Variation of photoautotrophic fatty acid production from a highly CO2 tolerant alga,Chlorococcum littorale,with inorganic carbon over narrow ranges of pH

Photoautotrophic fatty acid production of a highly CO₂‐tolerant green alga Chlorococcum littorale in the presence of inorganic carbon at 295 K and light intensity of 170 µmol‐photon m^?2 s^?1 was investigated. CO₂ concentration in the bubbling gas was adjusted by mixing pure gas components of CO₂ and N₂ to avoid photorespiration and β‐oxidation of fatty acids under O₂ surrounding conditions. Maximum content of total fatty acid showed pH‐dependence after nitrate depletion of the culture media and increased with the corresponding inorganic carbon ratio. Namely, [HCO₃^?]/([CO₂]+n[ ]) ratio in the culture media was found to be a controlling factor for photoautotrophic fatty acid production after the nitrate limitation. At a CO₂ concentration of 5% (vol/vol) and a pH of 6.7, the fatty acid content was 47.8 wt % (dry basis) at its maximum that is comparable with land plant seed oils. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1053–1057, 2015     

Optimization of growth and fatty acid composition of a unicellular marine picoplankton,Nannochloropsis sp., with enriched carbon sources

A unicellular marine picoplankton, Nannochloropsis sp., was grown under CO₂-enriched photoautotrophic or/and acetate-added mixotrophic conditions. Photoautotrophic conditions with enriched CO₂ of 2800 l CO₂ l^–1 and aeration gave the highest biomass yield (634 mg dry wt l^–1), the highest total lipid content (9% of dry wt), total fatty acids (64 mg g^–1 dry wt), polyunsaturated fatty acids (35% total fatty acids) and eicosapentaenoic acid (EPA, 20:53) (16 mg g^–1 dry wt or 25% of total fatty acids). Mixotrophic cultures gave a greater protein content but less carbohydrates. Adding sodium acetate (2 mM) decreased the amounts of the total fatty acids and EPA. Elevation of CO₂ in photoautotrophic culture thus enhances growth and raises the production of EPA in Nannochloropsis sp.     

Effect of different CO2 concentrations on biomass,pigment content,and lipid production of the marine diatom Thalassiosira pseudonana

The marine diatom Thalassiosira pseudonana grown under air (0.04% CO₂) and 1 and 5% CO₂ concentrations was evaluated to determine its potential for CO₂ mitigation coupled with biodiesel production. Results indicated that the diatom cultures grown at 1 and 5% CO₂ showed higher growth rates (1.14 and 1.29 div day⁻¹, respectively) and biomass productivities (44 and 48 mg_AFDWL⁻¹ day⁻¹) than air grown cultures (with 1.13 div day⁻¹ and 26 mg_AFDWL⁻¹ day⁻¹). The increase of CO₂ resulted in higher cell volume and pigment content per cell of T. pseudonana. Interestingly, lipid content doubled when air was enriched with 1–5% CO₂. Moreover, the analysis of the fatty acid composition of T. pseudonana revealed the predominance of monounsaturated acids (palmitoleic-16:1 and oleic-18:1) and a decrease of the saturated myristic acid-14:0 and polyunsaturated fatty acids under high CO₂ levels. These results suggested that T. pseudonana seems to be an ideal candidate for biodiesel production using flue gases.

     

Chlorella vulgaris as a lipid source: Cultivation on air and seawater‐simulating medium in a helicoidal photobioreactor

The freshwater microalga Chlorella vulgaris was cultured batchwise on the seawater‐simulating Schlösser medium either in a 1.1‐L‐working volume helicoidal photobioreactor (HeP) or Erlenmeyer flask (EF) as control and continuously supplying air as CO₂ source. In these systems, maximum biomass concentration reached 1.65 ± 0.17 g L^?1 and 1.25 ± 0.06 g L^?1, and maximum cell productivity 197.6 ± 20.4 mg L^?1 day^?1 and 160.8 ± 12.2 mg L^?1 day^?1, respectively. Compared to the Bold's Basal medium, commonly employed to cultivate this microorganism on a bench‐scale, the Schlösser medium ensured significant increases in all the growth parameters, namely maximum cell concentration (268% in EF and 126% in HeP), maximum biomass productivity (554% in EF and 72% in HeP), average specific growth rate (67% in EF and 42% in HeP), and maximum specific growth rate (233% in EF and 22% in HeP). The lipid fraction of biomass collected at the end of runs was analyzed in terms of both lipid content and fatty acid profile. It was found that the seawater‐simulating medium, despite of a 56–63% reduction of the overall biomass lipid content compared to the Bold's Basal one, led in HeP to significant increases in both the glycerides‐to‐total lipid ratio and polyunsaturated fatty acid content compared to the other conditions taken as an average. These results as a whole suggest that the HeP configuration could be a successful alternative to the present means to cultivate C. vulgaris as a lipid source. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:279–284, 2016     

