Ethanol production from seaweed (Undaria pinnatifida) using yeast acclimated to specific sugars

Abstract

Ethanol production from Undaria pinnatifida (Sea mustard, Miyuk) was performed using yeast acclimated to specific sugars. Pretreatment conditions were optimized by thermal acid hydrolysis and enzyme treatment to increase the monosaccharide yield. Pretreatment by thermal acid hydrolysis was carried out using seaweed powder at 8 ∼ 17% (w/v) solid content with a treatment time of 30 ∼ 60 min. Enzyme treatment was carried out with 1% (v/v) Viscozyme L (1.2 FGU/mL), 1% (v/v) Celluclast 1.5 L (8.5 EGU/mL), 1% (v/v) AMG 300 L (3.0 AGU/mL), and 1% (v/v) Termamyl 120 L (0.72 KNU/mL). All enzymes except Termamyl 120 L, which was applied during pretreatment, were treated at 45°C for 24 h following pretreatment. Optimal pretreatment and enzyme conditions were determined to be 75 mM H₂SO₄, 13% (w/v) slurry, and 2.88 KNU/mL Termamyl 120 L at 121°C for 60 min. A maximum monosaccharide concentration of 33.1 g/L with 50.1% theoretical yield was obtained. To increase the ethanol yield, Pichia angophorae KCTC 17574 was acclimated to a high concentration (120 g/L) of galactose and mannitol at 30oC for 24 h. Ethanol production of 12.98 g/L with 40.12% theoretical yield was obtained from U. pinnatifida through fermentation with 0.35 g dry cell weight/L P. angophorae KCTC 17574 acclimated to mannitol and galactose.