Additional Carbon Source Research Articles

Improvement of Plasmid Volumetric Yield by Addition of Glycerol and Phosphate Buffer in Escherichia coli TOP10 Batch Culture

The investigation of mRNA development has gained substantial interest, particularly in the ex vivo and in vivo therapy. mRNA is widely used for the development of gene editing-based therapies and mRNA vaccines. The aim of this study was to optimize the medium and harvest time to increase plasmid DNA production as part of mRNA production. This study modified used a medium modification approach to achieve high density culture of Escherichia coli TOP10 pGEMT-N in batch cultivation method. Various media formulations were assessed, including LB; LB with phosphate buffer (K2HPO4 12.549 g/L and KH2PO4 2.31 g/L); LB with glycerol (50 g/L); LB with glycerol and phosphate buffer; LB with phosphate buffer, glycerol, glucose (15 g/L), and galactose (15 g/L). The effect of additional carbon sources and phosphate buffer on culture density was measured through OD600 and wet cell weight analysis. The highest OD600 and wet cell weight was observed when LB with glycerol and phosphate buffer was used, with OD600 of 4.78±0.14 and wet cell weight of 36.00±0.63 mg/ml. Plasmid DNA was subsequently isolated from these cultures following 5- and 7.5-hour incubation periods. The utilization of LB medium with glycerol and phosphate buffer resulted in a substantial increase in the volumetric concentration of plasmid DNA of 1,516.97±385.00 ng/ml after 5 hours of incubation. In conclusion, a remarkable enhancement in plasmid DNA volumetric yield within 5 hours was achieved by addition of glycerol and phosphate buffer to LB medium, leading to incubation period.

Enrichment of anaerobic and facultative anaerobic bacteria from a graphite mine sample on graphene oxide

Graphene oxide (GO) is progressively synthesized and applied in various industrial fields, such as healthcare, medicine, gas transport, electric power industry, etc. Thus, its distribution in the environment increases, which leads to changes in various microbial communities. Mechanisms of interaction between bacterial communities and novel carbon-based nanomaterials, such as GO, are still to be elucidated. We developed stable consortia in order to identify bacteria with the ability to thrive in the presence of GO. Here, we show the results of metagenomic analyses of the graphite mine sample, a consortium with GO as a sole source of carbon and a consortium with fumarate as an additional carbon source. The aim of this study was to establish anaerobic enrichment cultures from a graphite mine sample and GO, and to identify their diversity/community composition.

Synthesis and characterization of hierarchical suspended carbon fiber structures decorated with carbon nanotubes

Carbon nanotubes (CNTs) and carbon microfibers (CMFs) have received significant attention due to their exceptional mechanical and electrical properties, which make them promising materials for various applications. This study introduces a novel approach to integrate CNTs and CMFs into a unified architecture by simultaneously conducting pyrolysis and chemical vapor deposition (CVD). The localized CVD of CNTs on suspended CMFs was achieved by utilizing Fe–Co nanoparticles (NPs) embedded in polyacrylonitrile (PAN) fibers as catalysts. Scanning electron microscopy and elemental analysis confirmed the formation of needle-like carbon structures on the pyrolyzed fiber surface, where carbon gases released from the pyrolyzing PAN fiber acted as the carbon source for the localized CVD. The incorporation of an additional carbon source, such as camphor vapor, significantly enhanced the growth and density of CNTs on the CMF. Various characterization techniques, including transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and Atomic Force Microscopy, were employed to analyse the properties of the synthesized materials. The substantial increase in electrical conductivity upon incorporating CNTs highlights their positive influence on electrical properties and defect reduction. These characterization results highlight the potential applications of the fabricated structures in various fields, including sensors, lithium-ion electrodes, and microfabrication. In addition, the economic advantages of optimizing the process by integrating CVD with pyrolysis were assessed, revealing decreased operation time, lower energy consumption, and reduced chemical costs in comparison to conventional methods involving multiple intermediate processing steps.Graphical

Performance optimization for Pb(II) -containing wastewater treatment in constructed wetland-microbial fuel cell triggered by biomass dosage and Pb(II) level.

