Inorganic Nitrogen Sources Research Articles

15N tracing reveals preference for different nitrogen forms of Fusarium oxysporum f. sp. cubense tropical race 4.

Plant uptake of nitrogen is often associated with increased incidence of banana Fusarium wilt, a disease caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4). However, the nitrogen metabolic preferences of Foc TR4 pathogens remain unknown. In this study, we investigated the ecophysiological patterns of Foc TR4 grown on different combinations of organic and inorganic nitrogen. Potato Dextrose Agar (PDA) and Rose Bengal Medium (RBM) were used as an organic nitrogen source, which was sequentially replaced with inorganic N (0, 50% or 90%) in the form 15NH4NO3 or NH4 15NO3 to reveal preferential assimilation of ammonium or nitrate. The results showed that mycelium biomass and nitrogen content decreased significantly, while the carbon content and C:N ratio increased in Foc TR4 grown on media containing inorganic nitrogen sources. Mycelium biomass was negatively correlated with C:N ratio. Mycelium 15N abundance increased significantly between the PDA50 + A50/RBM50 + A50 treatments (50% organic nitrogen+50%15NH4NO3) and the PDA10 + A90/RBM10 + A90 treatments (10% organic nitrogen+90%15NH4NO3). These results indicate that the higher C:N ratio reduced mycelium growth by reducing its biomass and diameter and showed that Foc TR4 preferred to use ammonium nitrogen to promote the growth. These findings suggest that treating banana crops with a combination of organic and inorganic (i.e., nitrate) nitrogen could be a better way to defend against Fusarium wilt of banana.

Nitrogen balance is a predictor of farm business performance in the English Farm Business Survey

Global environmental sustainability and food security are fundamental societal issues, and most crop production relies upon inputs from organic or inorganic nitrogen sources. Previous research in the Global North has demonstrated a typical over application of nitrogen across global agriculture with substantial negative impacts on the environment. The objective of this work was to draw on English Farm Business Survey (FBS) data of non-organic General Cropping and Cereal farms to explore the relationship between farm gate nitrogen balance, fertilizer application advice and farm business performance. A mixed effects generalized modeling approach was used to partition the variance into random (such as year, or farm ID) and fixed effects (those of interest). Whilst the financial performance of farm businesses is subject to high variance and multiple drivers, a negative relationship was detected between business performance and farm gate nitrogen balance, we demonstrate that nitrogen lost to the environment of >60 kg per hectare is associated with a significant negative impact on farm performance. Supplier-provided fertilizer advice was also associated with reduced farm performance. These results imply a positive effect on farm performance of enhancing on-farm understanding of crop nutrient requirements through the provision of accredited fertilizer advice. Within the stated bounds our model demonstrates good predictivity on randomly subsetted data, and is presented as a tool for use in scenario modeling of interventions such as agri-environment schemes, Natural Capital and Ecosystems Assessment, and the UN Sustainable Development Goals.

Effects of nitrate and ammonium on assimilation of nitric oxide by Heterosigma akashiwo

The harmful alga Heterosigma akashiwo possesses a hybrid nitrate reductase (NR) enzyme, NR2-2/2HbN, which has the potential to convert NO to nitrate for assimilation into biomass. In previous research, NR transcription in H. akashiwo was induced by nitrate while NR activity was inhibited by ammonium. Here, the capacity of H. akashiwo to use NO in the presence of nitrate and/or ammonium was investigated to understand the regulation of NO assimilation. Continuous cultures of H. akashiwo were acclimated to growth on nitrate, ammonium, or a mixture of both. Aliquots from these cultures were spiked with 15N-labeled NO. The expression of genes involved in nitrogen assimilation was evaluated, as well as nitrate reductase activity and assimilation of 15N-labeled nitrogen into algal biomass. Results showed that NO induced expression and activity of NR, and upregulated expression of GOGAT regardless of the presence of other inorganic nitrogen sources, while GS expression decreased over time. Furthermore, 15NO uptake and assimilation was significantly higher in cultures acclimated for growth on ammonium compared to cultures acclimated for growth on nitrate alone. Assimilation of NO may provide H. akashiwo with a competitive advantage in N-poor environments or areas with elevated NO.

