Organic Carbon Source Research Articles

Does Spartina invasion affect the carbohydrate assimilation of polychaetes in mangroves? A case study in the Zhangjiang Estuary Mangrove National Nature Reserve

Carbohydrates, which form a large pool of carbon in plant litter, are a major driver of litter dynamics and benthic food webs in Spartina-invaded mangrove ecosystems. However, there are large gaps in knowledge regarding the effects of exotic leaf litter carbohydrates on benthic carbon assimilation. In this study, the dynamics of carbohydrates, including cellulose, lignin and monosaccharides (glucose, mannose, galactose, xylose and arabinose), during the leaf litter decomposition of the exotic Spartina alterniflora (SA) and the native mangrove plant Kandelia obovata (KO) were analyzed and compared. Meanwhile, the differences in the δ13C values of cellulose and lignin were used to analyze the utilization of leaf litter carbohydrates by polychaetes after Spartina invasion. Our results showed that the decomposition rate of exotic SA leaf litter was lower than that of KO leaf litter. The contents of cellulose, glucose and galactose in SA leaf litter were higher than those in KO leaf litter (P < 0.05). The decomposition rates of cellulose and monosaccharides (arabinose, xylose, mannose and galactose) in KO leaf litter were faster than those in SA leaf litter (P < 0.05). However, there was no significant difference in the decomposition rates of lignin in the leaf litter between exotic SA leaf litter and native KO leaf litter (P > 0.05). In the native KO plot, the carbohydrates of KO leaf litter contributed to >55% (cellulose, 26.91–28.02%; lignin, 28.05–28.64%) of the organic carbon sources of polychaetes. However, in the exotic SA plot, the carbohydrates of exotic SA leaf litter contributed to >65% (cellulose, 36.83–38.30%; lignin, 28.47–30.52%) of the organic carbon sources of polychaetes. The obtained results suggested that Spartina invasion increased the assimilation of cellulose by polychaetes. The high content and low decomposition rate of cellulose in the carbohydrates of exotic SA leaf litter might be important mechanisms for the carbon assimilation changes in the benthos of Spartina-invaded mangrove ecosystems. Given that Spartina has colonized in the Zhangjiang Estuary Mangrove Reserve, this study provides a theoretical basis for the recovery of benthos after ecological restoration. Furthermore, the mechanisms of carbohydrate assimilation by different benthos of different ecosystems should be comprehensively considered in the future.

High-Efficiency Mixotrophic Denitrification for Nitrate Removal in High-Sulfate Wastewater Using UASB Reactor

The efficient removal of nitrate from industrial wastewater containing high concentrations of both sulfate and nitrate presents a major challenge in the field of water treatment. In this study, we investigated the use of an Upflow Anaerobic Sludge Blanket (UASB) reactor for the removal of nitrate from wastewater by gradually increasing the sulfate concentration (ranging from 1 g/L to 10 g/L) and the NO3−-N concentration (ranging from 30 mg/L to 300 mg/L). Through this approach, the activated sludge was successfully acclimated to tolerate high-sulfate conditions. The results demonstrated a remarkable NO3−-N removal capacity of 288 mg/L·d in wastewater with a high sulfate concentration of 10 g/L, leading to a nitrate removal efficiency exceeding 96.0%. The analysis of sulfate and sulfide concentrations, as well as the characterization of the microbial community, revealed the occurrence of autotrophic and heterotrophic denitrification processes in the reaction system. The autotrophic denitrifying bacteria found were Raoultella and Shinella, while the heterotrophic denitrifying bacteria included Klebsiella, Simplicispira, and Thauera. The organic carbon sources were found to be a critical factor influencing the denitrification performance of the system. Furthermore, the effects of different chemical oxygen demand (COD)/SO42− ratios (0.3, 0.5, and 1) were examined in wastewater containing a sulfate concentration of 10 g/L and a NO3−-N concentration of 300 mg/L. The results showed that increasing the COD/SO42− ratio enhanced the removal rate of NO3−-N, maintaining it above 98.0% when COD/SO42− was 1. Additionally, the enhancement of the sulfate reduction reaction in the system was observed, and the enrichment of heterotrophic microorganisms such as Megasphaera, Lactobacillus, and Buttiauxella was observed.