Three identical sets of constructed wetland-microbial fuel cells (CW-MFCs) fabricated with biomass carbon source addition were constructed and underwent the short- and long-term experiments. For this, the efficacy of biomass dosage and Pb(II) concentration towards Pb(II) removal and concurrent bioelectricity production of CW-MFCs were systematically explored. From the perspective of integrated capabilities and economic benefits, the solid biomass carbon sources equivalent to 500mg/L COD was regarded as the optimal dosage, and the corresponding device was labeled as CW-MFC-2. For the short-term experiment, the closed-circuit CW-MFC-2 produced maximum output voltages and power densities in a range of 386-657mV and 1.55 × 103-6.31 × 103 mW/m2 with the increasing Pb(II) level, respectively. Also, Pb(II) removal up to 94.4-99.6% was obtained in CW-MFC-2. With respect to long-term experiment, Pb(II) removal, the maximum output voltage, and power density of CW-MFC-2 ranged from 98.7 to 99.2%, 322 to 387mV, and 3.28 × 102 to 2.26 × 103 mW/m2 upon 200mg/L Pb(II) level, respectively. The migration results confirmed the potential of substrate and biomass for Pb(II) adsorption and fixation. For the cathode, Pb(II) was fixed and removed via binding to O. This study enlarges our knowledge of effective modulation of CW-MFCs for the treatment of high-level Pb(II)-containing wastewater and bioelectricity generation via adopting desirable biomass dosage.

Effects of carbon source addition in rearing water on sediment characteristics, growth and health of cultured marron (Cherax cainii)

Carbon sources are considered as critical input for the health and immunity of aquatic animals. The present study investigated the impact of different carbon sources on water quality parameters, carbon to nitrogen (C/N) ratio and microbial community in sediments, and health responses of marron (Cherax cainii) under laboratory conditions. Following one week of acclimation, 120 marron were randomly assigned to 12 experimental tanks. There were four treatments including one untreated control and three groups with carbon addition to maintain a C/N ratio of 12 maintained in culture water. Carbon supplementation groups included corn flour (CBC12), molasses (MBC12) and wheat flour (WBC12). At the end of the 60-day trial, MBC12 resulted in the highest sediment C/N ratio, followed by CBC12. Weight gain and specific growth rate were higher in MBC12, compared to control. The protease activity in marron hepatopancreas, total haemocyte count and lysozyme activity in haemolymph were highest in MBC12. Analysis of 16S rRNA sequence data of tank sediments revealed increased bacterial alpha diversity in MBC12 and WBC12. Proteobacteria was the most abundant phylum in MBC12 (88.6%), followed by control (82.4%) and CBC12 (72.8%). Sphingobium and Novosphingobium were the most abundant genera in control and MBC12 groups, respectively. Higher Aeromonas abundance in CBC12 and Flavobacterium in WBC12 were observed. Overall results indicated that MBC12 led to improved water quality, retaining high C/N ratio and enriched the bacterial populations in sediments resulting in improved growth and immune performance of marron.

Modulating poly(lactic acid) degradation rate for environmentally sustainable applications

The huge amount of plastics generated by the massive use of packaging makes it difficult to manage waste safely. Introducing biodegradable polymers, such as poly(lactic acid) (PLA), can at least partially reduce the environmental pollution from plastic waste. Biodegradable polymers must have a degradation rate appropriate for the intended use to replace durable plastics. This work aims to introduce PLA fillers that can modulate the degradation rate during hydrolysis and composting. For this purpose, fumaric acid and magnesium hydroxide have been proposed. The experimental findings demonstrated that magnesium oxide makes hydrolysis faster than fumaric acid. A model describing the hydrolysis reaction, which also considers the effect of crystallinity, is proposed. The model can capture the filler effect on the kinetic constants related to the autocatalytic part of the hydrolysis reaction.Degradation of the PLA and compounds was also conducted in a composting medium. The compound with fumaric acid shows faster degradation than the compound with magnesium oxide; this behavior is opposite to what is observed during hydrolysis. Degradation in a composting medium is favored in a narrow pH window corresponding to the optimum environment for microorganism growth. Magnesium oxide leads to a pH increase above the optimum level, making the environment less favorable to microorganism growth. Vice-versa, fumaric acid maintains the pH level in the optimum range: it represents an additional carbon source for microorganism growth.