CO2 utilization in the production of biomass and biocompounds by three different microalgae

The atmospheric CO₂ increase is considered the main cause of global warming. Microalgae are photosynthetic microorganisms that can help in CO₂ mitigation and at the same time produce value‐added compounds. In this study, Scenedesmus obliquus , Chlorella vulgaris , and Chlorella protothecoides were cultivated under 0.035 (air), 5 and 10% (v/v) of CO₂ concentrations in air to evaluate the performance of the microalgae in terms of kinetic growth parameters, theoretical CO₂ biofixation rate, and biomass composition. Among the microalgae studied, S. obliquus presented the highest values of specific growth rate (μ = 1.28 d^?1), maximum productivities (P _max = 0.28 g L^?1d^?1), and theoretical CO₂ biofixation rates (0.56 g L^?1d^?1) at 10% CO₂. The highest oil content was found at 5% CO₂, and the fatty acid profile was not influenced by the concentration of CO₂ in the inflow gas mixture and was in compliance with EN 14214, being suitable for biodiesel purposes. The impact of the CO₂ on S. obliquus cells’ viability/cell membrane integrity evaluated by the in‐line flow cytometry is quite innovative and fast, and revealed that 86.4% of the cells were damaged/permeabilized in cultures without the addition of CO₂.     

Heterotrophic production of Chlorella sp. TISTR 8990—biomass growth and composition under various production conditions

The green microalga Chlorella sp. TISTR 8990 was grown heterotrophically in the dark using various concentrations of a basal glucose medium with a carbon‐to‐nitrogen mass ratio of 29:1. The final biomass concentration and the rate of growth were highest in the fivefold concentrated basal glucose medium (25 g L^?1 glucose, 2.5 g L^?1 KNO₃) in batch operations. Improving oxygen transfer in the culture by increasing the agitation rate and decreasing the culture volume in 500‐mL shake flasks improved growth and glucose utilization. A maximum biomass concentration of nearly 12 g L^?1 was obtained within 4 days at 300 rpm, 30°C, with a glucose utilization of nearly 76% in batch culture. The total fatty acid (TFA) content of the biomass and the TFA productivity were 102 mg g^?1 and 305 mg L^?1 day^?1, respectively. A repeated fed‐batch culture with four cycles of feeding with the fivefold concentrated medium in a 3‐L bioreactor was evaluated for biomass production. The total culture period was 11 days. A maximum biomass concentration of nearly 26 g L^?1 was obtained with a TFA productivity of 223 mg L^?1 day^?1. The final biomass contained (w/w) 13.5% lipids, 20.8% protein and 17.2% starch. Of the fatty acids produced, 52% (w/w) were saturated, 41% were monounsaturated and 7% were polyunsaturated (PUFA). A low content of PUFA in TFA feedstock is required for producing high quality biodiesel. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1589–1600, 2017     

Biological CO<Subscript>2</Subscript> fixation using C<Emphasis Type="Italic">hlorella vulgaris</Emphasis> and its thermal characteristics through thermogravimetric analysis

The present research is focused on cultivation of microalgae strain Chlorella vulgaris for bio-fixation of CO₂ coupled with biomass production. In this regard, a single semi-batch vertical tubular photobioreactor and four similar photobioreactors in series have been employed. The concentration of CO₂ in the feed stream was varied from 2 to 12 % (v/v) by adjusting CO₂ to air ratio. The amount of CO₂ capture and algae growth were monitored by measuring decrease of CO₂ concentration in the gas phase, microalgal cell density, and algal biomass production rate. The results show that 4 % CO₂ gives maximum amount of biomass (0.9 g L^?1) and productivity (0.118 g L^?1 day^?1) of C. vulgaris in a single reactor. In series reactors, average productivity per reactor found to be 0.078 g L^?1 day^?1. The maximum CO₂ uptake for single reactor also found with 4 % CO_2, and it is around 0.2 g L^?1 day^?1. In series reactors, average CO₂ uptake is 0.13 g L^?1 day^?1 per reactor. TOC analysis shows that the carbon content of the produced biomass is around 40.67 % of total weight. The thermochemical characteristics of the cultivated C. vulgaris samples were analyzed in the presence of air. All samples burn above 200 °C and the combustion rate become faster at around 600 °C. Almost 98 wt% of the produced biomass is combustible in this range.     

