Production of astaxanthin, ethanol and methane from Chromochloris zofingiensis microalga in an integrated biorefinery

Abstract

Astaxanthin-rich carotenoids were produced from Chromochloris zofingiensis green alga through an integrated biorefinery. Simultaneous effects of high light intensity and nitrogen starvation resulted in the production of 10.2 mg total carotenoids per g biomass, including 80 % astaxanthin. A novel extraction method employing ultrasonic-milling pretreatment was then used to reduce the extraction time (33.5 min) and the amount of utilized solvent (30 mL ethanol per 1 g biomass). The extraction method provided the residual biomass with the same anaerobic digestibility as the raw biomass, accumulating 315 mL/g VS methane. Additionally, the residual biomass was hydrolyzed with four commercial enzymes providing a high glucose yield (78.2 %). Overall, the biorefinery consisted of producing ethanol from the algal biomass hydrolysate and biomethane from solids remaining after hydrolysis. Also, fermentation resulted in 8260 kJ energy, in addition to 10.2 g carotenoids from 1 kg biomass.