Inorganic Carbon Source Research Articles

Effect of the Carbon Source on Nitrifying in an Activated Sludge System Treating Aquaculture Wastewater

The nitrogen in the aquaculture wastewater can have significant effects on receiving water bodies like eutrophication and ammonia toxicity to fish communities. Removing nitrogen by nitrification-denitrification can reduce the potential impact of aquaculture wastewater discharge. Nitrification is affected by different factors including dissolved oxygen, temperature, pH, alkalinity, toxicity, unionized ammonia and substrate concentration. All these parameters affect ammonia-oxidizing and nitrite-oxidizing bacterial activity. The aim of this work is to study the effect of the carbon source on nitrifying bacterial activity in an activated sludge treating aquaculture wastewater. An activated sludge (AS) system was set up and operated continuously for 180 days. The operation was divided into two phases. During Phase I a source of organic carbon (CH 3 COONa) with a C/N level of 2.4 (operation days 1 to 101) was fed into the system, while in Phase II a source of inorganic carbon (NaHCO 3 ) with a C/N level of 16.2 was fed into the system (operation days: 102 to 180). The maximum NH 4 + -N removal efficiency was 49.7% during the Phase I, during which the NO 3 - -N and NH 3 + -N concentrations were 37.1 ± 14.0 and 2.9 ± 1.1 mg/L, respectively. In Phase II, the maximum NH 4 + -N removal efficiency was 45% and NO 3 - -N and NH 3 + -N effluent concentrations were 2.8 ± 0.3 mg/L and 210 ± 49 mg/L, respectively. Ammonia- and nitrite-oxidation decreased in Phase I from 0.231 ± 0.005 mg NH 4 + /gVSS min to 0.018 ± 0.004 mg NH 4 + -N/gVSS min and in Phase II from 0.049 ± 0.011 mgNO 2 - -N/gVSS min to 0.010 ± 0.002 mgNO 2 - -N/gVSS min.

Evaluation of cyanobacterial endolith Leptolyngbya sp. ISTCY101, for integrated wastewater treatment and biodiesel production: A toxicological perspective

The present study evaluates the ability of an endolithic cyanobacterial strain to synergistically treat municipal wastewater and produce biomass. Leptolyngbya sp. ISTCY101 was cultivated in undiluted wastewater influent in batch mode and semi-continuous mode. A semicontinuous marble slab photobioreactor was designed to exploit the endolith's innate capability of developing biofilm and utilizing bicarbonate as source of inorganic carbon. Biomass productivities averaged to 85mgL−1d−1 and 2.93gm−2d−1 in batch mode and semi-continuous mode respectively. The endolith produced 25% (% w/dw) of lipids mainly consisting of saturated and monounsaturated (C16:0, C16:1, C18:0, C18:1) fatty acids (>65%). Maximum Nitrogen and Phosphorus removal rates of 4.37mgL−1d−1 and 1.01mgL−1d−1 were attained in semi-continuous mode. Post treatment analyses of wastewater via GC-MS and ICP-OES showed remarkable removal of major organic contaminants and trace metals respectively. Methyltetrazolium (MTT) assay for cytotoxicity and Comet assay for genotoxicity were carried out in human hepato-carcinoma cell line HepG2 to validate the treatment efficiency of the strain. A 2.3-fold reduction in MTT EC50 value and 10-fold reduction in olive tail moment after cyanobacterial treatment envisage its potential application in integrated wastewater treatment and biodiesel production.