Exploring the capabilities of fluorometric online monitoring on chinese hamster ovary cell cultivations producing a monoclonal antibody

Online monitoring of Chinese hamster ovary fed‐batch cell cultures via two‐dimensional fluorescence spectroscopy (2DFS) was evaluated in this work. Particular attention was directed toward different process strategies regarding the use of nutrient‐rich feed media and temperature shifts. These intentionally performed process manipulations broadened the variances in the obtained fluorescence spectra and this was suspected to hamper the generation of reliable soft sensors. Principal component analysis of the obtained fluorescence data showed that temperature shift and feeding strategy had a considerable impact on the fluorescence signals. Partial least square regression models were calculated for the prediction of glucose, lactate, monoclonal antibody (mAb), and viable cell concentrations (VCC). It was aimed to integrate all 2DFS datasets in the respective calibration models regardless of the process‐strategy‐dependent diversity. Contrary to the expectations, it was feasible to calibrate soft sensors for the online prediction of glucose (7 latent variables (LVs), = 0.97, rout mean squared error of prediction (RMSEP) = 1.1 g L^?1), lactate (5 LV; = 0.96; RMSEP = 0.5 g L^?1) and mAb concentrations (4 LV; = 0.99; RMSEP = 11.4 mg L^?1). Feeding and temperature shifts had the highest impact on the VCC model (3 LV; = 0.94; RMSEP 3.8 × 10⁵ mL^?1), nevertheless the prediction of VCC from the fed‐batch 2DFS data was feasible. The results strongly indicate that variances in the datasets due to the process strategy can be tolerated to some extent by the respective soft sensors. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1592–1600, 2016     

Effect of daytime CO2 supplement on productivity and biochemical composition of Scenedesmus armatus under outdoor cultivation

The cultivation of Scenedesmus armatus was carried out under outdoor Thailand climate conditions. The highest actual growth rate occurred at around 9:00 a.m. to 3:00 p.m., with a wide pH range of 6.4 to 11. The supply of CO₂ had slight influence on growth characteristics but did exert some observable effects on nutritional accumulations. Adding CO₂ from 2 to 15% by volume in the aeration (0.2 vvm) caused an increase in lipid and protein from 19.8 to 25.6 and 37.8 to 48.2% w/w, respectively, whereas carbohydrate decreased from 42.5 to 26.2% w/w. Scenedesmus armatus cultivated with 2% CO₂-enriched air provided the highest the average of the average biomass productivity of 91.25 mg L^?1 d^?1, which corresponded to a CO₂ fixation of 165 mg CO₂ L^?1 d^?1 with the average lipid, protein, and carbohydrate productivities of 22.24, 38.34, and 30.67 mg L^?1 d^?1.     

Effect of initial bacteria concentration on hydrogen gas production from cheese whey powder solution by thermophilic dark fermentation

Dark fermentative hydrogen gas production from cheese whey powder solution was realized at 55°C. Experiments were performed at different initial biomass concentrations varying between 0.48 and 2.86 g L^?1 with a constant initial substrate concentration of 26 ± 2 g total sugar (TS) per liter. The highest cumulative hydrogen evolution (633 mL, 30°C), hydrogen yield (1.56 mol H₂ mol^?1 glucose), and H₂ formation rate (3.45 mL h^?1) were obtained with 1.92 g L^?1 biomass concentration. The specific H₂ production rate decreased with increasing biomasss concentration from the highest value (47.7 mL g^?1 h^?1) at 0.48 g L^?1 biomass concentration. Total volatile fatty acid concentration varied beetween 10 and 14 g L^?1 with the highest level of 14.2 g L^?1 at biomass concentration of 0.48 g L^?1 and initial TS content of 28.4 g L^?1. The experimental data were correlated with the Gompertz equation and the constants were determined. The most suitable initial biomass to substrate ratio yielding the highest H₂ yield and formation rate was 0.082 g biomass per gram of TS. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 28: 931–936, 2012     

Identification,biochemical composition and phycobiliproteins production of Chroococcidiopsis sp. from arid environment

