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Potential of lipid metabolism in marine diatoms for biofuel production.

d'Ippolito G, Sardo A, Paris D, Vella FM, Adelfi MG, Botte P, Gallo C, Fontana A - Biotechnol Biofuels (2015)

Bottom Line: The effect was less pronounced in cultures where silicon was reduced to 20% of the standard supply.Nitrogen limitation did not affect growth rates but led to lipid remodeling and de novo synthesis of triacylglycerols.Triacylglycerols in T. weissflogii and C. cryptica can account for up to 82% and 88% of total glycerolipids, thereby suggesting that the two species are promising candidates for large-scale experimentation for biofuel production.

View Article: PubMed Central - PubMed

Affiliation: Istituto di Chimica Biomolecolare (ICB) - CNR, Via Campi Flegrei 34, 80078 Pozzuoli, NA Italy.

ABSTRACT

Background: Diatoms are an ecologically relevant group of microalgae that are not commonly considered for bio-oil production even if they are responsible for massive blooms at sea. Seventeen diatom species were screened for their capacity to produce biomass and lipids, in relation to their growth rate. Triglyceride levels were also assessed as a preferential source of biofuels.

Results: Using statistical analysis, two centric diatoms, Thalassiosira weissflogii and Cyclotella cryptica, were selected as good candidates for oil production. Lipid levels significantly increased when the two diatoms were cultivated in a two-stage process under nitrogen limitation. The effect was less pronounced in cultures where silicon was reduced to 20% of the standard supply. Nitrogen limitation did not affect growth rates but led to lipid remodeling and de novo synthesis of triacylglycerols.

Conclusions: Triacylglycerols in T. weissflogii and C. cryptica can account for up to 82% and 88% of total glycerolipids, thereby suggesting that the two species are promising candidates for large-scale experimentation for biofuel production.

No MeSH data available.


Effect of nutrient depletion on biomass and lipid production in the centric diatoms T. weissoflogii (white) and C. cryptica (gray). t0 = starting point of limitation experiments; Rp = replete conditions; −N = nitrogen limitation (20% of standard concentration in f/2 medium); −Si = silicon limitation (20% of standard concentration in f/2 medium).
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Fig3: Effect of nutrient depletion on biomass and lipid production in the centric diatoms T. weissoflogii (white) and C. cryptica (gray). t0 = starting point of limitation experiments; Rp = replete conditions; −N = nitrogen limitation (20% of standard concentration in f/2 medium); −Si = silicon limitation (20% of standard concentration in f/2 medium).

Mentions: Simple refreshment with nutrient-replete media (Rp culture) strongly boosted biomass productivity that doubled in the case of T. weissflogii and quadrupled in C. cryptica (Figure 3). On the other hand, replacement with both replete and depleted-nutrient media induced a general reduction in the percentage of total lipids in the biomass of T. weissflogii even if absolute productivity increased due to biomass accumulation. In comparison with Rp conditions, nitrogen and silicon limitation did not cause significant changes in growth probably because cultures were already partially nutrient limited when they entered into the stationary phase. Under the tested growth conditions, only C. cryptica showed a slight increase in biomass in N-limited conditions but this effect did not result in a similar increase in lipids. Surprisingly, these results were not consistent with previous reports that showed a boost in lipid production of diatoms when silicon was limited compared to nitrogen limitation [14]. In fact, silicon is not directly coupled to cellular metabolism of diatoms [34,35], but its depletion leads to arrest of cell division and consequent accumulation of organic carbon, mostly in the form of TAG [36,37]. Nevertheless, the response is not general. To the best of our knowledge, the effects of nutrient modulation on lipid metabolism in T. weissflogii have been never reported even if heterogeneity in neutral lipid accumulation over time and within individual cells of C. cryptica under silicon or nitrogen limitation has been recently described [14,28]. In line with this study, Jeffryes and co-workers have also underlined the importance of tuning silicon delivery in order to improve lipid productivity and to maintain a basal concentration that is necessary to maintain physiological activity of the cells [30].Figure 3


