Autotrophic Microorganisms Research Articles

Distribution and correlation of iron oxidizers and carbon-fixing microbial communities in natural wetlands

Most microaerophilic Fe(II)-oxidizing bacteria (mFeOB) belonging to the family Gallionellaceae are autotrophic microorganisms that can use inorganic carbon to drive carbon sequestration in wetlands. However, the relationship between microorganisms involved in Fe and C cycling is not well understood. Here, soil samples were collected from different wetlands to explore the distribution and correlation of Gallionella-related mFeOB and carbon-fixing microorganisms containing cbbL and cbbM genes. A significant positive correlation was found between the abundances of mFeOB and the cbbL gene, as well as a highly significant positive correlation between the abundances of mFeOB and the cbbM gene, indicating the distribution of mFeOB in co-occurrence with carbon-fixing microorganisms in wetlands. The mFeOB were mainly dominated by Sideroxydans lithotrophicus ES-1 and Gallionella capsiferriformans ES-2 in all wetland soils. The structures of the carbon-fixing microbial communities were similar in these wetlands, mainly consisting of Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. The extractable Fe(II) concentrations affected the community composition of mFeOB, resulting in a significant difference in the relative abundances of the dominant FeOB. The main factors affecting cbbL-related microbial communities were dissolved inorganic carbon and oxygen, soil redox potential, and sodium acetate-extracted Fe(II). The composition of cbbM-related microbial communities was mainly affected by acetate-extracted Fe(II) and soil redox potential. In addition, the positive correlation between these functional microorganisms suggests that they play a synergistic role in Fe(II) oxidation and carbon fixation in wetland soil ecosystems. Our results suggest a cryptic relationship between mFeOB and carbon-fixing microorganisms in wetlands and that the microbial community structure can be effectively altered by regulating their physicochemical properties, thus affecting the capacity of carbon sequestration.

Effects of salinity on sulfur-dominated autotrophic denitrification microorganisms: Microbial community succession, key microorganisms and response mechanisms

This study investigated the performance of sulfur-dominated autotrophic denitrification (SAD) process under four different salinities of 0 %, 0.5 %, 3 %, and 6 %, simulating groundwater, sewage, seawater, and industrial wastewater scenarios, respectively. In terms of removal efficiency, the nitrate removal rates at 0.5 % and 3 % salinities decreased by 5.8 % and 16.8 %, respectively, compared to 0 % salinity. At 6 % salinity, the efficiency fluctuated during long-term operation, ranging from 56.0 % to 89.9 % of the value at 0 % salinity. According to the succession of microbial communities across time and salinity gradients, the dominant denitrification functional microorganisms were ranked by their salinity-tolerance ability as low-tolerant bacteria (0 %–0.5 %: Simplicispira, Herpetosipin, and Thermomonas), medium-tolerant bacteria (0 %–3 %: Thiobacillus and Sulfurimonas), high-tolerant bacteria (3 %–6 %: Thiogranum, Xanthomarina, and Vicingus), and halophilic bacteria (6 %: Aequorivita). Additionally, Aequorivita and Thiogranum, as the top 2 genera under 6 % salinity, presented positive and negative correlations with nitrate removal efficiency. The molecular ecological network revealed that increased positive interactions of 58.7 % among dominant genera occurred at 6 % salinity, confirming an effective cooperation coping with the high-salinity stress. In addition, the microbial responses to high-salinity primarily exhibited 22 %–45 % decrease in protein content, a 15 % decrease in live cells proportion, and a comparable level of individual functional gene expression. The results indicate that the efficiency of SAD by high salinity is determined by biomass amount and individual microbial capacity. This study offered new sights for understanding microbial succession and relationships in response to saltwater with diverse origins and varying water qualities in SAD systems.