Molecular and microscopic studies were performed to identify Chroococcidiopsis sp., an endolithic cyanobacterium, isolated from gypsum rocks of Atacama Desert (Chile). It was adapted to grow in mineral liquid medium, with 9 mM nitrate, bubbled with CO₂-enriched air (2.5 % v/v), and continuously illuminated with a white light of 70 μmol photons m^–2 s^–1. The obtained biomass (productivity of 0.21 g L^–1 d^–1) had a C/N ratio of 6.67, and it contained carbohydrates (45.40 % of dry weight), proteins (36.72 %), lipids (5.60 %) nucleic acids (3.90 %) and ashes (8.28 %). The lipid fraction was particularly rich in palmitic (29.86 % of total fatty acids), linoleic (18.20 %), palmitoleic (12.75 %), linolenic (10.92 %), stearic (9.64 %) and capric acid (6.29 %). Chroococcidiopsis sp. accumulated phycobiliproteins in a light-dependent process and produced 204 mg g^–1, under incident light of 10 μmol photons·m^–2·s^–1, with a relative abundance of 40.9 % for phycocyanin, 23.3 % for phycoerythrin, and 35.8 % for allophycocyanin. The biomass from this cyanobacterium can be a good source of these pigments, especially APC (maximum of 95 mg g dw⁻¹), which are of interest for pharmacological, cosmetic, and food industries.     

Improvement of both lipid and biomass productivities of Qatar Chlorocystis isolate for biodiesel production and food security

Microalgae are considered a very promising alternative for biofuel production. Several strategies were developed to modulate and improve algae metabolites production to meet the requirements for biodiesel production. Most previous research evidenced that the increase of the lipid content is accompanied by a decrease of the biomass production, which increases the cost of the downstream processing. Hence, the challenge is to find special culture conditions that increase the lipid and the biomass productivities simultaneously. In the present work, we developed a strategy for the improvement of biomass and lipid productivities in a novel local microalga isolate, Chlorocystis sp. QUCCCM14, which was not previously known as a promising strain. Indeed, culturing QUCCCM14 using f/2 medium with 10× NaH₂PO₄ (0.15 g L^?1 NaNO₃ and 5.6 mg L^?1 NaH₂PO₄) resulted in an improvement of 3.178 folds the lipid productivity reaching 56.121 mg L^?1 day^?1 and enhanced the biomass productivity reaching 141.363 mg L^?1 day^?1, simultaneously. Comparative analyses of the FAME profiles demonstrated that fed‐batch culture with phosphate or nitrate separately leads to a high production of the omega 3 fatty acids (Linolenic acid), whereas fed‐batch culture with phosphate and nitrate simultaneously increased the production of fatty acids suitable for biodiesel production.     

A practical approach in bioreactor scale‐up and process transfer using a combination of constant P/V and vvm as the criterion

Bioreactor scale‐up is a critical step in the production of therapeutic proteins such as monoclonal antibodies (MAbs). With the scale‐up criterion such as similar power input per volume or O₂ volumetric mass transfer coefficient ( ), adequate oxygen supply and cell growth can be largely achieved. However, CO₂ stripping in the growth phase is often inadequate. This could cascade down to increased base addition and osmolality, as well as residual lactate increase and compromised production and product quality. Here we describe a practical approach in bioreactor scale‐up and process transfer, where bioreactor information may be limited. We evaluated the sparger and (CO₂ volumetric mass transfer coefficient) from a range of bioreactor scales (3–2,000 L) with different spargers. Results demonstrated that for oxygen is not an issue when scaling from small‐scale to large‐scale bioreactors at the same gas flow rate per reactor volume (vvm). Results also showed that sparging CO₂ stripping, , is dominated by the gas throughput. As a result, a combination of a minimum constant vvm air or N₂ flow with a similar specific power was used as the general scale‐up criterion. An equation was developed to determine the minimum vvm required for removing CO₂ produced from cell respiration. We demonstrated the effectiveness of using such scale‐up criterion with five MAb projects exhibiting different cell growth and metabolic characteristics, scaled from 3 to 2,000 L bioreactors across four sites. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1146–1159, 2017     

Extracellular secretion of free fatty acids by the chrysophyte Ochromonas danica under photoautotrophic and mixotrophic growth