A gulf-wide synoptic isoscape of zooplankton isotope ratios reveals the importance of nitrogen fixation in supporting secondary production in the central Gulf of Mexico

A synoptic gulf-wide isoscape of carbon (δ13C) and nitrogen (δ15N) in the Gulf of Mexico based on mesozooplankton (335-1000 um) was used as a proxy for the isotopic baseline and for calculating regional contributions of dissolved inorganic nitrogen sources. Mesozooplankton were sampled at 0-200 m (depth permitting) during the XIXIMI-06 and GOMECC-3 cruises held during the summer of 2017. A striking latitudinal gradient was found in δ15N values of zooplankton, with the highest values (10.4 ± 1.2‰) found over the northern shelf, and lowest values in the central, oligotrophic gulf (1.9 ± 0.5‰). To estimate the fractional contribution of potential nitrogen sources, the gulf was divided into six regions based on the spatial distribution of surface Chl-a, SST from remote sensing products and likely region-specific source contributions. A literature survey of (δ13C and δ15N values of particulate organic matter was used to characterize region-specific endpoint isotope ratios for use in a Bayesian isotope mixing model. Regional differences in δ15N values and the results of mixing models indicated nitrogen fixation is most likely an important source (45-74% contribution) of new nitrogen in the oceanic regions of the Gulf, the Loop Current and the Yucatan Shelf. In the oligotrophic gulf, the potential input of relatively light nitrate that reflects remineralization of surface layer POM or the excretion of light nitrogen by heterotrophs was insufficient to explain the low δ15N values found in the central Gulf, although it could account for about 40% of the N supporting secondary production. The high nitrogen isotope ratios found in the northern shelf were attributed to denitrified N (60%) and the inflow of heavy nitrogen from the Mississippi-Atchafalaya river system. Our results support the potential importance of fixed nitrogen in the deep waters of the Gulf of Mexico during the summer, characteristic for its highly stratified surface waters.

Optimization of glutathione production in Saccharomyces cerevisiae HBSD-W08 using Plackett–Burman and central composite rotatable designs

BackgroundGlutathione is an important bioactive tripeptide and is widely used in the food, medicine, and cosmetics industries. The aim of this study was to provide an efficient method for producing GSH and to explore its synthesis mechanism. Saccharomyces cerevisiae strain HBSD-W08 was screened for GSH production, and its fermentation medium was optimized using single-factor experiments of the Plackett-Burman and central composite rotatable designs. This method was used to analyze the effects of the presence and concentration of various carbon sources, organic and inorganic nitrogen sources, metal ions, and precursor amino acids on GSH production and catalase, superoxide dismutase, and γ-glutamylcysteine synthetase activity.ResultsThe three most significant factors affecting GSH production were peptone (optimal concentration [OC]: 2.50 g L− 1), KH2PO4 (OC: 0.13 g L− 1), and glutamic acid (OC: 0.10 g L− 1). GSH productivity of HBSD-W08 was obtained at 3.70 g L− 1 in the optimized medium. The activity of γ-GCS, which is a marker for oxidative stress, was found to be highly positively correlated with GSH production.ConclusionsThis finding revealed an underlying relationship between GSH synthesis and oxidative stress, providing useful information for developing effective GSH fermentation control strategies.

Effect of nutritional parameters on microbial production of L-Asparaginase by novel Brevibacillus borstelensis ML12

L-Asparaginase owes considerable significance in food and pharmaceutical applications. L-Asparaginase is an antineoplastic enzyme that finds application in the treatment of Acute Lymphoblastic Leukemia (ALL) and in mitigating acrylamide (a potent carcinogen) production during baking. In this study, we aimed to optimize nutritional parameters that are significant in initiating and regulating a bioprocess system in order to maximize enzyme production from a novel isolated bacterial species Brevibacillus borstelensis ML12 so the high-yielding enzyme producers can be selected and utilized for better efficacy of this commercially viable enzyme in pharmaceutical field, food industry, in biosensors and as an antioxidant growth kinetics study of the organism was performed and the maximum specific growth rate µo (min−1) and Monod half saturation constant Ks for L-Asparagine came out to be µo = 0.0189 min−1 and Ks = 2.44 mM, respectively at 0.04 M asparagine concentration and 37 °C. Effect of different nutritional parameters like carbohydrates, organic and inorganic nitrogen sources, L-Asparagine, minerals, surfactants and bile were performed. Maximum L-Asparaginase production occurred at 0.01% dextrose, 20 g L−1 L-Asparagine, 10 mM cobalt chloride, 0.1% Tween 80 and 1% bile concentrations (237.319 IU mL−1).