From Rags to Riches: Exploiting the Calvin‐Benson‐Bassham Cycle for Biomanufacturing

AbstractIndustrial chemical production largely relies on fossil fuels, resulting in the unavoidable release of carbon dioxide (CO2) into the atmosphere. The concept of a circular carbon bioeconomy has been proposed to address this issue, wherein CO2 is captured and used as a raw material for manufacturing new chemicals. Microbial cell factories and, in particular, autotrophic microorganisms capable of utilizing CO2 as the sole carbon source, emerged as potential catalysts for upcycling CO2 to valuable products. The Calvin‐Benson‐Bassham cycle (CBBc), the best‐known CO2 fixation pathway, is widely distributed in Nature. While extensively studied, microbial engineering programmes based on the CBBc remains relatively underexplored. In this review, we discuss avenues towards biotechnological exploitation of the CBBc to engineer CO2‐utilizing microbial cell factories, with a focus on chemically‐derived electron donors. We also highlight the advantages and challenges of implementing the CBBc in heterotrophic microbial hosts and its potential to advance a true circular carbon bioeconomy. Moreover, based on the pathway's architecture, we argue about the ideal value‐added products to generate from this metabolic route. Altogether, studying and engineering the CBBc in both natural‐ and synthetic‐autotrophs will enhance our understanding on this CO2 fixation pathway, enabling further exploration of biomanufacturing avenues with CO2 as feedstock.

Impact of dust deposition on the growth of marine autotrophic and heterotrophic microorganisms: Evidence from the South China Sea

Aeolian dust can provide nutrients for the ocean and affect the growth of phytoplankton. However, the impacts of dust deposition on autotrophic and heterotrophic microorganisms have rarely been studied. In this study, we conducted two microcosm experiments in the low-nutrient and low-chlorophyll environment of the South China Sea and found that dust did not stimulate the abundance of autotrophic and heterotrophic microorganisms. Our results show that dust contains most of the unreacted iron-bearing minerals, and thus provides limited bioavailable iron and nitrogen for bacterioplankton and phytoplankton growth. These results elucidate the overlooked impacts of the properties of the iron-bearing minerals in aeolian dust on microbial communities, which may play an important role in marine ecosystems and climate change.

Optimized start-up strategies for elemental sulfur packing bioreactor achieving effective autotrophic denitrification

The start-up efficiency of the elemental sulfur packing bioreactor (S0PB) is constrained by the slow growth kinetics of autotrophic microorganisms, which is essentially optimized. This study aims to optimize start-up procedures and offer scientific guidance for the practical applications of S0PB. Through comparing the start-up efficiencies under various conditions related to inoculation, backwashing, and EBCT, it was found that these conditions did not significantly influence start-up time, but they did impact denitrification performance in detail. Using activated sludge as the inoculum was not recommended as the 2.5 ± 0.2 mg-N/L higher nitrite accumulation and 26.0 ± 5.1 % lower TN removal rate, compared to self-enrichment. Starting with a long-to-short EBCT (1 → 0.33 h) achieved higher nitrate removal of 11.5 ± 0.6 mg-N/L and eliminated nitrite accumulation compared to constantly short EBCT (0.33 h) conditions. Daily and postponed backwashing were suggested for long-to-short EBCT and constantly short EBCT start-up, respectively. Enrichment of Sulfurimonas was beneficial for the effective nitrite reduction process.

Unlocking the potential of elemental sulfur autotrophic denitrification through inorganic nutrient optimization

Elemental sulfur packed-bed (S0PB) bioreactors are increasingly employed to treat secondary effluents from wastewater treatment plants. Limited availability of inorganic nutrients, such as ammonium, phosphate, and inorganic carbon, significantly determines the growth of autotrophic microorganisms and the denitrification efficiency. This study investigated the constraining thresholds of inorganic nutrients on the elemental sulfur autotrophic denitrification process. In the absence of ammonium, phosphate, and bicarbonate, the denitrification rate decreased. Specifically, the ammonium assimilation process could be replaced by nitrate assimilation pathways, resulting in a 29.5 % decline in denitrification efficiency when the ammonium-N feed was reduced from 2.0 to 0 mg-N/L. However, the absence of phosphate-P and bicarbonate-C led to substantial drops in denitrification efficiency by 66.7 % and 77.5 %, respectively. This was primarily attributed to diminished biomass yield, as evidenced by reductions of 77.8–82.6 % in ATP and 35.7–44.3 % in protein content, along with a 12.4 %–14.7 % decrease in the relative abundances of dominant sulfur-oxidizing bacteria. Correlation analyses established specific thresholds for desired nitrate removal amounts: 0.131 for ammonium-N, 0.053 for phosphate-P, and 0.597 for bicarbonate-C. These thresholds provided valuable guidance for adjusting real-life wastewater through external supplementation when employing a pilot-scale S0PB bioreactor, leading to a significant enhancement of denitrification efficiency. This study emphasizes the significance of considering the concentrations of inorganic nutrients in wastewater when implementing S0PB bioreactors, which is a context that frequently neglects potential negative consequences.

