Abstract: Using Hubbard-U-corrected density functional theory calculations, lattice Monte Carlo simulations, and spin Monte Carlo simulations, we investigate the impact of dopant clustering on the magnetic properties of WSe2 doped with period four transition metals. We use manganese (Mn) and iron (Fe) as candidate n-type dopants and vanadium (V) as the candidate p-type dopant, substituting the tungsten (W) atom in WSe2. Specifically, we determine the strength of the exchange interaction in Fe-, Mn-, and V-doped WSe2 in the presence of clustering. We show that the clusters of dopants are energetically more stable than discretely doped systems. Further, we show that in the presence of dopant clustering, the magnetic exchange interaction significantly reduces because the magnetic order in clustered WSe2 becomes more itinerant. Finally, we show that the clustering of the dopant atoms has a detrimental effect on the magnetic interaction, and to obtain an optimal Curie temperature, it is important to control the distribution of the dopant atoms.

Abstract: Due to the high water- and nutrient-use efficiency, hydroponic cultivation is increasingly vital in progressing to environment-friendly food production. To further alleviate the environmental impacts of synthetic fertilizer production, the use of recovered nutrients should be encouraged in horticulture and agriculture at large. Solid organic fertilizers can largely contribute to this, yet their physical and chemical nature impedes application in hydroponics. This study proposes a bioreactor for mineralization and nitrification followed by a supplementation step for limiting macronutrients to produce nitrate-based solutions from solid fertilizers, here based on a novel microbial fertilizer. Batch tests showed that aerobic conversions at 35 °C could realize a nitrate (NO₃−-N) production efficiency above 90% and a maximum rate of 59 mg N L−1 d−1. In the subsequent bioreactor test, nitrate production efficiencies were lower (44–51%), yet rates were higher (175–212 mg N L−1 d−1). Calcium and magnesium hydroxide were compared to control the bioreactor pH at 6.0 ± 0.2, while also providing macronutrients for plant production. A mass balance estimation to mimic the Hoagland nutrient solution showed that 92.7% of the NO₃−-N in the Ca(OH)₂ scenario could be organically sourced, while this was only 37.4% in the Mg(OH)₂ scenario. Besides, carbon dioxide (CO₂) generated in the bioreactor can be used for greenhouse carbon fertilization to save operational expenditure (OPEX). An estimation of the total OPEX showed that the production of a nutrient solution from solid organic fertilizers can be cost competitive compared to using commercially available liquid inorganic fertilizer solutions.

Abstract: Purple non‑sulfur bacteria (PNSB) possess significant potential for bioresource recovery from wastewater. Effective operational tools are needed to boost productivity and direct the PNSB biomass towards abundant value-added substances (e.g., protein and co-enzyme Q10, CoQ10). This study aimed to investigate the impact of light, oxygen and volatile fatty acids (VFAs) on PNSB growth (i.e., Rhodobacter sphaeroides) and productivity of protein and CoQ10. Overall, the biomass yields and specific growth rates of PNSB were in the ranges of 0.57–1.08 g biomass g−1 CODremoved and 0.48–0.71 d−1, respectively. VFAs did not influence the biomass yield, yet acetate and VFA mixtures enhanced the specific growth rate with a factor of 1.2–1.5 compared to propionate and butyrate. The most PNSB biomass (1.08 g biomass g−1 CODremoved and 0.71 d−1) and the highest biomass quality (protein content of 609 mg g−1 dry cell weight (DCW) and CoQ10 content of 13.21 mg g−1 DCW) were obtained in the presence of VFA mixtures under natural light and microaerobic (low light alternated with darkness; dissolved oxygen (DO) between 0.5 and 1 mg L−1) conditions (vs. light anaerobic and dark aerobic cultivations). Further investigation on VFAs dynamics revealed that acetate was most rapidly consumed by PNSB in the individual VFA feeding (specific uptake rate of 0.76 g COD g−1 DCW d−1), while acetate as a co-substrate in the mixed VFAs feeding might accelerate the consumption of propionate and butyrate through providing additional cell metabolism precursor. Enzymes activities of succinate dehydrogenase and fructose-1,6-bisphosphatase as well as the concentration of photo pigments confirmed that light, oxygen and VFAs regulated the key enzymes in the energy metabolism and biomass synthesis to boost PNSB growth. These results provide a promising prospect for utilization of fermented waste stream for the harvest of PNSB biomass, protein and CoQ10.