Ammonium Uptake, Mediated by Ammonium Transporters, Mitigates Manganese Toxicity in Duckweed, Spirodela polyrhiza.

Nitrogen is an essential nutrient that affects all aspects of the growth, development and metabolic responses of plants. Here we investigated the influence of the two major sources of inorganic nitrogen, nitrate and ammonium, on the toxicity caused by excess of Mn in great duckweed, Spirodela polyrhiza. The revealed alleviating effect of ammonium on Mn-mediated toxicity, was complemented by detailed molecular, biochemical and evolutionary characterization of the species ammonium transporters (AMTs). Four genes encoding AMTs in S. polyrhiza, were classified as SpAMT1;1, SpAMT1;2, SpAMT1;3 and SpAMT2. Functional testing of the expressed proteins in yeast and Xenopus oocytes clearly demonstrated activity of SpAMT1;1 and SpAMT1;3 in transporting ammonium. Transcripts of all SpAMT genes were detected in duckweed fronds grown in cultivation medium, containing a physiological or 50-fold elevated concentration of Mn at the background of nitrogen or a mixture of nitrate and ammonium. Each gene demonstrated an individual expression pattern, revealed by RT-qPCR. Revealing the mitigating effect of ammonium uptake on manganese toxicity in aquatic duckweed S. polyrhiza, the study presents a comprehensive analysis of the transporters involved in the uptake of ammonium, shedding a new light on the interactions between the mechanisms of heavy metal toxicity and the regulation of the plant nitrogen metabolism.

Electrochemical nitration for organic C–N bond formation: a current view on possible N-sources, mechanisms, and technological feasibility

Rethinking nitration: sustainable electrochemical C-N functionalization. This work reviews diverse inorganic nitrogen sources for fine chemical production, with a perspective on innovative pathways to harness alternative nitrogen sources' potential.

Changes in Soil Microbial Communities under Mixed Organic and Inorganic Nitrogen Addition in Temperate Forests

Investigating the response of soil microbial communities to nitrogen (N) deposition is critical to understanding biogeochemical processes and the sustainable development of forests. However, whether and to what extent different forms of N deposition affect soil microbial communities in temperate forests is not fully clear. In this work, a field experiment with three years of simulated nitrogen deposition was conducted in temperate forests. The glycine and urea were chosen as organic nitrogen (ON) source, while NH4NO3 was chosen as inorganic nitrogen (IN) source. Different ratios of ON to IN (CK = 0:0, Mix-1 = 10:0, Mix-2 = 7:3, Mix-3 = 5:5, Mix-4 = 3:7, Mix-5 = 0:10) were mixed and then used with equal total amounts of 10 kg·N·ha−1·a−1. We determined soil microbial diversity and community composition for bacteria and fungi (16S rRNA and ITS), and soil parameters. Different forms of N addition significantly changed the soil bacterial and fungal communities. Mixed N sources had a positive effect on soil bacterial diversity and a negative effect on fungal diversity. Bacterial and fungal community structures were significantly separated under different forms of N addition. Soil pH was the main factor affecting the change in fungal community structure, while bacterial community structure was mainly controlled by STN. We also found that Proteobacteria, Acidobacteriota, Basidiomycota and Ascomycota were the most abundant phyla, regardless of the form of N addition. RDA showed that C/P and NH4+ were the main factors driving the change in bacterial community composition, and C/P, pH and C/N were the main factors driving the change in fungal community composition. Our results indicate that different components of N deposition need to be considered when studying the effects of N deposition on soil microorganisms in terrestrial ecosystems.

Effect of Inorganic and Organic Nitrogen Sources and Biofertilizer on Murcott Mandarin Fruit Quality.