Seasonal and interannual variability of the pelagic ecosystem and of the organic carbon budget in the Rhodes Gyre (eastern Mediterranean): influence of winter mixing

Abstract. The Rhodes Gyre is a cyclonic persistent feature of the general circulation of the Levantine Basin in the eastern Mediterranean Sea. Although it is located in the most oligotrophic basin of the Mediterranean Sea, it is a relatively high primary production area due to strong winter nutrient supply associated with the formation of Levantine Intermediate Water. In this study, a 3D coupled hydrodynamic–biogeochemical model (SYMPHONIE/Eco3M-S) was used to characterize the seasonal and interannual variability of the Rhodes Gyre's ecosystem and to estimate an annual organic carbon budget over the 2013–2020 period. Comparisons of model outputs with satellite data and compiled in situ data from cruises and Biogeochemical-Argo floats revealed the ability of the model to reconstruct the main seasonal and spatial biogeochemical dynamics of the Levantine Basin. The model results indicated that during the winter mixing period, phytoplankton first progressively grow sustained by nutrient supply. Then, short episodes of convection driven by heat loss and wind events, favoring nutrient injections, organic carbon export, and inducing light limitation on primary production, alternate with short episodes of phytoplankton growth. The estimate of the annual organic carbon budget indicated that the Rhodes Gyre is an autotrophic area, with a positive net community production in the upper layer (0–150 m) amounting to 31.2 ± 6.9 gCm-2yr-1. Net community production in the upper layer is almost balanced over the 7-year period by physical transfers, (1) via downward export (16.8 ± 6.2 gCm-2yr-1) and (2) through lateral transport towards the surrounding regions (14.1 ± 2.1 gCm-2yr-1). The intermediate layer (150–400 m) also appears to be a source of organic carbon for the surrounding Levantine Sea (7.5 ± 2.8 gCm-2yr-1) mostly through the subduction of Levantine Intermediate Water following winter mixing. The Rhodes Gyre shows high interannual variability with enhanced primary production, net community production, and exports during years marked by intense heat losses and deep mixed layers. However, annual primary production appears to be only partially driven by winter vertical mixing. Based on our results, we can speculate that future increase of temperature and stratification could strongly impact the carbon fluxes in this region.

Study of Different Types of Fermentation in Wine-Making Process and Considering Aromatic Substances and Organic Acid.

Fermentation is being utilized since ages as a safe process for food preservation. Fermentation in winemaking is the process which converts grapes juice into wine. Alcoholic fermentation is the principle for the manufacturing of alcoholic beverages like wine and beer. Several by-products are produced by the alcoholic fermentation of organic carbon sources by Saccharomyces cerevisiae. The secondary bacterial fermentation is malolactic fermentation which is carried out in most red and some kinds of white wines. Malolactic fermentation causes acid reduction, flavor modification, and also is accountable for microbial stability. The present searching was carried out by the keywords in major indexing systems including PubMed/MEDLINE, Scopus, Institute for Scientific Web of Science and the search engine of Google Scholar. The keywords were alcoholic fermentation, malolactic fermentation, bottle fermentation, carbonic maceration, Saccharomyces, Lactobacillus, Oenococcus oeni, aromatic substances, flavour quality, terpenes, esters, lactones, aldehydes, organic acid, pyrazines, mercaptans, and traditional fermented food. This review was done to highlight the significance, and introduce different kinds of fermentations carried out in wine-making process, specially alcoholic and malolactic fermentation, survey on aromatic substances, flavour quality, and organic acids, and introduce the most notable traditional fermented food in China.

