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Fremyella diplosiphon is an ideal third-generation biofuel source due to its ability to produce transesterified lipids. While nanofer 25s zero-valent iron nanoparticles (nZVIs) improve lipid production, an imbalance between reactive oxygen species (ROS) and cellular defense can be catastrophic to the organism. In the present study, the effect of ascorbic acid on nZVI and UV-induced stress in F. diplosiphon strain B481-SD was investigated, and lipid profiles in the combination regimen of nZVIs and ascorbic acid compared. Comparison of F. diplosiphon growth in BG11 media amended with 2, 4, 6, 8, and 10 mM ascorbic acid indicated 6 mM to be optimal for the growth of B481-SD. Further, growth in 6 mM ascorbic acid combined with 3.2 mg/L nZVIs was significantly higher when compared to the combination regimen of 12.8 and 51.2 mg/L of nZVIs and 6 mM ascorbic acid. The reversal effect of UV-B radiation for 30 min and 1 h indicated that ascorbic acid restored B481-SD growth. Transesterified lipids characterized by gas chromatography–mass spectrometry indicated C16 hexadecanoate to be the most abundant fatty acid methyl ester in the combination regimen of 6 mM ascorbic acid and 12.8 mg/L nZVI-treated F. diplosiphon. These findings were supported by microscopic observations in which cellular degradation was observed in B481-SD cells treated with 6 mM ascorbic acid and 12.8 mg/L nZVIs. Our results indicate that ascorbic acid counteracts the damaging effect of oxidative stress produced by nZVIs.
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Nitrogen Deprivation in Fremyella diplosiphon Augments Lipid Production without Affecting Growth
Metabolic products such as lipids and proteins produced in cyanobacteria represent an excellent source of biomass and do not compete with agricultural land use unlike soybean and corn. Given their potential use as novel materials for biodiesel production, we aimed to explore the e ect of cultivation period and nitrogen concentration on the growth rate and lipid content of Fremyella diplosiphon, a model cyanobacterium. In this study, F. diplosiphon grown in BG11/HEPES medium supplemented with 1.5 g L1 sodium nitrate (NaNO3) for 7, 10, 15, and 20 days were compared to the untreated control in media amended with 0.25, 0.5, and 1.0 g L1 NaNO3. Cultures were inoculated in liquid media and grown under continuous fluorescent light in an orbital incubator shaker, and extracted lipids subjected to gravimetric analysis and gas chromatography-mass spectroscopy to determine the best culture conditions for lipid production. Our results demonstrated that a reduction in nitrogen concentration had no significant effect on the growth rate across all cultivation periods; however, the accumulation of total lipid content was significantly influenced by nitrogen concentration. A maximum lipid production (40%) with no reduction in growth was observed in 10-day old cultures in a BG11/HEPES medium supplemented with 1.0 g L1 NaNO3. Fatty acid methyl ester composition of transesterified lipids demonstrated high amounts of methyl palmitate (50–70%) followed by methyl octadecenoate (17–30%) in the accumulated lipids at all treatments. Trace quantities of methyl dodecanoate, methyl hexadecanoate, methyl octadecanoate, and methyl octadecadienoate (1–8%) were also observed in all tested samples, indicating that nitrogen deprivation in culture media increases lipid production without affecting growth.
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- Award ID(s):
- 1900966
- PAR ID:
- 10248770
- Date Published:
- Journal Name:
- Energies
- ISSN:
- 1996-1073
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/en13215769
