Carbon Source For Microorganisms Research Articles

Effect of Various Types of Sugars on Antioxidant Activity and Physico-chemical Properties of Kombucha Fermented Whey

Kombucha or known as SCOBY (Symbiotic Culture of Bacteria and Yeast) is a fermented tea beverage with the addition of sugar then fermented for 7-14 days. Recent studies showed kombucha conceivably used for milk fermentation, such as fermented whey, yogurt, and fermented milks. Sugar is added to kombucha as carbon source for microorganisms in kombucha. Type of sugar, sugar concentration, tea concentration, temperature and incubation time are factors that affect kombucha fermentation. The aims of this study were to determine the effect of various types of sugars on antioxidant activity (2,2-diphenyl-1-picrylhydrazyl (DPPH)) and physicochemical properties (pH, titratable acidity, total dissolved solid, and CIE L* a* b* color space value). The various types of sugars were granulated white sugar (G1), coconut sugar (G2), palm sugar (G3) and no sugar addition as control (G0). Fermented whey using 10% kombucha liquor, 3% kombucha cellulose and 10% sugar addition, whey then fermented at 37oC for 14 hours. Result demonstrated that using of various types of sugars significantly affected antioxidant activity, CIE L*a*b* color space value, pH, titratable acidity, total dissolved solid and vitamin C content. The highest vitamin C content was G3 (0.91±0.05 mg/100ml), kombucha fermented whey using palm sugar. Any type of sugar could be used on kombucha fermented whey, and the highest antioxidant activity (DPPH) was fermented whey kombucha with the addition of coconut sugar (G2) (86.79±10.94%).

Functional diversity of microbial communities in herbaceous vegetation patches in coal mine heaps

AbstractCoal mine heaps represent unique novel environments, suitable for studying plant succession and its influence on the activity of microbes inhabiting the rhizosphere. Our aim was to verify if the functional diversity and catabolic activity of soil microorganisms would increase along with the plant succession from non‐vegetated and forbs‐dominated to grass‐dominated communities. The study was conducted on coal mine heaps located in Upper Silesia (Southern Poland), focusing on non‐vegetated patches, patches dominated by forbs–Tussilago farfara and Daucus carota (in the early stages of succession), and by grasses–Poa compressa and Calamagrostis epigejos (in later stages of primary succession). The catabolic activity and functional diversity of soil microbial communities were analyzed based on community‐level physiological profiles using BIOLOG EcoPlatesTM and the activity of dehydrogenase, alkaline phosphatase, acid phosphatase, and urease. Our results showed that spontaneous vegetation on coal mine heaps strongly affects the physicochemistry of the substrate and the functional diversity of soil microbial communities. Grasses' rhizosphere was hosting more active and functional diversified microbial communities, while non‐vegetated and T. farfara‐vegetated patches were accompanied by a reduced development of soil microbiota. Furthermore, grasses were mainly associated with a substantial delivery of plant litter to the substrate, providing a source of carbon for microorganisms.

Appropriate stoichiometric ratios of dissolved organic carbon and nitrate can trigger a transition in nitrate removal in groundwater around plateau lakes, Southwest China

Increasing dissolved organic carbon (DOC) in groundwater as a carbon source for microorganisms that stimulate nitrate attenuation is considered a sustainable strategy to mitigate nitrate pollution in groundwater. However, little is known on the stoichiometric ratio of DOC and nitrate required in groundwater nitrate reduction processes, which has become an obstacle for evaluating the current status of DOC limitations on nitrate reduction. Here, the NO3—-N and DOC concentrations in groundwater around 8 plateau lakes were investigated, and a microcosm experiment was performed to elucidate the effects of different DOC:NO3—-N levels in groundwater on NO3—-N reduction, and the current status of DOC limitations on groundwater NO3—-N reduction around 8 lakes was further evaluated. The results indicated that nearly 41 % of the groundwater NO3—-N concentrations exceeded the WHO threshold for drinking water (11.3 mg L−1) and 79 % of the groundwater DOC concentrations exceeded 5 mg L−1. The differences in groundwater NO3—-N and DOC concentrations among the 8 lakes were controlled by the intensity of agricultural and human activities and hydrogeological background. The stoichiometric ratio of DOC:NO3—-N regulated the NO3—-N reduction process, and groundwater NO3—-N accumulation rate appeared to become limited and sharply decreased when the DOC concentration was approximately 10 mg L−1 or when the DOC:NO3—-N ratio was close to 1:1, and the DOC:NO3—-N ratio threshold for limiting the NO3—-N reduction process was approximately 2.25. Based on this threshold, >33 %–86 % of the groundwater samples around the 8 plateau lakes were strongly limited in the reduction of groundwater NO3—-N due to a lack of sufficient DOC provides energy for heterotrophic microorganisms. Additionally, we highlight that the sustainable strategy of increasing DOC to stimulate groundwater NO3— attenuation should be combined with short-term strategies to jointly coordinate and control groundwater NO3— pollution.

