title: Simultaneous saccharification and fermentation of steam-exploded corn stover at high glucan loading and high temperature.
abstract: BACKGROUND
  Simultaneous saccharification and fermentation (SSF) is a promising process for bioconversion of lignocellulosic biomass. High glucan loading for hydrolysis and fermentation is an efficient approach to reduce the capital costs for bio-based products production. The SSF of steam-exploded corn stover (SECS) for ethanol production at high glucan loading and high temperature was investigated in this study.
  
  
  RESULTS
  Glucan conversion of corn stover biomass pretreated by steam explosion was maintained at approximately 71 to 79% at an enzyme loading of 30 filter paper units (FPU)/g glucan, and 74 to 82% at an enzyme loading of 60 FPU/g glucan, with glucan loading varying from 3 to 12%. Glucan conversion decreased obviously with glucan loading beyond 15%. The results indicated that the mixture was most efficient in enzymatic hydrolysis of SECS at 3 to 12% glucan loading. The optimal SSF conditions of SECS using a novel Saccharomyces cerevisiae were inoculation optical density (OD)600 = 4.0, initial pH 4.8, 50% nutrients added, 36 hours pre-hydrolysis time, 39°C, and 12% glucan loading (20% solid loading). With the addition of 2% Tween 20, glucan conversion, ethanol yield, final ethanol concentration reached 78.6%, 77.2%, and 59.8 g/L, respectively, under the optimal conditions. The results suggested that the solid and degradation products' inhibitory effect on the hydrolysis and fermentation of SECS were also not obvious at high glucan loading. Additionally, glucan conversion and final ethanol concentration in SSF of SECS increased by 13.6% and 18.7%, respectively, compared with separate hydrolysis and fermentation (SHF).
  
  
  CONCLUSIONS
  Our research suggested that high glucan loading (6 to 12% glucan loading) and high temperature (39°C) significantly improved the SSF performance of SECS using a thermal- and ethanol-tolerant strain of S. cerevisiae due to the removal of degradation products, sugar feedback, and solid's inhibitory effects. Furthermore, the surfactant addition obviously increased ethanol yield in SSF process of SECS.
authors.affiliation: Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, 92 Weijin Road, Nankai District Tianjin, 300072 China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, 92 Weijin Road, Nankai District Tianjin, 300072 China.
authors.forename: Zhi-Hua
authors.initials: ZH
authors.lastname: Liu
authors.affiliation: Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, 92 Weijin Road, Nankai District Tianjin, 300072 China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, 92 Weijin Road, Nankai District Tianjin, 300072 China.
authors.forename: Lei
authors.initials: L
authors.lastname: Qin
authors.affiliation: Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, 92 Weijin Road, Nankai District Tianjin, 300072 China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, 92 Weijin Road, Nankai District Tianjin, 300072 China.
authors.forename: Jia-Qing
authors.initials: JQ
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, 92 Weijin Road, Nankai District Tianjin, 300072 China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, 92 Weijin Road, Nankai District Tianjin, 300072 China.
authors.forename: Bing-Zhi
authors.initials: BZ
authors.lastname: Li
authors.affiliation: Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, 92 Weijin Road, Nankai District Tianjin, 300072 China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, 92 Weijin Road, Nankai District Tianjin, 300072 China.
authors.forename: Ying-Jin
authors.initials: YJ
authors.lastname: Yuan
keywords: Corn stover biomass; High glucan loading; High temperature; Mass balance; Simultaneous saccharification and fermentation (SSF); Surfactant