Inorganic Carbon Source Research Articles

The Process of Soil Carbon Sequestration in Different Ecological Zones of Qingtu Lake in the Arid–Semi-Arid Region of Western China

As a vital component of the global carbon pool, soils in arid and semi-arid regions play a significant role in carbon sequestration. In the context of global warming, increasing temperatures and moisture levels promote the transformation of barren land into wetlands, enhancing carbon sinks. However, the overdevelopment of oases and excessive extraction of groundwater lead to the opposite effect, reducing carbon sequestration. This study examines two soil types—meadow soil (MS) and swamp soil (SS)—from Qingtu Lake, an arid lake in western China. It analyzes the sources of soil inorganic carbon, the composition and origin of dissolved organic matter (DOM), and the relationships between microbes, soil organic carbon (SOC), soil inorganic carbon (SIC), mineral composition, and soil texture. The results indicate that inorganic carbon in the study area consists of both primary carbonate minerals and secondary pedogenic carbonates. The DOM primarily consists of two components, both identified as terrestrial humic substances. In meadow soils, bacterial activity drives the weathering of plagioclase, which releases Ca2+ necessary for the formation of pedogenic carbonates. Plagioclase also provides colonization sites for microbes and, along with microbial activity, participates in the soil carbon cycle. Within the soil community, bacteria appear to play a more critical role than fungi. In contrast, microbial contributions to the carbon cycle in swamp soils are weaker, with minerals predominantly interacting with organic carbon to form mineral-associated organic matter, thus promoting the soil carbon cycle. These findings have important implications for understanding soil carbon sinks under different micro-ecological conditions in arid and semi-arid regions. Through targeted human intervention, it is possible to enhance carbon sequestration in these areas, contributing to the mitigation of global climate change.

Coupling Iron Coagulation and Microalgal–Bacterial Granular Sludge for Efficient Treatment of Municipal Wastewater: A Proof–of–Concept Study

The rapid expansion of global urbanization and industrialization has significantly increased the discharge of municipal wastewater, leading to issues of carbon emissions and energy consumption when using traditional biological treatment processes. This study proposes an innovative process that couples iron coagulation with microalgal–bacterial granular sludge (MBGS), with optimization and regulation based on operational conditions. The study found that the coagulation performance achieved optimal levels at an iron concentration of 25 mg/L and an anionic polyacrylamide concentration of 1 mg/L, which could remove approximately 61% of the organics and over 90% of phosphorus from raw wastewater. By relying on heterotrophic microorganisms, such as Proteobacteria, Bacteroidota, and Chloroflexi, along with the synergistic interaction between algae and bacteria, the subsequent MBGS process could further effectively remove organics over the day-night cycles. Moreover, the addition of inorganic carbon sources of NaHCO3 increased the abundance of denitrification-related genes, reduced the accumulation of nitrite within MBGS, and led to effective total nitrogen removal. These results indicate that the iron coagulation–MBGS coupling process can efficiently treat municipal wastewater, offering potential for environment-sustainable pollutant removal with reduced energy consumption. These findings provide valuable insights for the practical engineering application of MBGS in wastewater treatment systems aiming for carbon-neutral wastewater treatment.

Perspectives on optimizing microalgae cultivation: Harnessing dissolved CO2 and lactose for sustainable and cost-efficient protein production

Microalgae, known for their land-sparing cultivation and remarkable photosynthetic efficiency, play a crucial role in advancing sustainable development goals. This study explored the use of cost-effective inorganic carbon (the ionic form of CO2) and organic carbon sources (lactose, a primary sugar in whey wastewater) to support the growth of Chlorellasorokiniana UTEX 1230, and improved protein content through nitrogen supply optimization. NaHCO3 proved to be more effective than Na2CO3, resulting in a 3.4-fold increase in biomass concentration, with an initial 5 mM HCO3‾ concentration compared to the basal medium. Further addition of 0.75 % lactose led to a 4.05-fold increase in biomass concentration, with the maximum specific growth rate at 1.28/d, maximum biomass concentration at 695.88 mg/L, and maximum biomass productivity at 250.91 mg/L/d. Nitrogen supplementation greatly increased protein concentration from 16.41 % (250 mg/L NaNO3) to 52.95 % (1000 mg/L NaNO3). These results support the potential for utilizing whey wastewater bioremediation to produce high-value protein via microalgal cultivation.