Recently, microalgae have gained a lot of attention because of their ability to produce fatty acids in their surrounding environments. The present paper describes the influence of organic carbon on the different fatty acid pools including esterified fatty acids, intracellular free fatty acids and extracellular free fatty acids in Ochromonas danica. It also throws light on the ability of O. danica to secrete free fatty acids in the growth medium under photoautotrophic and mixotrophic conditions. Biomass production of photoautotrophically grown O. danica was higher than that of mixotrophically grown, where a cellular biomass formation of 1.8 g L^?1 was observed under photoautotrophic condition which was about five folds higher than that under mixotrophic conditions. Contrary, the esterified fatty acid content reached up to 99 mg g^?1 CDW under photoautotrophic conditions at the late exponential phase, while during mixotrophic conditions a maximum of 212 mg g^?1 CDW was observed at the stationary phase. Furthermore, O. danica cells grown under mixotrophic conditions showed higher intracellular free fatty acid and extracellular free fatty acid contents (up to 51 and 20 mg g^?1 CDW, respectively) than cells grown under photoautotrophic conditions (up to 26 and 4 mg g^?1 CDW, respectively). The intra- and extracellular free fatty acids consisted of a high proportion of polyunsaturated fatty acids, mainly C18:2n?6, C18:3n?3 and C20:4n?6.     

Enzymatic synthesis of ethyl esters from waste oil using mixtures of lipases in a plug‐flow packed‐bed continuous reactor

This work describes the continuous synthesis of ethyl esters via enzymatic catalysis on a packed‐bed continuous reactor, using mixtures of immobilized lipases (combi‐lipases) of Candida antarctica (CALB), Thermomyces lanuginosus (TLL), and Rhizomucor miehei (RML). The influence of the addition of glass beads to the reactor bed, evaluation of the use of different solvents, and flow rate on reaction conditions was studied. All experiments were conducted using the best combination of lipases according to the fatty acid composition of the waste oil (combi‐lipase composition: 40% of TLL, 35% of CALB, and 25% of RML) and soybean oil (combi‐lipase composition: 22.5% of TLL, 50% of CALB, and 27.5% of RML). The best general reaction conditions were found to be using tert‐butanol as solvent, and the flow rate of 0.08 mL min^?1. The combi‐lipase reactors operating at steady state for over 30 days (720 h), kept conversion yields of ～50%, with average productivity of 1.94 g_{ethyl esters} h^?1, regardless of the type of oil in use. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:952–959, 2018     

Biotransformation of β‐hydroxypyruvate and glycolaldehyde to l‐erythrulose by Pichia pastoris strain GS115 overexpressing native transketolase

Transketolase is a proven biocatalytic tool for asymmetric carbon‐carbon bond formation, both as a purified enzyme and within bacterial whole‐cell biocatalysts. The performance of Pichia pastoris as a host for transketolase whole‐cell biocatalysis was investigated using a transketolase‐overexpressing strain to catalyze formation of l ‐erythrulose from β‐hydroxypyruvic acid and glycolaldehyde substrates. Pichia pastoris transketolase coding sequence from the locus PAS_chr1‐4_0150 was subcloned downstream of the methanol‐inducible AOX1 promoter in a plasmid for transformation of strain GS115, generating strain TK150. Whole and disrupted TK150 cells from shake flasks achieved 62% and 65% conversion, respectively, under optimal pH and methanol induction conditions. In a 300 μL reaction, TK150 samples from a 1L fed‐batch fermentation achieved a maximum l ‐erythrulose space time yield (STY) of 46.58 g L^?1 h^?1, specific activity of 155 U , product yield on substrate (Y_p/s) of 0.52 mol mol^?1 and product yield on catalyst (Y_p/x) of 2.23g . We have successfully exploited the rapid growth and high biomass characteristics of Pichia pastoris in whole cell biocatalysis. At high cell density, the engineered TK150 Pichia pastoris strain tolerated high concentrations of substrate and product to achieve high STY of the chiral sugar l ‐erythrulose. © 2017 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 34:99–106, 2018     

<Emphasis Type="Italic">Scenedesmus vacuolatus</Emphasis> cultures for possible combined laccase-like phenoloxidase activity and biodiesel production

A key aspect of the industrial development of microalgal production processes is the excessive cost of biomass production. A solution is a combination of biodiesel production and wastewater treatment. The microalga Scenedesmus has a high lipid content and a potential extracellular phenoloxidase activity, which could improve the phycoremediation of phenolic pollutants. In this work, the most suitable growth conditions to obtain this twofold aim were analyzed. First, different strains of Scenedesmus vacuolatus microalga were tested at different pH, salinity and CO₂ concentration in the gas phase. The two most promising strains were then cultivated in autotrophic and heterotrophic conditions, and were investigated in terms of efficient nitrogen removal, fatty acid profile and maximized extracellular phenoloxidase activity in the medium. The results showed two extreme conditions: (1) biomass productivity doubled when photobioreactors were sparged with 5% CO₂ supplemented air with respect to cultures sparged with air (the steady state values of strain 53 were 0.138 g L^?1 day^?1 in the presence of air, and 0.243 in the presence of CO₂ addition), and N-starvation under 5% CO₂enhanced the transesterified fraction of lipids (strain 53 FAME fraction in the presence of N-starvation was 33%, in the presence of nitrogen FAME fraction was 22%); (2) phenoloxidase activity was completely suppressed by presence of 5% CO₂ in the gas phase (strain 53 0.21 U mL^?1), indicating clear catabolite repression for the induction of this enzyme in the algal metabolism.     

