Variations In Carbon Sources Research Articles

Production of Antibiotics from Endophyte Fungi Isolates of Bidara Plants (Ziziphus mauritina L.) Isolates Codes IFAZ-6, IFBZ-6, IFDZ-8 With Variations in Carbon Sources

Research has been carried out on antibiotic production from endophytic fungal isolates coded IFAZ-6, IFBZ-6, and IFDZ-8 from bidara plants (Ziziphus mauritina L.) with variations in carbon sources. This research aims to determine antibiotic production with variations in carbon sources. The first stage was the purification of each selected endophytic fungal isolate. The endophytic fungal isolate was inoculated into the fermentation medium using a variety of carbon sources, namely glucose, fructose, and galactose for 21 days. The antibiotic activity was carried out using the agar diffusion method against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli bacteria. The results obtained showed that the glucose carbon source was better in producing antibiotic compounds than the galactose carbon source in endophytic fungal isolates coded IFAZ-6, the glucose carbon source was better in producing antibiotic compounds than the fructose and galactose sources in endophytic fungal isolates coded IFBZ-6, and the fructose carbon source is better at producing antibiotic compounds than the galactose source in endophytic fungal isolates coded IFDZ-8.

Sweet sorghum as alternative carbon sources for Chlorella sp. valued-added compounds production: A mechanistic insight using transcriptomics

Substituting agricultural by-products for glucose as a carbon source is an effective strategy for reducing the cultivation cost of Chlorella sp. However, the response mechanism of Chlorella sp. to variations in carbon sources remains unclear, and the potential of microalgal biomass for food development warrants further exploration. This study used hydrolysate of sweet sorghum stem juice (HSJ) for the mixotrophic cultivation of Chlorella sp. And transcriptomic analysis was performed to investigate the physiological and metabolic mechanisms as well as the biosynthesis of value-added compounds (e.g., pigments and proteins) of Chlorella sp. in response to changes in carbon sources. The HSJ + NM group (HSJ supplemented with nitrogen and minerals) significantly increased total chlorophyll, carotenoids, lutein, and protein levels by 18.02 %, 13.34 %, 35.95 %, and 20.36 %, respectively, compared to the control (adjusted BG-11 medium supplemented with 10 g/L glucose). Notably, transcript levels of genes for multiple key enzymes involved in glycolysis/gluconeogenesis, TCA cycle, oxidative phosphorylation pathway, and photosynthesis pathways were significantly up-regulated. The activity of these pathways promoted the pigments and proteins synthesis in Chlorella sp. Encouragingly, the cost of cultivating Chlorella sp. with HSJ + NM (0.495 USD/kg) was 43.35 % of glucose (1.142 USD/kg). Further, by fermenting Chlorella sp. cultures with Saccharomyces cerevisiae and further homogenizing and blending the fermentation broth, we developed a nutritious and palatable Chlorella sp. fermented beverage, addressing the common issue of algal odor in such products. This study provides theoretical and practical foundations for the mixotrophic cultivation of microalgae and the application of microalgal biomass in food innovation.

Spatiotemporal Variations in Carbon Sources and Sinks in National Park Ecosystem and the Impact of Tourism

The capacity of carbon sinks varies among the different types of ecosystems, and whether national parks, as an important type of nature reserve, have a high carbon sink capacity (CSC) and whether eco-tourism in national parks affects their CSC are the main scientific issues discussed. Using MODIS Net Primary Production (NPP) product data, this study analysed the spatiotemporal variation in carbon sources and sinks (CSSs) in the ecosystem of Huangshan National Park from 2000 to 2020, as well as the impact of tourism on these carbon sources and sinks. The findings indicate that, while the ecosystems of national parks generally have a strong CSC, they may not always function as carbon sinks, and during the study period, Huangshan National Park served as a carbon source for four years. Temporally, the CSSs in the ecosystem of the national park exhibit a cyclical pattern of change with a four-year cycle and strong seasonality, with spring and autumn functioning as carbon sinks, and summer and winter as carbon sources. Spatially, the CSSs of the national park ecosystem exhibited a vertical band spectrum of spatial distribution, and the CSC showed a trend of gradual enhancement from low altitude to high altitude. Tourism is a major factor that has an impact on the CSC of national park ecosystems.

