CO2 Fixation Rate Research Articles

Improved photosynthetic characteristics of Chlorella mutant MS700 induced by nuclear radiation

Chlorophyll a variable fluorescence and oxygen evolution were measured in microalgae Chlorella and its mutant MS700, which was mutated by nuclear radiation with an increased biomass yield. The mutant MS700 showed an improvement in photosynthetic characteristics under various CO2 concentrations. Results showed that chlorophyll-based flash oxygen yield was 104% higher in MS700 than in the wild type, indicating more available electron acceptors in the plastoquinone pool and a higher light to chemical energy conversion efficiency. The higher chlorophyll a variable fluorescence at the end of PQ pool-regulated phase implied a more robust mechanism for consumption of electrons generated in PSII, indicating a more efficient downstream process. Monitoring of CO2 fixation in the Calvin cycle showed that the mutant had a 27.7% higher capability of incorporating its dissolved inorganic carbon. The oxygen evolution rate was 31.4% higher in MS700, which also indicated a higher CO2 fixation rate. These results consistently demonstrated carbon fixation efficiency in the mutant MS700, resulting in the higher biomass yield.

Using non-metric multi-dimensional scaling analysis and multi-objective optimization to evaluate green algae for production of proteins, carbohydrates, lipids, and simultaneously fix carbon dioxide

Eight green-algae species were investigated to elucidate the effects of growth phases on biomass productivity (CO2 fixation rate) and accumulation of algal macromolecules (proteins, carbohydrates, and lipids). Non-metric multi-dimensional scaling (NMDS) and multiple-objective optimization were applied to evaluate the effects of algal species and growth phases on biomass productivity and algal macromolecule accumulation. Algal species and growth phases had significant impacts on biomass production and composition. NMDS delineated that biomass productivity and protein accumulation of all species were dominant in the log phase, while the stationary phase was favorable for lipid and carbohydrate accumulation. Among the eight algal species, Chlorella vulgaris had the highest biomass productivity (75 mg/L/day) and a high protein content in the exponential phase (53%). Scenedesmus obliquus had the highest protein content (55%) in the log phase, Botryococcus braunii showed the highest lipid content (40%) in the stationary phase, and Staurastrum sp. presented the highest carbohydrate content (37%) in the stationary phase. Two-objective optimization for algal biomass productivity and composition led to the conclusion that Chlorella vulgaris, Botryococcus braunii, and Coelastrum microporum are the preferred strains for accumulation of proteins, lipids, and carbohydrates, respectively, along with good CO2 fixation (biomass productivity). NMDS and multi-objective optimization are useful tools to select preferred strains and corresponding culture conditions from a large pool of candidates for simultaneous biomass and macromolecule accumulation.

Rates of dark CO2 fixation are driven by microbial biomass in a temperate forest soil

Soils substantially contribute to the terrestrial fluxes of CO2 to the atmosphere. Dark CO2 fixation, the microbial process by which pore space CO2 is reduced to organic matter, may recycle and trap some of the CO2 respired in soils before it can escape to the atmosphere. To evaluate its potential significance for global temperate forest soil carbon stocks, we quantified dark CO2 fixation rates in a temperate beech forest soil down to 1 m depth over a range of 2–20% (v:v) headspace CO2 concentrations, by tracing incorporation of a13C–CO2 label into microbial biomass carbon and soil organic matter. We found that fixation rates under a concentration of 2% CO2 decreased with depth from 0.86 to 0.06 μg C normalized to g(dw) soil−1 d−1. However, when dark CO2 fixation rates were normalized to soil microbial biomass carbon, no significant differences between depths were observed. Higher CO2 concentrations increased fixation rates, with a linear 2-fold increase between 2% and 10% CO2. Molecular analysis revealed the dominance of heterotrophs, along with the presence of autotrophs mainly employing the Calvin Benson Bassham (CBB) pathway followed by the reductive citric acid (rTCA) pathway. Although community composition varied with depth, the relative fraction of autotrophs determined by qPCR of RuBisCO (cbbL IA, cbbL IC) and ATP-citrate lyase (aclA) genes remained stable at approximately 0.5% of the total community. Dark CO2 fixed carbon accounted for up to 1.1% of microbial biomass carbon and up to 0.035% of soil organic carbon after 28 days. We estimated a fixation flux of 25 ± 7.2 g C m−2 yr−1 to 1 m depth for the Hainich forest soil under field conditions. Without this process, Hainich forest soil CO2 emissions would be 5.6% higher, recycling a fraction of carbon large enough to potentially affect carbon isotope signatures in SOC. If this is held for all temperate forest soils globally, the annual rate of dark CO2 fixation would be 0.26 ± 0.07 Pg C yr−1 to a depth of 1 m, without considering contributions from other biomes. In conclusion, microbial biomass carbon and CO2 concentration appear to be the main drivers of dark CO2 fixation in temperate forest soils, and dark CO2 fixation may maintain Hainich forest soil carbon stocks by moderating a significant fraction of soil CO2 emissions annually.