Synergistic effect of LDHs/loofah composites for in-situ remediation of nitrate in contaminated groundwater

Permeable reaction barrier (PRB) is an innovative technology for in-situ remediation of nitrate-contaminated groundwater. In this study, layered double hydroxides (LDHs)/loofah composites were prepared and used as active fillers for PRB to facilitate nitrate removal from groundwater. Under the conditions of initial nitrate concentration of 5 mg/L, a hydraulic retention time (HRT) of 4 h, and without additional carbon source, the nitrate removal rates of the natural loofah, MgAl-LDHs, and CaMgAl-LDHs composite were 69.31 %, 85.35 %, and 97.82 %, respectively. The CaMgAl-LDHs composite exhibits the highest denitrification capacity, attributed to the presence of Ca2+and Mg2+. Ca2+ and Mg2+is an essential element for the structural integrity of microbial cells, which demonstrated that Ca2+ reduces the surface charge of bacteria, leading to hydrophobicity and facilitating biofilm formation. Electrochemical tests demonstrate that LDHs with distinctive two-dimensional layered structure, contribute to the augmentation of electron transfer during denitrification. LDHs can also promote the formation of highly active biofilms and the secretion of extracellular polymeric substances (EPS) on the surface of loofah, thereby enhancing the metabolic activity of microorganisms. Metagenomic analysis revealed that LDHs enhance the enrichment of denitrifying bacteria and the activity of key enzymes involved in denitrification. Therefore, the adsorption-biological coupled degradation of the LDHs/loofah composites have great potential to enhance the efficiency of biological denitrification, making it promising filling materials for PRB technology applied in groundwater remediation.

Screening of Factors Influencing Keratinase Fermentation from Bacillus Haynesii BK1H using The Plackett-Burman Design (PBD)

Keratinase is a class of proteases that degrade keratin into polypeptides and amino acids by breaking peptide and disulfide bonds in keratinous proteins. Protease is one of the largest industrial enzymes, the global protease market is increasing rapidly every year. In previous studies, a keratinase-producing microbe was isolated from Bleduk Kuwu which was identified as Bacillus haynesii BK1H. However, further study needs to be done to optimize the production by observing microenvironmental factors that influence keratinase production. In this study, screening some microenvironmental factors is reported. Screening factors including carbon sources, type and concentration of metal ions, agitation speed, amount of inoculum, pH, and temperature. Screening for these factors was started with the One Factor at A Time (OFAT) method and followed by the Plackett-Burman Design (PBD) method. In this study, sequential work was done: (1) Regeneration of Bacillus haynesii BK1H Microbes, (2) Preparation of Tyrosine Standard Series Solutions, (3) Screening of Factors Affecting Protease Fermentation of Bacillus haynesii BK1H using the One Factor at A Time (OFAT) method. ), and (4) Maintaining Significantly Influential Factors by Using Plackett-Burman Design (PBD). The results of the OFAT approach showed that the best condition for keratinase production was achieved at rice husk concentration, additional carbon source, of 1%; pH of 7; a temperature of 35°C; the amount of inoculum of 1%; agitation speed of 150 rpm; magnesium sulfate concentration of 0.04 g/mL, and calcium chloride concentration of 0.0005 g/m. Justification of those factors using PBD confirmed that only additional rice husk, magnesium sulfate and calcium chloride concentration, and agitation speed were significantly important toward keratinase production at selected experiment level limits.

Root-based inorganic carbon uptake increases the growth of Arabidopsis thaliana and changes transporter expression and nitrogen and sulfur metabolism.