Biochar as sustained-release carbon source and carrier for microbial denitrification

The biochar used to improve the soil also affects the nitrogen cycle in the water after flowing into the waterbody. In this paper, the function of biochar prepared at different pyrolysis temperatures in the denitrification process in water is studied. Some substances on the surface of biochar can be used as a carbon source for microorganisms, but the carbon source provided by biochar is limited. With the increase of pyrolysis temperature, the effectiveness of biomass on the surface of biochar shows a downward trend. When the pyrolysis temperature is 300°C, the C element content on the surface of biochar is the highest, which is 1.76 mg·g−1, and the oxidizable part increases. Scanning electron microscopy (SEM) analysis confirmed that the surface of biochar was enriched with denitrifying bacteria and provided a usable carbon source.

Bioethanol production from sugarcane molasses with supplemented nutrients by industrial yeast

Sugarcane molasses, a sugar industry by-product, is being used as a convenient source of carbon for microorganisms to produce bioethanol. The industrial yield of bioethanol derived from Saccharomyces cerevisiae decreases with increasing temperature in the summer season and it is a common issue in the tropical region. It is inevitable to boost the production of bioethanol on an industrial scale to make it commercially profitable. This study has been conducted to analyze and compare the effect of three supplements on boosting alcohol products including thiamine (vitamin B1), pyridoxine (vitamin B6), and D-biotin (vitamin H). Collected molasses were diluted to 20 Brix to make them consumable by yeast, and thiamine, pyridoxine, and biotin were added as 1 mg/l, 1 mg/l, and 0.44 µg/l, respectively. Results depicted that the addition of vitamins impacted very positively on increasing alcohol production, yeast growth, and dry yeast weight where the residual glucose concentration was further decreased. Despite an extended lag phase resulting from higher vitamin doses, there was a significant improvement observed in both alcohol generation and yeast cell growth. This study presents the optimal dosing of supplements in the fermentation broth as a strategy to enhance bioethanol production.

Optimizing mixotrophic cultivation of oil-rich Tribonema minus using volatile fatty acids and glycerin: A promising approach for pH-controlling and enhancing lipid productivity

Volatile Fatty Acids (VFAs) have become a subject of significant interest recently, primarily because they can serve as a carbon source for microorganisms that produce bioactive compounds, biodegradable materials, and energy. VFAs can be produced from various waste streams via anaerobic fermentation (AF) in a cost-effective manner, providing a potential avenue for producing biofuels and biochemicals while reducing waste volume. In this study, different VFAs and glycerin individually or in combination were used as the sole carbon source in the mixotrophic cultivation of oil-rich filamentous Tribonema minus. Using different VFAs or glycerin individually caused pH fluctuation in the culture, which led to the accumulation of free ammonia, which produced protons, acidifying the environment and inhibiting microalgae growth. To minimize pH fluctuation, different proportions of organic carbon sources were combined. Under combined organic carbon sources, the growth and photosynthetic performance of T. minus were all higher than those of the single carbon source groups. When Cacetic acid:Cbutyric acid:Cglycerin was set to 0.5:0.5:1, pH in the culture remained close to neutrality, and the removal of NH4+-N and carbon reached the maximum of 81.17 and 97.79%, respectively. The microalgal biomass and lipid productivity reached the highest of 223.80 and 108.16 mg L−1 d−1, respectively. Under the optimized carbon source condition, the fatty acids and biodiesel-related qualities of T. minus were improved. This study provided a reference for the precise design of carbon sources to maximize the resource utilization of butyric acid-type AF effluent by oil-rich T. minus. These conditions also can be achieved on a large scale by adding glycerin wastes to butyric acid-type AF effluent, mainly composed of acetic and butyric acids to get the recommended ratio for microalgae cultivation.