ISOLATION OF POTENTIAL PROBIONTS FROM BRACKISHWATER ENRICHED WITH HIGH LEVELS OF CARBON SOURCE

The majority of shrimp producers utilize probiotics derived from terrestrial sources as part of their aquaculture management. The beneficial effects of terrestrial probiotics on shrimp may be affected due to environmental differences between the cultivated species and the source of the probiotics. To ensure maximum effects on the host, it is essential to use probionts derived from the host or the environment of the cultured organism. Consequently, the objective of this study was to isolate and characterize potential probionts from brackishwater by enriching the water with organic sources containing a high ratio of carbon to nitrogen (C:N). Six 10-li containers were filled with brackishwater from an estuary for a mesocosm experiment. To stimulate bacterial growth, water was enriched with either molasses or brown sugar at a C:N ratio of 15. After twenty days, all heterotrophic bacteria in the enriched water were enumerated. The in vitro antagonistic activities of distinct bacterial colonies against Vibrio harveyi, a crustacean pathogen, were evaluated on fresh Nutrient Agar plates containing 1% sodium chloride. There were 10 bacterial isolates with in vitro antibacterial activity. These bacterial isolates are categorized as belonging to the putative genera Acinetobacter, Pseudomonas, Sphingobium, and Rheinheimera. The implications of this study suggest that enriching brackishwater with organic carbon sources at high C:N ratios may increase the likelihood of isolating and developing potential probionts for shrimp aquaculture.

Contributions of the Yangtze River and Yellow River to terrestrial organic carbon deposition in the Yangtze River Estuary during the last 700 years

Terrestrial organic carbon (OC) could be transported to marginal oceans by large rivers and deposited under different hydrological conditions. A mixture of the fresh & lithospheric OC, superimposed by the OC from different rivers, makes it challenging to distinguish sources and contributions of terrestrial OC. Here, we employed multiple geochemical proxies, including the hydrogen isotopic composition of leaf wax (δDwax), the carbon isotopic composition of total organic carbon (δ13Corg), TOC/TN ratio, and major element distributions, to investigate the variability in sources of terrestrial OC in the Yangtze River Estuary (YRE) since 1270 CE. Our results revealed that the terrestrial OC deposition in the YRE was lower before 1950 CE and considerably increased after 1950 CE. The δDwax record in core A3 indicates that the OC deposition in the YRE was primarily modulated by the variability of El Niño-Southern Oscillation (ENSO) and East Asia Summer Monsoon. The strengthened El Niño-like state since 1600 CE resulted in increased precipitation in the middle and lower reaches of the Yangtze River basin and in turn, affected the terrestrial OC deposition in the YRE. Several episodes with lower carbon preference index (CPI) values of n-alkanes (CPI < 3) were identified. These episodes were concurrent with the streamflow shift of the ancient Yellow River during the transitions from wet to dry conditions, highlighting the potential contribution of the ancient Yellow River to the aged OC deposition in the YRE.

Metabolic inhibitor-free assessment of the heterotrophic ammonia-oxidizing activity in activated sludge

When the contributions of three ammonia-oxidizing pathways (heterotrophic or autotrophic aerobic ammonia oxidization, and anammox) to wastewater biological nitrogen removal systems was compared by determining their ammonia-oxidizing activities, the key question is how to accurately determine the potential heterotrophic aerobic ammonia-oxidizing (PHAe) activity when the potential autotrophic aerobic ammonia-oxidizing (PAAe) activity (by ammonia-oxidizing bacteria (AOB) or archaea, or complete ammonia oxidization bacteria) also contributes to ammonia oxidization in PHAe activity assay medium. Using a AOB species and three heterotrophic AOB species as inocula, we demonstrated the feasibility of PHAe activity evaluation in the absence of a metabolic inhibitor, i.e., by subtracting the PAAe activity determined in PAAe activity assay medium from a combination of PAAe and PHAe activity determined in PHAe activity assay medium. Binary organic carbon sources (i.e., glucose and acetate) were included in the PHAe activity assay medium to fulfill the carbon requirements of most heterotrophic AOB genera. Higher ammonia-oxidizing activity in AOB biomass than heterotrophic AOB biomass (35.6 vs. 2.6–10.0 mg NH4+–N g−1 MLSS h−1) provides the remarkable advantages of autotrophic aerobic ammonia oxidization in biological nitrogen removal systems. Ammonia removal in three full-scale biological nitrogen removal systems for sewage treatment was predominantly mediated by PAAe activity (1.9–3.3 vs. 0.0–0.3 mg NH4+–N g1 MLSS h−1).

