A laboratory study of producing docosahexaenoic acid from biodiesel-wasteglycerol by microalgal fermentation

Crude glycerol is the primary by-product in the biodiesel industry, whichis too costly to be purified into to higher quality products used in thehealth and cosmetics industries. This work investigated the potential ofusing the crude glycerol to produce docosahexaenoic acid (DHA, 22:6 n-3)through fermentation of the microalga Schizochytrium limacinum. Theresults showed that crude glycerol supported alga growth and DHA production,with 75-100 g/L concentration being the optimal range. Among other medium andenvironmental factors influencing DHA production, temperature, trace metal(PI) solution concentration, ammonium acetate, and NH sub(4)Cl had significanteffects (P < 0.1). Their optimal values were determined 30 mL/L of PI,0.04 g/L of NH sub(4)Cl, 1.0 g/L of ammonium acetate, and 19.2 C. A highestDHA yield of 4.91 g/L with 22.1 g/L cell dry weight was obtained. The resultssuggested that biodiesel-derived crude glycerol is a promising feedstock forproduction of DHA from heterotrophic algal culture.