Enriched Biomass Research Articles

Optimizing the Recovery of Rare Earth Elements from Spent Fluorescent Lamps by Living Ulva sp.

Given the significant industrial applications of rare earth elements (REEs), supply chain constraints, and negative environmental impacts associated with their extraction, finding alternative sources has become a critical challenge. Previously, we highlighted the potential of living Ulva sp. in the removal and pre-concentration of Y from a solution obtained by sequential acid leaching of spent fluorescent lamps (SFLs). Here, we extended that study to other REEs extracted from SFLs and evaluated the effect of pH (4.5-9.0), light exposure (absence, natural and supplemented with artificial light), and Hg (presence and absence). The results showed small differences in the removal of Y (23-30%) and other REEs at the different pH values, opening the scope of the methodology. However, Ulva sp. relative growth rate (RGR) was negatively affected in the higher acidity condition, without any visible signs of decay. In the absence of light, the RGR also decreased, which was accompanied by a halving of the removal efficiency compared to that with artificial light supplementation (40% for Y). Although Hg had minimal influence on the removal and concentration of REEs by Ulva sp., its presence in the enriched biomass is undesirable. Therefore, this contaminant was selectively removed from the solution using Fe3O4@SiO2/SiDTC nanoparticles before contact with the macroalgae (70% removal in 30 min; 99% in 72 h). In addition to easy solubilization, macroalgae enriched with REEs have a simpler composition compared to SFLs. Calcination of the biomass allowed the REEs to be further concentrated, with concentrations (130 mg/g for Y) up to 240 times higher than in typical apatite ore. This highlights enriched biomass as a sustainable alternative to traditional mining for obtaining these critical raw materials.

Mineralized nitrogen uptake by plants of the use of synthetic nitrogen fertilization in agriculture

The underground transfer of nitrogen from non-food crop residues to cash crops is an important tool to ensure decent crop yields and balance N use in agroecosystems. Laboratory experiments were performed to determine nitrogen migration in spring wheat at different growth stages using labelled nitrogen. In the first stage of the experiment, Artemisia dubia was grown in climate chambers (Climacell CLC-707-TV), with air temperature cycles of 8 h at 15 °C and 16 h at 20 °C, and fertiliz using 15N isotope enriched ammonia nitrate. In the second stage of the experiment, spring wheat was sown and grown to full maturity in two soils of differing soil acidity (pH 3.93 ± 0,04 and pH 7.07 ± 0,08) and mixed with the chopped pieces (3–5 cm mean length) of Artemisia dubia above-ground biomass obtained in the first stage of the experiment. Each soil had four experimental treatments: non-enriched biomass; non-enriched biomass and fertilizer (170 N kg h−1); biomass enriched by 15N and no fertilizer, and 15N enriched biomass and fertilizer (170 N kg h−1). Spring wheat and soil were sampled every two weeks for dry matter (DM), total N and 15N content measurements during the experiment (13 weeks). The results showed that improved crop nitrogen utilization from Artemisia dubia residues were achieved when additional crop fertilizers was not used. It implies that adding additional nitrogen might increase the degradation of plant biomass, but at the same time cause environmental pollution by leaching as plants use it slightly for their growth.

Granular sludge characterization and microbial response in a hydroxyapatite (HAP)- anammox coupled process at different nitrogen loading rates

To enhance the treatment capacity and operational stability of the anammox process for nutrient-rich wastewater disposal, a hydroxyapatite (HAP)-anammox coupled process was developed in a granular sludge-based upflow bioreactor. The impact of nitrogen loading rate (NLR) on process performance was investigated by gradually increasing the NLR from 1 to 1.5, 3, and 5 kgN/m3/d for 264 days continuous operation. TN and TP removal rates of 82.51 ± 3.58 % and 60.49 ± 2.82 % were achieved at the NLR of 5 kgN/m3/d. The precipitation of Ca and phosphorus resulted in HAP crystals formation evidenced by sludge morphology and component analysis, which enhanced sludge settling properties and facilitated biomass enrichment. The HAP-anammox granular sludge was characterized by the outer layer HAP crystals formed on inner anammox granules, while highly mineralized granular sludge with higher density distributed at the bottom of the reactor is conducive to HAP-based phosphorus recovery. After a long-term accumulation, the abundance of Planctomycetota phylum gradually increased (from 7.7 % to 14.1 %), consisting of three species of anammox bacteria, namely Candidatus_Brocadia_sapporoensis, Candidatus_Brocadia_sinica and Candidatus_Kuenenia_stuttgartiensis. Nitrogen metabolic pathway analysis illustrated that denitrification was also present except the anammox reaction, synergistically contributing to superior nitrogen removal in the HAP-anammox process.

