Continual production of glycerol from carbon dioxide by Dunaliella tertiolecta

Chow, Yvonne; Goh, Serena J.M.; Su, Ziheng; Ng, Daphne H.P.; Lim, Chan Yuen; Lim, Natalie Y.N.; Lin, Huixin; Fang, Lei; Lee, Yuan Kun

doi:10.1016/j.biortech.2013.03.040

Cited by 29 publications

(29 citation statements)

References 23 publications

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“…2e). This is consistent with findings in current literature implicating the continued release of glycerol by D. tertiolecta into the culture medium3536. The amount of extracellular glycerol produced was able to reach higher quantities as it is not restricted by cell volume, enabling it to deliver microgram levels per cell not achievable with intracellular glycerol, starch or lipids.…”

Section: Resultssupporting

confidence: 91%

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Nitrogen-induced metabolic changes and molecular determinants of carbon allocation in Dunaliella tertiolecta

Tan

Lin

Shen

et al. 2016

Sci Rep

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Certain species of microalgae are natural accumulators of lipids, while others are more inclined to store starch. However, what governs the preference to store lipids or starch is not well understood. In this study, the microalga Dunaliella tertiolecta was used as a model to study the global gene expression profile regulating starch accumulation in microalgae. D. tertiolecta, when depleted of nitrogen, produced only 1% of dry cell weight (DCW) in neutral lipids, while starch was rapidly accumulated up to 46% DCW. The increased in starch content was accompanied by a coordinated overexpression of genes shunting carbon towards starch synthesis, a response not seen in the oleaginous microalgae Nannochloropsis oceanica, Chlamydomonas reinhardtii or Chlorella vulgaris. Genes in the central carbon metabolism pathways, particularly those of the tricarboxylic acid cycle, were also simultaneously upregulated, indicating a robust interchange of carbon skeletons for anabolic and catabolic processes. In contrast, fatty acid and triacylglycerol synthesis genes were downregulated or unchanged, suggesting that lipids are not a preferred form of storage in these cells. This study reveals the transcriptomic influence behind storage reserve allocation in D. tertiolecta and provides valuable insights into the possible manipulation of genes for engineering microorganisms to synthesize products of interest.

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Section: Resultssupporting

confidence: 91%

“…Glycerol content was measured using the Free Glycerol Determination Kit (FG0100; Sigma-Aldrich) as previously reported by Chow et al 35. Harvested cells were centrifuged (10,000 g for 10 mins, 4 °C) and the cell pellet and supernatant were separated for measurement of intracellular and extracellular glycerol respectively.…”

Section: Methodsmentioning

confidence: 99%

Nitrogen-induced metabolic changes and molecular determinants of carbon allocation in Dunaliella tertiolecta

Tan

Lin

Shen

et al. 2016

Sci Rep

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“…Cells of D. tertiolecta for instance have been reported to have a specific transport protein for taking up exogenous glycerol [37] or excreting it [38]. Nevertheless Chow, et al [38] recently described the continuous extraction Applied centrifugal forces of 10000 g were used for 20 min in a bench-top centrifuge to harvest D. tertiolecta cells and most of the glycerol was found in the supernatant rather than in the harvested cell pellets. This would be as anticipated based on the results presented here.…”

Section: Resultsmentioning

confidence: 99%

Effects of centrifugal stress on cell disruption and glycerol leakage from Dunaliella salina

Milledge

Abubakar

et al. 2015

Microalgae Biotechnology

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Dunaliella salina accumulates large amounts of intracellular glycerol in response to the increases in salt concentration, thus is a potential source for producing fuel grade glycerol as an alternative to biodiesel-derived crude glycerol. D. salina lacks a cell wall; therefore the mode of harvesting Dunaliella cells is critical to avoid cell disruption caused by extreme engineering conditions. This study explored cell disruption and glycerol leakage of D. salina under various centrifugal stresses during cell harvesting. Results show a centrifugal g-force lower than 5000 g caused little cell disruption, while a g-force higher than 9000 g led to ~40% loss of the intact cells and glycerol yields from the recovered algal pellets. Theoretical calculations of the centrifugal stresses that could rupture Dunaliella cells were in agreement with the experimental results, indicating optimisation of centrifugation conditions is important for recovering intact cells of D. salina enriched in glycerol.

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“…Hence, the extracellular glycerol accumulated is equivalent to 55% of dry cell biomass weight. This continues to accumulate with time and is several times higher than the average intracellular glycerol content (2.5 × 10 −8 mg cell −1 ) which amounts to 14% of dry cell biomass weight (Chow et al, ).…”

Section: Resultsmentioning

confidence: 99%

“…While previously thought to be maintained intracellularly, it is also continually released by D . tertiolecta cells (Chow et al, ). The rate of production of extracellular glycerol depends linearly on cell density, unaffected by cell shading at least up to 2 × 10 7 cells mL −1 (Fig.…”

Section: Discussionmentioning

confidence: 99%

The role of micronutrients and strategies for optimized continual glycerol production from carbon dioxide by Dunaliella tertiolecta

Chow

Wang

et al. 2015

Biotech & Bioengineering

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The microalga Dunaliella tertiolecta synthesizes intracellular glycerol as an osmoticum to counteract external osmotic pressure in high saline environments. The species has recently been found to release and accumulate extracellular glycerol, making it a suitable candidate for sustainable industrial glycerol production if a sufficiently high product titre yield can be achieved. While macronutrients such as nitrogen and phosphorus are essential and well understood, this study seeks to understand the influence of the micronutrient profile on glycerol production. The effects of metallic elements calcium, magnesium, manganese, zinc, cobalt, copper, and iron, as well as boron, on glycerol production as well as cell growth were quantified. The relationship between cell density and glycerol productivity was also determined. Statistically, manganese recorded the highest improvement in glycerol production as well as cell growth. Further experiments showed that manganese availability was associated with higher superoxide dismutase formation, thus suggesting that glycerol production is negatively affected by oxidative stress and the manganese bound form of this enzyme is required in order to counteract reactive oxygen species in the cells. A minimum concentration of 8.25 × 10(-5) g L(-1) manganese was sufficient to overcome this problem and achieve 10 g L(-1) extracellular glycerol, compared to 4 g L(-1) without the addition of manganese. Unlike cell growth, extracellular glycerol production was found to be negatively affected by the amount of calcium present in the normal growth medium, most likely due to the lower cell permeability at high calcium concentrations. The inhibitory effects of iron also affected extracellular glycerol production more significantly than cell growth and several antagonistic interaction effects between various micronutrients were observed. This study indicates how the optimization of these small amounts of nutrients in a two-stage system can lead to a large enhancement in D. tertiolecta glycerol production and should be considered during the design of a large scale bioprocess for this alternative route to glycerol.

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Continual production of glycerol from carbon dioxide by Dunaliella tertiolecta

Cited by 29 publications

References 23 publications

Nitrogen-induced metabolic changes and molecular determinants of carbon allocation in Dunaliella tertiolecta

Nitrogen-induced metabolic changes and molecular determinants of carbon allocation in Dunaliella tertiolecta

Effects of centrifugal stress on cell disruption and glycerol leakage from Dunaliella salina

The role of micronutrients and strategies for optimized continual glycerol production from carbon dioxide by Dunaliella tertiolecta

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