Figure 8

Effect of initial pH on the inhibition of organic acids. All organic acids were tested at their respective molar concentrations of the tested organic acids that caused 50% inhibition of the lipid yield. Cultures with 5% inoculum size were incubated at 25°C and 160 rpm for 7 days. Results are expressed relative to controls without organic acids. Biomass, lipid content and lipid yield of cultures lacking organic acids at pH 5.5, pH 6.5 and pH 7.5 were, respectively, 18.4 g/L, 57.2% and 10.5 g/L; 24.0 g/L, 61.7% and 14.8 g/L; and 21.5 g/L, 56.3% and 12.1 g/L. Ac, acetic acid; Fo, formic acid; Le, levulinic acid; Hy, 4-hydroxybenzoic acid; Fu, furoic acid; Ca, caproic acid; Ga, gallic acid; Fe, ferulic acid; Sy, syringic acid; Va, vanillic acid.