Microbial mat-induced microfacies in clastic deposits – An overview

Abstract This contribution reviews microbial microfacies recognisable in vertical sections through modern or fossil mat-overgrown sediment. Microfacies are products of endobenthic or epibenthic microbial mats interacting with sediment dynamics. Laminae of such mats form during sediment dynamic quiescence by organisation of filaments to an interwoven mat fabrics (binding), and biomass enrichment (growth) by cell replication and the production of extracellular polymeric substances (EPS). Vertical sections through mat-covered sediment may show buried stacks of subrecent mat laminae (biolaminites) that rose from alternating periods of mat development and sediment deposition. Mat laminae that drape ripple marks are visible as sinoidal structures in sediment core or sections. If the sediment-stabilising properties of a microbial mat is overcome by currents or waves of high strengths, cm-size mat fragments (mat chips and roll-ups) are ripped off and redeposited. Intrasedimenary gases, trapped beneath mat layers, may cause a high secondary porosity (sponge pore sand) in the sandy substrates. The internal build-up (microfabrics) of mat laminae is investigated under high magnification. Endobenthic microbial mat fabrics include filamentous and coccoid cells forming a network, EPS, and sedimentary grains. The grains derived from interaction of the endobenthic mats with bed load. Epibenthic microbial mat fabrics may include also silt-size particles syndepositionally enriched by baffling and trapping of suspension load. The fabrics of these mats commonly also include oriented sedimentary grains. These grains (now aligned bedding parallel) were dragged upward from the substrate during the development and growth of the mat. Overall, microbial microfacies provide insight into the sedimentation pattern of the (paleo-)environment and into the types of the substrate-colonising microbial mats.

From 13C-lignin to 13C-mycelium: Agaricus bisporus uses polymeric lignin as a carbon source.

Plant biomass conversion by saprotrophic fungi plays a pivotal role in terrestrial carbon (C) cycling. The general consensus is that fungi metabolize carbohydrates, while lignin is only degraded and mineralized to CO2. Recent research, however, demonstrated fungal conversion of 13C-monoaromatic compounds into proteinogenic amino acids. To unambiguously prove that polymeric lignin is not merely degraded, but also metabolized, carefully isolated 13C-labeled lignin served as substrate for Agaricus bisporus, the world's most consumed mushroom. The fungus formed a dense mycelial network, secreted lignin-active enzymes, depolymerized, and removed lignin. With a lignin carbon use efficiency of 0.14 (g/g) and fungal biomass enrichment in 13C, we demonstrate that A. bisporus assimilated and further metabolized lignin when offered as C-source. Amino acids were high in 13C-enrichment, while fungal-derived carbohydrates, fatty acids, and ergosterol showed traces of 13C. These results hint at lignin conversion via aromatic ring-cleaved intermediates to central metabolites, underlining lignin's metabolic value for fungi.

A mass balance approach for quantifying the role of natural decay and fate mechanisms on SARS-CoV-2 genetic marker removal during water reclamation.

