Nitrogen Source Research Articles

Nitrogen cycling during an Arctic bloom: from chemolithotrophy to nitrogen assimilation.

In the Arctic, phytoplankton blooms are recurring phenomena occurring during the spring-summer seasons and influenced by the strong polar seasonality. Bloom dynamics are affected by nutrient availability, especially nitrogen, which is the main limiting nutrient in the Arctic. This study aimed to investigate the changes in an Arctic microbial community using omics approaches during a phytoplankton bloom focusing on the nitrogen cycle. Using metagenomic and metatranscriptomic samples from the Dease Strait (Canada) from March to July (2014), we reconstructed 176 metagenome-assembled genomes. Bacteria dominated the microbial community, although archaea reached up to 25% of metagenomic abundance in early spring, when Nitrososphaeria archaea actively expressed genes associated with ammonia oxidation to nitrite (amt, amo, nirK). The resulting nitrite was presumably further oxidized to nitrate by a Nitrospinota bacterium that highly expressed a nitrite oxidoreductase gene (nxr). Since May, the constant increase in chlorophyll a indicated the occurrence of a phytoplankton bloom, promoting the successive proliferation of different groups of chemoorganotrophic bacteria (Bacteroidota, Alphaproteobacteria, Gammaproteobacteria). These bacteria showed different strategies to obtain nitrogen, whether it be from organic or inorganic sources, according to the expression patterns of genes encoding transporters for nitrogen compounds. In contrast, during summer, the chemolithotrophic organisms thriving during winter reduced their relative abundance and the expression of their catabolic genes. Based on our functional analysis, we see a transition from a community where nitrogen-based chemolitotrophy plays a relevant role to a chemoorganotrophic community based on the carbohydrates released during the phytoplankton bloom, where different groups seem to specialize in different nitrogen sources.IMPORTANCEThe Arctic is one of the environments most affected by anthropogenic climate change. It is expected that the rise in temperature and change in ice cover will impact the marine microbial communities and the associated biogeochemical cycles. In this regard, nitrogen is the main nutrient limiting Arctic phytoplankton blooms. In this study, we combine genetic and expression data to study the nitrogen cycle at the community level over a time series covering from March to July. Our results indicate the importance of different taxa (from archaea to bacteria) and processes (from chemolithoautotrophy to incorporation of different nitrogen sources) in the cycling of nitrogen during this period. This study provides a baseline for future research that should include additional methodologies like biogeochemical analysis to fully understand the changes occurring on these communities due to global change.

Predicting growth parameters of biofertilizer inoculated pepper, using root capacitance assessments and artificial neural networks in two soils.

Monitoring the root system plays an important role in understanding plant physiological processes; however, its assessment using non-destructive methods remains challenging. Here, we evaluate the utility of root capacitance (CR) as a practical indicator of root function and its relationship to plant growth parameters in Capsicum annuum L. To improve the accuracy of root function assessment, we applied artificial neural networks (ANN) as a novel data evaluation approach, comparing its predictive performance against multiple linear regression (MLR). Across two soil types (sandy and sandy loam), we applied multiple treatments ranging from microbial inoculants to wool pellet and inorganic nitrogen sources primarily to test whether CR could detect differences in root activity and biomass production under different conditions. We measured root dry biomass, shoot dry biomass, and leaf N content, treating these variables as independent predictors in a statistical framework. Multiple linear regression (MLR) initially showed strong relationship between CR and both root and shoot biomass in sandy soil, and between CR and total plant N content in sandy loam. However, an ANN model consistently outperformed MLR in predicting CR from plant physiological parameters, as evidenced by lower mean absolute error (MAE) in all treatments. These findings confirm that CR correlates strongly with plant growth parameters and can reliably distinguish the effects of different soil amendments even those with markedly different nutrient-release profiles.