Spatiotemporal variability of dissolved carbon and sources of dissolved inorganic carbon influenced by freeze–thaw and subsurface flow in an alpine headwater catchment of the Qinghai-Tibetan Plateau

The temporal freeze–thaw (FT) and the spatial rock distribution have great impacts on riverine dissolved carbon transport and dissolved inorganic carbon (DIC) sources. However, the effects of the subsurface flow (SSF) process during the FT process and spatial riverine transport on dissolved carbon transport and DIC sources are still unclear due to the lack of available spatiotemporal measurements. Herein, we designed and implemented a complete scheme of water sampling including stream water (from upper headwater to the middle and downward) and SSF (in the soil, saprolite, and weathered bedrock layers) in an alpine headwater catchment. The characteristics of the dissolved organic and inorganic carbon (DOC and DIC), and δ13C-DIC were analyzed, and the spatiotemporal variability of the DIC source was explored. Our findings reveal that the impact of the FT process on the dissolved carbon dynamics and DIC sources is revealed in the dissolved carbon transport process controlled by the SSF process. Specifically, the deepening of the active layer during the FT process enhances the movement of SSF into the deeper layer, thereby activating DIC in this deep layer. Concurrently, DOC from the shallow layer rapidly infiltrates deeper layers, leading to minimal differences in DOC concentrations across layers. This results in an enriched behavior of DOC (b = 0.21) and a depleted behavior of DIC (b = −0.27) during the FT process. In terms of influence on DIC sources, the deepening active layer promotes silicate weathering in the silicate-rich deep layers and strengthens organic carbon mineralization. On a spatial scale, the rock distribution, particularly the Si/Ca ratio, predominantly controls the chemical weathering process and, consequently, determines the DIC sources. In contrast, the influence of organic carbon mineralization on DIC sources becomes less significant. In this study, the impact mode of SSF on dissolved carbon transport and transformation is elucidated, and the spatial influence of rock distribution on riverine DIC sources is emphasized.

Stable isotope labeling and functional gene prediction elucidate the carbon metabolism in fermentative bacteria and microalgae coupling system

The application of the fermentative bacteria and microalgae coupling system in the wastewater treatment has been studied, but there remains few knowledge regarding the organic and inorganic carbon metabolism within this system. In this study, the carbon metabolism of microalgae and fermentative bacteria was elucidated by 13C stable isotope labeling and functional gene prediction, respectively. The 13C glucose and 13C NaHCO3 were used as stable isotope tracers to clarify the organic and inorganic carbon metabolism of microalgae, indicating that approximately 71.5 % of the Acetyl-CoA in microalgae was synthesized from organic carbon sources, while 26.8 % was synthesized through the utilization of inorganic carbon sources. Inorganic carbon sources can enhance the activity of photosynthetic system and facilitate the Calvin cycle. Considering the adequate organic carbon sources and insufficient inorganic carbon sources in the fermentative bacteria and microalgae coupling system, NaHCO3 was added to improve carbon utilization of microalgae. The maximum microalgal lipid yield reached 1130.37 mg/L with 1000 mg/L NaHCO3 supplementation. Functional gene prediction was used to analysis the effect of various carbon composition on the bacterial carbon metabolism. Notably, the additional inorganic carbon sources increased the abundance of bacterial functional genes associated with the fermentation and acetic acids synthesis, which was advantageous for VFAs production and further promoted microalgae growth. This study can gain a deeper understanding of microbial metabolic mechanisms during the operation of fermentative bacteria and microalgae system, and improve its sustained operational stability.