Denitrification fractionates N and O isotopes of nitrate following a ratio independent of carbon sources in freshwaters.

The stable isotope technique has been used in tracking nitrogen cycling processes, but the isotopic characteristics are influenced by environmental conditions. To better understand the variability of nitrate isotopes in nature, we investigated the influence of organic carbon sources on isotope fractionation characteristics during microbial denitrification. Denitrifying cultures were inoculated with freshwater samples and enriched with five forms of organic compounds, that is, acetate, citrate, glucose, cellobiose, and leucine. Though the isotope enrichment factors of nitrogen and oxygen (15 ε and 18 ε) changed with carbon sources, 18 ε/15 ε always followed a proportionality near 1. Genome-centred metagenomics revealed the enrichment of a few populations, such as Pseudomonas, Enterobacter, and Atlantibacter, most of which contained both NapA- and NarG-type nitrate reductases. Metatranscriptome showed that both NapA and NarG were expressed but to different extents in the enrichments. Furthermore, isotopic data collected from a deep reservoir was analysed. The results showed δ18 O- and δ15 N-nitrate did not correlate in the surface water where nitrification was active, but 18 ε/15 ε followed a proportionality of 1.05 ± 011 in deeper waters (≥ 12 m) where denitrification controlled the nitrate isotope. The independence of 18 ε/15 ε from carbon sources provides an opportunity to determine heterotrophic denitrification and helps the interpretation of nitrate isotopes in freshwaters.

Denitrification effect and strengthening mechanism of SAD/A system at low temperature by gel-immobilization technology

Sulfur autotrophic denitrification coupled anaerobic ammonia oxidation (SAD/A) has several advantages over other denitrification processes; for example, it does not consume the organic carbon source, has low operation costs, and produces less excess sludge; however, it has certain disadvantages as well, such as a long start-up time, easy loss of bacteria, and low microbial activity at low temperature. The use of microbial immobilization technology to embed functional bacteria provides a feasible method of resolving the above problems. In this study polyvinyl alcohol‑sodium alginate was used to prepare a composite carrier for fixing anaerobic ammonia oxidizing bacteria (AAOB) and sulfur oxidizing bacteria (SOB), and the structure and morphology of the encapsulated bodies were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. Subsequently, the nitrogen removal performance of the immobilized microbial carriers in the gradient cooling process (30 °C to 10 °C) was determined, and the corresponding mechanism was discussed. The results showed that the nitrate-removal efficiencies observed with granular sludge and gel embedding were at 10 °C 21.44 % and 14.31 % lower, than those at 30 °C, respectively, whereas the ammonia-removal efficiency decreased by up to approximately three-fold. The main mechanism was the ‘insulation’ provided by the external gel composed of PVA and SA for the internal sludge and subsequent improvement of its low temperature resistance, while protecting AAOB and SOB from oxygen inhibition, which is conducive to enriching denitrifying bacteria. In addition, the gel does not change the internal sludge species, it can shift the dominance of specific microorganisms and improve the removal efficiency of nitrogen. In summary, the immobilization of AAOB and SOB by the gel can achieve effectively mitigate nitrogen pollution in low temperature environments, thus indicating that the SAD/A process has broad engineering application prospects.

Distribution, sources and influencing factors of organic carbon in the surface sediments of the coastal tidal flats in Jiangsu Province