The recent SARS-CoV-2 outbreak yielded substantial data regarding virus fate and prevalence at water reclamation facilities (WRFs), identifying influential factors as natural decay, adsorption, light, pH, salinity, and antagonistic microorganisms. However, no studies have quantified the impact of these factors in full scale WRFs. Utilizing a mass balance approach, we assessed the impact of natural decay and other fate mechanisms on genetic marker removal during water reclamation, through the use of sludge and wastewater genetic marker loading estimates. Results indicated negligible removal of genetic markers during P/PT (primary effluent (PE) p value: 0.267; preliminary and primary treatment(P/PT) accumulation p value: 0.904; and thickened primary sludge (TPS) p value: 0.076) indicating no contribution of natural decay and other fate mechanisms toward removal in P/PT. Comparably, adsorption and decomposition was found to be the dominant pathway for genetic marker removal (thickened waste activated sludge (TWAS) log loading 9.75 log10 GC/day); however, no estimation of log genetic marker accumulation could be carried out due to high detections in TWAS. PRACTITIONER POINTS: The mass balance approach suggested that the contribution of natural decay and other fate mechanisms to virus removal during wastewater treatment are negligible compared with adsorption and decomposition in P/PT (p value: 0.904). During (P/PT), a higher viral load remained in the (PE) (14.16 log10 GC/day) compared with TPS (13.83 log10 GC/day); however, no statistical difference was observed (p value: 0.280) indicting that adsorption/decomposition most probably did not occur. In secondary treatment (ST), viral genetic markers in TWAS were consistently detected (13.41 log10 GC/day) compared with secondary effluent (SE), indicating that longer HRT and the potential presence of extracellular polymeric substance-containing enriched biomass enabled adsorption/decomposition. Estimations of total solids and volatile solids for TPS and TWAS indicated that adsorption affinity was different between solids sampling locations (p value: <0.0001).

PHA and EPS production from industrial wastewater by conventional activated sludge, membrane bioreactor and aerobic granular sludge technologies: A comprehensive comparison

The present study has focused on the mainstream integration of polyhydroxyalkanoate (PHA) production with industrial wastewater treatment by exploiting three different technologies all operating in sequencing batch reactors (SBR): conventional activated sludge (AS-SBR), membrane bioreactor (AS-MBR) and aerobic granular sludge (AGS). A full aerobic feast/famine strategy was adopted to obtain enrichment of biomass with PHA-storing bacteria. All the systems were operated at different organic loading (OLR) rate equal to 1-2-3 kgCOD/m3∙d in three respective experimental periods. The AS-MBR showed the better and stable carbon removal performance, whereas the effluent quality of the AS-SBR and AGS deteriorated at high OLR. Biomass enrichment with PHA-storing bacteria was successfully obtained in all the systems. The AS-MBR improved the PHA productivity with increasing OLR (max 35% w/w), whereas the AS-SBR reduced the PHA content (max 20% w/w) above an OLR threshold of 2 kgCOD/m3∙d. In contrast, in the AGS the increase of OLR resulted in a significant decrease in PHA productivity (max 14% w/w) and a concomitant increase of extracellular polymers (EPS) production (max 75% w/w). Results demonstrated that organic carbon was mainly driven towards the intracellular storage pathway in the AS-SBR (max yield 51%) and MBR (max yield 61%), whereas additional stressors in AGS (e.g., hydraulic selection pressure, shear forces) induced bacteria to channel the COD into extracellular storage compounds (max yield 50%) necessary to maintain the granule's structure. The results of the present study indicated that full-aerobic feast/famine strategy was more suitable for flocculent sludge-based technologies, although biofilm-like systems could open new scenarios for other biopolymers recovery (e.g., EPS). Moreover, the AS-MBR resulted the most suitable technology for the integration of PHA production in a mainstream industrial wastewater treatment plant, considering the greater process stability and the potential reclamation of the treated wastewater.

Is enrichment with inorganic and organic compounds feasible for improving the quality of vermicomposting using water hyacinth biomass?

In eutrophic environments, aquatic weeds reproduce rapidly, occupying extensive areas of the water body and preventing the multiple use of water resources. The use of the biomass of these plants in vermicomposting represents a sustainable alternative utilization of the excess biomass produced by eutrophication. The enrichment of macrophyte biomass during vermicomposting was tested using aninorganic solution (NPK 1.75 % and NPK 3.50 %) and an organic solution with glucose (0.25 g/L and 0.50 g/L) to improve the quality of the vermicompost. The consumption of biomass of the macrophytes by the Eisenia fetida increased as the vermicomposting progressed, reaching the highest values at the end of the experimental period. The control treatment, i.e., without earthworms, remained stable.The electrical conductivity tended to increase for the treatments NPK 1.75 %, Glucose 0.25 g/L and Glucose 0.50 g/L. The pH of the vermicomposting tended to be neutral in all treatments. The control and inorganic treatments showed a reduction in macrophyte biomass and the number of individuals of Eisenia fetida. The additions of NPK and glucose slightly improved vermicompost quality andbiomass consumption by the earthworms. However, using vermicompost alone does not meet the requirements for its use as a fertilizer. Thus, we suggest the use of vermicompost in association with other fertilizers, adding moisture and structuring the soil.

