Double CO2 fixation in photosynthesis–fermentation model enhances algal lipid synthesis for biodiesel production

Xiong, Wei; Gao, Chunfang; Dong, Yan; Wu, Chao; Wu, Qingyu

doi:10.1016/j.biortech.2009.11.041

Cited by 159 publications

(98 citation statements)

References 25 publications

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“…Consistent with the rapid accumulation of malate M3 isotopomer, malic enzyme channels 36% of the flux through phosphoenolpyruvate. The glyoxylate shunt (isocitrate lyase encoding gene Cpr004092.1 and malate synthase encoding gene Cpr001903.2) was included in our model while measured to be inactive in heterotrophic cells, which agrees with our previous study (Xiong et al, 2010a(Xiong et al, , 2010b. Another noteworthy result is the high use rate of acetyl-CoA for fatty acids in heterotrophically grown C. protothecoides, exhibiting 33-fold higher flux than that in autotrophic growth (Fig.…”

supporting

confidence: 81%

“…Higher accuracy could be further realized if more dynamic isotope labeling trajectories of central carbon metabolites can be included in the system, and the genomebased FBA model, thus, offered an open framework for improved flux estimate. We also exploit this model by fitting it with the steady-state 13 C labeling data generated in our previous work (Xiong et al, 2010a(Xiong et al, , 2010b. A noncompartmented and simplified model was used to investigate fluxes of heterotrophic cells, because no detailed genomic information was available at that time.…”

Section: Discussionmentioning

confidence: 99%

“…cells undergoing glucose bleaching, in which the growth is switched from photoautotrophic to heterotrophic mode and accompanied by chlorophyll degradation. This metabolic transition has been incorporated into a highly efficient biofuel production process (Xiong et al, 2010a), whereas many global changes in metabolism, such as degeneration of the chloroplast, redistribution of carbon flux, and reprogrammed nitrogen assimilation, remain poorly understood.…”

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confidence: 99%

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Genome-Based Metabolic Mapping and 13C Flux Analysis Reveal Systematic Properties of an Oleaginous Microalga Chlorella protothecoides

Xiong

Dai

et al. 2014

Plant Physiology

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Integrated and genome-based flux balance analysis, metabolomics, and 13 C-label profiling of phototrophic and heterotrophic metabolism in Chlorella protothecoides, an oleaginous green alga for biofuel. The green alga Chlorella protothecoides, capable of autotrophic and heterotrophic growth with rapid lipid synthesis, is a promising candidate for biofuel production. Based on the newly available genome knowledge of the alga, we reconstructed the compartmentalized metabolic network consisting of 272 metabolic reactions, 270 enzymes, and 461 encoding genes and simulated the growth in different cultivation conditions with flux balance analysis. Phenotype-phase plane analysis shows conditions achieving theoretical maximum of the biomass and corresponding fatty acid-producing rate for phototrophic cells (the ratio of photon uptake rate to CO 2 uptake rate equals 8.4) and heterotrophic ones (the glucose uptake rate to O 2 consumption rate reaches 2.4), respectively. Isotope-assisted liquid chromatography-mass spectrometry/mass spectrometry reveals higher metabolite concentrations in the glycolytic pathway and the tricarboxylic acid cycle in heterotrophic cells compared with autotrophic cells. We also observed enhanced levels of ATP, nicotinamide adenine dinucleotide (phosphate), reduced, acetyl-Coenzyme A, and malonyl-Coenzyme A in heterotrophic cells consistently, consistent with a strong activity of lipid synthesis. To profile the flux map in experimental conditions, we applied nonstationary 13 C metabolic flux analysis as a complementing strategy to flux balance analysis. The result reveals negligible photorespiratory fluxes and a metabolically low active tricarboxylic acid cycle in phototrophic C. protothecoides. In comparison, high throughput of amphibolic reactions and the tricarboxylic acid cycle with no glyoxylate shunt activities were measured for heterotrophic cells. Taken together, the metabolic network modeling assisted by experimental metabolomics and 13 C labeling better our understanding on global metabolism of oleaginous alga, paving the way to the systematic engineering of the microalga for biofuel production.