Production of polyhydroxyalkanoate from nipa sap using Cupriavidus necator DSM545

Polyhydroxyalkanoate or PHA is produced through microbial fermentation of sugar and lipid where in nature it is stored as energy and carbon source for microorganisms. Most of the carbon feedstock used for PHA production are derived from biomass as they remain the cheapest carbon source to date. In this study, nipa palm sap was proposed as an alternative carbon feedstock since it is underutilized and widely distributed along river estuaries in Malaysia. This nipa sap contains high sugar content and essential nutrients which are required for PHA production. The aim of this work was to explore potential of nipa sap as a carbon source and to investigate effect of added and non-added nutrient nipa media on PHA production during batch fermentation using Cupriavidus necator DSM545. Extraction of PHA using chloroform showed that 2 g/L of PHA was recovered when nipa added with nutrient was used while nipa only media produced 2.16 g/L of PHA. All the samples showed presence of PHA carbonyl band (C=O) from extracted PHA granules by using FTIR while peak obtained using UV Spectrophotometer confirmed the presence of PHA. These findings proved that nipa palm sap as a novel and alternative carbon source for PHA production.

Photosensitizing properties of dissolved organic carbon in Canadian prairie pothole wetland ponds change in response to sunlight

Dissolved organic carbon (DOC) is an important component of the global carbon cycle providing ecological services such as carbon sources for microorganisms and the provision of a protective barrier between ultraviolet radiation and aquatic organisms. Our study examined the impacts of photodegradation on the optical properties of DOC in prairie wetland ponds in central Saskatchewan, Canada. Surface water was collected from two ponds with seasonal average DOC concentrations of 71.1 mg L−1 (More-DOC Pond) and 32.7 mg L−1 (Less-DOC Pond) and filtered through 1.2 µm GF/Fs into Teflon bottles transparent to UV light. Samples divided into dark and light treatments were incubated in situ at three different depths (surface, 0.25m, and 0.5 m) and collected every 2 weeks for 4 months. Excitation emission matrix scans from 300 to 800 nm and absorbance at 254 nm were measured. Absorbance at 254 nm in the More-DOC Pond and Less-DOC Pond waters decreased by 34% and 50%, respectively. Two fluorescence components were identified corresponding to previous published peaks C and M. Although bulk DOC concentrations did not show significant differences over time, fluorescence intensity of peak C decreased by 39% and 47%, and of peak M increased by 19% and 29%, in the More-DOC Pond and Less-DOC Pond, respectively. Increases in other fluorescence indicators such as fluorescence index (35% and 22%) and FRESH (29% and 30%) were also observed. Overall, terrestrial DOC from our sampling ponds became less aromatic, more aliphatic, of lower molecular weight, and lost absorptivity and fluorescence intensity after 12 weeks of incubation. Results of this study will provide a better understanding of optical characterizations and sources of DOC, and act as a foundation to further study on the role of DOC in prairie wetland ponds.

Toxicity of pulp and paper industry effluent on the bioremediation activity of saprophytic and nitrifying microorganisms

In this work, initially, the effluent of pulp and paper industry was subjected to analyse physical, chemical and physicochemical parameters and concentration of heavy metals. The detrimental effects of the effluent of pulp and paper industry on the biological activity of saprophytic and nitrifying bacteria has been studied using different volume percentages of effluent (0-6.67%). A concentration of 5.0 mg/L glucose was used as control and source of carbon for microorganisms. An increase in percentage inhibition of biological activity of microorganisms has been observed with the increasing concentration of the effluent in the proposed systems. The kinetic parameters, i.e., rate constant (K) and ultimate biochemical oxygen (L) were also evaluated using first and second order kinetics. Overall study resulted in the high resistivity of nitrifying bacteria than saprophytic bacteria to the pulp and paper industry waste.

