Gepresenteerd op conferentie R&D Management 2016 door Inge Oskam
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.
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.
MULTIFILE
The valorization of biowaste, by exploiting side stream compounds as feedstock for the sustainable production of bio-based materials, is a key step towards a more circular economy. In this regard, chitin is as an abundant resource which is accessible as a waste compound of the seafood industry. From a commercial perspective, chitin is chemically converted into chitosan, which has multiple industrial applications. Although the potential of chitin has long been established, the majority of seafood waste containing chitin is still left unused. In addition, current processes which convert chitin into chitosan are sub-optimal and have a significant impact on the environment. As a result, there is a need for the development of innovative methods producing bio-based products from chitin. This project wants to contribute to these challenges by performing a feasibility study which demonstrates the microbial bioconversion of chitin to polyhydroxyalkanoates (PHAs). Specifically, the consortium will attempt to cultivate and engineer a recently discovered bacterium Chi5, so that it becomes able to directly produce PHAs from chitin present in solid shrimp shell waste. If successful, this project will provide a proof-of-concept for a versatile microbial production platform which can contribute to: i) the valorization of biowaste from the seafood industry, ii) the efficient utilization of chitin as feedstock, iii) the sustainable and (potentially low-cost) production of PHAs. The project consortium is composed of: i) Van Belzen B.V., a Dutch shrimp trading company which are highly interested in the valorization of their waste streams, hereby making their business model more profitable and sustainable. ii) AMIBM, which have recently isolated and characterized the Chi5 marine-based chitinolytic bacterium and iii) Zuyd, which will link aforementioned partners with students in creating a novel collaboration which will stimulate the development of students and the translation of academic knowledge to a feasible application technology for SME’s.
It is known that several bacteria in sewage treatment plants can produce attractive quantities of biodegradable polymers within their cell walls (up to 80% of the cell weight). These polymers may consist of polyhydroxyalkanoates (PHA), a bioplastic which exhibits interesting characteristics like excellent biodegradation, low melting point and good environmental footprint. PHA bioplastics or PHBV are still quite expensive because cumbersome downstream processing steps of the PHAcontaining bacteria are needed before PHA can be applied in products. In this proposal, the consortium investigates the possibilities for eliminating these expensive and environmentally intensive purification steps, and as a result contribute to speeding up the up-take of PHA production of residual streams by the market. The objective of the project is to investigate the possibilities of direct extrusion of PHAcontaining bacteria and the application opportunities of the extruded PHA. The consortium of experienced partners (Paques Biomaterials, MAAN Group, Ecoras and CoEBBE) will investigate and test the extrusion of different types of PHA-containing biomass, and analyse the products on composition, appearance and mechanical properties. Moreover, the direct extrusion process will be evaluated and compared with conventional PHA extraction and subsequent extrusion. The expected result will be a proof of principle and provide an operational window for the application of direct extrusion with PHA-containing biomass produced using waste streams, either used as such or in blends with purified PHA. Both the opportunities of the direct extrusion process itself as well as the application opportunities of the extruded PHA will be mapped. If the new process leads to a cheaper, more environmentally friendly produced and applicable PHA, the proof of principle developed by the consortium could be the first step in a larger scale development that could help speeding up the implementation of the technology for PHA production from residual streams in the market.
The environmental toll of oil-based plastics has spurred the search for sustainable alternatives. One promising solution is the utilization of biobased degradable plastics, such as polyhydroxyalkanoates (PHA). Polyhydroxyalkanoates are a family of bacteria-made polyesters with versatile properties and high biodegradability. However, production of PHA is still too expensive compared to conventional polymers, hindering the use at commercial level in a wider range of applications. The separation of PHA from the bacterial biomass through a solvent extraction is currently one of the main reasons for high costs. In 2022, Avans UAS, together with Paques Biomaterials, Ecoras and Maan Group have executed an exploratory study on a Kiem GoChem project to look into the possibilities to directly process PHA-rich biomass into biocomposites without first extracting PHA. The results showed that it is possible to process the PHA-rich biomass. This can be done with pure PHA-rich biomass or with blends with other polymers, resulting in a material with thermoplastic behaviour. This opens opportunities for all kinds of commercially interesting applications. In the PHAst Thermoplast project these options will be further investigated with a consortium consisting of research institutes (Avans, Zuyd, Hanze), PHA producers (Paques Biomaterials, Mango Materials), biopolymer processing companies (RB Biobased Institute, ColorFabb), companies that look into applications for PHA (Craze, Ecoras, NPSP), and the Dutch rubber and plastic industry federation NRK. The main goal of PHAst Thermoplast is to improve the processability and the technical properties of PHA-rich biomass composites in order to create added value biodegradable products with an industrial potential. For that, different material blends will be tested and applied in injection moulding and 3D-printing. A thorough investigation will be conducted to assess potential marketable product applications for the developed materials. This will be strengthened by an assessment of end-of-life options for the material.