Root-based uptake of inorganic carbon has been suggested as an additional carbon source. Our study aimed to characterize and understand the root-based uptake and fixation mechanisms and their impact on plant growth. 13C-labeled bicarbonate fed to Arabidopsis roots was assimilated into aspartic acid but mainly into sucrose, indicating that the added inorganic carbon was transported to the leaves. A hydroponic treatment was also established for A. thaliana using 2 mM NaHCO3 at pH 5.6, which enhanced the photosynthetic and growth parameters. According to transcriptome sequencing data, the observed enhancement in growth may be orchestrated by trehalose-6-phosphate signaling and supported by augmented nitrogen and sulfur assimilation. The analysis also revealed regulatory and transporter activities, including several nitrate (NRT2.1), and sulfate transporter (SULTR1;1 and SULTR1;2) candidates that could participate in bicarbonate uptake. Different transporters and carbon fixation mutants were assessed. Arabidopsis homologs of SLOW-TYPE ANION CHANNEL 1 (slah3) CARBONIC ANHYDRASE (βca4), and SULFATE TRANSPORTER (sultr1;2) mutants were shown to be inferior to the bicarbonate-treated wild types in several growth and root ultrastructural parameters. Besides, aquaporin genes PIP1;3 and PIP2;6 could play a negative role in the carbon uptake by venting carbon dioxide out of the plant. The findings support the hypothesis that the inorganic carbon is taken up by the root anion channels, mostly transported up to the shoots by the xylem, and fixed there by RuBisCo after the conversion to CO2 by carbonic anhydrases. The process boosts photosynthesis and growth by providing an extra carbon supply.

Optimization of cultural parameters for lipase production by indigenous stenotrophomonas sp. And pseudomonas aeruginosa isolated from lipid-rich environments

The present study aims to identify prospective lipase-producing bacteria and optimize different culture parameters to produce maximum lipase. A total of 37 lipase-positive bacteria were isolated from lipid-rich environments. Among them, strains S1N-2 and S10P-1 were found to have potential and were molecularly identified as Stenotrophomonas species ICMM10 and Pseudomonas aeruginosa BA7823, respectively. For maximum lipase production, the optimum pH was 7 and the temperature was 37ºC. Using these conditions, the isolates were grown on media with additional carbon and nitrogen sources along with different inoculum concentrations. The maximum amount of lipase produced by Stenotrophomonas sp. ICMM10 was 136.47 ± 1.63 U/ml, which is 5-fold higher than before. Pseudomonas aeruginosa BA7823 produced a maximum lipase of 96.33 ± 0.21 U/ml, which was about 9-fold higher than before. These results would provide useful information about lipase production by indigenous isolates, which may be employed as a potential bacterial lipase source of biotechnological interest. Bangladesh J. Bot. 52(4): 979-988, 2023 (December)

Autotrophic denitrification based on sulfur-iron minerals: advanced wastewater treatment technology with simultaneous nitrogen and phosphorus removal.

Autotrophic denitrification technology has many advantages, including no external carbon source addition, low sludge production, high operating cost efficiency, prevention of secondary sewage pollution, and stable treatment efficiency. At present, the main research on autotrophic denitrification electron donors mainly includes sulfur, iron, and hydrogen. In these autotrophic denitrification systems, pyrite has received attention due to its advantages of easy availability of raw materials, low cost, and pH stability. When pyrite is used as a substrate for autotropic denitrification, sulfide (S2-) and ferrous ion (Fe2+) in the substrate will provide electrons to convert nitrate (NO3-) in sewage first to nitrite (NO2-), then to nitrogen (N2), and finally to discharge the system. At the same time, sulfide (S2-) loses electrons to sulfate (SO42-) and ferrous ion (Fe2+) loses electrons to ferric iron (Fe3+). Phosphates (PO43-) in wastewater are chemically combined with ferric iron (Fe3+) to form ferric phosphate (FePO4) precipitate. This paper aims to provide a detailed and comprehensive overview of the dynamic changes of nitrogen (N), phosphorus (P), and other substances in the process of sulfur autotrophic denitrification using iron sulfide, and to summarize the factors that affect wastewater treatment in the system. This work will provide a relevant research direction and theoretical basis for the field of sulfur autotrophic denitrification, especially for the related experiments of the reaction conversion of various substances in the system.