Impact of seawater carbonate chemistry on the calcification of marine bivalves

Abstract. Bivalve calcification, particularly of the early larval stages, is highly sensitive to the change in ocean carbonate chemistry resulting from atmospheric CO2 uptake. Earlier studies suggested that declining seawater [CO32−] and thereby lowered carbonate saturation affect shell production. However, disturbances of physiological processes such as acid-base regulation by adverse seawater pCO2 and pH can affect calcification in a secondary fashion. In order to determine the exact carbonate system component by which growth and calcification are affected it is necessary to utilize more complex carbonate chemistry manipulations. As single factors, pCO2 had no effects and [HCO3-] and pH had only limited effects on shell growth, while lowered [CO32−] strongly impacted calcification. Dissolved inorganic carbon (CT) limiting conditions led to strong reductions in calcification, despite high [CO32−], indicating that [HCO3-] rather than [CO32−] is the inorganic carbon source utilized for calcification by mytilid mussels. However, as the ratio [HCO3-] / [H+] is linearly correlated with [CO32−] it is not possible to differentiate between these under natural seawater conditions. An equivalent of about 80 μmol kg−1 [CO32−] is required to saturate inorganic carbon supply for calcification in bivalves. Below this threshold biomineralization rates rapidly decline. A comparison of literature data available for larvae and juvenile mussels and oysters originating from habitats differing substantially with respect to prevailing carbonate chemistry conditions revealed similar response curves. This suggests that the mechanisms which determine sensitivity of calcification in this group are highly conserved. The higher sensitivity of larval calcification seems to primarily result from the much higher relative calcification rates in early life stages. In order to reveal and understand the mechanisms that limit or facilitate adaptation to future ocean acidification, it is necessary to better understand the physiological processes and their underlying genetics that govern inorganic carbon assimilation for calcification.

Response of a natural phytoplankton community from the Qingdao coast (Yellow Sea, China) to variable CO 2 levels over a short-term incubation experiment

Since marine phytoplankton play a vital role in stabilizing earth's climate by removing significant amount of atmospheric CO 2 , their responses to increasing CO 2 levels are indeed vital to address. The responses of a natural phytoplankton community from the Qingdao coast (NW Yellow Sea, China) was studied under different CO 2 levels in microcosms. HPLC pigment analysis revealed the presence of diatoms as a dominant microalgal group; however, members of chlorophytes, prasinophytes, cryptophytes and cyanophytes were also present. δ 13 C POM values indicated that the phytoplankton community probably utilized bicarbonate ions as dissolved inorganic carbon source through a carbon concentration mechanism (CCM) under low CO 2 levels, and diffusive CO 2 uptake increased upon the increase of external CO 2 levels. Although, considerable increase in phytoplankton biomass was noticed in all CO 2 treatments, CO 2 -induced effects were absent. Higher net nitrogen uptake under low CO 2 levels could be related to the synthesis of CCM components. Flow cytometry analysis showed slight reduction in the abundance of Synechococcus and pico-eukaryotes under the high CO 2 treatments. Diatoms did not show any negative impact in response to increasing CO 2 levels; however, chlorophytes revealed a reverse tend. Heterotrophic bacterial count enhanced with increasing CO 2 levels and indicated higher abundance of labile organic carbon. Thus, the present study indicates that any change in dissolved CO2 concentrations in this area may affect phytoplankton physiology and community structure and needs further long-term study.

Effects of ocean acidification on the photosynthetic performance, carbonic anhydrase activity and growth of the giant kelp Macrocystis pyrifera.

Under ocean acidification (OA), the 200 % increase in CO2(aq) and the reduction of pH by 0.3-0.4 units are predicted to affect the carbon physiology and growth of macroalgae. Here we examined how the physiology of the giant kelp Macrocystis pyrifera is affected by elevated pCO2/low pH. Growth and photosynthetic rates, external and internal carbonic anhydrase (CA) activity, HCO3 (-) versus CO2 use were determined over a 7-day incubation at ambient pCO2 400 µatm/pH 8.00 and a future OA treatment of pCO2 1200 µatm/pH 7.59. Neither the photosynthetic nor growth rates were changed by elevated CO2 supply in the OA treatment. These results were explained by the greater use of HCO3 (-) compared to CO2 as an inorganic carbon (Ci) source to support photosynthesis. Macrocystis is a mixed HCO3 (-) and CO2 user that exhibits two effective mechanisms for HCO3 (-) utilization; as predicted for species that possess carbon-concentrating mechanisms (CCMs), photosynthesis was not substantially affected by elevated pCO2. The internal CA activity was also unaffected by OA, and it remained high and active throughout the experiment; this suggests that HCO3 (-) uptake via an anion exchange protein was not affected by OA. Our results suggest that photosynthetic Ci uptake and growth of Macrocystis will not be affected by elevated pCO2/low pH predicted for the future, but the combined effects with other environmental factors like temperature and nutrient availability could change the physiological response of Macrocystis to OA. Therefore, further studies will be important to elucidate how this species might respond to the global environmental change predicted for the ocean.