Exploring the Effects of Integrated Nitrogen Nutrition on Boro Rice Growth and Yield: A Sustainable Approach

This study evaluates the impact of integrated nitrogen nutrition on the growth, yield, and nitrogen use efficiency of boro rice (Oryza sativa). Four rice cultivars (BRRI dhan29, BRRI dhan59, BRRI dhan28, and Binadhan-10) were tested under six nitrogen treatments, including prilled urea (PU), urea super granules (USG), and combinations of PU with organic amendments (poultry manure, cowdung, and vermicompost). The experiment was conducted in a randomized complete block design (RCBD) with three replications. Significant variations in growth and yield parameters were observed among cultivars and nitrogen treatments. Binadhan-10 (V4) exhibited superior growth, with the highest plant height (90.62 cm), total tillers per hill (10.46), and grain yield (4.999 t ha⁻¹). Among nitrogen sources, the combination of 105 kg N ha⁻¹ from PU + 3 t ha⁻¹ poultry manure (N4) resulted in the highest grain yield (5.85 t ha⁻¹), straw yield (6.21 t ha⁻¹), and biological yield (12.07 t ha⁻¹). The interaction between Binadhan-10 and N4 produced the highest combined grain (6.03 t ha⁻¹) and straw yield (6.33 t ha⁻¹), as well as the highest biological yield (12.36 t ha⁻¹). Integrated nutrient management significantly improved nitrogen use efficiency compared to conventional prilled urea alone, with reductions in nitrogen loss and enhanced yield attributes. This research highlights the potential of integrated nutrient management, combining organic and inorganic fertilizers, to optimize rice yield, improve nitrogen efficiency, and ensure sustainable agricultural practices.

A Robust Oxysalt-Tolerant Bacterium Marinobacter sp. for Simultaneous Nitrification and Denitrification of Hypersaline Wastewater

Robust strains with high simultaneous nitrification and denitrification (SND) capabilities in hypersaline wastewater, particularly those containing different oxysalts, are rarely reported. Here, an isolated oxysalt-tolerant bacterium, Marinobacter sp. Y2, showed excellent nitrogen removal capabilities of around 98% at 11% salinity of NaCl or oxysalts such as Na2SO4, Na2HPO4, NaHCO3, and NaNO3 through response surface methodology optimization. At >5% salinities, Marinobacter sp. Y2 showed superior nitrogen removal performance in oxysalt-laden wastewater compared to chloride-based wastewater. In contrast, other SND strains, including Pseudomonas sp. and Halomonas sp., experienced significant activity inhibition and even bacterial demise in oxysalt-rich wastewater, despite their high halotolerance to NaCl. The excellent SND activities of the oxysalt-tolerant strain were further validated using single and mixed nitrogen sources at 11% Na2SO4 salinity. Moreover, the amplification of nitrogen removal functional genes and the corresponding enzyme activities elucidated the nitrogen metabolism pathway of the strain in harsh oxysalt environments.

Bioconversion of sterol esters to steroid intermediates through Mycobacterium sp. fermentation.

Sterol esters are naturally present in the by-product of edible oil processing, which is generally converted to sterols through saponification. Steroid intermediates play a crucial role in the production of pharmaceuticals, and these intermediates are predominantly synthesized via fermentation of sterol. This research explored the direct conversion of sterol esters into steroid intermediates using Mycobacterium sp. as a fermentation agent. The results demonstrated the successful identification of four steroid intermediates: androstenedione, 1,4-androstadienedione, 22-hydroxy-23,24-bisnorchol-4-ene-3-one, and 22-hydroxy-23,24-bisnorchol-1,4-dien-3-one, their individual intermediate concentrations were as follows: 144.2, 176.2, 30.8, 53.6mg/L, with a total yield of 404.8mg/L and a conversion rate of 29.5%. The optimized fermentation conditions included soybean oil at 3%, an initial pH of 7.0, a nitrogen source of 4.5g/L, and hydroxypropyl-β-cyclodextrin of 15.0g/L. Proteomic analysis revealed that sterol esters conversion pathway mirrors that of sterol, with an additional hydrolysis process. This work significantly expands our understanding of steroid intermediates production and offers valuable insights for the bioproduction industry.

Optimization of trace metal composition utilizing Taguchi orthogonal array enhances biomass and superoxide dismutase production in Tetraselmis chuii under mixotrophic condition: implications for antioxidant formulations.