Attaining superior nitrogen removal from integrated mature landfill leachate and kitchen waste digestion liquid via a two-stage partial nitrification/anammox (PN/A) process

The advanced nitrogen removal of mature landfill leachate (MLL) with low carbon to nitrogen ratio (C/N) is a topic worthy of further research. A two-stage partial nitrification/anammox (PN/A) system for integrated MLL and kitchen waste digestion liquid (KWDL) treatment was established in this study. The nitrogen removal efficiency (NRE) of this process was 98.1 ± 1.3 %, with an effluent TIN concentration of 15.2 ± 1.8 mg/L. In the partial nitrification-sequencing batch reactor (PN-SBR), aerobic hydraulic retention time (HRT) accounted for just 36.4 % of the whole process with dissolved oxygen (DO) < 0.3 mg/L, which significantly reduced energy consumption. Furthermore, the introduction of KWDL heightened anoxic denitrification and aerobic simultaneous nitrification and denitrification (SND) processes, contributing to 74.2 ± 4.3 % and 25.8 ± 4.3 % of the total NRE, respectively. This greatly strengthened the nitrogen removal capacity of PN-SBR. Batch tests indicated that the capacity of KWDL as a carbon source to drive the process of partial denitrification coupled with anammox (PDA) was equal to that of sodium acetate. Adding KWDL in the later phase of each cycle in the anammox-sequencing batch reactor (A-SBR) facilitated achieving stable PDA and advanced nitrogen removal. The nitrate accumulation problem in the traditional two-stage PN/A process has been resolved without the addition of carbon sources. Nitrosomonas (3.7 %→7.9 %), Thauera (0.04 %→40.7 %) and a salt-tolerant AnAOB microbe, unclassified_f_Brocadiaceae (0 %→5.3 %) were dominant in the combined system. This study revealed a pioneering avenue for efficient high-strength wastewater treatment.

Optimization of Carbon and Nitrogen Source to Enhance Antibacterial Activity from a Sponge-derived Bacillus tequilensis

In our endeavor to find antibacterial from marine bacteria, we screened the microbiota from a Lithistid sponge, collected from Seribu Island, Jakarta. One of the promising strains was K 2.4.2. Identification of the strain using 16S rRNA Sanger sequencing resulted a sequence similarity of 100% to Bacillus tequilensis. Response surface methodology was applied to optimize the culture conditions for enhancing antibacterial activity of the strain. The optimization was carried out using Box-Behnken design experiment to determine the optimum carbon and nitrogen sources in order to produce maximum antibacterial activity. The optimum media with high antibacterial activity was marine broth with the addition of carbon and nitrogen concentration source of sucrose 2.15 % and peptone 1.08%, respectively. In addition, the optimum temperature was 31.18oC. The antibacterial activity response was predicted using a statistical model and compared to the activity in the experiment. The difference between the model and the laboratory experiment was less than 5% which showed a good accuracy. The results of this study once again showed that optimization method effectively reduced time, chemicals, and energy.

Growth Performance of Critically Endangered Hypselobarbus pulchellus in Biofloc Systems with Various C/N Ratios

Background: Biofloc technology relies on adding a carbon source to maintain optimal carbon to nitrogen ratio for transforming the waste into microbial biomass that aquatic animals can use. In the present study, the growth performance of the critically endangered Hypselobarbus pulchellus in biofloc-based seed rearing with different Carbon to Nitrogen ratio was studied. Methods: Healthy early fry (0.01 g) was randomly stocked into 15 circular FRP tanks (1000 L) at a density of 100 individuals/m3 and reared for 90 days. The carbon to nitrogen ratios of 5:1(CN5), 10:1(CN10), 15:1(CN15) and 20:1(CN20) were maintained using jaggery without considering carbon content derived from the feed and the control group received no additional source of carbon. Result: The results indicated that H. pulchellus had better growth performance in biofloc systems having higher C/N ratios. The highest weight gain (0.48±0.01 g) and weight gain percentage (3931.15±120.68%) and specific growth rate (4.11±0.03% per day) were found in the CN10 group (P less than 0.05), followed by CN15 and CN20, while the control group values were lowest. In terms of survival, all treatments had high survival rates ranging from 92% to 94.67%, with no significant variations (P greater than 0.05). The CN10, CN15 and CN20 treatments had significantly higher amylase, protease and lipase activities than control (P less than 0.05). Moreover, the immunological and antioxidant activity increased with CN ratios. The CN10, CN15 and CN20 groups had significantly lower total ammonia nitrogen, nitrite and nitrate levels than control group (P less than 0.05). Overall, this study suggests that C/N ratios of 10:1 to 20:1 are optimal for rearing H. pulchellus fingerlings from early fry, with 10:1 presenting the best growth results.