Ethylene glycol-assisted hydrothermal synthesis and characterization of bow-tie-like lithium iron phosphate nanocrystals for lithium-ion batteries

In this work, we present a novel binary solvent of ethylene glycol/water medium (W/EG 50:50) that play an important role in the formation of the hierarchical meso-structures of bow-tie-like composition units composed of self-assembly lithium iron phosphate (LFP) nano-sheets. Citric acid uses as inorganic carbon source and no other surfactant or template agent is applied. Results show that the crystallinity and the size of the particles depend on the nature of the solvent used. TEM results show that the sample prepared in ethylene glycol (EG-LFP/C) consists of well-distributed nanoparticles of size approximately 50 nm in diameter, which is uniformly embedded in thin carbon layers. The EG-LFP/C composite delivers the first discharge capacity of 166 mAh g−1, i.e. 97.6% of the theoretical capacity, when tested under a discharge rate of 0.1C. This material shows specific discharge capacities as high as 114 mAh g−1 at 10C rates and exhibits a long-term cycling stability with a capacity loss of only 1.4% after 100 cycles. The high rate performance could be attributed to the amount and/or the quality of the thin carbon coating, improved crystallinity as well as high specific surface area and porosity induced by the special bow-tie-like mesostructures.

Source-age dynamics of estuarine particulate organic matter using fatty acid δ 13 C and Δ14 C composition

This study used a multiproxy approach to elucidate the source and age composition of estuarine particulate organic matter (POM) using bulk stable isotopes (δ13CPOC), fatty acid (FA) biomarkers, and compound specific isotopic analyses in surface waters along the Delaware River and Bay (Delaware Estuary, hereafter). δ13C values of FA (δ13CFA) ranged more widely (−30.9‰ to −21.8‰) than δ13CPOC (−27.5‰ to −23.5‰), providing greater insight about POM sources along the estuary. δ13C values of C16:0 phospholipid FA (primarily, aquatic sources) increased along the salinity gradient (−29.8‰ to −23.4‰), while δ13CFA values of long-chain neutral fatty acid (terrestrial sources) decreased (−28.6‰ to −30.9‰). δ13CFA values for C18's FA indicated the importance of marsh-derived organic matter within Delaware Estuary. Compound specific radiocarbon analysis showed the heterogeneous age structure of FA associated with POM (FAPOM). 14C ages of FA ranged from modern (postbomb) to 1790 BP; aged FA (120 BP to 1700 BP) derived primarily from the watershed, whereas modern FA were produced within Delaware Estuary. 14C ages of short-chain FA (aquatic sources) reflected differences in the age of dissolved inorganic carbon along the estuary and had older 14C ages at the river end-member. 14C ages of FA from terrigenous sources were older than water and sediment residence times indicating this source derived from the watershed. This study is the first to document the complex age distribution of FAPOM along the estuarine salinity gradient and shows that inorganic carbon sources, watershed inputs and autochthonous production contribute to variation in the ages of POM.