Integrated system of electro-catalytic oxidation and microbial fuel cells for the treatment of recalcitrant wastewater

The emission of recalcitrant wastewater poses serious threats to the environment. In this study, an integrated approach combining electrocatalytic oxidation (EC) for pretreatment and microbial fuel cells (MFC) for thorough pollutant degradation is proposed to ensure efficient degradation of target substances, with low energy input and enhanced bioavailability of refractory organics. When phenol was used as the pollutant, an initial concentration of 2000 mg/L phenol solution underwent EC treatment under constant current-exponential attenuation power supply mode, resulting in a COD removal rate of 54.53%, and a phenol degradation rate of 99.83%. Intermediate products such as hydroquinone and para-diphenol were detected in the solution. After subsequent MFC treatment, only minor amounts of para-diphenol were left, and the degradation rate of phenol and its intermediate products reached 100%, with an output power density of 110.4 mW m−2. When coal chemical wastewater was used as the pollutant, further examination of the EC-MFC system performance showed a COD removal rate of 49.23% in the EC section, and a 76.21% COD removal rate in the MFC section, with an output power density of 181.5 mW m−2. Microbiological analysis revealed typical electrogenic bacteria (such as Pseudomonas and Geobacter), and specific degrading functional bacteria (such as Stenotrophomonas, Delftia, and Brevundimonas). The dominant microbial communities and their proportions adapted to environmental changes in response to the variation of carbon sources.

Influence of carbon sources on silicon oxides for lithium-ion batteries: a review

Silicon oxides/carbon composites are classified based on the variation of carbon sources, and representative developments are systematically reviewed, providing a comprehensive perspective for the design and construction of SiOx/C composites.

Phytochemical Screening and Antioxidant Activity in Ecoenzymes with Variations in Carbon Sources

Ecoenzyme is a fermented solution from a mixture of fruit skin waste, vegetables, water and sugar. The fermentation process of various types of natural ingredients is known to be able to increase the content of various phytochemical compounds and antioxidants in these products. Phytochemicals are secondary metabolites that act as antioxidants. Antioxidants are compounds that can overcome oxidative damage due to reactive oxygen compounds that play a role in capturing free radicals. The purpose of this study was to determine the phytochemical and antioxidant content of each ecoenzyme. This type of research is descriptive. Ecoenzyme extraction was carried out by maceration method using three different solvents namely distilled water, methanol and ethanol. Phytochemical screening was carried out by qualitative methods. The antioxidant activity test was measured using the DPPH (1,1-Diphenyl-2-Prikrylhidrazil) method. The results showed that the ecoenzymes identified alkaloids, flavonoids and saponins. The antioxidant activity of the ecoenzyme with methanol extract (IC50 value) was 100.052 ppm (moderate activity category), while the antioxidant activity of the other ecoenzyme sample extracts had weak antioxidant properties. The conclusion from this study is that ecoenzyme contains phytochemicals and antioxidant activity that can be applied to some field research.

