Use of phenol-induced oxidative stress acclimation to stimulate cell growth and biodiesel production by the oceanic microalga Dunaliella salina

There is steadily increasing interest in the use of microalgae as a source of biomass for biodiesel conversion and hydrocarbon based products. At the same time, microalgae have shown promise for the bioremediation of polluted water. This study evaluates the effect of prior phenol exposure on microalgal biomass production and quality of biodiesel yielded by the oceanic microalga Dunaliella salina. Phenol had an EC50 of 155.03 mg L-1 on algal growth and caused lowered chlorophyll a/b ratios and biomass yields. Phenol also increased malondialdehyde content and elevated superoxide dismutase enzyme activities indicative of phenol-induced oxidative stress. After prior exposure to phenol at 150 mg L-1 with subsequent transfer to culture without phenol, D. salina cells increased 41% faster and had 26% higher lipid content than were obtained from the control group that had no prior phenol exposure. Prior exposure to phenol altered fatty acid methyl ester compositions, increased levels of methyl linolenate (C18:3(n-3)) and gamma-linolenic acid methyl ester (C18:3(n-6)), decreased levels of cis-10-heptadecanoic acid methyl ester and methyl stearate (C18:0), and decreased cetane number, all in a concentration-dependent manner. The results suggested that the use of prior acclimation by toxic chemicals could potentially support efficient microalgal biomass production. (C) 2016 Elsevier B.V. All rights reserved.