Long-term chemical fertilization-driving changes in soil autotrophic microbial community depresses soil CO2 fixation in a Mollisol

Soil is the largest C pool in the terrestrial ecosystem. Numerous studies have been devoted to the decomposition of soil organic C as influenced by agricultural management. However, little is known about the effect of fertilization on the microbial CO2 fixation potential. Here, we examined the atmospheric CO2 fixation rates and structure of autotrophic cbbL-containing bacterial communities and accA-containing archaeal communities in response to 38 years of chemical and/or organic fertilizer application in a Mollisol. The autotrophic microbial abundance and community composition were analyzed by quantitative polymerase chain reaction and high throughput sequencing, respectively. Our results showed that chemical fertilization additions significantly decreased CO2 fixation rates by 57%, but organic manure use resulted in no notable differences compared to no fertilizer regimes (0.38 mg CO2 kg−1 soil d−1) through stable isotope methods. The declining soil pH and increasing Olsen-phosphorus in soils with chemical fertilization dramatically reduced the cbbL gene diversity and accA gene abundances and altered both the autotrophic bacterial and archaeal community compositions. The changes in CO2-fixation rate were more greatly attributed to the shifts in autotrophic bacterial community composition than to the diversity and abundance. The C fixation potentials were positively correlated with the relative abundances of Acidiphilium and Methylibium but were negatively related to those of Azospirillum and Nitrosospira. Both composition and abundance of the autotrophic archaeal community contributed together to the CO2 fixation activities. Our finding suggests that long-term chemical fertilization has a strong impact on the soil microbial CO2 fixation activity and autotrophic microorganisms in upland soils and highlight the important roles of the CO2 fixing process in soil organic carbon sequestration.

Enhancing Photosynthetic Characterization and Biomass Productivity of Nannochloropsis Oceanica by Nuclear Radiation

Microalgae with a high growth rate and a carbon fixation rate present a promising potential to produce diverse renewable energy products and reduce greenhouse gas emissions. However, some microalgal species may have limited light-use efficiency and specific growth rate. To alleviate these issues, Nannochloropsis oceanica was subjected to 137Cs –γ radiation to obtain the desired mutant with enhanced light-use efficiency and increased biomass productivity. The N. oceanica mutant ZJU700 showed a 26.7% increase in biomass productivity after nuclear irradiation at a 700GY dosage. It was found that the mutant had a 30.2% higher oxygen evolution rate than the wild type cells. High-throughput transcriptome sequencing showed that expression of photosynthetic related genes in the mutant were much higher than in wild type cells. Expression of the psbO gene increased by 455% in mutant ZJU700, contributing to an increased oxygen evolution rate by splitting water. Three up-regulated genes, namely petC, petF and petH, resulted in enhanced electron transport during the photoreaction process. Up-regulation of many genes involved in the Calvin cycle indicated that CO2 fixation rate was likely to be increased to produce more carbohydrates in mutant, thereby contributing to the increased biomass productivity in mutant ZJU700.

Outdoor cultivation of microalgae in a coal-fired power plant for conversion of flue gas CO2 into microalgal direct combustion fuels

Microalgae have piqued renewed interest as a sustainable biofuel feedstock owing to their high CO2 conversion efficiency. However, the major limitation of microalga-based biofuel production is low productivity. In this study, CO2 in flue gas emitted from the coal-fired power plants was fixed through mass microalgal cultivation using only sunlight as an energy source. To minimize the cost and energy required to supply the flue gas and efficiently utilize the microalgal biomass, a polycarbonate (PC) greenhouse and polymeric photobioreactors were installed near the power plant stack. Four different microalgal strains (Chlamydomonas reinhardtii, Chlorella sorokiniana, Neochloris oleoabundans, and Neochloris oleoabundans #13) were subjected to semi-continuous culturing for 1 month. The maximum biomass productivity was achieved by the N. oleoabundans #13 strain (0.703 g L−1 day−1). Additionally, polymerase chain reaction analysis revealed that the individual microalgal culture was not cross-contaminated with other microalgal cultures in this cultivation system, owing to the structural properties of photobioreactor comprising individual modules. The lipid content and calorific productivity of N. oleoabundans #13 biomass were 45.70% and 3.553 kJ L−1 day−1, respectively, which indicate satisfactory performance of biomass as a direct combustion fuel. The CO2 fixation rate, which was calculated based on the carbon content in the biomass, was 0.309 g CO2 L−1 day−1. Therefore, large amounts of CO2 can be reduced using the large-scale microalgal cultivation system, which enables efficient biological CO2 conversion and maximizes microalgal biomass utilization.