The natural ageing process in all organisms is majorly influenced by the production rate and dismutation of reactive oxygen species (ROS) within cells. Certain microalgae, such as Tetraselmis chuii, possess the ability to produce superoxide dismutase (SOD), a powerful antioxidant enzyme that mitigates oxidative damage caused by ROS during oxygen metabolism. This study investigated the impact of trace elements (nickel, manganese, copper, zinc, and iron) and nitrogen sources in the growth medium on both the biomass and SOD synthesis of T. chuii under mixotrophic conditions. Initially, the one-factor-at-a-time (OFAT) approach was employed to filter out the most significant factors in the production medium. Next, Taguchi orthogonal array method, known for its robustness in experimental design, was employed to analyse the effects of various media components on algal biomass and SOD production. Using only a few well-defined experimental sets, Taguchi's L18 orthogonal array facilitated a 1.21-fold increase in biomass yield, reaching a maximum of 0.643g/L. Furthermore, SOD activity was enhanced from 85.28 to 91.94% following optimization. Notably, nitrogen source, nitrogen concentration, and zinc concentration emerged as significant influencers of biomass and SOD production. The Taguchi optimization thereby improved SOD yield in a cost-effective manner. The heightened antioxidation activity of SOD holds promising applications in formulating antioxidants and topical ointments in pharmaceutical and cosmeceutical industries.

Dhurrin: a potential endogenous nitrogen turnover source for early seedling growth in sorghum

Dhurrin is a cyanogenic glucoside found in all vegetative tissues of Sorghum bicolor, functioning as a herbivore repellent, antifungal agent, osmoprotectant, and nitrogen (N) storage. Dhurrin concentration is usually highest in young seedlings, where it rapidly accumulates following germination, after which its biosynthesis decreases and its turnover increases as the seedling ages. To avoid prussic acid poisoning from dhurrin catabolism in cattle grazing or foraging on sorghum, numerous research studies now focus on breeding for dhurrin-free or acyanogenic sorghum using EMS (Ethyl methanesulfonate) mutants with a non-functional dhurrin biosynthetic pathway. However, there has been limited and conflicting research investigating the role dhurrin plays as a potential nitrogen source in sorghum’s early seedling growth, especially under N deficiency. It is plausible that the presence of background mutations in dhurrin-free sorghum mutants could mask or confound how the absence of dhurrin affects early seedling growth. Using a naturally occurring (non-mutant) ultra-low dhurrin genotype and known low and high dhurrin genotypes, the current research investigated the importance of dhurrin as a potential endogenous nitrogen source for early seedling growth in simulated non-marginal (N-available) and marginal (N-deficient) media. Dhurrin was implicated to be an N source for seedling growth from 8 to 13 days after planting under deficient N conditions. In N-deficient media at 13 days after planting, high-dhurrin-level genotypes accumulated more seedling fresh shoot biomass than low-dhurrin-level genotypes. Thus, while acyanogenic sorghum will be beneficial in expanding sorghum’s economic value, the use of dhurrin knock-out mutants can prove problematic since the complete lack of dhurrin may affect field germination and stand establishment, particularly under N-deficient or low-N-input conditions.

Assessment of Polyhydroxybutyrate (PHB) in Bacillus tequilensis KUMBNGBT-64a Isolated from Trash Yard Soil

Biodegradable polymers represent a hot topic in current environment. Biodegradable polymers can be decomposed into simple molecules like CO2, CH4, H2O and residual biomass. Bacillus sp. KUMBNGBT-64a, isolated from leftover soil that was gathered at Sagar taluk located in Shivamogga, Karnataka, India, was identified as Bacillus tequilensis KUMBNGBT-64a. Phenotypic and genotypic characteristics were used to identify the bacteria. Various conditions were employed to maximize the highest production of PHB by the bacteria. The bacterial isolate was grown on affordable agro-industrial wastes to lower production cost and scale up PHB production. The quantity of PHB contained in the isolated bacterial cells was measured using bio-spectrophotometric analysis. Bacillus sp. KUMBNGBT-64a, a gram positive, motile and spore forming bacterium, was confirmed as Bacillus tequilensis KUMBNGBT-64a by using 16S r-RNA sequence and deposited to GenBank, NCBI. Consent No. PV124813. Additionally, the following conditions of nutritional broth medium, a 72-h incubation period, 37°C temperature, pH 7.0, glucose as a carbon source, ammonium chloride as a nitrogen source, and a 4:1 carbon-nitrogen ratio were shown to be responsible for the greatest generation of PHB. A liquid hydrolysate of feed stock had the highest level of PHB production, and the ʎ-max of 270 nm was used to quantify and validate PHB production. In the present investigation, Bacillus tequilensis KUMBNGBT-64a produced maximum PHB using low cost substrates, which helped to reduce the production cost, and could be used for the large-scale production of the bio plastics.