Mandarin 'Murcott' (Citrus reticulata Blanco) trees aged five years that were grafted onto lemon 'Volkamer' (Citrus volkameriana) rootstock and grown in sandy soil under a drip irrigation system were used in this study during the growing seasons of 2018 and 2019. Ten different fertilization treatments combining inorganic, organic, and biofertilization in a completely randomized block were performed. The results revealed that fertilizing 'Murcott' mandarin trees with 75% of the recommended dose (RD) of nitrogen as inorganic nitrogen (33.5% N) in the form of NH4NO3 + 25% of RD as organic nitrogen in the form of chicken manure (3% N) per tree per year without or with a biofertilizer (Effective Microorganisms, EM1) at 150 mL/tree increased the weight, size, pulp, and peels of mandarin fruit, as well as the fruit juice volume, juice volume/fruit, and vitamin C, but reduced the total acidity in both seasons. However, fertilizing 'Murcott' mandarin trees with 100% of RD as inorganic nitrogen increased the pulp/fruit ratio, and fertilizing with 25% of RD as inorganic nitrogen + 75% of RD as organic nitrogen + biofertilizer EM1 increased the peel/fruit ratio, peel thickness, and fruit firmness. Fertilizing 'Murcott' mandarin trees with 100% organic nitrogen + biofertilizer EM1 increased total soluble solids (TSS) and total sugar contents while producing the lowest nitrate (NO3) percentage in 'Murcott' mandarin fruit compared with trees fertilized with inorganic nitrogen only. The fruit produced by 'Murcott' mandarin trees fertilized with 100% of RD as organic nitrogen with or without biofertilizer EM1 contained higher TSS, total carbohydrates, and sugars and lower nitrate percentages than those fertilized with inorganic nitrogen and biofertilizer EM1. This study contributes to reducing the use of inorganic fertilizers by adding a percentage of an organic fertilizer to obtain a healthy product that contains a lower percentage of NO3, which affects the health of the consumer, and is of high quality and suitable for export.

Genome-Wide Identification of AMT2-Type Ammonium Transporters Reveal That CsAMT2.2 and CsAMT2.3 Potentially Regulate NH4+ Absorption among Three Different Cultivars of Camellia sinensis

Ammonium (NH4+), as a major inorganic source of nitrogen (N) for tea plant growth, is transported and distributed across membranes by the proteins of ammonium transporters (AMTs). However, the AMT2-type AMTs from tea plants remain poorly understood. In this study, five CsAMT2 subfamily genes were identified in tea plant genomes, and their full-length coding sequences (CDS) were isolated from roots. Then, a NH4+ uptake kinetic comparison of Fudingdabaicha (FD), Huangdan (HD), and Maoxie (MX) showed that FD was a high N efficiency (HNE) cultivar that had a wide range of adaptability to NH4+, HD was a high N efficiency under high N conditions (HNEH) cultivar, in which it was easy to obtain higher yield in a high N environment, and MX was a high N efficiency under low N conditions (HNEL) cultivar, which had a higher affinity for NH4+ than the other two. Tissue-specific expression analysis suggested that CsAMT2.2 and CsAMT2.3 were highly expressed in the roots, indicating that these two members may be unique in the CsAMT2 subfamily. This is further supported by our findings from the temporal expression profiles in the roots among these three different N adaptation cultivars. Expression levels of CsAMT2.2 and CsAMT2.3 in FD and HD were upregulated by a short time (2 h) under high NH4+ treatment, while under low NH4+ treatment, CsAMT2.2 and CsAMT2.3 were highly expressed at 0 h and 2 h in the HNEL-type cultivar-MX. Furthermore, the functional analysis illustrated that CsAMT2.2 and CsAMT2.3 could make a functional complementation of NH4+-defective mutant yeast cells at low NH4+ levels, and the transport efficiency of CsAMT2.3 was higher than that of CsAMT2.2. Thus, we concluded that CsAMT2.2 and CsAMT2.3 might play roles in controlling the NH4+ uptake from the soil to the roots. These results will further the understanding of the NH4+ signal networks of AMT2-type proteins in tea plants.

Chemoselective carbene insertion into the N-H bonds of NH3·H2O.

The conversion of inexpensive aqueous ammonia (NH3·H2O) into value-added primary amines by N-H insertion persists as a longstanding challenge in chemistry because of the tendency of Lewis basic ammonia (NH3) to bind and inhibit metal catalysts. Herein, we report a chemoselective carbene N-H insertion of NH3·H2O using a TpBr3Ag-catalyzed two-phase system. Coordination by a homoscorpionate TpBr3 ligand renders silver compatible with NH3 and H2O and enables the generation of electrophilic silver carbene. Water promotes subsequent [1,2]-proton shift to generate N-H insertion products with high chemoselectivity. The result of the reaction is the coupling of an inorganic nitrogen source with either diazo compounds or N-triftosylhydrazones to produce useful primary amines. Further investigations elucidate the reaction mechanism and the origin of chemoselectivity.