Temporal variation in the spectrum and concentration of airborne microalgae and cyanobacteria in the urban environments of inland temperate climate.

Despite their non-negligible representation among the airborne bioparticles and known allergenicity, autotrophic microorganisms-microalgae and cyanobacteria-are not commonly reported or studied by aerobiological monitoring stations due to the challenging identification in their desiccated and fragmented state. Using a gravimetric method with open plates at the same time as Hirst-type volumetric bioparticle sampler, we were able to cultivate the autotrophic microorganisms and use it as a reference for correct retrospective identification of the microalgae and cyanobacteria captured by the volumetric trap. Only in this way, reliable data on their presence in the air of a given area can be obtained and analysed with regard to their temporal variation and environmental factors. We gained these data for an inland temperate region over 3 years (2018, 2020-2021), identifying the microalgal genera Bracteacoccus, Desmococcus, Geminella, Chlorella, Klebsormidium, and Stichococcus (Chlorophyta) and cyanobacterium Nostoc in the volumetric trap samples and three more in the cultivated samples. The mean annual concentration recorded over 3 years was 19,182 cells*day/m3, with the greatest contribution from the genus Bracteacoccus (57%). Unlike some other bioparticles like pollen grains, autotrophic microorganisms were present in the samples over the course of the whole year, with greatest abundance in February and April. The peak daily concentration reached the highest value (1011 cells/m3) in 2021, while the mean daily concentration during the three analysed years was 56 cells/m3. The analysis of intra-diurnal patterns showed their increased presence in daylight hours, with a peak between 2 and 4 p.m. for most genera, which is especially important due to their potential to trigger allergy symptoms. From the environmental factors, wind speed had a most significant positive association with their concentration, while relative air humidity had a negative influence.

Nitrogen use efficiency of microalgae application in wheat compared to mineral fertilizer

AbstractBackgroundWastewater from sewage treatment plants contains high levels of nutrients, which can be used for plant nutrition. Classical wastewater treatment plants use complex microbial consortia of autotrophic and heterotrophic microorganisms for biological wastewater treatment. Certain autotrophic microalgae (e.g., species of the genera Chlorella, Scenedesmus, and Pediastrum) accumulate nutrients from wastewater very effectively.AimsWe investigated the potential of microalgae biomass obtained from a prototype wastewater treatment plant as a source of nutrients for crops, focusing on nitrogen.MethodsWe provided wheat plants with different levels of algae biomass equivalent to 60, 120, and 180 kg N per hectare or with mineral fertilizer (N, P, and K) equivalent to the amounts contained in the algal biomass. Physiological and phenotypic traits were measured during growth, including vegetation indices, photosynthetic performance, growth, and nitrogen use efficiency (NUE). In addition, the adundances of Bacteria, Archaea and fungi and genes of ammonium oxidizing Bacteria and Archaea were determined in the rhizosphere of differently fertilized plants.ResultsMicroalgal application at fertilizer levels of 120 and 180 kg N ha–1 showed significantly improved physiological performance, growth, yield and nutrient uptake compared to the unfertilized control. Nevertheless, their yields and NUE were lower than with the application of equal amounts of mineral fertilization, while the adundance of rhizosphere microbes and ammonia‐oxidizing microorganisms were not significantly affected.ConclusionsMicroalgae from wastewater treatments form a suitable source of organic fertilizer for wheat plants with only moderate reductions in N use efficiency compared to mineral fertilizer.

Automatic Control of Chemolithotrophic Cultivation of Cupriavidus necator: Optimization of Oxygen Supply for Enhanced Bioplastic Production