Synthesis and Fluorescence Mechanism of Nitrogen-Doped Carbon Dots Utilizing Biopolymer and Urea

Fluorescent carbon dots are nontoxic nanoparticles composed of carbon, exhibiting advantageous properties for applications in bioimaging and functional materials. We present a methodology for synthesizing fluorescent nitrogen-doped carbon dots (N-CDs) using starch, a biopolymer, and urea as the sources of nitrogen, via the microwave-assisted hydrothermal method. Furthermore, the dependence of the fluorescence spectra and fluorescence quantum yield of N-CDs on the initial concentration of urea in the reactant solution was examined, thereby providing a comprehensive understanding of the influence of nitrogen doping on the CDs. The fluorescence of N-CDs was tunable by varying the excitation wavelength. Stronger fluorescence intensity was observed for a moist phosphate salt/N-CD composite, in contrast to the weaker fluorescence exhibited by a dried one. Fluorescence lifetime measurements revealed that the change in fluorescence intensity can be attributed to the suppression of the non-radiative deactivation process. This observation highlights the critical importance of the interaction between water molecules and surface functional groups in controlling the photophysics of the excited state of N-CDs.

Synergistic Cu-Pd Nanocatalysts on MOF-Derived N-Doped Carbon for Selective Hydrogenolysis of Lignin to Aromatic Monomers

Catalytic hydrogenolysis of lignin to produce high-value monophenols has emerged as a pivotal strategy in modern biorefineries. In this study, we synthesized spherical nitrogen-doped porous carbon (SNCB) materials by using Al/Co-BTC as a precursor, introducing melamine as a supplementary carbon and nitrogen source, and activating the material with NaOH solution. The SNCB framework was decorated with Cu-Pd bimetallic nanoparticles, exhibiting outstanding catalytic activity in the hydrogenolytic depolymerization of organosolv lignin. The Cu-Pd@SNCB catalyst exhibited remarkable activity, attributed to the hierarchical porous structure of SNCB that facilitated metal nanoparticle dispersion and reactant accessibility. The synergistic effect between Cu as the reactive site for reactant adsorption and Pd as the reactive site for H2 adsorption enhanced the catalytic activity of the catalyst. Systematically optimized conditions (2 MPa H2, 270 °C, 3 h) yielded 43.02 wt% phenolic monomers, with 4-(3-hydroxypropyl)-2,6-dimethoxyphenol dominating the product profile at 46.3% selectivity. The catalyst and its reaction products were analyzed using advanced characterization techniques, including XPS, XRD, TEM, SEM, BET, GC-MS, GPC, 2D HSQC NMR, and FT-IR, to elucidate the reaction mechanism. The mechanism proceeds through: (1) nucleophilic substitution of the β-O-4 hydroxyl group by MeOH, followed by (2) simultaneous hydrogenolytic cleavage of Cβ-O and Cα-O bonds mediated by Cu-Pd@SNCB under H2 atmosphere, which selectively produces 4-(3-hydroxypropyl)-2,6-dimethoxyphenol and 4-propyl-2,6-dimethoxyphenol. This study proposes a bimetallic synergistic mechanism, offering a general blueprint for developing selective lignin valorization catalysts.