The expression of the Cuphea palustris thioesterase CpFatB2 in Yarrowia lipolytica triggers oleic acid accumulation

The conversion of industrial by‐products into high‐value added compounds is a challenging issue. Crude glycerol, a by‐product of the biodiesel production chain, could represent an alternative carbon source for the cultivation of oleaginous yeasts. Here, we developed five minimal synthetic glycerol‐based media, with different C/N ratios, and we analyzed the production of biomass and fatty acids by Yarrowia lipolytica Po1g strain. We identified two media at the expense of which Y. lipolytica was able to accumulate ～5 g L^?1 of biomass and 0.8 g L^?1 of fatty acids (0.16 g of fatty acids per g of dry weight). These optimized media contained 0.5 g L^?1 of urea or ammonium sulfate and 20 g L^?1 of glycerol, and were devoid of yeast extract. Moreover, Y. lipolytica was engineered by inserting the FatB2 gene, coding for the CpFatB2 thioesterase from Cuphea palustris, in order to modify the fatty acid composition towards the accumulation of medium‐chain fatty acids. Contrary to the expected, the expression of the heterologous gene increased the production of oleic acid, and concomitantly decreased the level of saturated fatty acids. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 32:26–35, 2016     

Exploiting Synergistic Effect by Integrating Ruthenium–Copper Nanoparticles Highly Co‐Dispersed on Graphene as Efficient Air Cathodes for Li–CO2 Batteries

Li–CO₂ batteries are attractive electrical energy storage devices; however, they still suffer from unsatisfactory electrochemical performance, and the kinetics of CO₂ reduction and evolution reactions must be improved significantly. Herein, a composite of ruthenium–copper nanoparticles highly co‐dispersed on graphene (Ru–Cu–G) as efficient air cathodes for Li–CO₂ batteries is designed. The Li–CO₂ batteries with Ru–Cu–G cathodes exhibit ultra‐low overpotential and can be operated for 100 cycles with a fixed capacity of 1000 mAh g^?1 at 200 and 400 mA g^?1. The synergistic effect between Ru and Cu not only regulates the growth of discharge products, but also promotes CO₂ reduction and evolution reactions by changing the electron cloud density of the surface between Ru and Cu. This work may provide new directions and strategies for developing highly efficient air cathodes for Li–CO₂ batteries, or even practical Li–air batteries.     

Carbon dioxide and poultry waste utilization for production of polyhydroxyalkanoate biopolymers by <Emphasis Type="Italic">Nostoc muscorum</Emphasis> Agardh: a sustainable approach

The new paradigm is to view wastes as resources for sustainable development. In this regard, the feasibility of poultry waste and CO₂ utilization for cultivation of a filamentous nitrogen-fixing cyanobacterium, Nostoc muscorum Agardh, was investigated for production polyhydroxyalkanoates, the biodegradable polymers. This cyanobacterium showed profound rise in biomass yield with up to 10 % CO₂ supply in airstream with an aeration rate of 0.1 vvm. Maximum biomass yield of 1.12 g L^?1 was recorded for 8 days incubation period, thus demonstrating a CO₂ biofixation rate of 0.263 g L^?1 day^?1 at 10 % (v/v) CO₂-enriched air. Poultry litter (PL) supplementation also had a positive impact on the biomass yield. The nutrient removal efficiency of N. muscorum was reflected in the significant reduction in nutrient load of PL over the experimental period. A maximum poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) [P(3HB-co-3HV)] copolymer yield of 774 mg L^?1 (65 % of dry cell wt.), the value almost 11-fold higher than the control, was recorded in 10 g L^?1 PL-supplemented cultures with 10 % CO₂ supply under the optimized condition, thus demonstrating that N. muscorum has good potential for CO₂ biomitigation and poultry waste remediation while simultaneously producing eco-friendly polymers.