Effect of various carbon sources on biomass and lipid production of Chlorella vulgaris during nutrient sufficient and nitrogen starvation conditions

In this research, a two-stage process consisting of cultivation in nutrient rich and nitrogen starvation conditions was employed to enhance lipid production in Chlorella vulgaris algal biomass. The effect of supplying different organic and inorganic carbon sources on cultivation behavior was investigated. During nutrient sufficient condition (stage I), the highest biomass productivity of 0.158±0.011g/L/d was achieved by using sodium bicarbonate followed by 0.130±0.013, 0.111±0.005 and 0.098±0.003g/L/d for sodium acetate, carbon dioxide and molasses, respectively. Cultivation under nitrogen starvation process (stage II) indicated that the lipid and fatty acid content increased continuously to a maximum value at day 2. Using carbon dioxide resulted in highest cell density, while using sodium acetate led to the highest fatty acid content. Molasses was not as effective as other carbon sources, but by taking into account its lower price, it can be considered as a suitable carbon source for algal lipid productivity.

Optimization of inorganic carbon sources to improve the carbon fixation efficiency of the non-photosynthetic microbial community with different electron donors

As the non-photosynthetic microbial community (NPMC) isolated from seawaters utilized inorganic carbon sources for carbon fixation, the concentrations and ratios of Na2CO3, NaHCO3, and CO2 were optimized by response surface methodology design. With H2 as the electron donor, the optimal carbon sources were 270 mg/L Na2CO3, 580 mg/L NaHCO3, and 120 mg/L CO2. The carbon fixation efficiency in response to total organic carbon (TOC) was up to 30.59 mg/L with optimal carbon sources, which was about 50% higher than that obtained with CO2 as the sole carbon source. The mixture of inorganic carbon sources developed a buffer system to prevent acidification or alkalization of the medium caused by CO2 or Na2CO3, respectively. Furthermore, CO2 and HCO3−, the starting points of carbon fixation in the pathways of Calvin–Benson–Bassham and 3-hydroxypropionate cycles, were provided by the carbon source structure to facilitate carbon fixation by NPMC. However, in the presence of mixed electron donors composed of 1.25% Na2S, 0.50% Na2S2O3, and 0.457% NaNO2, the carbon source structure did not exhibit significant improvement in the carbon fixation efficiency, when compared with that achieved with CO2 as the sole carbon source. The positive effect of mixed electron donors on inorganic carbon fixation was much higher than that of the carbon source structure. Nevertheless, the carbon source structure could be used as an alternative to CO2 when using NPMC to fix carbon in industrial processes.

Photoinduced processes of hydrogen peroxide formation and decomposition and their role in photosynthesis and biosphere origin

Processes of mutual photocatalytic transformation of O2 and H2O2 in aqueous suspensions of chlorophyll and phthalocyanine immobilized on silica gel were investigated with application to the problem of the origin and evolution of the biosphere. It was demonstrated that chlorophyll affects the processes of H2O2 generation in water saturated in air oxygen and H2O2 decomposition in water upon illumination. The efficiency of these photocatalytic processes was shown to depend on pH of the medium and the amount of the pigment coating the substrate surface. The formation of organic products was detected at the irradiation of the suspensions of chlorophyll (phthalocyanine)/silica gel/water containing H2O2 and an inorganic carbon source.

Bacteria in Ostreococcus tauri cultures - friends, foes or hitchhikers?

Marine phytoplankton produce half of the oxygen we breathe and their astounding diversity is just starting to be unraveled. Many microbial phytoplankton are thought to be phototrophic, depending solely on inorganic sources of carbon and minerals for growth rather than preying on other planktonic cells. However, there is increasing evidence that symbiotic associations, to a large extent with bacteria, are required for vitamin or nutrient uptake for many eukaryotic microalgae. Here, we use in silico approaches to look for putative symbiotic interactions by analysing the gene content of microbial communities associated with 13 different Ostreococcus tauri (Chlorophyta, Mamilleophyceae) cultures sampled from the Mediterranean Sea. While we find evidence for bacteria in all cultures, there is no ubiquitous bacterial group, and the most prevalent group, Flavobacteria, is present in 10 out of 13 cultures. Among seven of the microbiomes, we detected genes predicted to encode type 3 secretion systems (T3SS, in 6/7 microbiomes) and/or putative type 6 secretion systems (T6SS, in 4/7 microbiomes). Phylogenetic analyses show that the corresponding genes are closely related to genes of systems identified in bacterial-plant interactions, suggesting that these T3SS might be involved in cell-to-cell interactions with O. tauri.

