Bioethanol production from Gracilaria verrucosa using Saccharomyces cerevisiae adapted to NaCl or galactose.

Abstract

This study examined the pretreatment, enzymatic saccharification, and fermentation of the red macroalgae Gracilaria verrucosa using adapted saccharomyces cerevisiae to galactose or NaCl for the increase of bioethanol yield. Pretreatment with thermal acid hydrolysis to obtain galactose was carried out with 11.7% (w/v) seaweed slurry and 373mM H2SO4 at 121°C for 59min. Glucose was obtained from enzymatic hydrolysis. Enzymatic saccharification was performed with a mixture of 16U/mL Celluclast 1.5L and Viscozyme L at 45°C for 48h. Ethanol fermentation in 11.7% (w/v) seaweed hydrolysate was carried out using Saccharomyces cerevisiae KCTC 1126 adapted or non-adapted to high concentrations of galactose or NaCl. When non-adapted S. cerevisiae KCTC 1126 was used, the ethanol productivity was 0.09g/(Lh) with an ethanol yield of 0.25. Ethanol productivity of 0.16 and 0.19g/(Lh) with ethanol yields of 0.43 and 0.48 was obtained using S. cerevisiae KCTC 1126 adapted to high concentrations of galactose and NaCl, respectively. Adaptation of S. cerevisiae KCTC 1126 to galactose or NaCl increased the ethanol yield via adaptive evolution of the yeast.