Potential microalgal strains for converting flue gas CO2 into biomass

A screening method using 15% CO2 (v/v) as screening stress and a spotting plate method was developed to isolate microalgae with the potential to convert flue gas CO2 to biomass. A total of six microalgal strains, belonging to the genera Chlorella, Heynigia, Desmodesmus, and Scenedesmus, were isolated from ponds near metallurgical/cement/power plants. The growth of these isolated strains was dramatically promoted at 5 to 15% CO2 when they were cultivated in bubble column photobioreactors aerating with 0.03%, 5%, 10%, and 15% CO2. The growth of Heynigia riparia SX01 in particular showed substantial improvement with the increase of CO2 concentrations from 5 to 15%. Furthermore, the maximum biomass, overall biomass productivity, maximum biomass productivity, and maximum CO2 fixation rate of these microalgal strains greatly increased at 5 to 15% CO2 as well. Chlorella sorokiniana GS03 showed the highest values in maximum biomass productivity (0.36 g L−1 day−1) and maximum CO2 fixation rate (0.66 g L−1 day−1) at 5% CO2. Heynigia riparia SX01 exhibited the highest values of maximum biomass (3.28 g L−1), overall biomass productivity (0.27 g L−1 day−1), maximum biomass productivity (0.39 g L−1 day−1), and maximum CO2 fixation rate (0.71 g L−1 day−1) at 15% CO2. This study provides not only an efficient screening method obtaining microalgae with wide CO2 tolerance but also microalgal strains utilizing high levels of CO2 up to 15% to produce biomass, which contributes to further exploration in converting real flue gas CO2 into biomass feedstock.

One third of the abiotically-absorbed atmospheric CO2 by the loess soil is conserved in the solid phase

It has frequently been noticed that alkaline soils in arid and semiarid areas can absorb atmospheric CO2 abiotically. However, the fate of the absorbed CO2 is largely unknown, limiting our ability to accurately assess the contribution of abiotic CO2 absorption to carbon sequestration. The hypothesis that some abiotically-absorbed carbon could be fixed in the soil solid phase is yet to be explicitly tested. From April to November 2016, we added 13CO2 to the natural alkaline loess soil at a depth of 0–17 cm and quantified the proportion of 13CO2 conserved in the soil solid phase on the central Loess Plateau of China. The results showed that natural surface soil absorbed 13CO2 at a rate of 475.9 mg m−2 d−1. Of the absorbed 13CO2, 33.2% was conserved in the soil solid phase. The rate of added 13CO2 conserved in the solid phase was positively correlated with mean monthly soil water content but negatively correlated with mean monthly soil temperature. Our results indicated that, loess soil can absorb CO2 from the atmosphere through abiotic processes, and part of the abiotically-absorbed CO2 is stably fixed in the soil solid phase. Soil with a higher water content and lower temperature may promote the abiotic CO2 fixation. The rate of CO2 fixation through abiotic processes at the surface soil accounted for approximately 10%-20% of the reported local annual net ecosystem exchange, implying that the abiotic CO2 uptake by loess soil may play an important role in assessing the capacity of CO2 sequestration in these areas.

Substrate-dependent CO2 fixation in heterotrophic bacteria revealed by stable isotope labelling

Virtually all heterotrophs incorporate carbon dioxide by anaplerotic fixation. Little explored, however, is the interdependency of pathways and rates of CO2fixation on the concurrent usage of organic substrate(s). Potentially, this could reveal which substrates out of a pool of dissolved organic carbon are utilised by environmental microorganisms. To explore this possibility, Bacillus subtilis W23 was grown in a minimal medium with normalised amounts of either glucose, lactate or malate as only organic substrates, each together with 1g/L NaH13CO3. Incorporation of H13CO3- was traced by elemental analysis-isotope ratio mass spectrometry of biomass and gas chromatography-mass spectrometry of protein-derived amino acids. Until the late logarithmic phase, 13C incorporation into the tricarboxylic acid cycle increased with time and occurred via [4-13C]oxaloacetate formed by carboxylation of pyruvate. The levels of 13C incorporation were highest for growth on glucose and lowest on malate. Incorporation of 13C into gluconeogenesis products was mainly detected in the lactate and malate experiment, whereas glucose down-regulated this path. A proof-of-principle study with a natural groundwater community confirmed the ability to determine incorporation from H13CO3- by natural communities leading to specific labelling patterns. This underlines the potential of the labelling approach to characterise carbon sources of heterotrophic microorganisms in their natural environments.