Citric Acid Promotes the Mobilization of Phosphorus under the Lower Concentration of Low Molecular Weight Organic Acids in Acidic Forest Soil

Low molecular weight organic acids (LMWOAs) secreted by plant roots enhanced the release of inorganic P (Pi) and organic P (Po) into the soil solution and thereby increased plant-available Pi in soils. Not the effect of LMWOAs on inducing organic P (Po) released into soil solution through soil microorganisms at different temperatures was poorly understood, but the transform mechanism for P fraction was also not well explained. This study used three experiments to determine the release of P and the transformation mechanism of P fractions induced by oxalic acid, citric acid, and malic acid in acidic forest soils. The results showed that LMWOAs, as carbon sources for microorganisms, mobilize Po more effectively than glucose. Inorganic P and organic P were released by LMWOAs followed by [Formula: see text] if the substrates of P and LMWOAs were enough. There may be a critical threshold for the concentration of citric acid and oxalic acid between 10 mM and 25 mM to require for the solution of adsorbed and precipitated P, respectively. In all, LMWOAs increased the concentration of labile P by decreasing the concentration of stable P. The results indicated that LMWOAs can significantly promote P availability in acidic forests soils, and the effect of microorganisms on soil available P was more inclined to use LMWOAs than glucose.

Genomic insights into diverse bacterial taxa that degrade extracellular DNA in marine sediments

Extracellular DNA is a major macromolecule in global element cycles, and is a particularly crucial phosphorus, nitrogen and carbon source for microorganisms in the seafloor. Nevertheless, the identities, ecophysiology and genetic features of DNA-foraging microorganisms in marine sediments are largely unknown. Here, we combined microcosm experiments, DNA stable isotope probing (SIP), single-cell SIP using nano-scale secondary isotope mass spectrometry (NanoSIMS) and genome-centric metagenomics to study microbial catabolism of DNA and its subcomponents in marine sediments. 13C-DNA added to sediment microcosms was largely degraded within 10 d and mineralized to 13CO2. SIP probing of DNA revealed diverse ‘Candidatus Izemoplasma’, Lutibacter, Shewanella and Fusibacteraceae incorporated DNA-derived 13C-carbon. NanoSIMS confirmed incorporation of 13C into individual bacterial cells of Fusibacteraceae sorted from microcosms. Genomes of the 13C-labelled taxa all encoded enzymatic repertoires for catabolism of DNA or subcomponents of DNA. Comparative genomics indicated that diverse ‘Candidatus Izemoplasmatales’ (former Tenericutes) are exceptional because they encode multiple (up to five) predicted extracellular nucleases and are probably specialized DNA-degraders. Analyses of additional sediment metagenomes revealed extracellular nuclease genes are prevalent among Bacteroidota at diverse sites. Together, our results reveal the identities and functional properties of microorganisms that may contribute to the key ecosystem function of degrading and recycling DNA in the seabed.

Variation in the content and fluorescent composition of dissolved organic matter in soil water during rainfall-induced wetting and extract of dried soil

Dissolved organic matter (DOM) is present in all soils, providing a readily available carbon source for microorganisms, which influences microbially mediated biogeochemical processes. Rainfall-induced wetting can alter the content and composition of soil DOM. However, conventional methods commonly used to extract DOM from soils involve air- or oven-drying followed by extraction with water, and the results vary considerably in terms of indexes used. Therefore, this study aimed to determine the variation in DOM content and composition of soil gravity water and capillary water during wetting, and establish a better method to obtain real soil DOM information. Following simulated rainfall (50 mm h−1, 0–24 h), gravity water and capillary water in fresh soil samples were separated using a high-speed refrigerated centrifuge. Additionally, DOM in dried soil samples was extracted using various soil/water ratios after drying by different methods. The DOM data obtained by conventional methods were compared with capillary water data. The results showed that DOM degradation occurred mainly in capillary water close to the surface of soil particles. Among the six fluorescent components of DOM identified, a tryptophan-like component (Ex/Em = 295/335 nm and 230/335 nm) was possibly derived from terrestrial plants, and a tyrosine-like component (Ex/Em = 265/305 nm) was likely derived from microbial secretion. Except for little variation in the fluorescence index, dissolved organic carbon concentrations in capillary water were double those in dried soil extracted by conventional methods. The humification index and spectral slope ratio of DOM extracted by conventional methods also markedly varied, and no clear patterns were observed for the variation in specific UV absorbance at 254 nm. These findings allow real information to be obtained regarding soil DOM during wetting, and better selection of the extraction method and indexes when studying soil DOM.