Extraction of Silicon From Silica Sand by Carbothermic Reduction in Mini DC-EAF

This study explores silicon extraction from silica sand using different carbon sources: graphite powder, coke, and coconut shell charcoal. Experiments were conducted to assess the influence of carbon source variation and briquetting on metallic silicon production. The silica sand sample was characterized using X-ray fluorescence, while proximate analysis was performed on the coke and coconut shell charcoal reductants. Each experiment used 50 grams of silica sand with varying amounts of carbon sources at a C:SiO2 mole ratio of 1.8:1. The reductants were tested both with and without briquetting using a DC electric arc furnace for 10 minutes. SEM-EDS and X-ray diffraction were employed for result analysis, with comparisons made to other materials. The experiment using coke as a reductant with briquetting yielded the best result with a Si content in the metal of 98.15%. The experiment with a mixture of silica sand and coconut shell charcoal briquette resulted in a SiC product with Si content of 54.46%. The experiment with a mixture of silica sand and graphite briquette resulted in a SiO2 and SiC product with Si content of 43.17%. The experiment without briquetting using coke as a reductant showed a high SiO2 content, as seen from the oxygen content of 36.44%. The experiment without briquetting using coconut shell charcoal as a reductant resulted in a SiO2 and SiC with Si content of 26.64%. The mixture of silica sand and graphite without briquetting produce SiC as a product with Si content of 70.6%.

Optimization of Antibacterial Metabolite Production and Antioxidant Activity of Endophytic Fungi Isolate from Kelakai (Stenochlaena palustris)

This research aims to optimize the production of antibacterial metabolites and test the antioxidant activity of endophytic isolates from kelakai (Stenochlaena palustris). The research results showed that the optimum growth profile of the isolate showed that exponential growth only started on day 1 and reached a maximum on day 17. Based on pH variations, it shows that pH 7 is the optimum pH in inhibiting bacterial growth, and based on variations in carbon sources, it shows that fructose is a better carbon source than glucose. Antimicrobial activity test using ethyl acetate extract from endophytic fungal fermentate based on differences in pH and carbon source showed antimicrobial activity against S. aureus and E. coli with the inhibition zone diameters being 13.50 mm and 11.35 mm, respectively.

Variation of carbon source and sink along the environmental gradient from lakeside to highlands in Yuanchi swamp wetlands, Changbai Mountains, China.

Lacustrine wetlands have long-term carbon storage capacity and contribute significantly to regional carbon cycle, but it is unclear how its carbon sinks respond to climate change. We measured soil heterotrophic respiration carbon emissions (CO2 and CH4), vegetation carbon sequestration, and related environmental factors (temperature, water level, etc.) of five kinds of natural swamps (Phragmites marsh-L, Carex schmidtii marsh-C, Rhododendron capitatum swamp-D, Betula fruticose swamp-H, Larix olgensis swamp-LT)by using static chamber gas chromatography and relative growth equation methods, along the water environmental gradients from lakeside to highlands in Yuanchi of Changbai Mountains. We quantified the carbon source/sink function (CSS) and global warming potential (GWP) of various swamp types by estimating ecosystem net carbon balance, and revealed the variation patterns and formation mechanisms of CSS and GWP along the environmental gradients, aiming to explore the response of carbon source/sink of lakeside wetland in high altitude area to climate change. The results showed that marshes (L and C) were weak sources (-1.018 and -0.090 t C·hm-1·a-1) at the lower habitats of the water environment gradient, shrub swamps (D and H) were strong or weak sinks (1.956 and 0.239 t C·hm-1·a-1) at the middle habitats, forest swamp (LT) was strong source (-3.214 t C·hm-1·a-1) at the upper habitat. The spatial changes were promoted by water level and suppressed by soil temperature. For GWP, strong thermal radiation for marshes (from 44.682 to 59.282 t CO2·hm-1·a-1), cold radiation for shrub swamps (from -0.920 to -7.008 t CO2·hm-1·a-1), and weak thermal radiation for forest swamp (11.668 t CO2·hm-1·a-1), and their GWP was only promoted by soil temperature. Under current climate change background, marshes and forest swamp at both ends of the water environment gradient from lakeside to highlands played a positive feedback effect due to the increases of CH4 or CO2 emissions, while the middle shrub swamp still maintained a negative feedback effect in Yuanchi located the high-altitude area of the temperate Changbai Mountains.