The pyrenoid.

Wang and Jonikas take a look at an unconventional organelle, the pyrenoid.

Tunable production of succinic acid at elevated pressures of CO2 in a high pressure gas fermentation reactor

Production of bio-based alternative of succinic acid (SA) has been growing due to the awareness on environmental advantages it offers, such as CO2 sequestration. Current study focuses on evaluating the impact of different CO2 partial pressures (0.6, 0.8, 1, 2 bar) on SA production and yield as well as on other parameters like acids profile and CO2 fixation rate in Citrobacter amalonaticus. Increasing partial pressure to 2 bar enhanced SA production and maximum of 14.86 gL−1 was achieved with a productivity of 0.36 gL−1h−1 and yield of 52.10%. Varying partial pressures depicted significant influence on total acids profile, where at lower pressures (0.6 bar) lactic (5.6 gL−1) and acetic acids (4.1 gL−1) became dominant products, while concentration of SA was 2.07 gL−1, by the end of cycle. The desirable effect of moderately elevated pressures for converting CO2 to platform chemicals can be a potential strategy in overcoming current challenges related to CO2 abatement.

Microbial nitrogen fixation and methane oxidation are strongly enhanced by light in Sphagnum mosses

Peatlands have acted as C-sinks for millennia, storing large amounts of carbon, of which a significant amount is yearly released as methane (CH4). Sphagnum mosses are a key genus in many peat ecosystems and these mosses live in close association with methane-oxidizing and nitrogen-fixing microorganisms. To disentangle mechanisms which may control Sphagnum-associated methane-oxidation and nitrogen-fixation, we applied four treatments to Sphagnum mosses from a pristine peatland in Finland: nitrogen fertilization, phosphorus fertilization, CH4 addition and light. N and P fertilization resulted in nutrient accumulation in the moss tissue, but did not increase Sphagnum growth. While net CO2 fixation rates remained unaffected in the N and P treatment, net CH4 emissions decreased because of enhanced CH4 oxidation. CH4 addition did not affect Sphagnum performance in the present set-up. Light, however, clearly stimulated the activity of associated nitrogen-fixing and methane-oxidizing microorganisms, increasing N2 fixation rates threefold and CH4 oxidation rates fivefold. This underlines the strong connection between Sphagnum and associated N2 fixation and CH4 oxidation. It furthermore indicates that phototrophy is a strong control of microbial activity, which can be directly or indirectly.

Light-Emitting Diode Power Conversion Capability and CO2 Fixation Rate of Microalgae Biofilm Cultured Under Different Light Spectra

Microalgae biofilm-based culture has attracted much interest due to its high harvest efficiency and low energy requirements. Using light-emitting diodes (LEDs) as light source for microalgae culture has been considered as a promising choice to enhance the economic feasibility of microalgae-based commodities. In this work, the LED power conversion capability and CO2 fixation rate of microalgae biofilms (Chlorella ellipsoidea and Chlorella pyrenoidosa) cultured under different light spectra (white, blue, green and red) were studied. The results indicated that the power-to-biomass conversion capabilities of these two microalgae biofilms cultured under blue and white LEDs were much higher than those under green and red LEDs (C. ellipsoidea: 32%–33% higher, C. pyrenoidosa: 34%–46% higher), and their power-to-lipid conversion capabilities cultured under blue LEDs were 61%–66% higher than those under green LEDs. The CO2 fixation rates of these two biofilms cultured under blue LEDs were 13% and 31% higher, respectively, than those under green LEDs. The results of this study have important implications for selecting the optimal energy-efficient LEDs using in microalgae biofilm-based culture systems.

Innovative development of membrane sparger for carbon dioxide supply in microalgae cultures.

