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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Growth conditions have been frequently studied in optimizing polyhydroxybutyrate (PHB) production, while few studies were performed to unravel the dynamic mixed microbial consortia (MMCs) in the process. In this study, the relationship between growth conditions (C/N ratios and pH) and the corresponding key-microbes were identified and monitored during PHB accumulation. The highest PHB level (70 wt% of dry cell mass) was obtained at pH 9, C/N 40, and acetic acid 10 g/L. Linking the dominant genera with the highest point of PHB accumulation, Thauera was the most prevalent species in all MMCs of pH 9, except when a C/N ratio of 1 was applied. Notably, dominant bacteria shifted at pH 7 (C/N 10) from Thauera (0 h) to Paracoccus, and subsequently to Alcaligenes following the process of PHB accumulation and consumption. Further understanding of the relationship between the structure of the microbial community and the performance will be beneficial for regulating and obtaining high PHB accumulation within an MMC. Our study illustrates the impact of C/N ratios and pH on microbial prevalence and PHB production levels using a mixed microbial starter culture. This knowledge will broaden industrial perspectives for regulating high PHB production and timely harvesting.
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In the field of ‘renewable energy resources’ formation of biogas is an important option. Biogas can be produced from biomass in a multistep process called anaerobic digestion (AD) and is usually performed in large digesters. Anaerobic digestion of biomass is mediated by various groups of microorganisms, which live in complex community structures. However, there is still limited knowledge on the relationships between the type of biomass and operational process parameters. This relates to the changes within the microbial community structure and the resulting overall biogas production efficiency. Opening this microbial black box could lead to an better understanding of on-going microbial processes, resulting in higher biogas yields and overall process efficiencies.
Water treatment companies are more and more interested in chemical-free water treatment. This is a solution that might not only decrease costs of chemicals, but also decrease possible formation of by-products and contribute to decreasing the introduction of emerging contaminants in the environment. A possible route for this is the use of magnetic fields based treatment. Magnetic fields exist around us (our planet is surrounded by such fields) but are not broadly used in water treatment. A reason for this situation isthe fact that water treatment is a rather traditional market and magnetic treatment, conversely, a rather controversial and (still) not completely understood. Even with such resistance, recently it has been shown that magnetic fields applied to drinking water resulted in significant structural change of its microbiome [1]. This community structural change was clearly detected with a newly developed flow cytometry method, where the phenotypic characteristics of the entire microbial community could be analysed instantly [2-9]. Lab-scale batch experiments have shown that magnetic fields can selectively boost the growth of smaller bacteria [1][3] and indicated as a next step that the same principle could be addressed in pilot scale tests. ISusMag is structured to apply the robust and instant flow cytometry method to examine the effect of magnetic fields on drinking water at pilot scale under realistic field conditions. For this purpose, groundwater will be evenly distributed into two (pipe)lines of the same length: one will be magnetically treated, and one will be used as control. Samples will be taken at the end of the two pipes for flow cytometry examination. Measurement results can help drinking water companies to understand whether a magnetic treatment is an alternative to control the growth of pathogenic bacteria instead of classical chemical treatment (disinfection).
The message we intend to communicate is that in the future, our cities can (partly) feed themselves with healthy foods grown in microbial gardens, which can be part of a household kitchen or community garden for providing fresh green "vegetables" where the energy for the artificial LED lighting for the microbial garden is coming from solar panels on roofs thereby making this system free from fossil energy.For Floriade 2022, we would like to introduce the Urban Microbial garden pop-up restaurant for feeding and greening the city. The menu will include a speciality microbiota vegan burger made from algae, seaweed, fungi and fava beans served on dishes made from baked mycelium. Our objective is to elicit consumer perception and opinion on the future of our new microbial food chain, which is fully sustainable and safer for the environment. Consumer opinions will be video recorded and compiled into a short movie/video for further inspiration and analysis for product/service development. This pop-up restaurant is a logical extension of the Art-Work by 4F.STUDIO (Kim van den Belt, Joshua Kelly, Steven Wobbes) already present in Kavel 123 at Floriade as part of the Light Challenge. The artwork depicts a future object for community gardens which supports the idea of locally produced microbes. Since we already have work at Floriade, this living-lab project has the benefit of broadening the vision of their work through more in-depth and visceral feedback.