Metabolomics Combined with Photosynthetic Analysis Reveals Potential Mechanisms of Phenolic Compound Accumulation in Lonicera japonica Induced by Nitrate Nitrogen Supply

Mineral nutrition is of vital importance in plant growth and secondary metabolites accumulation, and thereby in the nutritional value of plants. In Lonicera japonica, a preference to nitrate (NO3−−N) in comparison to ammonium (NH4+−N) was found in our previous study, which can be revealed from the rapid growth rate of L. japonica under NO3−−N. This study assessed whether a preference for nitrogen sources could invoke metabolic reprogramming and interrelationships between factors. NO3−−fed plants exhibited substantial enhancement of carbon stimulation, which was strongly and positively correlated with mesophyll conductance. As a result, the elevated carbon flux by NO3− supplement was shuttled to phenolic metabolites synthesis, including flavones and caffeoylquinic acids compounds. Notably, the stimulation was triggered by changes in the NO3− and C/N ratio and was mediated by the induction of several enzymes in the phenylpropanoid pathway. On the contrary, NH4+ plants showed an increment in the content of nitrogen, carbohydrates, and amino acids (mainly a strong increase in citrulline and theanine). Within secondary metabolism, NH4+ may involve active lignin metabolism, showing a dramatic increment in hydroxy−ferulic acid and lignin content. This work provides significant insights regarding the mechanisms of L. japonica in response to diverse nitrogen regimes and effective strategies of nitrogen fertilizer input for L. japonica.

One‐Pot Microwave‐Assisted Olefin Hydroaminomethylation Over Bifunctional Heterogeneous Rh Catalysts

AbstractCommercial Rh/C and lab‐made Rh/CNTs catalysts were compared in the one‐pot microwave‐assisted hydroaminomethylation of olefins to amines using EtOAc as the solvent. This reaction accounts for two steps: hydroformylation from the alkene, followed by aldehyde reductive amination. Acid sites exposed at the surface of the support promote the formation of a metal‐alkene coordination complex to preferentially form the linear aldehyde. Synthetic and natural olefins were converted with yields up to 99% under mild conditions (120 °C, 40 bar of syngas, 4 h). With the addition of catalytic amounts of acetic acid, the hydroformylation step proceeded with a 99% yield over both catalysts. The catalysts were recovered and reused, maintaining their activity for three reaction cycles (12 h). The hydroaminomethylation step again gave yields up to 99%, using 1‐hexene as substrate (120 °C, 4 h, 40 bar of N2/H2 1:1). Subsequent tests with different nitrogen sources resulted in amine yields ranging from 56% to 99%, even with ammonia. FESEM, XRD, and XPS were employed for an exhaustive surface characterization and structure‐to‐activity correlation of the catalysts.

Can Ammonium Nitrate Be a Strategic Tool by Replacing Urea as a Nitrogen Supplementation Source to Beef Cattle in Intensified Grazing Systems?

For cattle raised on tropical grass pastures, it is essential to explore strategies that circumvent climatic seasonality that affect forage availability and quality. We hypothesize that the intensification of grazing systems, with rotational and deferred methods, combined with ammonium nitrate or urea supplementation, are excellent strategies to increase ruminal efficiency and animal productivity. For this purpose, 8 cattle with cannulas were distributed in rotational and deferred grazing systems, supplemented with urea or ammonium nitrate, and evaluated throughout the four seasons of the year over a period of two years. Dry matter intake and digestibility were measured using indigestible neutral detergent fiber, titanium dioxide and chromium oxide markers. Ruminal kinetics and degradability of DM and nutrients were measured using the nylon bag technique. Urine parameters were used to estimate microbial nitrogen compounds synthesis and efficiency of microbial protein synthesis. The rotational grazing improves NPN intake, NDF and ADF digestibility, and gross energy. Ammonium nitrate supplementation showed improved efficiency in microbial protein synthesis without negatively affecting feed intake, positioning it as a valuable nitrogen source for grazing cattle.

