheap waste feedstock for PHAs production have been summarized in this work. Besides, to increase the competitiveness of PHAs in the mainstream plastics economy, the influencing parameters of PHAs production have been discussed. The PHAs degradation has been reviewed related to the type of bacteria, their metabolic pathways/enzymes, and environmental conditions. Finally, the applications of PHAs in different fields have been presented and discussed to induce comprehension on the practical potentials of PHAs.
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Positioning paper bij de inauguratie van Vincent Voet als lector Circular Plastics.
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![People. Planet. Polymer: een Wereld te Winnen [Inaugurele rede]](https://publinova-harvester-content-prod.s3.amazonaws.com/thumbnails/files/previews/pdf/20250506132442742072.Positioning20Paper20Vincent20Voet202024-thumbnail-400x300.png)
Polyhydroxyalkanoates (PHAs) form a highly promising class of bioplastics for the transition from fossil fuel-based plastics to bio-renewable and biodegradable plastics. Mixed microbial consortia (MMC) are known to be able to produce PHAs from organic waste streams. Knowledge of key-microbes and their characteristics in PHA-producing consortia is necessary for further process optimization and direction towards synthesis of specific types of PHAs. In this study, a PHA-producing mixed microbial consortium (MMC) from an industrial pilot plant was characterized and further enriched on acetate in a laboratory-scale selector with a working volume of 5 L. 16S-rDNA microbiological population analysis of both the industrial pilot plant and the 5 L selector revealed that the most dominant species within the population is Thauera aminoaromatica MZ1T, a Gram-negative beta-proteobacterium belonging to the order of the Rhodocyclales. The relative abundance of this Thauera species increased from 24 to 40% after two months of enrichment in the selector-system, indicating a competitive advantage, possibly due to the storage of a reserve material such as PHA. First experiments with T. aminoaromatica MZ1T showed multiple intracellular granules when grown in pure culture on a growth medium with a C:N ratio of 10:1 and acetate as a carbon source. Nuclear magnetic resonance (NMR) analyses upon extraction of PHA from the pure culture confirmed polyhydroxybutyrate production by T. aminoaromatica MZ1T.
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Polymeren, waaronder plastics, kennen we allemaal uit ons dagelijks leven. Van de plastic draagtas tot computeronderdelen en kopjes. Allemaal worden deze polymeren vervaardigd uit aardolie en afgeleide producten. De producten zijn zeer nuttig en breed toepasbaar, mede door de gunstige eigenschappen zoals warmteweerbaarheid, stevigheid en waterdichtheid. Daarentegen kennen polymeren ook een keerzijde, zoals het niet of moeilijk afbreekbaar zijn in de natuurlijke omgeving en de nadelen van het gebruik van fossiele bronnen: hun eindigheid en de ongecontroleerde emissie van broeikasgassen die verband houdt met klimaatverandering. Dit is een zichtbaar probleem bij onder meer De Plasticsoep, waar geen of beperkte afbraak plaatsvindt van plastics in de oceaan. De zoektocht naar alternatieven is daarom volop aan de gang.
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In het project Circulaire Biopolymerenwaardeketens voor PHA en cellulose wil men naar afbreekbare en biogebaseerde plastics, producten en afzetmarkten toe. Kansloos als die nieuwe plastics moeten gaan concurreren met oliegebaseerde plastics die al in grote hoeveelheden worden geproduceerd; kansrijk als die plastics toegevoegde waarde bieden en het productieproces ervan een hoge theoretische en praktische opbrengst heeft.
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Network Applied Design Research (NADR) made an inventory of the current state of Circular Design Research in the Netherlands. In this publication, readers will find a summary of six promising ‘gateways to circularity’ that may serve as entry points for future research initiatives. These six gateways are: Looped Systems; Extension of Useful Lifetime; Servitisation; New Materials and Production Techniques; Information Technology and Digitization; and Creating Public and Industry Awareness. The final chapter offers an outlook into topics that require more profound examination. The NADR hopes that this publication will serve as a starting point for discussions among designers, entrepreneurs, and researchers, with the goal of initiating future collaborative projects. It is the NADR's belief that only through intensive international cooperation, we can contribute to the realization of a sustainable, circular, and habitable world.
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