ANAMMOX-denitrification biomass in microbial fuel cell to enhance the electricity generation and nitrogen removal efficiency.

The inoculum biomass was collected from a pilot-scale (3 m3 process tank) nitritation-anaerobic ammonium oxidation (ANAMMOX) (deammonification moving bed biofilm (DeaMBBR)) reactor demonstrating the highest total nitrogen removal rate (TNRR) of 0.33 kg N m-3 day-1. This biomass was used for inoculating the anodic chamber of a microbial fuel cell (MFC) to investigate the capacity of DeaMBBR biomass to act as an exo-electrogenic consortia. Performance of MFCs inoculated with ANAMMOX-specific consortia collected from DeaMBBR (MFC-ANA) and another MFC-CON inoculated with a septic tank mixed anaerobic consortium as a control was investigated for electrochemical performance and wastewater treatment efficiency. These MFCs were operated for the total duration of 419 days during which regular feed was given and performance was monitored for first 30 cycles and last 30 cycles, with each cycle of 3 day duration. The MFC-ANA continuously generated bio-energy with higher volumetric power density (9.5 W m-3 and 6.0 W m-3) in comparison to MFC-CON (4.9 and 2.9 W m-3) during the first 30 and last 30 cycles of operational period, respectively. MFC-ANA also achieved 84 ± 2% and 80 ± 2% of COD removal efficiency and 89 ± 4% and 73 ± 2% of total nitrogen removal efficiency during first 30 and last 30 cycles of operational period, respectively. The improvement of nitrogen removal and power production in case of MFC-ANA over MFC-CON could be attributed to the ANAMMOX-denitrifiers populations and Trichococcus (14.92%) as denitrifying exo-electrogenic microbes (4.46%), respectively.

Microbial growth and adhesion of Escherichia coli in elastomeric silicone foams with commonly used additives.

Silicone is often used in environments where water repellency is an advantage. Contact with water promotes the adhesion of microorganisms and biofilm formation. Depending on the application, this may increase the possibility of food poisoning and infections, the material's degrading appearance, and the likelihood of manufacturing defects. The prevention of microbial adhesion and biofilm formation is also essential for silicone-based elastomeric foams, which are used in direct contact with human bodies but are often difficult to clean. In this study, the microbial attachment in and the retention from the pores of silicone foams of different compositions is described and compared to those of commonly used polyurethane foams. The growth of the gram-negative Escherichia coli in the pores and their leaching during wash cycles is characterised by bacterial growth/inhibition, adhesion assay, and SEM imaging. The structural and surface properties of the materials are compared. Despite using common antibacterial additives, we have found that non-soluble particles stay isolated in the silicone elastomer layer, thus affecting surface microroughness. Water-soluble tannic acid dissolves into the medium and seems to aid in inhibiting planktonic bacterial growth, with a clear indication of the availability of tannic acid on the surfaces of SIFs.

Mainstream-sidestream wastewater switching promotes anammox nitrogen removal rate in organic-rich, low-temperature streams.

The main issues with mainstream anammox application are loss of bacterial activity by low temperatures and by a high organic content of wastewater. We demonstrate a novel switching method between sidestream and mainstream wastewater. The wastewater flow was switched between sidestream (reject water at >22°C) and mainstream (municipal wastewater at 16.5°C), so that the anammox biomass activity and biomass growth could benefit from sidestream conditions. Real sidestream wastewater (biogas plant effluent) (≈1000 mg NH+ 4-N L-1) and synthetic mainstream (municipal wastewater-like source) (≈100 mg NH+ 4-N) wastewater were used for 20 L biofilm reactor feeding. The highest total nitrogen removal rate (TNRR) of 527 g N m-3 d-1 (average TNRR 180 (±140) g N m-3 d-1) was achieved with sidestream wastewater at a low chemical oxygen demand (COD)/TN ratio of 1.1/1. For reactor feeding with mainstream, the highest TNRR achieved was 61 g N m-3 d-1. Average TNRR for mainstream of 20 (±15) g N m-3 d-1 was low due to a higher COD/N ratio of 3.2/1. The highest TNRR in a batch test was achieved at the COD concentration of 480 mg L-1, reflecting a TNRR of ≈5 mg N g-1 TSS h-1. With a high COD concentration of 2600 mg L-1 (TOC/TN = 8/1), TNRR decreased similarly in both feeds to 1.6 mg N g-1 TSS h-1. The anammox microorganism's genus Candidatus Brocadia enrichment in deammonification biofilm reactor was higher in the mainstream operation (7.6% of all bacteria) than in sidestream operation period (<0.7% of all bacteria).