Gas fermentation is an upcoming technology to convert gaseous substrates into value-added products using autotrophic microorganisms. The hydrogen-oxidizing bacteria Cupriavidus necator efficiently uses CO2 as its sole carbon source, H2 as electron donor and O2 as electron acceptor. Surplus CO2 is stored in microbial storage material poly-(R)-3-hydroxybutyrate. O2 supply is the most critical parameter for growth and poly-(R)-3-hydroxybutyrate formation. A narrow O2 optimum between ~0.2 and ~4 mg/L was previously reported. Here, a standard benchtop bioreactor was redesigned for autotrophic growth of C. necator on explosive mixtures of CO2, H2 and O2. The bioreactor was equipped with mass flow control units and O2 and CO2 sensors. A controller for automated gas dosage based on a mathematical model including gas mass transfer, gas consumption and sensor response time was developed. Dissolved O2 concentrations were adjusted with high precision to 1, 2 and 4% O2 saturation (0.4, 0.8 and 1.5 mg/L dissolved O2, respectively). In total, up to 15 g/L cell dry weight were produced. Residual biomass formation was 3.6 ± 0.2 g/L under all three O2 concentrations. However, poly-(R)-3-hydroxybutyrate content was 71, 77 and 58% of the cell dry weight with 1, 2 and 4% dissolved O2, respectively.

Core autotrophic microbes drive functional stability of soil cbbL-containing autotrophic microbes during desertification

The desertification process is characterized by the degradation of soil habitats and attenuation of plant biomass, leading to decreased soil carbon (C) input and increased environmental stress gradients of soil microbes. C dioxide assimilation driven through autotrophic microorganisms is the main process of soil C cycling, and the ecological role of autotrophic microbes is critical for soil C sequestration. However, the feedback dynamics of autotrophic microbes and their functional activity in soil profiles during desertification have not been explored. Here, we analysed three typical stages of desertification (potential, moderate and severe desertification) by high-throughput sequencing and enzyme activity assays to investigate the variation trends of autotrophic microbes and the maintenance of C fixation activity along soil profiles (0–100 cm) as desertification proceeded. We found that the desertification process reduced the abundance and diversity of autotrophic microbes, but increased the activity of soil microbial C fixation enzymes, which highlights the importance of microbial CO2 fixation in oligotrophic soil profiles in desert ecosystems. In particular, we demonstrated that core autotrophic microbes drove the compositional difference of autotrophic microbes, which in turn affected soil C fixation activity, suggesting that core autotrophic microbes are critical for maintaining C sequestration during desertification. Taken together, these results strengthen our comprehension of the factors driving soil functional stability and emphasize that core microbes should be viewed as pivotal factors in maintaining functional activity and ecosystem sustainability during desertification.

Synergistic between autotrophic and heterotrophic microorganisms for denitrification using bio-S as electron donor

In recent years, biological sulfur (bio-S) was employed in sulfur autotrophic denitrification (SAD) in which autotrophic Thiobacillus denitrificans and heterotrophic Stenotrophomonas maltophilia played a key role. The growth pattern of T.denitrificans and S.maltophilia exhibited a linear relationship between OD600 and CFU when OD600 < 0.06 and <0.1, respectively. When S.maltophilia has applied alone, the NorBC and NosZ were undetected, and denitrification was incomplete. The DsrA of S.maltophilia could produce sulfide as an alternative electron donor for T.denitrificans. Even though T.denitrificans had complete denitrification genes, its efficiency was low when used alone. The interaction of T.denitrificans and S.maltophilia reduced nitrite accumulation, leading to complete denitrification. A sufficient quantity of S.maltophilia may trigger the autotrophic denitrification activity of T.denitrificans. When the colony-forming units (CFU) ratio of S.maltophilia to T.denitrificans was reached at 2:1, the highest denitrification performance was achieved at 2.56 and 12.59 times higher than applied alone. This research provides a good understanding of the optimal microbial matching for the future application of bio-S.

Extraction of Bio-pigments from the Green Microalgae Chlorella pyrenoidosa Under Different Solvent Ratios

Nowadays, the use of microalgae biomass is evolving rapidly for their various applications such as food, pharmaceutical, and cosmetics. One of the essential compounds in microalgae that have good perspectives in the market is pigment since it can be used as a natural colorant in food or cosmetics. However, the extraction of bio-pigments from the green microalgae Chlorella pyrenoidosa under different solvent ratios is still rarely reported. Therefore, this study aims to investigate the bio-pigment potential from C. pyrenoidosa extracted under different ethanol ratios. The algae-to-ethanol ratios of 1:5, 1:7.5, and 1:10 were employed in this study. Overall, C. pyrenoidosa contains total chlorophyll content much higher than carotenoids due to the fact that C. pyrenoidosa is the autotrophic microorganism that performs photosynthesis. The total chlorophyll content decreased with an increase in ethanol ratio, i.e., 134.47, 133.74, and 129.46 μg/mL at the ratio of 1:5, 1:7.5, and 1:10, respectively. In contrast, the carotenoid content slightly increased with an increase in ethanol ratio, i.e., 86.64, 87.08, 88.45 μg/mL at the ratio of 1:5, 1:7.5, and 1:10, respectively. The main chlorophyll compounds in the ethanol extract with the algae-to-ethanol molar ratio of 1:5 were identified as chlorophyll c (47.09 μg/mL), followed by chlorophyll b (38.50 μg/mL), chlorophyll a (28.67 μg/mL), and chlorophyll d (20.23 μg/mL).