Potential of lipid metabolism in marine diatoms for biofuel production.

d'Ippolito G, Sardo A, Paris D, Vella FM, Adelfi MG, Botte P, Gallo C, Fontana A - Biotechnol Biofuels (2015)

Effect of nutrient depletion on biomass and lipid production in the centric diatoms T. weissoflogii (white) and C. cryptica (gray). t0 = starting point of limitation experiments; Rp = replete conditions; −N = nitrogen limitation (20% of standard concentration in f/2 medium); −Si = silicon limitation (20% of standard concentration in f/2 medium).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
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getmorefigures.php?uid=PMC4355990&req=5

Fig3: Effect of nutrient depletion on biomass and lipid production in the centric diatoms T. weissoflogii (white) and C. cryptica (gray). t0 = starting point of limitation experiments; Rp = replete conditions; −N = nitrogen limitation (20% of standard concentration in f/2 medium); −Si = silicon limitation (20% of standard concentration in f/2 medium).
Mentions: Simple refreshment with nutrient-replete media (Rp culture) strongly boosted biomass productivity that doubled in the case of T. weissflogii and quadrupled in C. cryptica (Figure 3). On the other hand, replacement with both replete and depleted-nutrient media induced a general reduction in the percentage of total lipids in the biomass of T. weissflogii even if absolute productivity increased due to biomass accumulation. In comparison with Rp conditions, nitrogen and silicon limitation did not cause significant changes in growth probably because cultures were already partially nutrient limited when they entered into the stationary phase. Under the tested growth conditions, only C. cryptica showed a slight increase in biomass in N-limited conditions but this effect did not result in a similar increase in lipids. Surprisingly, these results were not consistent with previous reports that showed a boost in lipid production of diatoms when silicon was limited compared to nitrogen limitation [14]. In fact, silicon is not directly coupled to cellular metabolism of diatoms [34,35], but its depletion leads to arrest of cell division and consequent accumulation of organic carbon, mostly in the form of TAG [36,37]. Nevertheless, the response is not general. To the best of our knowledge, the effects of nutrient modulation on lipid metabolism in T. weissflogii have been never reported even if heterogeneity in neutral lipid accumulation over time and within individual cells of C. cryptica under silicon or nitrogen limitation has been recently described [14,28]. In line with this study, Jeffryes and co-workers have also underlined the importance of tuning silicon delivery in order to improve lipid productivity and to maintain a basal concentration that is necessary to maintain physiological activity of the cells [30].Figure 3

Bottom Line: The effect was less pronounced in cultures where silicon was reduced to 20% of the standard supply.Nitrogen limitation did not affect growth rates but led to lipid remodeling and de novo synthesis of triacylglycerols.Triacylglycerols in T. weissflogii and C. cryptica can account for up to 82% and 88% of total glycerolipids, thereby suggesting that the two species are promising candidates for large-scale experimentation for biofuel production.

View Article: PubMed Central - PubMed

Affiliation: Istituto di Chimica Biomolecolare (ICB) - CNR, Via Campi Flegrei 34, 80078 Pozzuoli, NA Italy.

ABSTRACT

Background: Diatoms are an ecologically relevant group of microalgae that are not commonly considered for bio-oil production even if they are responsible for massive blooms at sea. Seventeen diatom species were screened for their capacity to produce biomass and lipids, in relation to their growth rate. Triglyceride levels were also assessed as a preferential source of biofuels.

Results: Using statistical analysis, two centric diatoms, Thalassiosira weissflogii and Cyclotella cryptica, were selected as good candidates for oil production. Lipid levels significantly increased when the two diatoms were cultivated in a two-stage process under nitrogen limitation. The effect was less pronounced in cultures where silicon was reduced to 20% of the standard supply. Nitrogen limitation did not affect growth rates but led to lipid remodeling and de novo synthesis of triacylglycerols.

Conclusions: Triacylglycerols in T. weissflogii and C. cryptica can account for up to 82% and 88% of total glycerolipids, thereby suggesting that the two species are promising candidates for large-scale experimentation for biofuel production.

No MeSH data available.