Coastal tidal flats are situated in the interaction zone between the ocean and land and are vulnerable to natural changes, human activities, and global changes; these areas serve as an important mixing zone and burial area for carbon and nitrogen storage. Coastal tidal flats contribute significantly to the global carbon cycle due to their high biological productivity, high sedimentation rate, and low decomposition rate. However, there is a lack of research on the sources and influencing factors of organic carbon in surface sediments in the coastal tidal flat area of Jiangsu Province. In this study, fourteen surface sediment samples were collected from the Jiangsu coastal tidal flats, and the distribution of organic carbon was analyzed. The sources and influencing factors of sediment organic carbon were also investigated by analyzing the contents, ratios and stable isotopes of carbon and nitrogen in the sediments. The results indicated that the total organic carbon (TOC) and total nitrogen (TN) contents in the surface sediments of Jiangsu coastal tidal flats ranged from 0.09% to 0.82% and from 0.01% to 0.1%, with mean values of 0.36% and 0.04%, respectively, and that there was a significant positive correlation between TOC and TN. Moreover, the high-value areas were located mostly along the borders or in sections covered in vegetation, whereas the mudflat areas without vegetation had lower values. Considering the status of the Jiangsu coastal zone, the abandoned Yellow River estuary, Yangtze River inlet, marine benthic microalgae, C3 plants and C4 plants were selected as end members of organic carbon concentrations. The contributions of different sources were quantified using a Bayesian mixture model (MixSIAR). Among them, the abandoned Yellow River estuary and Yangtze River inlet contributed 28.1% and 19.3%, respectively, followed by marine benthic microalgae with a contribution of 26%, whereas C3 and C4 plants made limited contributions of 9% and 8.8%, respectively. Additionally, the sediment particle size, hydrodynamics, and tidal flat vegetation such as Spartina alterniflora were the key factors influencing the organic carbon distribution. In general, this study contributes to a better understanding of the biogeochemical processes and sources of organic carbon in coastal tidal flats. It also provides a solid foundation for the creation of carbon sink measures in nearshore tidal flats.

Functional Hydrogels for Agricultural Application.

Ten different hydrogels were prepared and analyzed from the point of view of their use in soil. FT-IR spectra, morphology, swelling ability, and rheological properties were determined for their characterization and appraisal of their stability. The aim was to characterize prepared materials containing different amounts of NPK as mineral fertilizer, lignohumate as a source of organic carbon, and its combination. This study of stability was focused on utility properties in their application in soil-repeated drying/re-swelling cycles and possible freezing in winter. Lignohumate supported the water absorbency, while the addition of NPK caused a negative effect. Pore sizes decreased with NPK addition. Lignohumate incorporated into polymers resulted in a much miscellaneous structure, rich in different pores and voids of with a wide range of sizes. NPK fertilizer supported the elastic character of prepared materials, while the addition of lignohumate shifted their rheological behavior to more liquid. Both dynamic moduli decreased in time. The most stable samples appeared to contain only one fertilizer constituent (NPK or lignohumate). Repeated re-swelling resulted in an increase in elastic character, which was connected with the gradual release of fertilizers. A similar effect was observed with samples that were frozen and defrosted, except samples containing a higher amount of NPK without lignohumate. A positive effect of acrylamide on superabsorbent properties was not confirmed.

Effect of a dark-colored substrate on the production of phycocyanin by the cyanobacterium Phormidium sp

As the biotechnological production of valuable compounds has recently gathered research interest, more and more photosynthetic microorganisms are being examined for the synthesis of proteins, fatty acids, pigments, and other biopolymers. In this work, a local isolate (lagoons of Western Greece), of the blue-green cyanobacterium Phormidium sp., was evaluated. Its cultures were considered to be promising for the recovery of the phycobiliprotein, called phycocyanin, even during mixotrophic growth. Interestingly, phycocyanin accumulation was favored by substrates with a low organic load. In order to minimize substrate cost, anaerobic digestion effluent was used as a nutrient and organic carbon source, replacing a synthetic medium containing glucose, to meet the cyanobacterium’s nutrient needs. The results from the cultures containing liquid digestate were surprising, as its addition at low concentrations not only allowed Phormidium sp. to grow but also enhanced the phycocyanin synthesis. The experiments that exhibited a notable phycocyanin production showed a final biomass concentration that barely exceeded 0.7 g L−1 regardless of the nature of the substrate. When Phormidium sp. was inoculated in a pure synthetic medium with 1 g L−1 of glucose, phycocyanin concentration approached 10 mg L−1, while it was measured being 1.75 times higher in the culture containing 10% v/v anaerobic effluent, due to greater cellular accumulation. The present work comes as evidence of the successful bioremediation of digestate accompanied by the production of a high added-value pigment, leading to the removal of organic carbon, total nitrogen, and phosphorous in percentages of 60%, 90%, and 40% respectively.