The present study was aimed to develop a membrane sparger (MS) integrated into a tubular photobioreactor to promote the increase of the carbon dioxide (CO2 ) fixation by Spirulina sp. LEB 18 cultures. The use of MS for the CO2 supply in Spirulina cultures resulted not only in the increase of DIC concentrations but also in the highest accumulated DIC concentration in the liquid medium (127.4 mg L-1 d-1 ). The highest values of biomass concentration (1.98 g L-1 ), biomass productivity (131.8 mg L-1 d-1 ), carbon in biomass (47.9% w w-1 ), CO2 fixation rate (231.6 mg L-1 d-1 ), and CO2 use efficiency (80.5% w w-1 ) by Spirulina were verified with MS, compared to the culture with conventional sparger for CO2 supply. Spirulina biomass in both culture conditions had high protein contents varying from 64.9 to 69% (w w-1 ). MS can be considered an innovative system for the supply of carbon for the microalgae cultivation and biomass production. Moreover, the use of membrane system might contribute to increased process efficiency with a reduced cost of biomass production.

Simultaneous fixation of carbon dioxide and purification of undiluted swine slurry by culturing Chlorella vulgaris MBFJNU-1

Microalgae biotechnology for wastewater treatment is a promising strategy to solve some severe environmental problems. In this work, carbon dioxide (CO2) fixation rate and performance of wastewater treatment by a unique Chlorella vulgaris MBFJNU-1 were deeply evaluated using undiluted swine slurry. The obtained results showed that C. vulgaris MBFJNU-1 achieved the highest biomass (3.08 g/L) under the optimized conditions (5% CO2, 24 h/d ventilation time and 1000 mL/min ventilation rate). Meantime, the biomass had 54.7% of protein and 36.25 mg/g of chlorophyll. Moreover, in the end of trials, C. vulgaris MBFJNU-1 to treat swine slurry attained the total nitrogen removal rate of 74%, ammonia nitrogen removal rate of 78% and total phosphorus removal rate of 87%. The greatest CO2 fixation rate (454 mg/(L·d)) was obtained by the microalgae. To illustrate the CO2 fixation and nutrients removal rates of wastewater, proteomic analysis for C. vulgaris MBFJNU-1 was assayed and results showed that a certain amount of CO2 could promote some enzymes in photosynthesis and nitrogen metabolism, which was consistent with the experimental results. Taken together, C. vulgaris MBFJNU-1 was the potential microalgae to effectively fix CO2 and remove some nutrients from undiluted swine slurry for microalgae biomass.

Phycoremediation of palm oil mill effluent (POME) and CO2 fixation by locally isolated microalgae: Chlorella sorokiniana UKM2, Coelastrella sp. UKM4 and Chlorella pyrenoidosa UKM7

The Malaysian palm oil industry generates large amount of palm oil mill effluent (POME) and carbon dioxide (CO2). Appropriate control of this industrial discharge through biological means is essential to achieve sustainable development. This study discloses the practical way of reducing pollutants in POME and fixing CO2 by using three locally isolated microalgae species: Chlorella sorokiniana UKM2, Coelastralla sp. UKM4 and Chlorella pyrenoidosa UKM7. The identification of the microalgal-assimilable organic carbon sources in POME is first reported in this paper. The microalgae strains were cultured independently in 10 % (v/v) POME aerated with 1% (v/v) CO2. Throughout the process, C. sorokiniana UKM2 showed the highest CO2 uptake rate of 567 mg L−1 day-1 and nutrient removal efficiency (NRE) of ammonium (NH4+), total nitrogen (TN) and total phosphate (TP) of 100 %, 65 % and 56 % respectively. Meanwhile, Coelastella sp. UKM4 and C. pyrenoidosa UKM7 exhibited CO2 fixation rates ranging from 396 to 486 mg L−1 day-1, whereas the NRE of NH4+-N was 100 %. The NRE of TN and TP ranged from 59 % to 63 % and 41%–56%, respectively. Both Chlorella species presented higher average nutrient removal rates (ANRR) of NH4+-N, TN and TP than Coelastralla sp. UKM4. This study indicated that these three native microalgal species possess great potential for integration into the phycoremediation of POME and CO2 fixation.