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confidence: 81%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Genome-Based Metabolic Mapping and 13C Flux Analysis Reveal Systematic Properties of an Oleaginous Microalga Chlorella protothecoides

Xiong

Dai

et al. 2014

Plant Physiology

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“…42,43 The conversion ratio of glucose to biomass (Y biomass/ glucose) was a vital indicator for heterotrophic or mixotrophic microalgal cultivation. 44 Normally, carbon accounts from 36% to 65% of the dry biomass, and the theoretical Y biomass/ glucose lies in the range of 0.62−1.08 when glucose is the sole carbon supplier. 45,46 As shown in Table 1, with the optimized process, a Y biomass/glucose of 1.77 was achieved, which is much higher than the theoretical value for heterotrophic cultivation, indicating that inorganic (CO 2 ) and organic (glucose) carbon are simultaneously assimilated in the mixtrophic mode, which in turn will significantly reduce the material cost for carbon.…”

Section: Discussionmentioning

confidence: 99%

Effective Biological DeNOx of Industrial Flue Gas by the Mixotrophic Cultivation of an Oil-Producing Green Alga Chlorella sp. C2

Chen

Zhang

Rong

et al. 2016

Environ. Sci. Technol.

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Nitrogen oxides (NOx) are the components of fossil flue gas that result in the most serious environmental concerns. We previously showed that the biological removal of NOx by microalgae appears superior to traditional treatments. This study optimizes the strategy for the microalgal-based DeNOx of flue gas by fed-batch mixotrophic cultivation. By using actual flue gas fixed salts (FGFS) as the nitrogen supply, the mixotrophical cultivation of the green alga Chlorella sp. C2 with high NOx absorption efficiency was optimized in a stepwise manner in a 5 L bioreactor and resulted in a maximum biomass productivity of 9.87 g L −1 d With an optimized mixotrophical cultivation, this study further proved the feasibility of using Chlorella for the combination of efficient biological DeNOx of flue gas and microalgae-based products production. Thus, this study shows a promising industrial strategy for flue gas biotreatment in plants with limited land area.

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“…In recent years, some oleaginous species are also found to be promising in the field of biofuels (Xiong et al 2010a). …”

Section: Introductionmentioning

confidence: 99%

Preparation of protoplasts from Chlorella protothecoides

Kong

2011

World J Microbiol Biotechnol

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This paper describes an enzymatic method for yielding protoplasts from the microalga Chlorella protothecoides. Four kinds of commercially available enzymes were tested. The enzymatic digestion was optimal with 2% cellulase R-10 and 1% snailase prepared in 25 mM Tris buffer (pH 6.0) containing 0.6 M D-mannitol, and the protoplast density could reach the peak after treatment at 30°C for 16 h. Nearly all liberated protoplasts were green in the presence of 0.01% phenosafranin, indicating their high viability. The regeneration rate was about 70% when 0.6 M D-mannitol was used as an osmotic stabilizer in the regeneration medium. This protocol will find useful applications in genetic studies of this algal species.

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Double CO2 fixation in photosynthesis–fermentation model enhances algal lipid synthesis for biodiesel production

Cited by 159 publications

References 25 publications

Genome-Based Metabolic Mapping and 13C Flux Analysis Reveal Systematic Properties of an Oleaginous Microalga Chlorella protothecoides

Genome-Based Metabolic Mapping and 13C Flux Analysis Reveal Systematic Properties of an Oleaginous Microalga Chlorella protothecoides

Effective Biological DeNOx of Industrial Flue Gas by the Mixotrophic Cultivation of an Oil-Producing Green Alga Chlorella sp. C2

Preparation of protoplasts from Chlorella protothecoides

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