High-level ethanol production from sago residue hydrolysate prepared with thermostable α-amylase and amyloglucosidase

Abstract

 Sago residue after starch extraction contains a considerable amount of starch. In this study, we aimed to develop a simple and effective method for producing bioethanol from sago residue. Starch in sago residue was efficiently liquefied with thermostable α-amylase at 90 °C using a mass ratio of sago residue to α-amylase solution of 1:6. The liquefied solution (approximately 100 g/L sugar) was subjected to both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes to produce ethanol. In SHF, glucose prepared with α-amylase and amyloglucosidase was almost consumed by yeast after 36 h of fermentation at 37 °C, and 34.2 g/L ethanol was produced with a yield of 66.0%. In SSF, 43.2 g/L ethanol was obtained with a yield of 86.4% after 72 h of saccharification and fermentation at 37 °C using the liquefied solution with added amyloglucosidase and yeast. This has been the highest ethanol concentration ever reported in bioethanol production from sago residue.