Metabolic Profiles and Microbial Synergy Mechanism of Anammox Biomass Enrichment and Membrane Fouling Alleviation in the Anammox Dynamic Membrane Bioreactor.

The anammox dynamic membrane bioreactor (DMBR) is promising in applications with enhanced anammox biomass enrichment and fouling alleviation. However, the metabolic mechanism underlying the functional features of anammox sludge and the biofilm membrane is still obscure. We investigated the metabolic networks of anammox sludge and membrane biofilm in the DMBR. The cooperation between anammox and dissimilatory nitrate reduction to ammonium processes favored the robust anammox process in the DMBR. The rapid bacterial growth occurred in the DMBR sludge with 1.33 times higher biomass yield compared to the MBR sludge, linked to the higher activities of lipid metabolism, nucleotide metabolism, and B vitamin-related metabolism of the DMBR sludge. The metabolism of the DMBR biofilm microbial community benefited the fouling alleviation that the abundant fermentative bacteria and their cooperation with the anammox sludge microbial community promoted organics degradation. The intensified degradation of foulants by the DMBR biofilm community was further evidenced by the active carbohydrate metabolism and the upregulated vitamin B intermediates in the biofilms of the DMBR. Our findings provide insights into key metabolic mechanisms for enhanced biomass enrichment and fouling control of the anammox DMBR, guiding manipulations and applications for overcoming anammox biomass loss in the treatment of wastewater under detrimental environmental conditions.

Modeling Physical and Physiological Processes Reveals the Role of Turbulence in the Prerequisites for Microcystis Blooms

AbstractHarmful algal blooms of Microcystis have become a global problem. Turbulence, a determining factor affecting blooms, not only disperses surface scum but also controls the growth of Microcystis. Numerous studies have analyzed the effects of turbulence on the growth and colony size of Microcystis in laboratories, but the turbulence thresholds for Microcystis growth and colony disaggregation in the field are difficult to determine due to the complex environment. In addition, the quantitative contribution of turbulence‐driven blooms and the intrinsic mechanisms of the spatial distribution responding to turbulence are unclear. In this study, a fully integrated filed scale computational model focusing on turbulence‐driven blooms was developed, which incorporates physical processes (turbulence‐induced vertical mixing, VMT) and physiological processes such as buoyancy‐controlling transport (BCT), turbulence‐induced colony size variation (CSV), and growth rate variation (GRV). We performed model sensitivity analysis and evaluated the effects of turbulence intensity and duration on the biomass and vertical distribution of Microcystis. The results show that the optimal turbulence dissipation rate for Microcystis growth in the field is 1.0 × 10−5 m2/s3 and the critical turbulence dissipation rate for aggregation distribution is 3.81 × 10−6 m2/s3 in shallow lakes. A quantitative comparison of the effects of physical/physiological processes on blooms shows that physiological processes (CSV, GRV, and BCT) are critical for biomass enrichment, and the accumulation of Microcystis at the water surface is dominated by physical processes (VMT). This study reveals the mechanisms of turbulence‐driven Microcystis blooms and provides new insights for algal bloom prediction and control.

Quest for Nitrous Oxide-reducing Bacteria Present in an Anammox Biofilm Fed with Nitrous Oxide.