Efficient production of single cell protein from biogas slurry using screened alkali-salt-tolerant Debaryomyces hansenii

Production of single cell protein (SCP) by recovering ammonia nitrogen from biogas slurry shows great potential against protein scarcity and unsustainable production of plant and animal proteins. Herein, a high-alkali-salt-tolerant yeast strain, Debaryomyces hansenii JL8-0, was isolated and demonstrated for high-efficient SCP production. This strain grew optimally at pH 8.50 and 2500 mg/L NH4+-N, and it could efficiently utilize acetate as the additional carbon source. Under optimal conditions, SCP biomass of 32.21 g/L and productivity of 0.32 g/L·h−1 were obtained in fed-batch fermentation. Remarkably, nearly complete (97.40 %) ammonia nitrogen from biogas slurry was recovered, probably due to its high affinity for NH4+-N. Altogether, this strain showed advantages in terms of cell biomass titer, productivity, and yield. A cultivation strategy was proposed by co-culturing D. hansenii with other compatible yeast strains to achieve high-efficient SCP production from biogas slurry, which could be a promising alternative technology for biogas slurry treatment.

N2O emission reduction in the biological nitrogen removal process for wastewater with low C/N ratios: mechanisms and strategies

Urban wastewater, as the main influent type of Waste Water Treatment Plants (WWTPs), has the characteristic of low carbon to nitrogen ratio (C/N). In the biological nitrogen removal (BNR) process, insufficient carbon source often affects the nitrogen removal efficiency and leads to more N2O emissions. We review recent researches on N2O emissions in the BNR process of wastewater with low C/N. The availability of carbon sources affects heterotrophic denitrification (HD) and autotrophic nitrification/denitrification processes, which are the main reasons for N2O emissions in BNR. For the sustainable development of BNR in WWTPs, we introduce strategies suitable for reducing N2O emissions in the BNR process of low C/N wastewater from two aspects: traditional process innovation and new process development. These strategies mainly include carbon source addition, adjustment of aeration strategy, optimization of oxidation ditch and biofilm facilities, and application of Anammox related processes. In the future, it is still necessary to further deepen this research direction through the normalization of N2O emission quantification standards, exploration of N2O metabolism mechanisms, assessment of environmental effects of emission reduction strategies, and practical application of new processes.

Effect of CNF in-situ growth on microstructure and mechanical properties evolution of RMI-deriver C/C–SiC composites

The present paper investigates the effect of carbon nanofibers (CNFs) on the microstructure and mechanical properties of Carbon fiber reinforced carbon and silicon carbide binary matrix (C/C–SiC) composite prepared by using the reactive melt infiltration technique. The CNFs used in this paper were generated through in-situ reaction in the pores of C/C preforms using the chemical vapor deposition. Results indicate introducing additional carbon sources in the form of CNFs in the C/C preform can remarkably improve the permeability of molten Si, resulting in higher density and more uniform microstructure of the RMI-deriver C/C–SiC composites. Consequently, the in-situ formation of CNFs reduces the residual Si content by 64.71% and increases the mechanical strength and modulus at room temperature by [22.31% and 17.89%] and after heat treatment at 1500 °C by [35.6% and 47.48%] with respect to no-CNF containing composites due to a lower amount of residual Si content and additional reinforcement effect of the unreacted CNFs.

Simultaneous nitrification/denitrification in a single-chamber stainless steel bioelectrochemical reactor

The removal of nitrogen from wastewater with a low C/N ratio often requires additional carbon sources to address the shortage of electron donors, which increases the cost. We explored a simple and energy effecient means for treating wastewater with a high concentration of ammonia nitrogen under anoxic conditions without the addition of carbon sources. We constructed a stainless steel tube as an anaerobic single-chamber microbial electrolysis cell (MEC) for investigating autotrophic simultaneous nitrification/denitrification (SND). Two different structures (carbon brush vs. stainless-steel) were used to construct biocathodes and compared their performances under different voltages (1.8 V, 1.5 V, 1.2 V) applied by DC power. When voltage was applied at 1.5 V, the removal rates of TN and NH4+-N reached 19.68 ± 0.02 mg L−1 d−1 and 21.04 ± 0.17 mg L−1 d−1, respectively. Simultaneously, it achieved maximum TN and NH4+-N removal over 14 days (44.97 ± 0.28 %, 48.16 ± 0.32 %). These rates were 1.8 and 5 times of that obtained with the conventional carbon brush electrode and open-circuit control. Furthermore, microbial community and SEM analysis indicate that species of Thermomonas, Thibacillus and Thauera were the predominant autotrophic electroactive denitrifying bacteria in the reactors. Overall, we achieved a high rate of nitrogen removal, electron utilization and energy recovery in a single-chamber stainless steel MEC.