Characterization of the first cultured free-living representative of Candidatus Izemoplasma uncovers its unique biology

Candidatus Izemoplasma, an intermediate in the reductive evolution from Firmicutes to Mollicutes, was proposed to represent a novel class of free-living wall-less bacteria within the phylum Tenericutes. Unfortunately, the paucity of pure cultures has limited further insights into their physiological and metabolic features as well as ecological roles. Here, we report the first successful isolation of an Izemoplasma representative from the deep-sea methane seep, strain zrk13, using a DNA degradation-driven method given Izemoplasma’s prominent DNA-degradation potentials. We further present a detailed description of the physiological, genomic and metabolic traits of the novel strain, which allows for the first time the reconstruction of the metabolic potential and lifestyle of a member of the tentatively defined Candidatus Izemoplasma. On the basis of the description of strain zrk13, the novel species and genus Xianfuyuplasma coldseepsis is proposed. Using a combined biochemical and transcriptomic method, we further show the supplement of organic matter, thiosulfate or bacterial genomic DNA could evidently promote the growth of strain zrk13. In particular, strain zrk13 could degrade and utilize the extracellular DNA for growth in both laboraterial and deep-sea conditions. Moreover, the predicted genes determining DNA-degradation broadly distribute in the genomes of other Izemoplasma members. Given that extracellular DNA is a particularly crucial phosphorus as well as nitrogen and carbon source for microorganisms in the seafloor, Izemoplasma bacteria are thought to be important contributors to the biogeochemical cycling in the deep ocean.

Interaction effect of phenanthrene degradation on nitrogen transformation in heterotrophic nitrification and aerobic denitrification systems

The heterotrophic nitrification and aerobic denitrification (HNAD) system plays an important role in treatment of nitrogen pollution in water, and nitrogen transformation is closely related to carbon source. In this study, in order to explore the interaction between nitrogen conversion and phenanthrene degradation under the HNAD system, different concentrations of phenanthrene (0, 3, 6, 9 mg/L) were used as the typical and only carbon source of microorganisms, and different concentrations of ammonium nitrogen (0, 25, 50, 75 mg/L) and nitrate nitrogen (0, 25, 50, 75 mg/L) were used as nitrogen sources of microorganisms. The results showed that with the increase of phenanthrene concentration, the degradation rate of ammonia nitrogen gradually increased, which was higher than that of the control by 24.9%. With the increase of phenanthrene concentration, the inhibition effect was more obvious, and the denitrification effect was weakened. The addition of ammonia nitrogen and nitrate nitrogen accelerated the degradation of phenanthrene. As the increase of the concentration of ammonia nitrogen and nitrate nitrogen, the degradation rate of phenanthrene gradually increased. The degradation rate of phenanthrene can reach 100% and 98.8% when the concentration of ammonia nitrogen and nitrate nitrogen was the highest. This may be related to the fact that a large amount of inorganic nitrogen can promote the assimilation of microorganisms and accelerate the co-metabolism of phenanthrene degradation by microorganisms. In short, there was an obvious interaction effect between the degradation of organic carbon source and the conversion of nitrogen in the HNAD system.

Comparative metabolomics of Phialemonium curvatum as an omnipotent fungus cultivated on crude palm oil versus glucose

BackgroundSugars and triglycerides are common carbon sources for microorganisms. Nonetheless, a systematic comparative interpretation of metabolic changes upon vegetable oil or glucose as sole carbon source is still lacking. Selected fungi that can grow in acidic mineral salt media (MSM) with vegetable oil had been identified recently. Hence, this study aimed to investigate the overall metabolite changes of an omnipotent fungus and to reveal changes at central carbon metabolism corresponding to both carbon sources.ResultsTargeted and non-targeted metabolomics for both polar and semi-polar metabolites of Phialemonium curvatum AWO2 (DSM 23903) cultivated in MSM with palm oil (MSM-P) or glucose (MSM-G) as carbon sources were obtained. Targeted metabolomics on central carbon metabolism of tricarboxylic acid (TCA) cycle and glyoxylate cycle were analysed using LC–MS/MS-TripleQ and GC–MS, while untargeted metabolite profiling was performed using LC–MS/MS-QTOF followed by multivariate analysis. Targeted metabolomics analysis showed that glyoxylate pathway and TCA cycle were recruited at central carbon metabolism for triglyceride and glucose catabolism, respectively. Significant differences in organic acids concentration of about 4- to 8-fold were observed for citric acid, succinic acid, malic acid, and oxaloacetic acid. Correlation of organic acids concentration and key enzymes involved in the central carbon metabolism was further determined by enzymatic assays. On the other hand, the untargeted profiling revealed seven metabolites undergoing significant changes between MSM-P and MSM-G cultures.ConclusionsOverall, this study has provided insights on the understanding on the effect of triglycerides and sugar as carbon source in fungi global metabolic pathway, which might become important for future optimization of carbon flux engineering in fungi to improve organic acids production when vegetable oil is applied as the sole carbon source.