Lipid accumulation by a novel microalga Parachlorella kessleri R-3 with wide pH tolerance for promising biodiesel production

In this study, a new microalgal strain was isolated and identified as Parachlorella kessleri R-3, which could utilize a variety of organic and inorganic carbon and nitrogen sources. More importantly, it was found that strain R-3 can accumulate large amount of biomass and lipids in a wide pH range from 3 to 11, and it can gradually adjust the pH of the medium to near neutrality during the cultivation. At the optimal glucose concentration of 10 g L−1, sodium nitrate concentration of 0.8 g L−1 and initial pH of 7, the highest algal biomass of 6.90 g L−1, lipid content of 45.12 % and lipid productivity of 340.94 mg L−1 d−1 were achieved. In addition, C16:0 iso 3OH and C16:1 w7c alcohol were the predominant fatty acids components, which accounted for as high as 88.04 %. These showed the potential of the new microalgal strain for application in biodiesel production.

Contemporary nitrogen management in maize (Zea mays)–Indian mustard (Brassica juncea) cropping system for maximizing yield, water productivity and profitability

A field experiment was conducted during 2018–19 and 2019–20 at the research farm of ICAR-Directorate of Rapeseed-Mustard Research, Bharatpur, Rajasthan to evaluate the effect of organic and inorganic nitrogen sources on yield, water productivity, system productivity and economics of maize (Zea mays L.)-mustard [Brassica juncea (L.) Czern.] cropping system. The experiment was conducted in split-plot design with recommended levels of fertilizers (RDF)/FYM/biofertilizer/mustard straw/Jivamrat in main-plots and recommended doses of nitrogen (RDN) 100, 125 and 150% in sub-plots to maize and Indian mustard and replicated thrice. Application of RDF + FYM @2.5 t/ha + Azotobacter + mustard straw @2.5 t/ha recorded highest SCMR (41.2), leaf area index (4.42), number of siliqua/ plant (440.7), number of seeds/siliqua (18.4), test weight (5.83 g) and seed yield (3.36 t/ha) of mustard. Application of RDN 150% recorded highest physiological and yield attributes and seed yield (3.22 t/ha) of mustard. Results also showed the highest physiological and yield attributes and grain yield (3.73 t/ha) of maize with RDF+FYM @2.5 t/ ha+Azotobacter+mustard straw @2.5 t/ha. System productivity (4.84 t/ha) and water productivity (2.14 kg seed/m3) were found higher with RDF+FYM @2.5 t/ha +Azotobacter+mustard straw @2.5 t/ha and RDN 150%. The highest net monetary return 51715, 81040 and 132755 `/ha and B:C ratio 3.09, 3.22 and 3.15 were recorded for maize, mustard and system with RDF+FYM @2.5 t/ha+Azotobacter+mustard straw @2.5 t/ha and RDN 150%, respectively. Thus, integrated use of RDF+FYM @2.5 t/ha+Azotobacter+mustard straw @2.5 t/ha with RDN @150% improved maize–mustard system yield and profitability under semi-arid climates.

Ammonium protects rice against rice stripe virus by activating HDA703/OsBZR1-mediated BR signaling

Ammonium (NH4+) is a major inorganic nitrogen source for plants and also as a signal regulates plant growth and defense. Brassinosteroids (BRs) are a class of steroid hormones that control plant developmental and physiological processes through its signaling pathway. Rice is a kind of NH4+-preferring plant which responds to virus infection involving in the regulation of BR biosynthesis and signaling. However, the BR-mediated regulatory mechanisms in rice-virus interactions are not fully understood. In addition, it remains unknown whether there is a direct link between NH4+ and BRs in regulating rice response to virus. HDA703, a histone deacetylase and OsBZR1, a transcription factor, are two positive regulator of BR signaling and interact with each other. In this study, we show that rice plants grown with NH4+ as the sole N source have enhanced resistance to rice stripe virus (RSV), one of the most devastating viruses of rice, than those grown with NO3- as the sole N source. We also show that in contrast to NO3-, NH4+ does not affect BR biosynthesis but promotes BR signaling by upregulating the expression of HDA703 and promoting the accumulation of OsBZR1 in rice shoots. We further show that BR biosynthesis and signaling is required for rice defense against RSV and BR-mediated resistance to RSV attributes to activating HDA703/OsBZR1 module, then decreasing the expression of Ghd7, a direct target of HDA703/OsBZR1. Consistently, increase of the expression of HDA703 or decrease of the expression of Ghd7 enhances rice resistance to RSV. Together, our study reveals that activation of HDA703/OsBZR1-Ghd7 signaling cascade is an undescribed mechanism conferring BR-mediated RSV resistance and NH4+ protects rice against RSV by activating HDA703/OsBZR1-Ghd7-mediated BR signaling in rice.