Spatio-Temporal Variation of Carbon Sources and Sinks in the Loess Plateau under Different Climatic Conditions and Land Use Types

The carbon balance of terrestrial ecosystems is intertwined with climate and changes in land use. Over the past 30 years, the Loess Plateau (LP) has experienced temperature increases and an expansion of forest and grassland. The net ecosystem productivity (NEP) underlying these changes is worth investigating. Using three periods (i.e., 1990–2000, 2000–2010, and 2010–2019) of annual average NEP and climatic, topographic, and land use data, we analyzed changes in the spatial distribution of carbon sources and sinks of the LP. Using an optimal parameter-based geographical detector model to discuss the driving factors of carbon sources and sinks, we found that: (1) The area of carbon sinks has been increasing continuously, and that the distributions of both of these elements are zonal. The carbon sinks show a downward trend from south to north, which is mainly driven by climate and land use type. (2) Carbon sources are mainly concentrated in the middle temperate zone, and they are mainly linked to impervious land, unused land, and grassland. The carbon sinks are mainly concentrated in the south temperate zone and plateau climatic zone, and they are mainly linked to forest, grassland, and cultivated land. Additionally, the southern temperate zone has been the most green, due to its superior hydrothermal conditions that sustain carbon sinks. (3) It is not uncommon for some forests, grasslands, and cultivated land to transition between being carbon sources and carbon sinks, especially when affected by human intervention and inadequate management measures. (4) NEP was primarily influenced by CO2 concentration, temperature, and precipitation, and the interaction of these factors greatly influenced the dynamics of carbon sources and sinks, while terrain exerted insignificant impacts on the NEP. This study highlights the importance of the carbon balance in terrestrial ecosystems and can be used to guide the creation of vegetation-based carbon sequestration policies.

Implementation of real-time image processing on bacterial cellulose formation using soybean-boiled wastewater with the variation of carbon sources during fermentation

Bacterial cellulose (BC) is produced by aerobic bacteria through oxidative fermentation in synthetic and non-synthetic mediums. Several mediums reported to be used as BC formation mediums are coconut water and soybean-boiled wastewater. Carbon sources are needed to optimize the BC formation process. Recent study has implemented a real-time image processing approach for monitoring BC formation. This study aimed to investigate the correlation between variables that influence the fermentation and to determine the kinetic model of BC formation using an image processing approach with the variation of carbon sources during the fermentation. The results showed that the correlation between fermentation time and thickness had the highest percentage for glucose, sucrose, and mannitol mediums. The kinetic observation of BC formation in the medium using glucose, sucrose, and mannitol followed the Gompertz model equation, with the medium using sucrose having the fastest rate of increase at the 44th hour, followed by the medium using mannitol at the 112th hour, and the medium using glucose at the 149th hour.

Effect of Carbon Source Variations on Growth, Physiological Stress, and Saponin Levels of <i>Talinum paniculatum</i> Gaertn. Adventitious Roots

Monosaccharide and disaccharide as carbon sources can affect the production of secondary metabolites. The study aims to determine the effect of variations in carbon sources on growth, physiological stress, and saponin levels of the adventitious roots of Talinum paniculatum Gaerthn. Adventitious roots are subculture in liquid MS medium treated with various sugars: 3% sucrose, 3% glucose, 3% fructose, 3% lactose, 3% maltose, 3% dextrose, sucrose + fructose (1.5% + 1.5%), sucrose + glucose (1.5% + 1.5%), glucose + fructose (1.5% + 1.5%), sucrose + dextrose (1.5% + 1.5%) for 6 weeks. The results of this study show that the 3% fructose treatment produces the highest fresh and dry biomass, which are 1.30 g and 0.23 g compared to the control. The morphology of adventitious roots in the treatment of carbon source variation is not different from the control treatment. The highest MDA (malondialdehyde) levels are found in the sucrose + fructose treatment (1.5% + 1.5%). Meanwhile, the highest proline levels are found in the 3% maltose treatment. Saponin levels analyzed using thin layer chromatography show the data in the form of color intensity and stain area based on ImageJ software analysis. The 3% fructose treatment shows the highest color intensity and stain area compared to the control. Variations in carbon sources affect physiological stress, biomass, and saponin levels of adventitious roots of T. paniculatum, but do not effect on root morphology.