Identification and Chemical Control of Stem Canker Pathogen of Idesia polycarpa

Idesia polycarpa is an important woody oilseed tree crucial for ensuring China’s grain and oil security. The expansion of I. polycarpa plantations has been accompanied by an increase in pests and diseases, with canker disease recently observed in two forests in Henan Province. Field surveys revealed a disease incidence of 70.12% among 328 surveyed trees, indicating a substantial threat to plantation health. The most virulent pathogen, strain SQ5, was identified as Botryosphaeria dothidea through molecular sequencing and morphological analyses. Strain SQ5 showed an optimum growth temperature of 25 °C and a mycelial lethal temperature of 60 °C. The pathogen thrives in acidic conditions and is promoted by light, with the ability to utilize various carbon and nitrogen sources. In vitro toxicity assessments identified four effective fungicides: 70% thiophanate-methyl (EC50 = 0.0169 µg/mL), 43% tebuconazole (EC50 = 0.0219 µg/mL), 20% octylamine acetate (EC50 = 0.0271 µg/mL), and 40% difenoconazole (EC50 = 0.0954 µg/mL). Field trials demonstrated that 43% tebuconazole (average efficacy = 35.29%) and 40% difenoconazole (average efficacy = 23.53%) exhibited superior control of I. polycarpa canker. This study represents the first systematic analysis of I. polycarpa canker and its control measures, laying a foundation for further research and field management strategies. Given the significance of I. polycarpa in Chinese forestry, this underscores the need for effective management strategies to sustain its productivity and mitigate risks associated with expanding plantations.

Application of Digester Effluent from Methane Fermentation to the Cultivation of the Haptophyte Tisochrysis lutea Promotes the Accumulation of Photosynthetic Pigments.

The microalgae attract attention by producing useful compounds, such as fatty acids, pigments, and biofuels, from CO2 via photosynthesis. This process requires not only CO2 but also water and micro- and minor nutrients. Applying seawater and marine microalgae, especially for large-scale industrial production, reduces the cost of acquiring large amounts of water for cultivation. However, the concentrations of combined nitrogen and certain metal ions, such as Fe, in the seawater are lower than in the general culture media for microalgae. We applied digester effluent from the methane fermentation as the source of these nutrients. In this study, we evaluated the application of digester effluent for cultivating a haptophyte, Tisochrysis lutea. At first, we confirmed the algal cells could grow by ammonium as a sole nitrogen source because ammonium was abundantly contained in the digester effluent. Then, we applied the digester effluent as a source of nutrients and found that the optimum growth was obtained when digester effluent was supplied at 2.8% (v/v) in artificial seawater. Surprisingly, the cells in this condition had increased photosynthetic pigment contents such as fucoxanthin and chlorophyll compared to those in the standard culture conditions. We surveyed ingredients in the digester effluent that could potentially increase pigment accumulation and found that iron was a critical nutrient that caused the accumulation of pigments. These findings might provide valuable information for applying digester effluent to cultivate microalgae.

Isolation of marine bacteria with potential for polyhydroxyalkanoate degradation and optimization for enzyme production

Plastic materials are widely used because of their strength, light weight, durability, and environmental resistance. However, their decomposition rates are significantly slower than their typical lifespans. The rapid and continuous increase in plastic consumption has caused severe environmental impacts due to the accumulation of plastic waste. We identified potential polyhydroxyalkanoate (PHA)-degrading bacteria from marine environments capable of producing extracellular PHA depolymerases crucial for biodegrading PHAs. Marine debris was collected to screen poly [(R)-3-hydroxybutyric acid] (P(3HB))-degrading bacteria. Six isolates showed the ability to produce clear zones surrounding their colonies by degrading the bioplastic P(3HB). The isolate SS1-2, exhibiting the greatest degradation index of 1.44, was chosen for optimization through the statistical technique. The results indicated that NH4Cl was the best nitrogen source for enzyme production, and the response surface methodology (RSM) suggested that the greatest P(3HB) depolymerase production could be achieved when the concentrations of substrate loading and NH4Cl both set at 0.5%. Analysis of the 16S rRNA sequence of isolate SS1-2 revealed similarity to Pseudooceanicola antarcticus CGMCC 1.12662 (97.81% similarity). The findings of this study indicate the potential for further exploitation of this depolymerase in enzyme kinetics studies and its application in PHA degradation experiments.

Asymbiotic Nitrogen Fixation in the Phyllosphere of Urban Green Spaces.