Effects of tillage management on cbbL-carrying bacteria and soil organic carbon dynamics across aggregate size classes in the farmland of North China Plain

Calvin-Benson-Bassham cycle (cbbL)-carrying bacteria in soil are essential to renew and circulate organic matter. However, the relation between cbbL-carrying bacteria and soil carbon dynamics under tillage managements, especially across the aggregate size remains unclear. Thus, in our study, soil organic carbon (SOC) storages, mineralization, and the cbbL-carrying bacterial community across five soil aggregate sizes were thoroughly investigated under four tillage treatments: conventional rotary tillage (CT), deep plowing (DP), subsoiling (SS), no-tillage (NT). We found macroaggregates (>2 mm) contributed most with regard to SOC stocks, whereas microaggregates (<0.25 mm) contributed the least among all the tillage managements (NT, DP, SS and CT). Macroaggregates (>1 mm) with the highest cumulative SOC mineralization were found in subsoiling, whereas microaggregates had the lowest cumulative mineralization under no-tillage. By physically protecting, no-tillage specifically inhibited carbon dioxide (CO2) emissions in macroaggregates (>1 mm), whereas increased SOC levels and encouraged CO2 releases across microaggregates. Shifts in the co-occurrence network demonstrated that subsoiling promoted the joint symbiotic function between cbbL-carrying bacteria, the efficiency of matter and energy, and information transfer. And the keystone species, the enhanced cooperation and stochastic processes of autotrophic microorganisms under subsoiling lead to increased carbon fixation and reduced CO2 emissions in microaggregates with limited oxygen and nutrients. Overall, our work verified physical protection of large aggregates under no-tillage and improvement of microbial interaction efficiency under subsoiling. This may offer a theoretical foundation for the choice of tillage practices in fluvo-aquic soil regions.

"Candidatus Hydrogenisulfobacillus filiaventi" strain R50 gen. nov. sp. nov., a highly efficient producer of extracellular organic compounds from H2 and CO2.

Production of organic molecules is largely depending on fossil fuels. A sustainable alternative would be the synthesis of these compounds from CO2 and a cheap energy source, such as H2, CH4, NH3, CO, sulfur compounds or iron(II). Volcanic and geothermal areas are rich in CO2 and reduced inorganic gasses and therefore habitats where novel chemolithoautotrophic microorganisms for the synthesis of organic compounds could be discovered. Here we describe "Candidatus Hydrogenisulfobacillus filiaventi" R50 gen. nov., sp. nov., a thermoacidophilic, autotrophic H2-oxidizing microorganism, that fixed CO2 and excreted no less than 0.54 mol organic carbon per mole fixed CO2. Extensive metabolomics and NMR analyses revealed that Val, Ala and Ile are the most dominant form of excreted organic carbon while the aromatic amino acids Tyr and Phe, and Glu and Lys were present at much lower concentrations. In addition to these proteinogenic amino acids, the excreted carbon consisted of homoserine lactone, homoserine and an unidentified amino acid. The biological role of the excretion remains uncertain. In the laboratory, we noticed the production under high growth rates (0.034 h-1, doubling time of 20 h) in combination with O2-limitation, which will most likely not occur in the natural habitat of this strain. Nevertheless, this large production of extracellular organic molecules from CO2 may open possibilities to use chemolithoautotrophic microorganisms for the sustainable production of important biomolecules.