Bioenergy feedstock production in Chlamydomonas reinhardtii (microalgae) cultivated under mixotrophic growth with cellulose hydrolysate from agricultural waste.

In the present study, cellulose purified from finger millet agricultural waste is subjected to enzymatic hydrolysis, and the hydrolysate (predominantly glucose) is used as a carbon source supplement in the media for the mixotrophic growth of Chlamydomonas reinhardtii. Interestingly, a switch between excess starch production and excess lipid (triacylglycerols, TAG) production occurs by a small change in hydrolysate concentration in the media. Starch production increased 4.5-fold with respect to the photoautotrophic control, with a glucose concentration of 3mg/mL in the media after hydrolysate addition. This culture had TAG production enhancement by 1.5-fold. However, mixotrophic cultivation with 4mg/mL glucose concentration in the media with hydrolysate addition resulted in TAG productivity enhancement by 4.2-fold compared to control and starch amount increase of 1.3-fold. The organic carbon source (glucose) and the inorganic carbon source (citrate ions) in the hydrolysate together played a role in this delicate switching between starch and lipid pathways. Proteins, starch, and TAG molecules are analyzed in the microalgal cells grown under different conditions with FTIR spectroscopy, a rapid, high-throughput method of biomolecular estimation. High-resolution single-cell AFM studies of the cell wall structure reveal enhanced corrugations in surface morphology during mixotrophic growth with cellulose hydrolysate, illustrating an adaptive mechanism with improved mechanical stress management. Lipid droplet morphology at the single-cell level points to two distinct mechanisms of lipid accumulation: one in which the lipids are segregated as droplets, and the other in which lipid molecules are uniformly dispersed in the cytosol as unresolved, ultra-small droplets. The present study therefore analyzes both the bulk and the single-cell level changes when cellulose hydrolysate is used as a carbon source for Chlamydomonas reinhardtii mixotrophic cultivation, which serves a four-fold purpose: value from waste, fixation of atmospheric CO2, production of lipids for biodiesel, and starch for bioethanol.

Substantial contribution of inorganic carbon sources to CO2 emissions in calcareous vineyard soils in Germany

AbstractIn light of climate change and increasing global temperatures, it is important to equally prioritize the study of inorganic carbon dynamics in calcareous soils within temperate ecosystems, as has been done for arid or semiarid environments. A significant area of vineyards in Germany is established on calcareous soils. However, the potential influence of inorganic carbon on CO2 emissions in these vineyards has not been sufficiently explored when evaluating the carbon footprint of management practices in relation to carbon storage. Therefore, we aimed to differentiate between organic and inorganic sources of CO2 emissions from six vineyard soils located in the southwest of Germany that had previously received organic soil amendments (OA). Inorganic carbon content varied between 8 and 55 g kg−1 across different sites, with variations observed in the inorganic‐to‐organic carbon ratio. Soil samples were incubated under standard laboratory conditions for 48 h, and the source of emitted CO2 was determined using a two‐end‐member mixing model. The contribution of inorganic carbon to CO2 emissions was influenced by the quantity of inorganic carbon, with an increase in contribution with increasing inorganic‐to‐organic carbon ratio. On average, abiotic sources accounted for 5% to 40% of the emitted CO2 at the different sites, with one site showing no significant contribution of inorganic carbon. CO2 production from inorganic carbon was higher in the subsoil compared with the topsoil, likely related to the higher content of inorganic carbon in the subsoil. Notably, there was no discernible influence of OA on carbonate dissolution. This study emphasizes the significance of considering abiotic sources of CO2 emissions in addition to soil respiration in calcareous soils and highlights the need for further investigation to apply these findings at the field scale.