N2O-reducing bacteria have been examined and harnessed to develop technologies that reduce the emission of N2O, a greenhouse gas produced by biological nitrogen removal. Recent investigations using omics and physiological activity approaches have revealed the ecophysiologies of these bacteria during nitrogen removal. Nevertheless, their involvement in‍ ‍anammox processes remain unclear. Therefore, the present study investigated the identity, genetic potential, and activity‍ ‍of N2O reducers in an anammox reactor. We hypothesized that N2O is limiting for N2O-reducing bacteria‍ ‍and an‍ ‍exogeneous N2O supply enriches as-yet-uncultured N2O-reducing bacteria. We conducted a 1200-day incubation of N2O-reducing bacteria in an anammox consortium using gas-permeable membrane biofilm reactors (MBfRs), which efficiently supply N2O in a bubbleless form directly to a biofilm grown on a gas-permeable membrane. A 15N tracer test indicated that the supply of N2O resulted in an enriched biomass with a higher N2O sink potential. Quantitative PCR and 16S rRNA amplicon sequencing revealed Clade II nosZ type-carrying N2O-reducing bacteria as protagonists of N2O sinks. Shotgun metagenomics showed the genetic potentials of the predominant Clade II nosZ-carrying bacteria, Anaerolineae and Ignavibacteria in MBfRs. Gemmatimonadota and non-anammox Planctomycetota increased their abundance in MBfRs despite their overall lower abundance. The implication of N2O as an inhibitory compound scavenging vitamin B12, which is essential for the synthesis of methionine, suggested its limited suppressive effect on the growth of B12-dependent bacteria, including N2O reducers. We identified Dehalococcoidia and Clostridia as predominant N2O sinks in an anammox consortium fed exogenous N2O because of the higher metabolic potential of vitamin B12-dependent biosynthesis.

Contrasted redox-dependent structural control on Fe isotope fractionation during its adsorption onto and assimilation by heterotrophic soil bacteria.

Despite the importance of structural control on metal stable isotope fractionation in inorganic and abiotic systems, the link between metal structural changes and related isotopic fractionation during reactions with organic surfaces and live cells remains poorly established. We conducted reversible adsorption of Fe(II) and Fe(III) on the surface of exopolysaccharide (EPS)-rich and EPS-poor Pseudomonas aureofaciens, and we allowed Fe intracellular uptake by growing cells. We analyzed the Fe isotopic composition of the remaining fluid and cell biomass, and compared the isotopic fractionation during adsorption and assimilation reaction with relative changes in Fe structural status between aqueous solution and bacterial cells, based on available and newly collected X-ray absorption spectroscopy (XAS) observations. Iron(III) adsorption onto P. aureofaciens at 2.8 ≤ pH ≤ 6.0 produced an enrichment of the cell surface in heavier isotopes with Δ57Fecell-solution ranging from +0.7 to +2.1‰, without a link to pH in EPS-rich cultures. In contrast, the magnitude of isotopic fractionation increased with pH in EPS-poor cultures. Iron(II) adsorption produced an even larger enrichment of the cell surface in heavier isotopes, by up to 3.2‰, tentatively linked to Fe(III) hydroxide precipitation. Intracellular assimilation of Fe(II) favored heavier isotopes and led to Δ57Fecell-solution of +0.8‰. In addition, Fe(III) cellular uptake produced an enrichment of the bacterial biomass in lighter isotopes with Δ57Fecell-solution of -1‰. The XAS analyses demonstrated the dominance of Fe(III)-phosphate complexes both at the cell surface and in the cell interior. We suggest that heavier isotope enrichment of the cell surface relative to the aqueous solution is due to strong Fe(III)-phosphoryl surface complexes and Fe complexation to ligands responsible for metal transfer from the surface to the inner cell. In case of Fe(II) adsorption or assimilation, its partial oxidation within the cell compartments may lead to cell enrichment in heavier isotopes. In contrast, loss of symmetry of assimilated Fe(III) relative to the aqueous Fe3+ ion and longer bonds of intracellular ions relative to aqueous Fe(III)-citrate or hydroxo-complexes could produce an enrichment of cells in lighter isotopes. The versatile nature of Fe(II) and Fe(III) fractionation without a distinct effect of pH and surface exopolysaccharide coverage suggests that, in natural soil and sedimentary environments, Fe isotope fractionation during interaction with heterotrophic bacteria will be primarily governed by Fe complexation with DOM and Fe redox status in the soil pore water.

The extent of nitrogen isotopic fractionation in rumen bacteria is associated with changes in rumen nitrogen metabolism.