Sustainable coating material based on chitosan-clay composite and paraffin wax for slow-release DAP fertilizer

The coating of fertilizers by polymers is one of the most efficient tools for their slow and control release into soil. This strategy avoids excessive use of the fertilizers and increases their availability to the crops needs. In the present paper, hydro-soluble diammonium phosphates (DAP) fertilizer was double coated following the dip-coating process by chitosan-clay composites as inner coating and paraffin wax as an outer coating. The chitosan composite preparation and characterization were deeply investigated. The montmorillonite (MMT) clay incorporation as filler improves the water barrier diffusion, mechanical properties, and thermal stability of the composite. The combination of the swelling behavior of the chitosan-clay composite (inner coating) and the hydrophobic property of paraffin wax (outer coating) was confirmed by the water holding capacity evaluation and the phosphorus release essays in water and soil. Indeed, the phosphorus dissolution from the coated DAP granules was significantly delayed compared to the uncoated DAP. Moreover, the biodegradation study of composite material in soil and the biochemical oxygen demand (BOD) tests revealed that the coating system proposed could be considered as a carbon source for microorganisms after the fertilization process, which confirms its sustainability.

Can biotechnology strategies effectively manage environmental (micro)plastics?

With the convenience of plastic products to daily life, the negative sides of the plastic-age have gradually emerged. Like other pollutants, complex environmental factors result in the ubiquitous presence of (micro)plastics worldwide, raising potential risks to the ecological systems. However, due to the limitation of traditional technologies in treating these materials, new strategies should be developed. More recently, researchers have showed that biotechnology strategies could be promising approaches to effectively manage and control (micro)plastics in the environment, because some microorganisms have been confirmed to be successfully capable of degrading (micro)plastics. Nevertheless, the biotechnology is still in its infancy, and most studies are carried out under laboratory conditions. The biodegradation process is affected by many factors: microorganism species, carbon sources, material types and sizes. Problematically, (micro)plastics are highly stable in the environment, which are difficult to be used as carbon sources for microorganisms. Biodegradation of (micro)plastics requires appropriate conditions, which are not always feasible in field conditions. As such, although biotechnology strategies might be a promising approach to remove environmental (micro)plastics, we believe it is not now at least.

HPLC-SEC-FTIR characterization of the dissolved organic matter produced by the microbial carbon pump

The microbial carbon pump (MCP) concept regroups different processes that contribute to the formation of refractory dissolved organic matter (DOM) from labile substrates. In this study, long-term (1 yr) incubation experiments in fresh- and sea-waters were done with glucose as the only source of carbon for microorganisms. Bulk carbon, glucose and amino acid enantiomers analyses confirmed that glucose was transformed into microbial biomass and complex non-labile DOM. Dissolved organic carbon concentrations decreased during the first four months and then remained constant at ~20% of the initial level. After one year, the microbial DOM and DOM from natural waters were concentrated by evaporation and a low volume solid-phase extraction (SPE) that resulted in a very high (70 to 85%) extraction efficiency. These SPE-DOM samples were characterized by size-exclusion chromatography (HPLC-SEC) coupled with Fourier transform infrared spectroscopy (FTIR). These are the first HPLC-SEC-FTIR analyses of microbial DOM and of such high proportions of natural DOM. Results revealed that microbial DOM showed all the FTIR absorption bands seen in the DOM from natural waters. However, amino acids, carbohydrates, and aliphatic CH were more abundant in the microbial DOM, whereas phenols and esters were more visible in DOM from natural waters. It was difficult to identify consistent (in all samples) compositional trends according to molecular weight (MW). Cluster analyses showed that 72% of the variability in the relative absorbance for all the bands was explained by the origin and the type of the DOM extracts. The microbial DOM from freshwater had the most unique bulk composition while the microbial DOM from seawater was more similar to the DOM from natural waters. The DOM from natural fresh- and sea-waters exhibited the most similar composition when all the bands and MW are considered. The lack of consistent trends in the composition of the samples having the same origin (e.g., the two microbial DOM or the two freshwater DOM) shows the high heterogeneity and complexity of DOM, including the microbial non-labile DOM produced by the MCP. This suggests that the MCP contributes to the heterogeneity and complexity of the DOM found in natural waters.