Abstract: To provide for the globally increasing demand for proteinaceous food, microbial protein (MP) has the potential to become an alternative food or feed source. Phosphorus (P), on the other hand, is a critical raw material whose global reserves are declining. Growing MP on recovered phosphorus, for instance, struvite obtained from wastewater treatment, is a promising MP production route that could supply protein-rich products while handling P scarcity. The aim of this study was to explore struvite dissolution kinetics in different MP media and characterize MP production with struvite as sole P-source. Different operational parameters, including pH, temperature, contact surface area, and ion concentrations were tested, and struvite dissolution rates were observed between 0.32 and 4.7 g P/L/d and a solubility between 0.23 and 2.22 g P-based struvite/L. Growth rates and protein production of the microalgae Chlorella vulgaris and Limnospira sp. (previously known as Arthrospira sp.), and the purple non‑sulfur bacterium Rhodopseudomonas palustris on struvite were equal to or higher than growth on conventional potassium phosphate. For aerobic heterotrophic bacteria, two slow-growing communities showed decreased growth on struvite, while the growth was increased for a third fast-growing one. Furthermore, MP protein content on struvite was always comparable to the one obtained when grown on standard media. Together with the low content in metals and micropollutants, these results demonstrate that struvite can be directly applied as an effective nutrient source to produce fast-growing MP, without any previous dissolution step. Combining a high purity recovered product with an efficient way of producing protein results in a strong environmental win-win.

Abstract: A soil history of exposure to extreme weather may impact future plant growth and microbial community assembly. Currently, little is known about whether and how previous precipitation regime (PR)-induced changes in soil microbial communities influence plant and soil microbial community responses to a subsequent PR. We exposed grassland mesocosms to either an ambient PR (1 day wet-dry alternation) or a persistent PR (30 days consecutive wet-dry alternation) for one year. This conditioned soil was then inoculated as a 10 % fraction into 90 % sterilized “native” soil, after which new plant communities were established and subjected to either the ambient or persistent PR for 60 days. We assessed whether past persistent weather-induced changes in soil microbial community composition affect soil microbial and plant community responses to subsequent weather persistence. The historical regimes caused enduring effects on fungal communities and only temporary effects on bacterial communities, but did not trigger soil microbial legacy effects on plant productivity when exposed to either current PR. This study provides experimental evidence for soil legacy of climate persistence on grassland ecosystems in response to subsequent climate persistence, helping to understand and predict the influences of future climate change on soil biota.

Abstract: Agricultural practices enhancing soil organic carbon (SOC) show potential to buffer negative effects of climate change on forage grass performance. We tested this by subjecting five forage grass varieties differing in fodder quality and drought/flooding resistance to increased persistence in summer precipitation regimes (PR) across sandy and sandy-loam soils from either permanent (high SOC) or temporary grasslands (low SOC) in adjacent parcels. Over the course of two consecutive summers, monoculture mesocosms were subjected to rainy/dry weather alternation either every 3 days or every 30 days, whilst keeping total precipitation equal. Increased PR persistence induced species-specific drought damage and productivity declines. Soils from permanent grasslands with elevated SOC buffered plant quality, but buffering effects of SOC on drought damage, nutrient availability and yield differed between texture classes. In the more persistent PR, Festuca arundinacea FERMINA was the most productive species but had the lowest quality under both ample water supply and mild soil drought, whilst under the most intense soil droughts, Festulolium FESTILO maintained the highest yields. The hybrid Lolium × boucheanum kunth MELCOMBI had intermediate productivity and both Lolium perenne varieties showed the lowest yields under soil drought, but the highest forage quality (especially the tetraploid variety MELFORCE). Performance varied with plant maturity stage and across seasons/years and was driven by altered water and nutrient availability and related nitrogen nutrition among species during drought and upon rewetting. Moreover, whilst permanent grassland soils showed the most consistent positive effects on plant performance, their available water capacity also declined under increased PR persistence. We conclude that permanent grassland soils with historically elevated SOC likely buffer negative effects of increasing summer weather persistence on forage grass performance, but may also be more sensitive to degradation under climate change.

Abstract: Long-term human Space missions will rely on regenerative life support as resupply of water, oxygen and food comes with constraints. The International Space Station (ISS) relies on an evaporation/condensation system to recover 74–85% of the water in urine, yet suffers from repetitive scaling and biofouling while employing hazardous chemicals. In this study, an alternative non-sanitary five-stage treatment train for one “astronaut” was integrated through a sophisticated monitoring and control system. This so-called Water Treatment Unit Breadboard (WTUB) successfully treated urine (1.2-L-d−1) with crystallisation, COD-removal, ammonification, nitrification and electrodialysis, before it was mixed with shower water (3.4-L-d−1). Subsequently, ceramic nanofiltration and single-pass flat-sheet RO were used. A four-months proof-of-concept period yielded: (i) chemical water quality meeting the hygienic standards of the European Space Agency, (ii) a 87-±-5% permeate recovery with an estimated theoretical primary energy requirement of 0.2-kWhp-L−1, (iii) reduced scaling potential without anti-scalant addition and (iv) and a significant biological reduction in biofouling potential resulted in stable but biofouling-limited RO permeability of 0.5 L-m−2-h−1-bar−1. Estimated mass breakeven dates and a comparison with the ISS Water Recovery System for a hypothetical Mars transit mission show that WTUB is a promising biological membrane-based alternative to heat-based systems for manned Space missions.