Improving light distribution and light/dark cycle of 900 L tangential spiral−flow column photobioreactors to promote CO2 fixation with Arthrospira sp. cells

The light distribution and light/dark cycle were improved in 900 L tangential spiral-flow column photobioreactors (TSCP) to promote CO2 fixation with Arthrospira sp. cells. Solar irradiation model was employed in CFD simulation to investigate light distribution and light/dark cycle in flow field composed of culture medium, CO2 bubbles and Arthrospira sp. cells under actual sunlight irradiation considering geolocation and time. An accurate way to divide light/dark zone based on saturate light intensity and light intensity field was adopted for the first time. When Arthrospira sp. cell concentration increased from 0.1 to 0.9 g/L, light/dark cycle frequency of cells firstly increased from 0.650 Hz to 0.868 Hz and then decreased to 0.117 Hz. Intracellular chlorophyll a content and carotenoids content of Arthrospira sp. cells in TSCP were 6% and 41% higher than those in conventional bubble column photobioreactor. This promoted cellular photosynthesis and stress resistance, which contributed to increase CO2 fixation rate of Arthrospira sp. cells by 59%. When CO2 aeration rate, CO2 volume concentration, and circulating pump power were 0.210 L/min, 15%, and 30 W, chlorophyll a content, helix pitch, and CO2 fixation rate of Arthrospira sp. cells all reached peak values of 8.769 mg/L, 78.26 μm and 0.358 g/L/d, respectively.

Microbial synergy and stoichiometry in heap biooxidation of low-grade porphyry arsenic-bearing gold ore.

Heap biooxidation method was used to evaluate the availability of Paodaoling gold ore in Anhui province, China. 15,000 tons of gold ores (≤ 10mm in diameter) were bioxidized under mesophilic conditions. Under the synergistic effect of microbial community, arsenic and sulfur were oxidized by 42% and 38% after 80 days. Relatively, leaching of gold was improved from 36 to 78% after heap biooxidation. The sequencing results showed there were 28 operational taxonomic units identified the microbial community in the heap. The main genera were Acidithiobacillus, Ferroplasma, Acidiferrobacter and Nitrospira. According to stoichiometry, the content of microorganisms with various functions tended to be balanced. The biomass production rate was 10g/s, the CO2 fixation rate was 18g/s, and the oxygen consumption rate was 60g/s. This study provides a good basis for the further design and application of heap biooxidation technology.

Microalgal remediation of anaerobic pretreated pharmaceutical wastewater for sustainable biodiesel production and electricity generation

Raw wastewater from final processing unit of pharmaceutical industry contains high organic loading and obstinate compounds causing treatment of this wastewater a major challenge. In this study a novel approach for the treatment of pharmaceutical wastewater has been discussed. Anaerobic pretreatment of raw pharmaceutical wastewater was done using microbial fuel cell (MFC), followed by aerobic microalgal treatment with T. indica in photobioreactor in batch mode. Combined MFC and algal treatment process showed potential reduction in heavy metals concentration along with decrease of COD, TOC, nitrate and phosphate content. The observed COD, TOC, nitrate and phosphate in raw wastewater was 90.29, 97.05, 81.60 and 94.87 %, respectively. However, after treatment of raw wastewater in photobioreactor without pretreatment, 66.30 % COD, 67.17 % nitrate, 70.03 % phosphate and 78.14 % TOC reduction were observed. T. indica achieved 16.40 and 15.69 mg L−1d−1 of lipid productivity in PW1 and PW2 whereas it showed 0.085 and 0.089 g CO2 L−1d-1 of CO2 Fixation rate. This study demonstrates combination treatment processes of wastewater improve environmental sustainability and enables greener routes of biofuels production.

Improvement of Thermosynechococcus sp. CL-1 performance on biomass productivity and CO2 fixation via growth factors arrangement

The enormous attraction on CO2 biofixation using photosynthetic microorganisms such as cyanobacteria has been risen due to its promising efficiency and valuable by-products production. In this study, an isolated cyanobacterium from hot spring in Taiwan, Thermosynechococcus sp. CL-1 (TCL-1) was evaluated for its growth factors arrangement effect on the biomass productivity and CO2 biofixation. The initial biomass concentration, and nutrient supply level variation influenced TCL-1 biomass productivity and CO2 biofixation rate while the adjusted and controlled pH value gave an insignificant difference on its performance. The initial biomass concentration of 3 g L−1 gave the best result on biomass productivity and CO2 fixation which reached 143.4 mg L−1 h−1 and 224 mg L−1 h−1 respectively. Regarding to the result of this study, controlled pH value by the CO2 supply inside the reactor, produced an insignificant difference in TCL-1 performance compared to those with the uncontrolled pH value. The variation of nutrient supply level was achieved by the variation of macronutrient and micronutrient supply inside the medium. The G-solution contains metals and other micronutrient elements which are necessary for the growth of TCL-1. The combination between 5–folds MF medium as the macronutrient, and 3-folds G-solution as the micronutrient supply, present the best TCL-1 performance on biomass productivity and CO2 fixation rate.