무기탄소원으로서의 NaHCO3가 미세조류 Scenedesmus dimorphus의 성장에 미치는 영향 평가

Abstract : This study investigates the effect of sodium bicarbonate (NaHCO 3 ) on growth of S.dimorphus. NaHCO 3 concentra-tion was varied from 0 to 2 g-C/L. As a result, the increase in concentration of NaHCO 3 up to 1.5 g-C/L increased dry weight of al-gae. The highest specific growth rate of S. dimorphus was 0.36 day -1 which was obtained at concentration of 0.5 g-C/L NaHCO 3 . pH showed a large variation range at the concentrations lower than 0.5 g-C/L NaHCO 3 whereas inorganic carbon, nitrate and phosphorus removal rates were almost same at the concentrations higher than 0.5 g-C/L NaHCO 3 (0.75, 1, 1.25, 1.5, 2 g-C/L NaHCO 3 ). Their average inorganic carbon, nitrate and phosphorus removal rate were 70 mg-C/L/d, 11.3 mg-N/L/d, and 1.6 mg-P/L/d, respectively. Thus, NaHCO 3 didn’t effect on inorganic carbon, nitrate and phosphorus removal rate of S. dimorphus. Key words : Microalgae, Scenedesmus dimorphus, Sodium bicarbonate, Inorganic carbon source, Specific growth rate주제어 : 미세조류, 세네데스무스 디모르푸스, 탄산수소나트륨, 무기탄소원, 비성장속도

Isolation and characterization of a furfural-degrading bacterium Bacillus cereus sp. strain DS1.

Furfural was found to be the main organic pollutant in the wastewater coming from the Diosgenin factory. This substance is derived from acidic pentosan in Dioscorea zingiberensis and is also found in a variety of agricultural byproducts, including corncobs, oat, wheat bran, and sawdust. It is regarded as a toxicant and an inhibitor to the growth of microorganism in both sewage disposal and biological fermentation. A furfural-degrading strain (DS1) was isolated from activated sludge of wastewater treatment plant in a diosgenin factory by continuous enrichment culture. The strain was identified as Bacillus cereus based on morphological, physiological tests, as well as on 16S rDNA sequence and Biolog analyses. The capacity of this strain to grow on a mineral salt medium, utilizing furfural as the sole carbon and energy source to degrade furfural, was investigated in this study. Under the condition of pH 9.0, temperature 35 °C, with rotating speed of 150 rpm, and an inoculum of 6 %, the strain showed that the furfural degradation capacity reaches 35 % in 7 days, as measured by high-performance liquid chromatography. The addition of inorganic carbon sources could bring down the biodegradation efficiency of the furfural. The strain DS1 showed better furfural removal capacity, as compared to other inorganic carbon sources in the media. Furthermore, a furfural concentration of as high as 4,000 mg L(-1) was tolerated by the culture. The capacity to degrade furfural was demonstrated for the first time by using the genus B. cereus. This study suggests the possible application in biodegradation strategies.

Integration of Carbon Assimilation Modes with Photosynthetic Light Capture in the Green Alga Chlamydomonas reinhardtii