An Approach for Incorporating Glycerol as a Co-Substrate into Unconcentrated Sugarcane Bagasse Hydrolysate for Improved Lipid Production in Rhodotorula glutinis

Sugarcane bagasse is a potential raw material for microbial lipid production by oleaginous yeasts. Due to the limited sugar concentrations in bagasse hydrolysate, increasing carbon the concentration is necessary in order to improve lipid production. We aimed to increase carbon concentration by incorporating glycerol as a co-substrate into unconcentrated bagasse hydrolysate in the cultivation of Rhodotorula glutinis TISTR 5159. Cultivation in hydrolysate without nitrogen supplementation (C/N = 42) resulted in 60.31% lipid accumulation with 11.45 ± 0.75 g/L biomass. Nitrogen source supplementation increased biomass to 26.29 ± 2.05 g/L without losing lipid accumulation at a C/N of 25. Yeast extract improved lipid production in the hydrolysate due to high growth without altering the lipid content of the cells. Mixing glycerol up to 10% v/v into the unconcentrated hydrolysate improved biomass and lipid production. A further increase in glycerol concentrations drastically decreased growth and lipid accumulation by the yeast. By maintaining C/N at 27 using yeast extract as the sole nitrogen source, hydrolysate mixed with 10% v/v glycerol resulted in the highest lipid yield, at 19.57 ± 0.53 g/L with 50.55% lipid content, which was a 2.8-fold increase compared to using the hydrolysate alone. In addition, yeast extracts were superior for promoting growth and lipid production compared to inorganic nitrogen sources.

Internal nitrogen and phosphorus loading in a seasonally stratified reservoir: Implications for eutrophication management of deep-water ecosystems.

Water eutrophication is a serious global issue because of excess external and internal nutrient inputs. Understanding the intensity and contribution of internal nitrogen (N) and phosphorus (P) loading in deep-water ecosystems is of great significance for water body eutrophication management. In this study, we combined intact sediment core incubation, high-resolution peeper (HR-Peeper) sampling, and analysis of N and P forms and other environmental factors in the water column and sediments to evaluate the contributions of internal N and P loading to water eutrophication by N and P fluxes across the sediment-water interface (SWI) of the Panjiakou Reservoir (PJKR), a deep-water ecosystem where eutrophication threatens the security of the local drinking water supply in North China. The results indicated that the PJKR showed obvious thermal and dissolved oxygen (DO) stratification in the warm seasons and full mixing in the cold seasons. The mean DO concentration was 9.9 and 3.55mg/L in the epilimnion and hypolimnion, respectively, in warm seasons and 10.7mg/L in cold seasons. The sediment acted as a source of soluble reactive phosphorus (SRP), NH4+-N, and NO2--N and a sink of NO3--N. The SRP fluxes were 5.28±4.34 and 2.30±1.93mgm-2·d-1 in warm and cold seasons, respectively, and the dissolved inorganic nitrogen (DIN) fluxes were -0.66±47.84 and 44.04±84.05mgm-2·d-1. Seasonal hypoxia accelerated the release of P rather than N from the sediments in warm seasons, which came mainly from Fe-P and Org-P under anoxic conditions. The strong negative NO3--N flux (diffusion from the water column to the sediment) implied an intensive denitrification process at the SWI, which can counteract the release flux of NH4+-N and NO2--N, resulting in the sediment acting as a weak dissolved inorganic nitrogen (DIN) source for the overlying water. We also found that internal N loading accounted for only ∼9% of the total N loading, while internal P loading accounted for 43% of the total P loading of the reservoir. Our results highlight that efforts to manage the internal loading of deep-water ecosystems should focus on P and seasonal hypoxia.

