Abstract
Synergistic effect of cellulase and hemicellulase (xylanase) was evaluated because lignocellulosic material is a heterogeneous complex of cellulose and hemicellulose. Various effects of HTec2 addition on enzymatic saccharification and fermentation were evaluated using two different substrates such as corn stover and rice straw. Corn stover and rice straw were pretreated by the LMAA (low-moisture anhydrous ammonia) method at the preselected same conditions (90 °C, 120 h, moisture content = 50%, NH3 loading = 0.1 g NH3/g). It was observed that the enzymatic saccharification yield of pretreated corn stover (76.4% for glucan digestibility) was higher than that of pretreated rice straw (70.9% for glucan) using CTec2 cellulase without HTec2 addition. Glucan digestibility of pretreated corn stover was significantly increased from 76.4% to 91.1% when the HTec2/CTec2 (v/v) increased from 0 to 10. However, it was interesting that the ethanol production was decreased from 89.9% to 76.3% for SSF and 118.0% to 87.9% for SSCF at higher HTec2/CTec2. As the glucan loading increased from 2.0% to 7.0%, the ethanol yields of both SSF and SSCF were decreased from 96.3% to 88.9% and from 116.6% to 92.4%, respectively. In addition, the smallest inoculum size (optical density of 0.25) resulted in the highest ethanol production (20.5 g/L).
Highlights
The world economy is largely dependent on fossil energy sources
An increase of pretreatment time from 24 to 120 h did not result in significant improvement on enzymatic digestibility of corn stover and rice straw
The glucan digestibility of low-moisture anhydrous ammonia (LMAA)-treated corn stover and rice straw increased from 79.1%
Summary
The world economy is largely dependent on fossil energy sources. Coal and crude oil are currently main sources of energy used for the productions of fuels, chemicals, power, and so on [1]. Various alternative sources of energy such as solar, wind, and biomass have attracted attention and are regarded as renewable sources Among those sources, lignocellulosic biomass has been studied as an important resource that can be converted into liquid transportation fuels (ethanol and butanol) and various industrial biochemical products by utilizing main components of biomass such as cellulose, hemicellulose, and lignin [3,4,5]. Sugar and starch obtained from sugarcane and corn grain have been primary source of fuel ethanol production, termed as the first-generation biomass and fuel, respectively [6]. These resources conflict with food use and have limited availability.
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