The unicellular green alga Chlamydomonas reinhardtii is capable of using organic and inorganic carbon sources simultaneously, which requires the adjustment of photosynthetic activity to the prevailing mode of carbon assimilation. We obtained novel insights into the regulation of light-harvesting at photosystem II (PSII) following altered carbon source availability. In C. reinhardtii, synthesis of PSII-associated light-harvesting proteins (LHCBMs) is controlled by the cytosolic RNA-binding protein NAB1, which represses translation of particular LHCBM isoform transcripts. This mechanism is fine-tuned via regulation of the nuclear NAB1 promoter, which is activated when linear photosynthetic electron flow is restricted by CO(2)-limitation in a photoheterotrophic context. In the wild-type, accumulation of NAB1 reduces the functional PSII antenna size, thus preventing a harmful overexcited state of PSII, as observed in a NAB1-less mutant. We further demonstrate that translation control as a newly identified long-term response to prolonged CO(2)-limitation replaces LHCII state transitions as a fast response to PSII over-excitation. Intriguingly, activation of the long-term response is perturbed in state transition mutant stt7, suggesting a regulatory link between the long- and short-term response. We depict a regulatory circuit operating on distinct timescales and in different cellular compartments to fine-tune light-harvesting in photoheterotrophic eukaryotes.

Study of a photosynthetic MFC for energy recovery from synthetic industrial fruit juice wastewater

In this system, a photosynthetic biocathode has been coupled to a MFC. This biocathode consists of a pure culture of Chlorella vulgaris which provides the oxygen (electron acceptor). Some experiments were conducted in order to determine the best flow-mode for feeding the anode chamber. It was found that working under continuous-flow mode (with biofilm and in-suspension microorganisms) the system reaches quicker and steadier output power in comparison with sequencing-batch-flow mode. The maximum power density (at 17:00 h, when steady state is reached) is higher in continuous mode, 23.97 vs 22.85 mW/m2 in sequencing-batch mode. Also, a substrate-load characterization was performed. It was determined that COD concentration up to 1066 mgCOD/L can be successfully treated in the system. However, when COD concentration of synthetic wastewater was increased from 343 to 1066 mgCOD/L, the cell voltage decreased from 15 to 10 mV. In addition, two different inorganic carbon (IC) sources for feeding the biocathode were studied.

Carbon partitioning in lipids synthesized by Chlamydomonas reinhardtii when cultured under three unique inorganic carbon regimes

Inorganic carbon is a fundamental component for microalgal lipid biosynthesis. Understanding how the concentration and speciation of dissolved inorganic carbon (DIC) influences lipid metabolism in microalgae may help researchers optimize the production of these high value metabolites. Using relatively straight forward methods for quantifying free fatty acids (FFAs), mono- (MAG), di- (DAG), tri-acylglycerides (TAG), and total cellular fatty acids (FAME), lipid profiles over time were established for Chlamydomonas reinhardtii when grown under three unique inorganic carbon regimes. Specifically, cultures sparged with atmospheric air were compared to cultures which were sparged with 5% CO2 (v/v) and cultures supplemented with 50mM NaHCO3 just prior to medium nitrogen depletion. All three conditions exhibited similar lipid profiles prior to nitrogen depletion in the medium, with FFA and MAG being the predominant lipid metabolites. However, these precursors were quickly reallocated into DAG and subsequently TAG after nitrogen depletion. C16 DAG did not accumulate significantly in any of the treatments, whereas the C18 DAG content increased throughout both exponential growth and stationary phase. C16 and C18 TAG began to accumulate after nitrogen depletion, with C16 TAG contributing the most to overall TAG content. C16 fatty acids exhibited a shift towards saturated C16 fatty acids after nitrogen depletion. Results provide insight into inorganic carbon partitioning into lipid compounds and how the organism's lipid metabolism changes due to N-deplete culturing and inorganic carbon source availability. The methodologies and findings presented here may be adapted to other organisms with high industrial relevance.

CO2 acquisition in Chlamydomonas acidophila is influenced mainly by CO2, not phosphorus, availability.