Kinetics study of bacterial cellulose production by Acetobacter xylinum FNCC 0001 with variation of carbon sources

Glucose and fructose (2.0% (w/v)) were used as the carbon sources and peptone was used as nitrogen source (1.5% (w/v)) in order to determine the kinetics study and yield of bacterial cellulose production. Coconut water was prepared as the fermentation medium. Data of the fermentation rate was observed at 19 points of certain time during 7 days of fermentation process. The number of cell biomass was calculated using cell dried weight method, total plate count method and optical density method which was observed at 660 nm. The remaining media substrate was analyzed using the DNS method, while the BC yield was determined by the gravimetric method. The results showed that the best values of μ, Td, Rx, Rs, Rp, Yp/s, Yp/x were achieved by fructose, while the best n and Yx/s value were achieved by glucose. The corresponding values were 0,1141/h, 6,0737 h, 0,1141 g/L/h, 0,0635 g/L/h, 0,3015 g/L/h, 0,317 g/g, 0,5927 g/g 1,3631 times and 0,0983 g/g respectively. The highest BC yield at the end of fermentation process was achieved by glucose carbon at 5.83 g/L, followed by fructose at 4.91 g/L.

Feeding habits of Baffin Bay polar bears Ursus maritimus: insight from stable isotopes and total mercury in hair

Loss of sea ice brought on by climate change affects polar bear Ursus maritimus access to prey. Here we investigated variation in feeding habits of the Baffin Bay (BB) polar bear subpopulation in relation to sea ice, habitat use, season, and demography using hair carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) stable isotope values and total mercury (THg) concentrations as ecological tracers. We analyzed hair samples from BB polar bears (n = 131) of all age and sex classes live-captured in West Greenland during the spring in 2009-2013. BB polar bears occupied a narrow isotopic space, suggesting limited variation in carbon sources and trophic position within the subpopulation. THg concentrations (median ± SE: 5.1 ± 0.2, range: 0.3-12.5 µg g-1 dry weight, DW) were related to age class, and nearly half exceeded the suggested threshold for neurological effects in polar bears at 5.4 µg g-1 DW. Although distinct coastal and offshore space-use strategies have been reported for BB polar bears, our results suggest that both strategies lead to similar carbon sources and trophic positions. We found seasonal variation in δ13C and δ34S across both space-use strategies, with δ34S suggesting that all BB polar bears may prey on a higher proportion of benthic-feeding bearded seals Erignathus barbatus in late summer relative to spring. Despite wide fluctuations in inter-annual sea ice conditions and differences in space-use strategies among individuals, stable isotope values and THg concentrations suggested limited variation in feeding habits among BB polar bears. The variation of habitat tracers (δ13C and δ34S) was related to season, whereas trophic tracer (δ15N and THg) variation was driven by demographic group. The specialized BB polar bear diet suggests limited feeding plasticity under continued climate warming.

Characterization of Peat Microbial Functional Diversity in Aerobic Rice Rhizosphere