Nitrogen use efficiency is an important index in ruminants and can be indirectly evaluated through the N isotopic discrimination between the animal and its diet (Δ15Nanimal-diet). The concentration and source of N may determine both the extent of the N isotopic discrimination in bacteria and N use efficiency. We hypothesised that the uptake and release of ammonia by rumen bacteria will affect the natural 15N enrichment of the bacterial biomass over their substrates (Δ15Nbacteria-substrate) and thereby further impacting Δ15Nanimal-diet. To test this hypothesis, two independent in vitro experiments were conducted using two contrasting N sources (organic vs inorganic) at different levels either in pure rumen bacteria culture incubations (Experiment #1) or in mixed rumen cultures (Experiment #2). In Experiment #1, tryptone casein or ammonium chloride were tested at low (1 mM N) and high (11.5 mM N) concentrations on three rumen bacterial strains (Fibrobacter succinogenes, Eubacterium limosum and Xylanibacter ruminicola) incubated in triplicate in anaerobic batch monocultures during 48h. In Experiment #2 mixed rumen cultures were incubated during 120 h with peptone or ammonium chloride at five different levels of N (1.5, 3, 4.5, 6 and 12-mM). In experiment #1, Δ15Nbacteria-substrate was lowest when the ammonia-consumer bacterium Fibrobacter succinogenes was grown on ammonium chloride, and highest when the proteolytic bacterial strain Xylanibacter ruminicola was grown on tryptone. In experiment #2, Δ15Nbacteria-substrate was lower with inorganic (ammonium chloride) vs organic (peptone) N source. A strong negative correlation between Δ15Nbacteria-substrate and Rikenellaceae_RC9_gut_group, a potential fibrolytic rumen bacterium, was detected. Together, our results showed that Δ15Nbacteria-substrate may change according to the balance between synthesis of microbial protein from ammonia versus non-ammonia N sources and confirm the key role of rumen bacteria as modulators of Δ15Nanimal-diet.

Peat Formation in Rewetted Fens as Reflected by Saturated n-Alkyl Acid Concentrations and Patterns

The conversion of cultivated fen peat soils into rewetted soils can mitigate global climate change. Specifically, carbon in newly formed peat can store atmospheric CO2 for a long time in soil, but alterations in the quality of soil organic matter are not well known. To shed light on the complex processes of peat degradation or new formation under dry or rewetting conditions, we investigated and quantified saturated n-alkyl acids as an indicator compound class of peatlands response to the contrasting management practices. The concentrations of saturated n-alkyl acids from two soil layers of the drained and rewetted were determined in two soil layers of drained and rewetted fenland types such as Alder Carr forest, coastal peatland, and percolation mire. The analytical methods were solvent extraction, methylation with tetramethylammonium hydroxide, and gas chromatography/mass spectrometry. The saturated n-alkyl acid distribution pattern showed that the concentrations of long C-chain lengths were larger by factors of up to 28 relative to the short C-chain lengths. The effect of rewetting was reflected by the ratios of the summed concentrations of long (n-C21:0 to n-C34:0) to short (n-C10:0 to n-C20:0) C-chain saturated n-alkyl acids for drained and rewetted peat soil samples. These ratios were consistently lower in samples from the rewetted sites, indicating a higher input of microbial bio- and necromass to soil organic matter, likely from algae and anaerobic bacteria, under rewetting. The results suggest that the enrichment of microbial biomass and necromass in rewetted soils may be an important contributor to the formation of new peat in fenlands, irrespective of fenland type.

Phosphorus recovery from agricultural waste via cactus pear biomass

In this study, the potential of cactus pear pruning waste (CPPW) as a low-cost adsorbent biomass for phosphorus (P) removal from aqueous solutions was investigated in batch mode. Biomass samples derived from cactus pear were collected and analyzed to investigate their properties when enriched with either calcium (Ca) or iron (Fe). The examination focused on the capacity of these samples to remove P. The P removal capacities were determined to be 2.27 mg g−1, 1.33 mg g−1, and 1.87 mg g−1 for Ca2+-enriched, Fe2+-loaded, and Fe3+-loaded biomass respectively. Among the various models studied, the Langmuir isotherm model was identified as the most appropriate for accurately describing the P adsorption the enriched biomass. The kinetics of the adsorption process were analyzed by applying the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The pseudo-second-order model provided the best fit to the experimental data. Furthermore, the desorption and regeneration process was investigated, revealing minimal P desorption (less than 8%) from Ca or Fe-loaded biomass, indicating the strong stability of the biomass-cation-P system.The estimated cost ranged from 8 to 161 euros per tonne, with an additional 230 euros when considering the pruning costs inherent to the crop. These costs fall below the threshold (320 euros per tonne) for the economically viable P reuse at the farm level. Consequently, CPPW, when reduced to powder and loaded with ions, emerges as an affordable adsorbent with good removal performance, offering a promising avenue for direct utilization in agriculture as both soil conditioner and fertiliser.

