Exogenous NaHCO3 enhances growth and lipid accumulation of the highly NaHCO3-tolerant Nannochloris sp. JB17

Abstract

The extremely saline-alkaline soil in the northeast of China is rich in Na2CO3 and NaHCO3. Previously, we isolated the green alga Nannochloris sp. JB17 (JB17) from this soil and found that it was resistant to high concentrations of NaHCO3. In this study, the biochemical characteristics of JB17 cultured with NaHCO3 were studied by measuring growth and photosynthesis, and biomass, starch, and lipid production. The final cell density and maximum dry weight of JB17 cultured with 300 mM NaHCO3 were 1.528 and 1040.8 mg L−1, respectively, and were higher than those of JB17 cultured with 50 mM NaHCO3 (control). The maximum chlorophyll-a content and oxygen evolution rate under 300 mM NaHCO3 treatment were 26.5 mg g−1and 182 μmol O2 mg−1 Chl h−1, respectively, and were higher than those of the control. The addition of 300 mM NaHCO3 increased the relative electron transfer rate (rETR) and maximum relative electron transfer rate of JB17. The total starch and lipids contents of JB17 significantly increased from 215 to 356 mg g−1 and from 263 to 531 mg g−1, respectively, after the addition of 300 mM NaHCO3. Including NaHCO3 in the culture medium greatly stimulated the growth, biomass accumulation, and lipid productivity of JB17. These results indicate that the accumulation of starch and lipids in JB17 cultured with NaHCO3 might be related to the promotion of photosynthesis.