Microorganisms in the rhizosphere possess numerous metabolic activities. The addition of inorganic substance such as fertilizer could affect the microbial functional diversity. This study was conducted to evaluate the effect of different rate of NPK fertilizer on microbial functional diversity in the rhizosphere of local aerobic rice variety. Aerobic rice variety MRIA 1 was used in this study. Peat was taken from a non-agricultural area in Klang, Malaysia. The effect of fertilizer rate was determined with 4 different rates (C = non-fertilized; T1 = 100 kg/ha NPK; T2 = 200 kg/ha NPK; T3 = 400 kg/ha NPK). Microbial functional diversity was performed using Biolog™ Ecoplate System and measured by microbial activities, such as average well color development (AWCD), species richness (R), Shannon-Weaver index (H index) and species evenness (E). As a result, microbial activity increased to 5.7% when fertilizer applied at T2, while fertilizer rate at T3 increased species richness by 3.2%. However, addition of fertilizer did not affect the H index while species evenness slightly decreased by 1.1% when applied at T3. Bacteria population was reduced when fertilizer added at T1. Fertilizer addition to the peat soil decreased the culturable population of nitrogen-fixing microbes while no effect was found on culturable fungal, actinomycetes and phosphate-solubilizing microbe population. Microbes in T2 utilized many carbon sources. Variation in carbon sources used by microbes was found when fertilizer was applied at different rates. D-cellobiose, pyruvic acid methyl ester, and L-serine were the carbon sources that influenced the microbial function in soil. It is concluded that fertilizer has an effect on microbial functional diversity in the peat rhizosphere of local aerobic variety. The recommended fertilizer rate (T2) increased the microbial activity while high fertilizer rate (T3) increased species richness and decreased species evenness.

Biosurfactants production using glucose and molasses as carbon sources by Azotobacter vinelandii and soil washing application in hydrocarbon-contaminated soil

The purpose of this research was to understand the influence of carbon source variation in the biosurfactant production by Azotobacter vinelandii as well as its potential application on remediation of hydrocarbon-contaminated soil by soil washing. The growth microorganism, biosurfactant quantity in exopolysaccharide and fatty acid fraction were examined. The quality of biosurfactant was analysed by emulsification index. The results show that biggest production was occurred at the 48th hour with μmax1 = 0.416/hour, μmax2 = 0.093/hour and Ks1 = 6.55 g/L, Ks2 = 4.69 g/L for glucose and molasses substrate respectively. Biosurfactant product of Azotobacter vinelandii in glucose 1.5%, 2%, 2.5%, and 3% showed emulsification index as much as 100%. While, emulsification index of the biosurfactant produced with molasses reached 100% within 1%, 1.5%, and 2% molasse concentration. These results showed that molasses has potential utilization as carbon source in biosurfactant production. In soil washing application, Biosurfactant and Tween 80 were used as emulsifier to removed Total Petroleum Hydrocarbons (TPH) by contacting in conical flask at rotary shaker. The results showed that highest removal achieved by using biosurfactant up to 48.89% which occurred at 100 rpm for 40 minutes.

Colonies of the fungus Aspergillus niger are highly differentiated to adapt to local carbon source variation.

SummarySaprobic fungi, such as Aspergillus niger, grow as colonies consisting of a network of branching and fusing hyphae that are often considered to be relatively uniform entities in which nutrients can freely move through the hyphae. In nature, different parts of a colony are often exposed to different nutrients. We have investigated, using a multi‐omics approach, adaptation of A. niger colonies to spatially separated and compositionally different plant biomass substrates. This demonstrated a high level of intra‐colony differentiation, which closely matched the locally available substrate. The part of the colony exposed to pectin‐rich sugar beet pulp and to xylan‐rich wheat bran showed high pectinolytic and high xylanolytic transcript and protein levels respectively. This study therefore exemplifies the high ability of fungal colonies to differentiate and adapt to local conditions, ensuring efficient use of the available nutrients, rather than maintaining a uniform physiology throughout the colony.