Temporal variations of mangrove-derived organic carbon storage in two tropical estuaries in Hainan, China since 1960 CE

Mangrove wetlands are important sites of carbon burial amounting to 15% of the global total for coastal environments even though they comprise only 0.5% of the coastal area. Carbon fixation and burial in mangrove wetlands are sensitive to environmental changes but difficult to quantify. In this paper, records of mangrove-derived organic carbon (OC) burial were analyzed for two mangrove wetlands, Bamen Bay estuary (BMB) and Danzhou Bay estuary (DZB), in Hainan Province, China, over timescales of the last few decades. The mangrove-specific biomarker taraxerol and the more established proxies of C/N ratio and δ13C of bulk OC were used to investigate OC sources and burial history. A mixing model based on C/N ratios, bulk OC δ13C values and taraxerol concentrations indicates that mangrove-derived OC accounts for 25 ± 14% (mean ± SD) of sedimentary OC burial in (BMB and 16 ± 7% in DZB since 1960 CE. The estimated top 100 cm organic carbon storage was 242 Mg/ha in BMB and 89 Mg/ha in DZB. The carbon sequestration rate in BMB increased from 0.29 Mg/ha/yr to 6.54 Mg/ha/yr after 2012 CE, likely as a response to local mangrove protection since 1981 CE. Compared to the less-protected DZB, mangroves in BMB contributed 31% more to the sedimentary OC pool after mangrove protection, suggesting that mangrove protection has the potential to increase ecosystem health and to increase carbon burial in coastal wetlands.

Terrestrial dominance of organic carbon in an Early Cretaceous syn-rift lake and its correlation with depositional sequences and paleoclimate

Organic carbon (OC) burial in lakes has been identified as an efficient sink in the global carbon cycle. Abundant input of terrestrial-derived OC leads to high variability in OC origin and type, but its role in determining organic-rich sediments has been overlooked in prior studies. Here, we investigated the OC source and concentration of the Lower Cretaceous (Middle Aptian to Lower Albian) Shahezi Formation (Songliao Basin, NE Asia) to reveal the burial of terrestrial OC in relation to syn-rift lake evolution and paleoclimate change. The sequence stratigraphic framework of fan-deltaic and lacustrine successions was established by identifying depositional facies and sequence boundaries. The lacustrine-dominated interval was further subdivided into four facies associations (i.e., lake shore to littoral siltstones, shallow-littoral mudstones, sublittoral, and profundal) and a few cyclic, parasequence-order packages, using 90 m of continuous cores and high sampling frequency of RoqSCAN SEM-EDS. Multiple independent proxies (macerals identified using correlative light and electron microscopy, pyrolysis indices, Ro, TOC/TN, and δ13Corg) suggest that the organic fraction of the highly mature mudstones was predominantly contributed by terrestrial-derived OC (gas-prone type III/IV kerogen). A direct correlation between depositional facies, chemical weathering proxies (CIA, CIAcorr, and Ln(Al2O3/Na2O)), and OC burial (TOC and HI) has been established. A steep syn-rift slope, a warm–humid climate, abundant vegetation, and the subaqueous transport of OC-bearing sediments (e.g., massive mud-rich conglomerates and sand- to pebble-bearing mudstones), may have jointly promoted the high input of terrestrial OC. A comparison between two Lower Cretaceous terrestrial records from high and low paleolatitudes suggests that the shift from the syn-rift to post-rift phase was accompanied by an increase in TOC concentration and a change toward Type I kerogen of aquatic origin. The tectonically-controlled evolution of rift basins might be an important forcing function for the change of OC sources and concentrations, which is responsible for long-term OC burial in hinterland environments.