Nickel-rich ternary cathode material as a novel capping layer to improve lithium iron phosphate electrochemical performance

We use a facile high-temperature solid-phase method to coat a layer of Ni-rich ternary material (LiNi0.8Co0.1Mn0.1O2) on the surface of lithium iron phosphate. This active coating greatly improves the intrinsic conductivity of LiFePO4. Compared to the conventional carbon material cladding, since this cladding layer is electrochemically active, the problem of decreasing the proportion of active material due to the addition of a cladding layer can be avoided to a certain extent. Compared with the samples capped with conventional organic carbon source (151.2 mAh g−1) and inorganic carbon source (155.9 mAh g−1) at 0.2 C, the discharge specific capacity was as high as 165.7 mAh g−1. Capacity retention after 200 cycles is up to 98 %, which is much higher than that of glucose and graphene oxide (GO)-coated samples (95.9 %, 96.6 %). Even when charging and discharging cycles are performed at different multipliers (2C and 10C), the retention rate remains higher than the latter.

Unveiling the ecological resilience and industrial potential of Skeletonema marinoi through mixotrophic cultivation in Nordic winter condition.

Mixotrophy, the concurrent use of inorganic and organic carbon in the presence of light for microalgal growth, holds ecological and industrial significance. However, it is poorly explored in diatoms, especially in ecologically relevant species like Skeletonema marinoi. This study strategically employed mixotrophic metabolism to optimize the growth of a strain of Skeletonema marinoi (Sm142), which was found potentially important for biomass production on the west coast of Sweden in winter conditions. The aim of this study was to discern the most effective organic carbon sources by closely monitoring microalgal growth through the assessment of optical density, chlorophyll a fluorescence, and biomass concentration. The impact of various carbon sources on the physiology of Sm142 was investigated using photosynthetic and respiratory parameters. The findings revealed that glycerol exhibited the highest potential for enhancing the biomass concentration of Sm142 in a multi-cultivator under the specified experimental conditions, thanks to the increase in respiration activity. Furthermore, the stimulatory effect of glycerol was confirmed at a larger scale using environmental photobioreactors simulating the winter conditions on the west coast of Sweden; it was found comparable to the stimulation by CO2-enriched air versus normal air. These results were the first evidence of the ability of Skeletonema marinoi to perform mixotrophic metabolism during the winter and could explain the ecological success of this diatom on the Swedish west coast. These findings also highlight the importance of both organic and inorganic carbon sources for enhancing biomass productivity in harsh winter conditions.

Glacier‐Fed Lakes Are Significant Sinks of Carbon Dioxide in the Southeastern Tibetan Plateau

AbstractDissolved inorganic carbon (DIC) sources, transportation, and transition in inland water bodies have been intensively studied due to their important role in the global carbon cycle. While glacier‐fed lakes play a crucial role in global carbon cycling, related studies are limited. In this study, we investigated the spatiotemporal variability of DIC in the maritime glacier‐fed lakes of the southeastern Tibetan Plateau, identifying the carbon sources and potential controlling factors of DIC pathways The results revealed significant temporal variations in DIC and δ13C‐DIC, with averages of 7.29 ± 0.45 mg C L−1 and –8.6 ± 0.2‰ in summer, and 3.40 ± 0.54 mg C L−1 and –7.4 ± 0.6‰ in winter, respectively. Temporal variations in DIC and δ13C‐DIC were mainly controlled by carbonates weathering and silicate weathering processes. The chemical weathering reactions facilitate the consumption of dissolved CO2. Undersaturated pCO2 (120.02 ± 29.18 μatm) relative to atmospheric equilibrium suggests considerable capacity for CO2 uptake within glacier‐fed lakes system. We estimated that the maritime glacier‐fed lakes in the southeastern Tibetan Plateau absorb a total of 9.6 ± 2.7 × 10−3 Tg C‐CO2 yr−1, highlighting their significant contribution to the global carbon budget. The distinctive landscape of the glacier‐fed system and the vulnerable weathering environment result in seasonal and spatial variations of DIC concentration and δ13C‐DIC values, as well as the chemical weathering‐induced CO2 sink in glacier regions. Given the accelerated glacier retreat observed in this area, further studies on the temporal variability of DIC in the water column are urgently needed to identify the mechanisms driving the biogeochemical reactions inside glacier‐fed lake. Our study highlights the unrecognized role of maritime glacier‐fed lakes as CO2 sinks and emphasizes their significance in regional carbon budgets.