Shifts in the Microbial Populations of Bioleach Reactors Are Determined by Carbon Sources and Temperature.

In the present study, the effect of additional carbon sources (carbon dioxide and molasses) on the bio-oxidation of a pyrite-arsenopyrite concentrate at temperatures of 40-50 °C was studied, and novel data regarding the patterns of the bio-oxidation of gold-bearing sulfide concentrates and the composition of the microbial populations performing these processes were obtained. At 40 °C, additional carbon sources did not affect the bio-oxidation efficiency. At the same time, the application of additional carbon dioxide improved the bio-oxidation performance at temperatures of 45 and 50 °C and made it possible to avoid the inhibition of bio-oxidation due to an increase in the temperature. Therefore, the use of additional carbon dioxide may be proposed to prevent the negative effect of an increase in temperature on the bio-oxidation of sulfide concentrates. 16S rRNA gene profiling revealed archaea of the family Thermoplasmataceae (Acidiplasma, Ferroplasma, Cuniculiplasma, and A-plasma group) and bacteria of the genera Leptospirillum, with Sulfobacillus and Acidithiobacillus among the dominant groups in the community. Temperature influenced the composition of the communities to a greater extent than the additional sources of carbon and the mode of operation of the bioreactor. Elevating the temperature from 40 °C to 50 °C resulted in increases in the shares of Acidiplasma and Sulfobacillus and decreases in the relative abundances of Ferroplasma, Leptospirillum, and Acidithiobacillus, while Cuniculiplasma and A-plasma were more abundant at 45 °C. A metagenomic analysis of the studied population made it possible to characterize novel archaea belonging to an uncultivated, poorly-studied group of Thermoplasmatales which potentially plays an important role in the bio-oxidation process. Based on an analysis of the complete genome, we propose describing the novel species and novel genus as "Candidatus Carboxiplasma ferriphilum" gen. nov., spec. nov.

Transcriptomics reveal how circadian regulation contributes to starch hyperaccumulation in marine alga Tetraselmis helgolandica

AbstractTetraselmis helgolandica var. Tsingtaoensis is a marine microalga. It can produce a large amount of starch, especially amylose, with addition of carbon source and specific circadian rhythm. The mechanism behind this phenomenon is still unclear. Analysis of this mechanism can help to develop T. helgolandica into a new green bioengineering chassis organism. We explained how circadian rhythm and glucose affect the rate of starch accumulation and starch structure in T. helgolandica based on the transcriptome. The glucose inhibited the photosynthetic system of T. helgolandica, while the circadian rhythm can alleviate the inhibition. Circadian rhythm induced the upregulation of Embden–Meyerhof–Parnas pathway and pentose phosphate pathway (PPP) in T. helgolandica, but had little effect on the tricarboxylic acid cycle. PPP pathway provides Ribulose‐1,5‐bisphosphate, which may be beneficial for dark reactions and nucleotide synthesis. And PPP pathway provides Nicotinamide adenine dinucleotide phosphate, which facilitates energy substance synthesis. This will further upregulate the starch metabolic pathway. The transcript level of the key gene ADP‐Glucose pyrophosphorylase is mainly regulated by glucose. The granule‐bound starch synthase (gbss), a key gene for amylose synthesis, is mainly influenced by circadian rhythm. In general, the increase of starch synthesis and amylose ratio requires both glucose addition and circadian rhythm. We report the first referenced transcriptome of T. helgolandica. Differences between transcripts reveal how circadian rhythm and glucose addition affected the rate of starch synthesis and structural variation. It provides a reference for an in‐depth study of starch synthesis in green algae.