Analysis of the mechanism of exogenous indole-3-acetic acid on the enrichment of d-glucose in Chlorococcum humicola cultured by sludge extracts

Addressing problems of high organic toxicity in the wastewater treatment process, microalgae have been used to reduce the toxicity in sludge and to synthesize non-toxic and recoverable biomass of resources. Phytohormone is a core regulator of plant growth and current research has generally focused on their promotion of cell division and cell expansion. Effects of phytohormone on the enrichment mechanism of microalgae directional polysaccharides accumulation remain poorly elucidated. This study was carried out to investigate the effects of exogenous indole-3-acetic acid (IAA) on growth characteristics, biomass accumulation, and photosynthesis capacity of Chlorococcum humicola cultured in sludge extract and further find the d-glucose enrichment mechanism of it through proteomic. The results indicated that the optimal culture conditions were the 75 % sludge extract and 25 % selenite enrichment (SE) medium with 5 × 10−6 mol/L indole-3-acetic acid. Polysaccharides increased significantly from day 20 and accumulated to (326.59 ± 13.06) mg/L on day 30, in which the d-glucose proportion increased to 61.53 %. Most notably, proteomic tests were performed and found that the photosynthesis-related proteins including the differential proteins of photosystem electron transport, ATP and NADPH catalytic synthesis were significantly up-regulated. At the end of the path, three pathways of d-glucose enrichment with α-d-Glucose-1P as a precursor were summarized through indole-3-acetic acid activation on amylase, endoglucanase and Beta-glucosidase, etc. These results provide insights to explore the directed enrichment of biomass in Chlorococcum humicola by indole-3-acetic acid.

Bioleaching of Valuable Elements from Red Mud: A Study on the Potential of Non-Enriched Biomass

Red mud (RM) is the main residue produced by the alkaline extraction of alumina (Al2O3) from bauxite, and it contains valuable metals such as iron (Fe), aluminium (Al), titanium (Ti), magnesium (Mg), manganese (Mn), rare earth elements, etc. This research aimed to investigate the biologically induced leaching of some valuable elements from raw RM without preliminary biomass enrichment and inoculum, simultaneously reducing RM polluting potential and extracting metals for their subsequent recovery within a circular economy-based approach. In addition to the missing inoculum, such an approach is challenging since high RM alkalinity and pH, as well as the absence of any sulphides, constrain the use of the most common biohydrometallurgical techniques. Red Muds from two European locations were tested (RM-I and RM-II, respectively). Bioleaching tests were performed at different temperatures (T = 22 °C and 28 °C; and also 15 °C for RM-II) and solid-to-liquid ratios (S/L = 2%, 5%). A sudden drop in pH from alkaline to constant neutral/acidic values was observed in almost all tests, and such results were attributed to biological activity since abiotic tests did not show any pH decrease. The best results in terms of extraction were achieved with RM-II, in particular for Al, Mg and Mn (17%, 42% and 47%, respectively). At 2% S/L, the highest temperature allowed for a better metal release, while at 5% S/L, the highest extraction of Al, Mg and Ti was observed at 22 °C. As expected, iron was less available to leach at the achieved pH values, as it was mostly present as hematite in both RMs. Finally, the first microbiological characterisation of the autochthonous biomass selected during the bioleaching treatment of RM was provided.