From 3G biofuels to high value-added bioproducts

The paper focused on the co-production of high-value-added product thermostable C-phycocyanin (C-PC) and biomass, further utilized in pyrolysis. The photobiosynthesis of CPC was carried out by the thermophilic cyanobacteria Synechococcus PCC6715 cultivated in the helical and flat panel photobioreactors (PBR). Despite the application of different inorganic carbon sources, both PBRs were characterized by the same growth efficiency and similar C-PC concentration in biomass. To release the intracellular C-PC the biomass was concentrated and disintegrated by the freeze-thaw method. The crude C-PC was then further purified by foam fractionation (FF), aqueous two-phase extraction (ATPE), membrane techniques (UF) and fast protein liquid chromatography (FPLC). Each of the tested methods can be used separately; however, from a practical and economic point of view, a three-stage purification system (FF, FPLC and UF) was proposed. The purity ratio of the final C-PC was about 3.9, which allows it to be classified as a reactive grade. To improve the profitability of 3G biorefinery, the solid biomass residue was used as a substrate to pyrolysis process, which leads to production of additional chemicals in the form of oils, gas (containing e.g. H 2) and biochar.

Microalgae biofuels: illuminating the path to a sustainable future amidst challenges and opportunities.

The development of microalgal biofuels is of significant importance in advancing the energy transition, alleviating food pressure, preserving the natural environment, and addressing climate change. Numerous countries and regions across the globe have conducted extensive research and strategic planning on microalgal bioenergy, investing significant funds and manpower into this field. However, the microalgae biofuel industry has faced a downturn due to the constraints of high costs. In the past decade, with the development of new strains, technologies, and equipment, the feasibility of large-scale production of microalgae biofuel should be re-evaluated. Here, we have gathered research results from the past decade regarding microalgae biofuel production, providing insights into the opportunities and challenges faced by this industry from the perspectives of microalgae selection, modification, and cultivation. In this review, we suggest that highly adaptable microalgae are the preferred choice for large-scale biofuel production, especially strains that can utilize high concentrations of inorganic carbon sources and possess stress resistance. The use of omics technologies and genetic editing has greatly enhanced lipid accumulation in microalgae. However, the associated risks have constrained the feasibility of large-scale outdoor cultivation. Therefore, the relatively controllable cultivation method of photobioreactors (PBRs) has made it the mainstream approach for microalgae biofuel production. Moreover, adjusting the performance and parameters of PBRs can also enhance lipid accumulation in microalgae. In the future, given the relentless escalation in demand for sustainable energy sources, microalgae biofuels should be deemed a pivotal constituent of national energy planning, particularly in the case of China. The advancement of synthetic biology helps reduce the risks associated with genetically modified (GM) microalgae and enhances the economic viability of their biofuel production.

Selective Electrosynthesis of Urea via C−N Coupling: Current Status, Challenges and Future Prospects

AbstractSelective electrosynthesis of urea from carbon source (CO2) and nitrogen (N2, NO3−, NO2−) source provides a sustainable strategy for production of essential nitrogen‐based fertilizers. The traditional technology of urea synthesis employs two consecutive processes, synthesis of NH3 from N2+H2 and urea from NH3+CO2, which always involves high energy consumption and environmental concerns. By contrast, urea electrosynthesis avoids the above harsh steps and meanwhile has higher atomic economy. Herein, we present a comprehensive review on the progress and prospect of urea electrosynthesis from abundant carbon and nitrogen sources via coupling of C−N under ambient conditions, and also discuss the mechanism researches, strategies of substrates activation, current challenges and future opportunities of urea electrosynthesis. The urea electrosynthesis via C−N coupling realizes abundant and low‐cost inorganic carbon and nitrogen sources for efficient resource utilization and provides guidance and reference for C−C, C−S or other coupling reactions.

