화학공학소재연구정보센터
Fuel, Vol.215, 647-654, 2018
Modified simultaneous saccharification and fermentation to enhance bioethanol titers and yields
To maintain our society's sustainability with respect to people, prosperity, and the planet, we must produce liquid transportation fuels such as bioethanol on the renewable basis at a competitive price to petroleum-based fuels. The major challenges to commercialize cellulosic biofuels are low fermentation efficiency, low ethanol titer, and lack of technology to fully utilize the byproduct from bioconversion process such as lignin which has been underutilized. To overcome these technical barriers, we have proposed a novel design to fully utilize each component of lignocellulosic biomass for biofuels and bio-chemicals production, which involves green technologies such as hydrothermal and organosolv pretreatments to produce a cellulose-rich solid with good recovery of clean lignin after solvent recycling for improvement of plant protein-based adhesives as well as xylose remained in the aqueous phase for furfural upgradation. The focus of this study, as a part of the whole biorefinery concept, is to develop modified simultaneous saccharification and fermentation (mSSF) to enhance ethanol titers and yields, which combines the advantages of both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) via unique decantation process. The mSSF achieved higher ethanol concentration of 58.5 g/L and ethanol yield of 83.5% as compared to the traditional SSF process (49.9 g/L and 71.1%) at the biomass loadings of 20% (w/v). The mSSF also enabled higher ethanol titers of 72.3 g/L at higher loadings of 30% (w/v) with yields of 70.0%. As compared to published high-gravity fermentation, ethanol concentration of 72.3 g/L achieved in this study was the highest one in the lab-scale process, which proved that the proposed mSSF was an effective process to increase ethanol titers without sacrificing ethanol yields. The improved ethanol titers and yields would significantly lower the distillation cost and accelerate the commercialization of cellulosic biofuel production.