Development and Evaluation of a Sustainable Long-release Carbon Material Applied for In-Situ Remediation of Groundwater Nitrogen Pollution

Due to slow flow rates and inter-substance reactions in groundwater, remediation requires the addition of materials with sustained release properties. This research uses agricultural waste and zero-valent iron (Fe0), coupling biology and chemistry, to research and develop a sustainable long-release carbon material with a synergistic physico-habitat, and to evaluate its performance, also taking into account the occurrence of nitrogen in groundwater. The material developed has a double-layer structure with an inner core and an outer shell. The core, consisting of agricultural waste, Fe0, and other raw materials, constitutes the repair layer. Agricultural waste provides a carbon source for microorganisms, and Fe0 can quickly remove nitrate via chemical reactions and reduce DO to develop an anaerobic environment in water. The shell provides a solute permeation layer and consists of primary minerals and other components. This can slow the release of TOC from the core and adsorb secondary contaminants. Physical properties testing showed that the materials core was uniformly cross-linked, and its shell exhibited a clear uniform pore structure (SEM). Favorable mechanical compression was recorded for particle strengths of up to 80-105 N. With a density of 1.1 g·cm-3, the material did not float in water. Experiments showed that the material had excellent sustained release. The amount[Max:21-25 mg·(g·L)-1] and rate[Max:0.185 mg·(g·L·d)-1] of TOC release exhibited a steady state trend, but fluctuated greatly in the case of agricultural wastes[(Max amount:53-75 mg·(g·L)-1, Max rate:0.455 mg·(g·L·d)-1]. In terms of further functional gene abundance, materials leachate was found to be conducive to denitrifying bacteria. In early denitrification and oxygen trapping experiments, the Fe0 chemical reaction was dominant for reduction of nitrogen and DO, facilitating denitrification. However, biological denitrification gradually dominated. Differences in denitrification rates between iron-free and iron-containing materials were smaller, as was the correlation between denitrification rate and iron content. These results indicate the formation of physico-habitat synergistic denitrification in the materials system.

Removal of Nitrogen in Municipal Secondary Effluent by a Vertical Flow Constructed Wetland Associated with Iron-carbon Internal Electrolysis

Aiming at the problem of high concentration of total nitrogen (TN) and low available carbon source for microorganisms in municipal secondary effluent, the vertical flow constructed wetland associated with iron-carbon internal electrolysis (ICIE-VFCW) was applied to investigate the removal efficiencies of pollutants in municipal secondary effluent. Moreover, the mechanism for enhanced nitrogen removal was primarily discussed by the applications of UV visible spectrum (UV-VIS) and gel filtration chromatography (GFC). The results showed that the ICIE-VFCW could improve the COD removal efficiencies and the effluent COD of less than 30 mg·L-1could be stably obtained. The average COD removal efficiencies of the whole year, warm months, and cold months could be increased by 10.16%, 9.81%, 11.22%, respectively, compared to the control group. The effluent TN of the ICIE-VFCW could be maintained below 10 mg·L-1, and the average TN removal efficiencies of the whole year, warm months and cold months could be increased by 13.72%,12.90%,16.17%, respectively. Besides, compared to the influent, the humification, aromaticity and average relative molecular weight (Mr) in the effluent obviously decreased, and the Mr decreased more significantly in the ICIE-VFCW. The ICIE-VFCW could promote the conversion of refractory organics in municipal secondary effluent to the small and readily biodegradable molecules, which could enhance the utilization of organic compounds by microorganisms, thus improving the removal efficiency of nitrogen.