Inorganic carbon sensing and signalling in cyanobacteria

AbstractCyanobacteria utilize CO2 and HCO3− as inorganic carbon (Ci) sources. In low Ci, like in ambient air, cyanobacteria efficiently collect Ci using a carbon concentrating mechanism (CCM). The CCM includes bicarbonate transporters SbtA, BicA and BCT1; the specialized NDH complexes NDH‐13 and NDH‐14, which convert CO2 to HCO3− in the cytoplasm; and carboxysomes that are protein shell encapsulated ribulose‐1,5‐bisphosphate carboxylase/oxygenase (RuBisCo) and carbonic anhydrase containing bodies in which the first reaction of carbon fixation occurs. Ci‐dependent regulation of bicarbonate transporters and specialized NDH complexes, especially the regulation of the SbtA transporter, are well understood. CcmR (also called NdhR), CyAbrB2, CmpR and RbcR act as transcription factors regulating CCM genes. Ci signalling molecules detecting the metabolic status of the cells include 2‐oxoglutarate, which accumulates when the Ci/nitrogen ratio of the cell is high, and 2‐phosphoglycolate, the first intermediate of the photorespiration pathway, whose accumulation indicates low Ci. These signalling molecules act as corepressors and coactivators of the CcmR repressor protein, whereas 2‐phosphoglycolate and ribulose‐1,5‐bisphosphate activate transcription activator CmpR. In addition, bicarbonate or CO2 activates the adenylyl cyclase that produces cAMP, and ATP/ADP/AMP provide information about the energy status of the cell. Less is known about the molecular mechanisms regulating carboxysome dynamics or how production, activity and degradation of photosynthetic complexes are regulated by prevailing Ci conditions or which mechanisms adjust cell division according to Ci. This minireview summarizes the present knowledge about molecular mechanisms regulating cyanobacterial acclimation to prevailing Ci.

Opportunities and challenges for n-alkane and n-alkene biosynthesis: A sustainable microbial biorefinery

Alkanes and alkenes are high-value platform chemicals that can be synthesized by microorganisms, utilizing organic residues from agri-food industries and municipalities, thereby offering an alternative opportunity in resource recovery. Current research and technological advancements for the biosynthesis of alkanes and alkenes are mainly impeded by low product titers, obstructing the bioprocess upscaling and large-scale applications. Thus, current scientific investigations aim to improve productivity by utilizing natural and engineered metabolic pathways in various microbial chassis to suppress competing metabolic pathways, coupled with bioprocess optimization. Additionally, to reduce costs, research is being conducted on utilizing inorganic carbon sources such as CO2 to promote the green synthesis of alkanes and alkenes. Therefore, this review critically discusses the opportunities and challenges in alkane and alkene biosynthesis, aiming to examine the current technological advancements. In this review, the limitations of five major metabolic pathways for alkane and alkene biosynthesis are thoroughly discussed, highlighting their shortcomings. Additionally, various techniques, including metabolic engineering, autotrophic metabolic pathways, and new non-biosynthetic routes, are investigated as potential methods to enhance product titers. Furthermore, this review offers valuable insights into the economic and environmental aspects of alkane and alkene biosynthesis while also presenting perspectives for future research directions.