Impact of ultrasound and medium condition on production of selenium-enriched yeast

BackgroundUltrasonication was used to stimulate the growth and selenium (Se) biotransformation in Saccharomyces cerevisiae. An optimization study for maximal Se accumulation in S. cerevisiae was conducted using the Plackett–Burman screening method and response surface methodology (RSM) for optimization of conditions. The variables influencing Se biotransformation by yeast, including duration and power of ultrasound, inoculum treatment with ultrasound, duty cycle, growth phase, time, shaking rate, inorganic salt concentration (Se, Zn, Mg, and K), and nitrogen and carbon sources as well as their concentrations were screened using the Plackett–Burman design. ResultsThe main variables were carbon and Se concentration as well as ultrasound power and duty cycle. The lack of fit was insignificant (P > 0.01). The optimum condition for Se accumulation was obtained at Se concentration of 60 µg/ml, carbon source brix of 15, ultrasound of 90 W/L, and duty cycle of 40%. ConclusionsThe results showed that optimization of parameters and application of ultrasonication lead to a successful enhancement (2.78-fold) in the accumulation of selenium by S. cerevisiae. Such enriched yeast can be utilized in bread for increasing consumption of Se in the diet of patients with Se deficiency.How to cite: Alijan S, Hosseini M, Esmaeili S, et al. Impact of ultrasound and medium condition on production of selenium-enriched yeast. Electron J Biotechnol 2022;60. https://doi.org/10.1016/j.ejbt.2022.09.004.

Recent advances in nanostructured heterogeneous catalysts for N-cycle electrocatalysis

To restore the natural nitrogen cycle (N-cycle), artificial N-cycle electrocatalysis with flexibility, sustainability, and compatibility can convert intermittent renewable energy (e.g., wind) to harmful or value-added chemicals with minimal carbon emissions. The background of such N-cycles, such as nitrogen fixation, ammonia oxidation, and nitrate reduction, is briefly introduced here. The discussion of emerging nanostructures in various conversion reactions is focused on the architecture/compositional design, electrochemical performances, reaction mechanisms, and instructive tests. Energy device advancements for achieving more functions as well as <i>in situ</i>/<i>operando</i> characterizations toward understanding key steps are also highlighted. Furthermore, some recently proposed reactions as well as less discussed C–N coupling reactions are also summarized. We classify inorganic nitrogen sources that convert to each other under an applied voltage into three types, namely, abundant nitrogen, toxic nitrate (nitrite), and nitrogen oxides, and useful compounds such as ammonia, hydrazine, and hydroxylamine, with the goal of providing more critical insights into strategies to facilitate the development of our circular nitrogen economy.

Upcycling waste organic acids and nitrogen into single cell protein via brewer's yeast

The food crisis due to the global population boom requires agriculture revolutions and a transition to sustainable, affordable sources of food proteins. Single cell protein (SCP) derived from microorganisms such as brewer's yeast is one of the best possible options to meet the protein challenges. Utilization of carbon and nitrogen recovered from waste streams, instead of sugar-rich substrate, for yeast-driving SCP production could improve the overall sustainability from both economic and environmental points of view. The lack of a comprehensive understanding of the process such as the interactions between different organic acids/ions and SCP production by yeast (e.g., Saccharomyces cerevisiae) has placed a major impediment to the valorization effort. This study tackles this challenge by exploring the impact of various organic acids, nitrogen and ionic species on SCP production by S. cerevisiae. It was found that the SCP production increased with acetate concentrations (2.6–20 g-COD/L). A maximal protein concentration of 0.75 g/L was harvested using 20 g-COD/L acetate. Intermittent acid addition for pH neutralization further enhanced SCP production by 67% at 0.94 g/L. Ammonia was the best inorganic nitrogen source for S. cerevisiae among nitrate and nitrite. S. cerevisiae was not able to utilize lactate, propionate and butyrate alone for growth, but it can catabolize lactate along with acetate. The addition of oleate and linoleate resulted in a significant increase in the protein content of biomass by 1.8- and 1.6-fold, respectively. S. cerevisiae using acetate required eight times fewer K+ than Na+. Typical anions including Cl−, NO3− and SO42− (20–500 mM) were not found harmful for SCP synthesis. The results help to fill the knowledge gap in yeast-driving waste-to-protein conversion process, bring high impacts and positive implications for waste valorization and future feed and food supply.