The extremophilic green microalga Chlamydomonas acidophila grows in very acidic waters (pH 2.3-3.4), where CO2 is the sole inorganic carbon source. Previous work has revealed that the species can accumulate inorganic carbon (Ci) and exhibits high affinity CO2 utilization under low-CO2 (air-equilibrium) conditions, similar to organisms with an active CO2 concentrating mechanism (CCM), whereas both processes are down-regulated under high CO2 (4.5% CO2) conditions. Responses of this species to phosphorus (Pi)-limited conditions suggested a contrasting regulation of the CCM characteristics. Therefore, we measured external carbonic anhydrase (CAext) activities and protein expression (CAH1), the internal pH, Ci accumulation, and CO2-utilization in cells adapted to high or low CO2 under Pi-replete and Pi-limited conditions. Results reveal that C. acidophila expressed CAext activity and expressed a protein cross-reacting with CAH1 (the CAext from Chlamydomonas reinhardtii). Although the function of this CA remains unclear, CAext activity and high affinity CO2 utilization were the highest under low CO2 conditions. C. acidophila accumulated Ci and expressed the CAH1 protein under all conditions tested, and C. reinhardtii also contained substantial amounts of CAH1 protein under Pi-limitation. In conclusion, Ci utilization is optimized in C. acidophila under ecologically relevant conditions, which may enable optimal survival in its extreme Ci- and Pi-limited habitat. The exact physiological and biochemical acclimation remains to be further studied.

Effects of Inorganic Carbon Limitation on the Metabolome of the Synechocystis sp. PCC 6803 Mutant Defective in glnB Encoding the Central Regulator PII of Cyanobacterial C/N Acclimation.

Cyanobacteria are the only prokaryotes performing oxygenic photosynthesis. Non-diazotrophic strains such as the model Synechocystis sp. PCC 6803 depend on a balanced uptake and assimilation of inorganic carbon and nitrogen sources. The internal C/N ratio is sensed via the PII protein (GlnB). We analyzed metabolic changes of the ΔglnB mutant of Synechocystis sp. PCC 6803 under different CO2 availability. The identified metabolites provided a snapshot of the central C/N metabolism. Cells of the ΔglnB mutant shifted to carbon-limiting conditions, i.e. a decreased C/N ratio, showed changes in intermediates of the sugar storage and particularly of the tricarboxylic acid cycle, arginine, and glutamate metabolism. The changes of the metabolome support the notion that the PII protein is primarily regulating the N-metabolism whereas the changes in C-metabolism are probably secondary effects of the PII deletion.

Mechanisms of inorganic carbon acquisition in two estuarine Rhodophyceans: Bostrychia scorpioides (Hudson) ex Kützing Montagne and Catenella caespitosa (Withering) L. M. Irvine.

Marine macroalgae possess a range of mechanisms to increase the availability of CO2 for fixation by ribulose-1,5-bisphosphate carboxylase/oxygenase. Of these, possession of a periplasmic or external carbonic anhydrase and the ability to use bicarbonate ions is widely distributed. The mechanisms of carbon acquisition were studied in two estuarine red macroalgae Bostrychia scorpioides and Catenella caespitosa using a range of techniques. pH-drift and CO2-depletion experiments at constant pH suggested that CO2 is the main source of inorganic carbon in both species. Inhibitors indicated that internal and external carbonic anhydrase were present in both species. Inhibitors also suggested that uptake of bicarbonate is unlikely to be present (P<0.05).

A soil infiltration system incorporated with sulfur-utilizing autotrophic denitrification (SISSAD) for domestic wastewater treatment

To enhance the denitrification performance of soil infiltration, a soil infiltration system incorporated with sulfur-utilizing autotrophic denitrification (SISSAD) for domestic wastewater treatment was developed, and the SISSAD performance was evaluated using synthetic domestic wastewater in this study. The aerobic respiration and nitrification were mainly taken place in the upper aerobic stage (AES), removed 88.44% COD and 89.99% NH4(+)-N. Moreover, autotrophic denitrification occurred in the bottom anaerobic stage (ANS), using the CO2 produced from AES as inorganic carbon source. Results demonstrated that the SISSAD showed a remarkable performance on COD removal efficiency of 95.09%, 84.86% for NO3(-)-N, 95.25% for NH4(+)-N and 93.15% for TP. This research revealed the developed system exhibits a promising application prospect for domestic wastewater in the future.