Optimization of Photoautotrophic Growth Regimens of Scenedesmaceae alga: The Influence of Light Conditions and Carbon Dioxide Concentrations

Improving methods for landless production of bioproducts is considered an important stage in the development of the modern bioeconomy. In this context, microalgal biomass is one of the most promising sources of valuable substances due to its rich biochemical composition. Despite the high adaptability of microalgae to various environmental factors, the effectiveness of cultivation systems depends on precisely selected parameters. Both the light conditions and the supply of inorganic carbon sources are key in determining the efficiency of photoautotrophic cultivation. In this work, the effect of a high daily photosynthetic photon flux density (PPFD) ranging from 37.44 to 112.32 mol m−2 day−1 on the growth and productivity of a novel Scenedesmaceae alga, strain EZ-B1, was assessed. The next stage of cultivation consisted of selecting the optimal CO2 concentration. Improved performance of microalga during cultivation in a photobioreactor was achieved at 112.32 mol m−2 day−1 (24 h photoperiod) and by supplying 2% CO2, as evidenced by the high biomass productivity (0.69 g L−1 day−1), total biomass yield (5.23 g L−1), and ammonium nitrogen consumption rate. The data obtained suggest that a higher level of PPFD led to the highest growth rate of the novel strain and the highest biomass productivity, which, in practice, will increase production capacity.

Sodium percarbonate effectively enhances medium-chain fatty acids production from waste activated sludge via facilitating electron acceptor formation, providing inorganic carbon and enriching functional microorganisms

Medium-chain fatty acids (MCFA) production from waste activated sludge (WAS) has been a promising approach for resource and energy recovery. However, the poor sludge biodegradability and existence of competitive microorganisms result in inefficient electron donor utilization and low MCFA output. Therefore, a percarbonate (SPC)-based strategy is proposed to effectively enhance MCFA production. SPC pretreatment largely boosts substrate accessibility and organics transformation through the dual function of chemical oxidation and alkaline hydrolysis in the acidogenic fermentation stage, providing abundant electron acceptors directly available for functional microorganisms in the chain elongation (CE) stage. Consequently, MCFA production is significantly enhanced from 3522 mg COD/L of the control to 10,437 mg COD/L of 0.15 g SPC/g TSS, while decreased to 1898 mg COD/L at 0.25 g SPC/g TSS. Meanwhile, long-chain alcohols (LCA) production is apparently reduced by 68.3%, implying a decrease in the flow of electrons to byproducts. Importantly, SPC pretreatment with an appropriate level can provide inorganic carbon source for CE microbes to further increase the MCFA yield. Mechanistic studies suggest that SPC pretreatment with appropriate levels improves microbial metabolisms contributing to MCFA production and functional gene expression involved in CE pathways. Additionally, SPC enriches functional microorganisms from 19.25% to 59.75%, such as MCFA (i.e., Proteiniclasticum sp.) and butyrate (i.e., Romboutsia sp. and Alkaliphilus sp.) producers.

Single-species dinoflagellate cyst carbon isotope fractionation in core-top sediments: environmental controls, CO2 dependency and proxy potential

Abstract. Sedimentary bulk organic matter and various molecular organic components exhibit strong CO2-dependent carbon isotope fractionation relative to dissolved inorganic carbon sources. This fractionation (εp) has been employed as a proxy for paleo-pCO2. Yet, culture experiments indicate that CO2-dependent εp is highly specific at genus and even species level, potentially hampering the use of bulk organic matter and non-species-specific organic compounds. In recent years, significant progress has been made towards a CO2 proxy using controlled growth experiments with dinoflagellate species, also showing highly species-specific εp values. These values were, however, based on motile specimens, and it remains unknown whether these relations also hold for the organic-walled resting cysts (dinocysts) produced by these dinoflagellate species in their natural environment. We here analyze dinocysts isolated from core tops from the Atlantic Ocean and Mediterranean Sea, representing several species (Spiniferites elongatus, S. (cf.) ramosus, S. mirabilis, Operculodinium centrocarpum sensu Wall and Dale (1966) (hereafter referred to as O. centrocarpum) and Impagidinium aculeatum) using laser ablation–nano-combustion–gas-chromatography–isotope ratio mass spectrometry (LA/nC/GC-IRMS). We find that the dinocysts produced in the natural environment are all appreciably more 13C-depleted compared to the cultured motile dinoflagellate cells, implying higher overall εp values, and, moreover, exhibit large isotope variability. Where several species could be analyzed from a single location, we often record significant differences in isotopic variance and offsets in mean δ13C values between species, highlighting the importance of single-species carbon isotope analyses. The most geographically expanded dataset, based on O. centrocarpum, shows that εp correlates significantly with various environmental parameters. Importantly, O. centrocarpum shows a CO2-dependent εp above ∼ 240 µatm pCO2. Similar to other marine autotrophs, relative insensitivity at low pCO2 is in line with active carbon-concentrating mechanisms at low pCO2, although we here cannot fully exclude that we partly underestimated εp sensitivity at low pCO2 values due to the relatively sparse sampling in that range. Finally, we use the relation between εp and pCO2 in O. centrocarpum to propose a first pCO2 proxy based on a single dinocyst species.