Impact of organic carbon reworking upon GDGT temperature proxies during the Paleocene-Eocene Thermal Maximum

Glycerol dialkyl glycerol tetraethers (GDGTs) have been widely applied to coastal marine sediments to reconstruct past temperature variability. However, coastal environments are characterised by variability in the source, age and/or thermal maturity of different organic carbon (OC) pools and may bias various GDGT-based proxies. Here we analyse TEX86 and MBT5MEvalues within a shallow marine sediment core (South Dover Bridge, Maryland) from the Paleocene-Eocene Thermal Maximum (PETM; 56 million years ago (Ma)) to explore how changes in OC reworking influence GDGT-derived sea surface and terrestrial temperature estimates, respectively. We demonstrate that TEX86 values are unaffected by an increase in soil- and fossil organic carbon during the PETM. In contrast, we find large and unexpected variations in MBT5ME-derived temperature estimates (∼6 to 25 °C) during the onset and core of the PETM at some sites. This coincides with input of reworked terrestrial OC from the Cenomanian-aged Raritan Formation. However, there is also an increase in the degree of cyclisation of tetramethylated branched GDGTs, suggesting that branched GDGTs are also derived from marine in-situ production. These factors preclude terrestrial temperature reconstructions at this site. We explored whether OC reworking is problematic in other PETM-aged coastal environments. Using GDGT metrics and the Branched and Isoprenoid GDGT Machine learning Classification algorithm (BIGMaC), we demonstrate that TEX86 values are mostly unaffected by changes in OC sources. However, MBT5ME values are affected by marine and/or freshwater overprints, especially in environments with low terrestrial OC input. Taken together, this study highlights the importance of constraining the provenance of different GDGTs in marine and lacustrine environments.

EFFECT OF VARIOUS CARBON SOURCES ON THE GROWTH PROPERTIES AND MORPHOLOGY OF $SPIRULINA~PLATENSIS$

Cyanobacteria generate biomass under photoautotrophic conditions during photosynthesis. Cultivation of cyanobacteria under photoheterotrophic conditions using various organic carbon sources can increase yield of biomass. In the current study, the effect of organic carbon sources on the growth properties and morphology of cyanobacteria Spirulina platensis, as well as the production of the photosynthetic pigments: chlorophyll a, carotenoids, and phycocyanin were investigated. Carbon sources, such as glucose, fructose and succinate, caused not only an increase in the cyanobacterial growth rate, but also morphological changes in S. platensis trichomes. An increase in the amounts of photosynthetic pigments was also observed. Thus, glucose, fructose, and succinate are more efficient substrates for photoheterotrophic cultivation of these cyanobacteria.

Promoting heterotrophic denitrification of Pseudomonas hunanensis strain PAD-1 using pyrite: A mechanistic study

Denitrification is critical for removing nitrate from wastewater, but it typically requires large amounts of organic carbon, which can lead to high operating costs and secondary environmental pollution. To address this issue, this study proposes a novel method to reduce the demand for organic carbon in denitrification. In this study, a new denitrifier, Pseudomonas hunanensis strain PAD-1, was obtained with properties for high efficiency nitrogen removal and trace N2O emission. It was also used to explore the feasibility of pyrite-enhanced denitrification to reduce organic carbon demand. The results showed that pyrite significantly improved the heterotrophic denitrification of strain PAD-1, and optimal addition amount was 0.8–1.6 g/L. The strengthening effect of pyrite was positively correlated with carbon to nitrogen ratio, and it could effectively reduce demand for organic carbon sources and enhance carbon metabolism of strain PAD-1. Meanwhile, the pyrite significantly up-regulated electron transport system activity (ETSA) of strain PAD-1 by 80%, nitrate reductase activity by 16%, Complex III activity by 28%, and napA expression by 5.21 times. Overall, the addition of pyrite presents a new avenue for reducing carbon source demand and improving the nitrate harmless rate in the nitrogen removal process.