Microbiome assembly mechanism and functional potential in enhanced biological phosphorus removal system enriched with Tetrasphaera-related polyphosphate accumulating organisms

Tetrasphaera-related polyphosphate accumulating organisms (PAOs) are the key functional guilds for enhanced biological phosphorus removal (EBPR) systems. Their biomass enrichment can be enhanced by the nitrification inhibitor allylthiourea (ATU). However, the underlying assembly mechanism and the functional potential of the EBPR microbiome regulated by ATU are unclear. This study investigates the effect of ATU on microbiome assembly and functional potential by closely following the microbiota dynamics in an EBPR system enriched with Tetrasphaera-related PAOs for 288-days before, during and after ATU addition. The results showed that ATU addition increased microbiota structural similarity and compositional convergence, and enhanced determinism in the assembly of EBPR microbiome. During exposure to ATU, Tetrasphaera-related PAOs were governed by homogeneous selection and the dominant species revealed by 16S rRNA gene-based phylogenetic analysis shifted from clade III to clade I. Meanwhile, ATU supply promoted significant enrichment of functional genes involved in phosphate transport (pit) and polyphosphate synthesis and degradation (ppk1 and ppk2), whereas both Nitrosomonas and ammonia monooxygenase-encoding genes (amoA/B/C) assignable to this group of nitrifying bacteria decreased. Moreover, ATU addition relieved the significant abundance correlation between filamentous bacteria Ca. Promineofilum and denitrifying Brevundimonas (FDR-adjusted P < 0.01), damaging their potential synergic or cooperative interactions, thus weakening their competitiveness against Tetrasphaera-related PAOs. Notably, ATU withdrawn created opportunistic conditions for the unexpected explosive growth and predominance of Thiothrix filaments, leading to a serious bulking event. Our study provides new insights into the microbial ecology of Tetrasphaera-related PAOs in EBPR system, which could guide the establishment of an efficient microbiota for EBPR.

Short-term responses of nutrients and algal biomass in a eutrophic shallow lake to different scales of water transfer

With the expansion of water transfer projects worldwide, the original hydrological and physicochemical states of the systems receiving the transferred water have experienced dynamic temporal and spatial changes, especially shallow lakes with that are more vulnerable to these changes. Understanding the short-term response of lakes to human-managed water transfer events can provide specific information on the seasonal regularity and long-term evolution pattern of lakes. The present study selected an annual water transfer event that is uniform and relatively independent. Then, field monitoring was conducted, and a hydrodynamic-eutrophication model was established to investigate the effects of the water transfer scales and regulation on TN, TP and algal biomass in Lake Nansi, a main regulating lake on the eastern route of the South-to-North Water Transfer Project (SNWDP-ER), China. The results showed that the timing of the water transfer event had an important effect on the enrichment of algal biomass. When the water transfer occurred in the spring, algal growth increased, but the reverse occurred in the summer. Under a high P concentration and the current management regulations (TP 0.05 mg/L), an algal bloom resulted in 21 % and 22 % increases in Chl-a and TP in the receiving system. When the inflow rate increased to the maximum level (100 m3/s), the algal biomass in the first mixing zone was briefly diluted, but the subsequent deterioration in water quality in the first mixing zone was more significant. Sixty days after the water transfer event began, the proportion of middle eutrophication (26 ≤ Chl-a < 160 μg/L) increased from 84 % to 92 %. The results emphasize the importance of water transfer scales on water quality in shallow lakes and provide a reference for determining the long-term stability and maintenance of specific ecosystems and optimization of water transfer practices.

Bioaccumulation of selenium in halotolerant microalga Dunaliella salina and its impact on photosynthesis, reactive oxygen species, antioxidative enzymes, and neutral lipids

Selenium (Se) is an essential element for living systems, however, toxic at higher levels. In the present study, Dunaliella salina cells were exposed to different Se concentrations for their growth (EC50 195 mg L−1) as well as Se accumulation. The cells exposed to 50 mg L−1 Se showed photoautotrophic growth parallel to control and accumulated 65 μg Se g−1 DW. A decrease in photosynthetic quantum yield, chlorophyll content, and the increase in intracellular reactive oxygen species, proline content, and lipid peroxidation accompanied by higher neutral lipid accumulation, were recorded at higher Se level. The enzymes superoxide dismutase and catalase played a pivotal role in antioxidative defense. Heterogeneity in accumulated carotenoids at varying concentrations of selenium was prevalent. The cells exposed to 200 mg L−1 Se resulted in the disorganization of organelles. Thus, the Se enriched biomass obtained at 50 mg L−1 may be explored for bio-fortification of food and feed.