Biological nitrogen fixation (BNF) is an important source of nitrogen in ecosystems. Compared to symbiotic nitrogen-fixing microorganisms, free-living diazotrophic bacteria have a broader distribution and greater diversity, demonstrating greater potential for application. Leaf surfaces constitute one of the largest microbial reservoirs on Earth, harboring a variety of free-living diazotrophic bacteria, contributing significantly to plant N acquisition and growth. The distribution patterns, abundance, diversity, and the environmental variables affecting the asymbiotic nitrogen fixation (ANF) rates of free-living diazotrophic bacteria of non-leguminous plants in urban green spaces were investigated using high-throughput sequencing of nifH gene amplicons and the acetylene reduction method. Both green space type and plant species significantly impact ANF rates and nifH gene abundance in the phyllosphere, with green space type having a more pronounced effect. Leaf metal elements iron (Fe), molybdenum (Mo), and the free-living diazotrophic bacteria of the genus Skermanella collectively influence the ANF rates in the phyllosphere of urban green spaces. Linear regression analysis revealed that metal elements Fe, Mo, and potassium (K) in the leaves were significantly positive correlated with the diversity of the free-living diazotrophic bacteria and the abundance of the N-fixing gene nifH. The alpha diversity and symbiotic network structure of the free-living diazotrophic bacterial community in the phyllosphere indicated a significant negative correlation between human disturbance and environmental perturbation and the biodiversity and network complexity of these bacteria. This study provides a crucial foundation for understanding the nitrogen-fixing functions of microbes in urban ecosystems and their contributions to the nitrogen cycle.

Determination of Optimal Culture Medium Conditions for Mass Production of Beauveria bassiana Clone EF 46

The issue of food safety has become a major concern due to the use of chemical pesticides, which have deleterious effects on human health, the environment and biodiversity. Biological pest control, which uses entomopathogenic agents, is an alternative that is more respectful of the health of living beings and the environment. This study aimed to determine the optimal culture medium parameters for the indigenous strain Beauveria bassiana clone EF 46, aiming to facilitate the development of biopesticides. Potato Dextrose Agar (PDA) medium was used to evaluate the influence of physical (temperature, photoperiod, pH) and nutritional (carbon and nitrogen sources) parameters on the sporulation of B. bassiana. Concurrently, rice husk supplemented with different types of starch flours was used to determine the best substrate for solid-state fermentation. This study revealed that the optimal physical parameters for sporulation were: a temperature of 25 °C, an alkaline medium with a pH of 9, and a 12h: 12h light/dark photoperiod. Regarding nutritional parameters, fulvic acid and baker's yeast were identified as the best carbon and nitrogen sources, respectively. Concerning the culture substrate for solid-state fermentation, yellow corn flour proved to be the best supplement for rice husk.

Solid-State Fermentation of Orange Peels for Recovery of Orange Oil Using Aspergillus species NCIM 1432

The available orange peel extraction processes have several drawbacks including the need of solvents and high temperatures which affect the quality of orange oil. Thus there is a need to develop an alternate green process for extraction of orange oil. In present study, solid state fermentation (SSF) of fresh orange peels by Aspergillus species NCIM -1432 to extract extra-cellular enzymes and orange peel oil are noted. Additionaly, the effect of methods of orange peel sterilisation, importance of selection of the fermentation strain, effect of external nitrogen source, and particle size of the peels are detailed. The process used here gave 0.95 % w/w yield of orange oil. The color of the extracted oil is noted with 56.8, 4.7 and 12.2 CIE L*a*and b* values respectively typical to the orange colour. Also, the oil has been noted with typical orange fruit aroma. Further, the chemical composition of the extracted oil has been monitored by GC-MS, HPLC –MS which showed 96 % w/w limonene content. The oil is noted with anti-oxidant property upon its DPPH assay, with 0.87 of specific gravity. All the properties of the oil indicate a good quality oil. The crude hydrolytic enzymes produced during fermentation showed 155 U. g-1 and 239 CMC. g-1 of pectinase and cellulase activity respectively. The developed method of orange oil extraction is green, needs low tech equipment and can be an alternative to the available orange peel oil extraction methods at small scale.

Physiological and molecular responses to urea environment in Cladocopium goreaui (Symbiodiniaceae).

Physiological and molecular responses to urea environment in Cladocopium goreaui (Symbiodiniaceae).