Optimized inorganic carbon regime for enhanced growth and lipid accumulation in Chlorella vulgaris

Table 1 C. vulgaris culture characteristics during nitrogen limited growth when supplemented with various bicarbonate salts

Treatment	Cell concentration (×10⁷ cells mL⁻¹)	Cell doublings^a	Dry weight (g L⁻¹; DCW)^b	Endpoint pH	Total chlorophyll (mg L⁻¹)	Total chlorophyll per cell (pg)	Dry weight per cell (ng)
0 mM HCO₃ ⁻	3.48 ± 0.17	2.47 ± 0.23	0.37 ± 0.03	8.08 ± 0.07	1.82 ± 0.08	0.052 ± 0.004	0.011 ± 0.001
50 mM ACS grade NaHCO₃	2.15 ± 0.17^*	1.35 ± 0.19^*	0.58 ± 0.06^**	9.82 ± 0.03^**	2.00 ± 0.34	0.093 ± 0.011^**	0.027 ± 0.001^**
50 mM industrial grade NaHCO₃	1.78 ± 0.13^*	0.64 ± 0.40^*	0.60 ± 0.02^**	9.82 ± 0.06^**	1.72 ± 0.18	0.097 ± 0.016^**	0.034 ± 0.003^**
50 mM KHCO₃	1.56 ± 0.13^*	0.88 ± 0.27^*	0.54 ± 0.03^**	9.77 ± 0.03^**	2.01 ± 0.21	0.129 ± 0.013^**	0.035 ± 0.003^**
50 mM NH₄HCO₃	0.62 ± 0.04^*	−0.25 ± 0.47^*	0.15 ± 0.04^*	9.31 ± 0.05^**	0.31 ± 0.17^*	0.031 ± 0.014	0.016 ± 0.005
50 mM Na₂CO₃	1.21 ± 0.22^*	0.83 ± 0.15^*	0.35 ± 0.01	9.98 ± 0.02^**	1.37 ± 0.15^*	0.115 ± 0.024^**	0.029 ± 0.006^**
25 mM NaHCO₃∙Na₂CO₃	1.21 ± 0.16^*	0.38 ± 0.42^*	0.49 ± 0.04^**	9.83 ± 0.03^**	1.77 ± 0.22	0.149 ± 0.036^**	0.041 ± 0.008^**

Values are reported for the completion of the experiment (5.75 days) (n = 3)
^* p value <0.05 as determined by a two-tailed t test, statistically significantly lower [difference between treatment and control group (0 mM HCO₃ ⁻)]
^** p value <0.05 as determined by a two-tailed t test, statistically significantly higher [difference between treatment and control group (0 mM HCO₃ ⁻)]
^aCell doublings are calculated as n = log₂(C_f/C_i); where n is the number of cell doublings and C _f and C _i are final and initial cell concentrations, respectively
^bDry cell weight (DCW) determined gravimetrically with lyophilized biomass

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