A New Direction in Microfluidics: Printed Porous Materials.

In this work, the feasibility of a novel direction for microfluidics is studied by demonstrating a set of new methods to fabricate microfluidic systems. Similarly to microfluidic paper-based analytical devices, porous materials are being used. However, alternative porous materials and different printing methods are used here to give the material the necessary pattern to act as a microfluidic system. In this work, microfluidic systems were produced by the following three separate methods: (1) by curing a porous monolithic polymer sheet into a necessary pattern with photolithography, (2) by screen printing silica gel particles with gypsum, and (3) by dispensing silica gel particles with polyvinyl acetate binder using a modified 3D printer. Different parameters of the printed chips were determined (strength of the printed material, printing accuracy, printed material height, wetting characteristics, repeatability) to evaluate whether the printed chips were suitable for use in microfluidics. All three approaches were found to be suitable, and therefore the novel approach to microfluidics was successfully demonstrated.

Metabolism Control in 3D-Printed Living Materials Improves Fermentation.

The three-dimensional (3D) printing of cell-containing polymeric hydrogels creates living materials (LMs), offering a platform for developing innovative technologies in areas like biosensors and biomanufacturing. The polymer material properties of cross-linkable F127-bis-urethane methacrylate (F127-BUM) allow reproducible 3D printing and stability in physiological conditions, making it suitable for fabricating LMs. Though F127-BUM-based LMs permit diffusion of solute molecules like glucose and ethanol, it remains unknown whether these are permissible for oxygen, essential for respiration. To determine oxygen permissibility, we quantified dissolved oxygen consumption by the budding yeast-laden F127-BUM-based LMs. Moreover, we obtained data on cell-retaining LMs, which allowed a direct comparison between LMs and suspension cultures. We further developed a highly reliable method to isolate cells from LMs for flow cytometry analysis, cell viability evaluation, and the purification of macromolecules. We found oxygen consumption heavily impaired inside LMs, indicating that yeast metabolism relies primarily on fermentation instead of respiration. Applying this finding to brewing, we observed a higher (3.7%) ethanol production using LMs than the traditional brewing process, indicating improved fermentation. Our study concludes that the present F127-BUM-based LMs are useful for microaerobic processes but developing aerobic bioprocesses will require further research.

Physical Confinement Impacts Cellular Phenotypes within Living Materials.

Additive manufacturing allows three-dimensional printing of polymeric materials together with cells, creating living materials for applications in biomedical research and biotechnology. However, an understanding of the cellular phenotype within living materials is lacking, which is a key limitation for their wider application. Herein, we present an approach to characterize the cellular phenotype within living materials. We immobilized the budding yeast Saccharomyces cerevisiae in three different photo-cross-linkable triblock polymeric hydrogels containing F127-bis-urethane methacrylate, F127-dimethacrylate, or poly(alkyl glycidyl ether)-dimethacrylate. Using optical and scanning electron microscopy, we showed that hydrogels based on these polymers were stable under physiological conditions, but yeast colonies showed differences in the interaction within the living materials. We found that the physical confinement, imparted by compositional and structural properties of the hydrogels, impacted the cellular phenotype by reducing the size of cells in living materials compared with suspension cells. These properties also contributed to the differences in immobilization patterns, growth of colonies, and colony coatings. We observed that a composition-dependent degradation of polymers was likely possible by cells residing in the living materials. In conclusion, our investigation highlights the need for a holistic understanding of the cellular response within hydrogels to facilitate the synthesis of application-specific polymers and the design of advanced living materials in the future.

Cell-Laden Hydrogels for Multikingdom 3D Printing.

Living materials are created through the embedding of live, whole cells into a matrix that can house and sustain the viability of the encapsulated cells. Through the immobilization of these cells, their bioactivity can be harnessed for applications such as bioreactors for the production of high-value chemicals. While the interest in living materials is growing, many existing materials lack robust structure and are difficult to pattern. Furthermore, many living materials employ only one type of microorganism, or microbial consortia with little control over the arrangement of the various cell types. In this work, a Pluronic F127-based hydrogel system is characterized for the encapsulation of algae, yeast, and bacteria to create living materials. This hydrogel system is also demonstrated to be an excellent material for additive manufacturing in the form of direct write 3D-printing to spatially arrange the cells within a single printed construct. These living materials allow for the development of incredibly complex, immobilized consortia, and the results detailed herein further enhance the understanding of how cells behave within living material matrices. The utilization of these materials allows for interesting applications of multikingdom microbial cultures in immobilized bioreactor or biosensing technologies.