Diatom-inspired stiffness optimization for plates and cellular solids

Diatoms, a class of aquatic autotrophic microorganisms, are characterized by silicified exoskeletons with highly complex architectures. These morphologies have been shaped by the selection pressure that the organisms have been subjected to during their evolutionary history. Two properties which are highly likely to have contributed to the evolutionary success of current diatom species are lightweightness and structural strength. Thousands of diatom species are present in water bodies today, and although each has its unique shell architecture, a strategy that is common across species is the uneven and gradient solid material distribution across their shells. The aim of this study is to present and evaluate two novel structural optimization workflows inspired by material grading strategies in diatoms. The first workflow mimics the Auliscus intermidus diatoms’ surface thickening strategy and generates continuous sheet structures with optimal boundaries and local sheet thickness distributions when applied to plate models subjected to in-plane boundary conditions. The second workflow mimics the Triceratium sp. diatoms’ cellular solid grading strategy, and produces 3D cellular solids with optimal boundaries and local parameter distributions. Both methods are evaluated through sample load cases, and prove to be highly efficient in transforming optimization solutions with non-binary relative density distributions into highly performing 3D models.

Metabolic Performance and Fate of Electrons during Nitrate-Reducing Fe(II) Oxidation by the Autotrophic Enrichment Culture KS Grown at Different Initial Fe/N Ratios.

Autotrophic nitrate-reducing Fe(II)-oxidizing (NRFeOx) microorganisms fix CO2 and oxidize Fe(II) coupled to denitrification, influencing carbon, iron, and nitrogen cycles in pH-neutral, anoxic environments. However, the distribution of electrons from Fe(II) oxidation to either biomass production (CO2 fixation) or energy generation (nitrate reduction) in autotrophic NRFeOx microorganisms has not been quantified. We therefore cultivated the autotrophic NRFeOx culture KS at different initial Fe/N ratios, followed geochemical parameters, identified minerals, analyzed N isotopes, and applied numerical modeling. We found that at all initial Fe/N ratios, the ratios of Fe(II)oxidized to nitratereduced were slightly higher (5.11 to 5.94 at Fe/N ratios of 10:1 and 10:0.5) or lower (4.27 to 4.59 at Fe/N ratios of 10:4, 10:2, 5:2, and 5:1) than the theoretical ratio for 100% Fe(II) oxidation being coupled to nitrate reduction (5:1). The main N denitrification product was N2O (71.88 to 96.29% at Fe/15N ratios of 10:4 and 5:1; 43.13 to 66.26% at an Fe/15N ratio of 10:1), implying that denitrification during NRFeOx was incomplete in culture KS. Based on the reaction model, on average 12% of electrons from Fe(II) oxidation were used for CO2 fixation while 88% of electrons were used for reduction of NO3- to N2O at Fe/N ratios of 10:4, 10:2, 5:2, and 5:1. With 10 mM Fe(II) (and 4, 2, 1, or 0.5 mM nitrate), most cells were closely associated with and partially encrusted by the Fe(III) (oxyhydr)oxide minerals, whereas at 5 mM Fe(II), most cells were free of cell surface mineral precipitates. The genus Gallionella (>80%) dominated culture KS regardless of the initial Fe/N ratios. Our results showed that Fe/N ratios play a key role in regulating N2O emissions, for distributing electrons between nitrate reduction and CO2 fixation, and for the degree of cell-mineral interactions in the autotrophic NRFeOx culture KS. IMPORTANCE Autotrophic NRFeOx microorganisms that oxidize Fe(II), reduce nitrate, and produce biomass play a key role in carbon, iron, and nitrogen cycles in pH-neutral, anoxic environments. Electrons from Fe(II) oxidation are used for the reduction of both carbon dioxide and nitrate. However, the question is how many electrons go into biomass production versus energy generation during autotrophic growth. Here, we demonstrated that in the autotrophic NRFeOx culture KS cultivated at Fe/N ratios of 10:4, 10:2, 5:2, and 5:1, ca. 12% of electrons went into biomass formation, while 88% of electrons were used for reduction of NO3- to N2O. Isotope analysis also showed that denitrification during NRFeOx was incomplete in culture KS and the main N denitrification product was N2O. Therefore, most electrons stemming from Fe(II) oxidation seemed to be used for N2O formation in culture KS. This is environmentally important for the greenhouse gas budget.