Effect of Particulate Organic Carbon Deposition on Nitrate Reduction in the Hyporheic Zone

AbstractThe hyporheic zone (HZ), where surface water and groundwater interact in sediments beneath streams, presents unique conditions for nutrient dynamics, such as carbon and nitrogen (N) cycling. Organic carbon (OC) in aquatic systems has two distinct forms: dissolved organic carbon and particulate organic carbon (POC). OC affects N reduction and controls the occurrence of denitrification, a primary process by which nitrate (NO3−) is removed as gas (N2 or N2O) to the atmosphere. When POC is the predominant form of OC in streams, how POC influences NO3− reduction within a HZ remains unclear. We established a new reactive transport model incorporating POC transport and filtration processes to assess how POC deposition affects NO3− removal. Sediment permeability decreases as POC is filtrated in the streambed. Nitrate influx is reduced due to POC‐induced sediment clogging. The deposited POC in the shallow streambed serves as an OC source and supports higher biogeochemical reaction kinetics because OC is an important substrate promoting microbial activities. The filtrated POC pool enhances denitrification, thus causing a higher NO3− removal efficiency. In contrast, the POC pool is typically assumed to be distributed homogeneously in sediments, potentially causing a significant underestimation of stream‐borne NO3− removal. A lower hydraulic conductivity, a smaller POC grain size, and a larger POC filtration efficiency and in‐stream POC concentration allow for extensive POC deposition within the shallow streambed that favors nitrate removal. This study provides a better understanding of N processing and an accurate estimation of NO3− removal potential in HZs.

Different carbon source alternative medium improves Euglena sp. growth and paramylon production

Euglena sp. is a type of microalgae are widely recognized for producing an important compound called paramylon. If Euglena sp. is grown in a medium containing a carbon source, it can produce more paramylon. The culture medium alternative must be optimized to maximize biomass production and specifically targeted metabolites. This study aims to compare the effects of glucose and glutamic acid as carbon sources on the growth rate, biomass, and paramylon (β-1,3-glucan) content of Euglena species. The treatment that carried out as the different organic carbon sources were glucose and glutamic acid. About one g/l of each treatment were added to Cramers and Myers (CM) culture medium to see how they affected growth rate, biomass, and paramylon content in Euglena sp. culture. The optical density based on absorbance was used to calculate the density of the cells, biomass was known by measuring the dry weight, and paramylon content produced was analyzed using the phenol-sulfuric acid method. The CM medium treatment with glucose added (CM+Glucose) had the highest specific growth rate, biomass, and paramylon content, with values of 2.902±0.338 (OD680/dx10-1), 0.476±0.023 g/l, and 2.416±0.129 mg/ml Euglena sp. can be utilized to produce paramylon on an industrial scale, so it is necessary to carry out further identification process regarding the species of Euglena sp. local strain, and it is hoped that there will be further research on other possible methods to increase the paramylon content in Euglena sp., such as using organic waste to replace the organic carbon source in the medium.

Elemental sulfur-driven autotrophic denitrification process for effective removal of nitrate in mariculture wastewater: Performance, kinetics and microbial community

To date, there is a lack of systematic investigation on the elemental sulfur-driven autotrophic denitrification (SDAD) process for removing nitrate (NO3−-N) from mariculture wastewater deficient in organic carbon sources. Therefore, a packed-bed reactor was established and continuously operated for 230 days to investigate the operation performance, kinetic characteristics and microbial community of SDAD biofilm process. Results indicate that the NO3−-N removal efficiencies and rates varied with the operational conditions including HRT (1–4 h), influent concentrations of NO3−-N (25–100 mg L−1) and DO (0.2–7.0 mg L−1), and temperature (10oC–30 °C), in the ranges of 51.4%–98.6% and 0.054–0.546 g L−1 d−1, respectively. Limestone could partially neutralize the produced acidity. Small portions of NO3−-N were converted to nitrite (<4.5%) and ammonia (<2.8%) in the reactor. Operational conditions also influenced the production of acidity, nitrite and ammonia as well as sulfate. Shortening HRT and increasing influent NO3−-N concentration turned the optimal fitting model depicting the NO3−-N removal along the reactor from half-order to zero-order. Furthermore, the NO3−-N removal was accelerated by a higher temperature and influent NO3−-N concentration and a lower HRT and influent DO concentration. Microbial richness, evenness and diversity gradually decreased during the autotrophic denitrifier enrichment cultivation and the reactor start-up and operation. Sulfurimonas constituted the predominate genus and the primary functional bacteria in the reactor. This study highlights the SDAD as a promising way to control the coastal eutrophication associated with mariculture wastewater discharge.