Removal of Ammonia Nitrogen by Activated Sludge Process Using Simultaneous Nitrification Denitrification Method

Nitrogen concentrations are often found in ammonia, nitrite, nitrate, and neutral nitrogen waters. This research has investigated the simultaneous removal of biological nitrogen nitrification and denitrification (SND) in a continuous flow system of activated sludge processes. This research was conducted by variations in carbon sources is namely glucose and methanol. Variations of C / N ratios of 5, 10, and 20 were also carried out. The main parameters were analyzed every day until the end of the research period. The main parameter analyzed is ammonia-nitrogen. Besides, additional parameters were also analyzed in the form of COD, nitrate-nitrogen, nitrite-nitrogen, pH, MLSS, SVI, and DO. The results of research indicate artificially excess nitrogen wastewater can be treated using SND and can produce sufficiently good effluent quality if the operations are running optimally. The highest ammonia-nitrogen removal efficiency of 100% shown by the variation of the carbon methanol source and value of the C / N 20 ratio then followed by the C / N 10 ratio of 78% and the C / N 5 ratio of 59%. Overall, the data shown appropriate controls for carbon and nitrogen inputs are needed to achieve an efficient SND. Proper SND technology can save operating time and energy, and may replace two traditional stages: biological nitrification and denitrification processes.

Fossil and Non-fossil Fuel Sources of Organic and Elemental Carbonaceous Aerosol in Beijing, Shanghai, and Guangzhou: Seasonal Carbon Source Variation

ABSTRACT We measured the radiocarbon isotope signals in various fractions of carbonaceous aerosols sampled across four seasons (Oct 2013–Jul 2014) in three megacities of China, viz., Beijing, Shanghai, and Guangzhou. The contributions of fossil fuel (FF) and non-fossil fuel (NF) to the carbonaceous aerosol were estimated based on the radiocarbon content in the organic carbon (OC), water-soluble organic carbon (WSOC), water-insoluble organic carbon (WIOC), and elemental carbon (EC). Although NF generated the primary share (> 55%) during autumn in all of the cities, the seasonal contributions of the sources differed by location during the rest of the year. During winter, FF emissions constituted the majority of the carbonaceous pollution (64%) in Beijing, probably as a result of increased coal combustion for heating. On average, the EC, WSOC, and WIOC generated by FF composed ~10%, 35%, and 19% of the total carbon (TC). Overall, NF was identified as the largest source of carbonaceous aerosol in Guangzhou (63%), whereas FF was the largest source, contributing slightly more than NF, in Shanghai (54%). During spring and summer, FF played a greater role than NF in Beijing (~55%) and Guangzhou (~63%); additionally, based on our limited number of samples, it contributed 71% in Shanghai during the latter season, with a significant portion due to fuel combustion (i.e., industrial, vehicular, fishing-boat, and large-vessel emissions).

Intensified nutrients removal in a modified sequencing batch reactor at low temperature: Metagenomic approach reveals the microbial community structure and mechanisms.

To achieve efficient biological nutrients removal at low temperature, a modified sequencing batch reactor (SBR) was developed at 10°C by extending sludge retention time (SRT), shortening aerobic stage and compensating anoxic stage. The average removal rates of ammonium (NH4+-N), total nitrogen (TN) and total phosphorus (TP) were 98.82%, 94.12% and 96.04%, respectively. Variation of carbon source in a typical cycle demonstrated the maximum synthesis of poly-β-hydroxybutyrate (PHB) (60mg/L) occurred after feast period. Furthermore, the TP in sludge reached 50.4mg/g mixed liquor suspended solids (MLSS) (78.4% was inorganic phosphorus and 21.6% was organic phosphorus) after 120 days of operation, indicating an excellent P-accumulating capacity was achieved in this system. Ammonia oxidizing bacteria (AOB) activity inhibition test verified both AOB and ammonia oxidizing archaea (AOA) were involved in ammonia-oxidizing process and the latter accounted for 17%-19%. Metagenomic-based taxonomy revealed the dominant genera were Candidatus Accumulibacter (12.18%), Dechloromonas (7.54%), Haliangium (6.69%) and Candidatus Contendobacter (3.40%). As described from the denitrifying genes perspective, with the exception of nitrite reduction (performed by denitrifiers), denitrifying phosphorus-accumulating organisms (DPAOs) played a leading role in denitrification pathway, showing that poly-β-hydroxyalkanoates (PHA)-driven nutrients removal was the dominate process.