Carbon capture and utilization: More than hiding CO2 for some time

Carbon capture and utilization: More than hiding CO2 for some time

Enhanced nutrient removal of agricultural waste-pyrite bioretention system for stormwater pollution treatment

Pyrite as filler applied to bioretention cells has the potential for simultaneous nitrogen and phosphorus removal, but its low electron supply rate cannot adapt to the demand for nitrogen and phosphorus removal under high rainfall intensity and continuous rainfall conditions. In this study, novel pyrite-based bioretention cells with agricultural waste amendment (corn cobs, rice husks, wood chips) were developed, and the pollution removal of each cell was evaluated under simulated complex rainfall conditions. The bioretention cell amended with woodchips achieved significantly higher efficiency and stability for dissolved nutrient removal compared with the pyrite bioretention cell. Its average removal efficiency of nitrate nitrogen, total nitrogen, and phosphate phosphorus was 69.39%, 45.60%, and 60.01% higher than that of the control group. The average chemical oxygen demand (COD) and total iron (TFe) concentrations in the effluent were slightly higher than those from the pyrite bioretention cell but were significantly lower than those from the corn cob and the rice husk-pyrite bioretention cell. Microbiological analysis revealed that the addition of woodchips significantly increased the relative abundance of Thiobacillus (the main functional genus of autotrophic denitrification) and Thauera (the main functional genus of heterotrophic denitrification) in the bioretention cell to 25.17% and 3.06%. The results indicated that woodchips promoted the proliferation of both heterotrophic and autotrophic microorganisms, therefore enhancing the nitrogen removal efficiency of mixotrophic denitrification.

Biofuel Production Via in Situ Resource Utilization on Mars

This paper is based on the fundamentals and principles of materials science and resource utilization. In-situ resource utilization (ISRU) can make full use of materials in space to produce the resources needed for human survival and even interstellar migration programs. Bio-based biofuel production solutions can address human consumption in space exploration while allowing the production of fuels in a sustainable manner, with minimal inputs and producing cleaner, more environmentally friendly fuels.ISRU biofuel production can be achieved by directly converting inorganic carbon (atmospheric CO2) into target compounds as biofuels by autotrophic microorganisms, or by fixing carbon and then use metabolic engineering to convert biomass or complex substrates into target compounds, completing a two-step biofuel production process. In this paper, we investigate a potential microbial cell factory for biofuel production on Mars via ISRU, leading to some relevant breakthroughs and discoveries. This paper advances the development of the research content through a series of studies.In this paper, we have studied and optimized the use of new energy fuels based on basic fuel performance studies. This paper provides a new way of thinking and research in the field of energy research, based on the previous basic research.

Exploring the effects of organic loading rate and domestic wastewater treatment by algal‐bacterial granules under natural daylight conditions

Algal-bacterial granules or phototrophic granules (PGs) comprising phototrophic microorganisms and bacteria are explored in wastewater treatment for achieving both environmental and economic sustainability. This study describes development of PGs and their use in biological treatment of synthetic and real domestic wastewater (sewage) under natural daylight conditions and low organic loading rate (OLR). Development of PGs was sequentially recorded in a photobioreactor operated in photo-sequencing batch reactor (photo-SBR) mode at a low OLR of 1 kgCOD.m-3 .day-1 and the developed PGs was evaluated for treating synthetic wastewater and real municipal wastewater with 0.14 kg COD m-3 .day-1 . PGs formed in the photo-sequential batch reactor (SBR) were compact and dense and exhibited excellent settling properties. The removal efficiencies were determined to be up to 95%, 93%, 97%, 72%, and 88% for turbidity, COD, TOC, NH4 + -N, and NO2 - -N/NO3 - -N, respectively. Additionally, a reduction in total viable bacterial counts and fecal coliform bacteria up to 1.7 × 103 and 7.8 × 102 cfu.mL-1 , respectively, during treatment of real municipal wastewater was achieved. This study demonstrated cultivation of algal-bacterial granules or PGs and their application for treating real municipal wastewater under natural daylight and tropical climate conditions. Further studies are needed on understanding interactions among phototrophic, autotrophic, and heterotrophic microorganisms of complex algal-bacterial consortium for emerging applications in bioremediation and wastewater treatment. PRACTITIONER POINTS: Phototrophic granules (PGs) were cultivated from algal consortium and activated sludge inoculum in photo sequencing batch reactors. Granular photobioreactor was operated at low OLR of 1 kgCOD.m3 .day-1 for developing well-settling algal-bacterial granules. PGs were stable and showed efficient biological treatment of synthetic wastewater and real sewage. Removals for turbidity, pathogens, and ammonium were at 95%, 3-log, and 72%, respectively, from real sewage.