Biodegradation of chromium by laccase action of Ganoderma multipileum

Laccase is a fungal enzyme that play a crucial role in bioremediation. The purified laccase from Ganoderma multipileum and its effectiveness in bioremediation of Cr (VI) was determined in this study. Two strains of G. multipileum were identified by ITS sequences and their phylogeny was compared with G. multipileum taken from GenBank (KF494997, LC149613, MG739453, MG739455). The fungi were grown on guaiacol substrate for laccase optimization using different environmental and nutritional conditions. Laccase Glacc113 (75 kDa) was partially purified and characterized under different parameters. Glacc113 (GIAPTAD) was confirmed by using a Precise Protein Sequencing System to analyze sequence of N-terminal amino acid. Laccase exhibited maximum optimal activity (1355.5 ± 8.8 U/L) at pH 3.0 and can tolerate the maximum temperature upto 70 °C. During submerged fermentation, on 7th day after inoculum of 3 fungal discs at 100 rpm yielded maximum laccase. The production of laccase increased by optimization of inorganic and organic nitrogen and carbon sources. The purified laccase from G. multipileum was used to reduce (>94%) 100 μg/mL of Cr (VI) into less toxic chromium Cr (III). The catalytic kinetic parameters Vmax and Km for guaiacol were 1.817 (mM min−1) and 1.4617 (mM), respectively. This study determined the conditions that enhance production and an ecofriendly approach to bio remediate the Cr (VI) to Cr (III). The purified enzyme exerted maximum durability and reliability for industrial usage also.

Physical and Biological Controls on the Annual CO2 Cycle in Agua Hedionda Lagoon, Carlsbad, CA

Agua Hedionda Lagoon (AHL), a tidal estuary located on the southern California coast, supports a diverse ecosystem while serving numerous recreation activities, a marine fish hatchery, a shellfish hatchery, and the largest desalination plant in the western hemisphere. In this work, a 1-year time series of carbon dioxide data is used to establish baseline average dissolved inorganic carbon conditions in AHL. Based on a mass balance model of the outer basin of the lagoon, we propose that AHL is a source of inorganic carbon to the adjacent ocean, through advective export, at a rate of 5.9 × 106 mol C year−1, and a source of CO2 to the atmosphere of 0.21 × 106 mol C year−1 (1 mol C m−2 year−1), implying a net heterotrophic system on the order of 6.0 × 106 mol C year−1 (30 mol C m−2 year−1). Although variable with a range throughout the year of 80% about the mean, the ecosystem remained persistently heterotrophic, reaching peak rates during the summer season. Using results from the mass balance, the annual cycle of selected properties of the aqueous CO2 system (pH, pCO2, and CaCO3 saturation state) were mathematically decomposed in order to examine the relative contribution of drivers including advection, ecosystem metabolism, and temperature that act to balance their observed annual cycle. Important findings of this study include the identification of advection as a prime driver of biogeochemical variability and the establishment of a data-based estimate of mean flushing time for AHL.