Butanol production from wheat straw by simultaneous saccharification and fermentation using Clostridium beijerinckii: Part II—Fed-batch fermentation

The alkaline-pretreated wheat straw was used as raw materials, and the fed-batch simultaneous saccharification and fermentation (SSF) process for ethanol production with higher substrate loading (up to 16% (w/v)) was investigated. Firstly, the Fed-batch SSF with different feeding strategy was optimized. The highest ethanol concentration reached to 37.9 g/L with an initial substrate loading of 10% (w/v), and equal substrate addition (3%) at 8h and 16h respectively. Then the effects of Tween-20 were also investigated. The results showed that Tween-20 addition with 2.0 g/L can improved the ethanol production. Furthermore, a nonisothermal fed-batch SSF was proposed, and the ethanol concentration of 41.5 g/L, corresponds to 81.0 % of the theoretical yield was achieved within 72 h.

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Enhanced butanol production from ammonium sulfite pretreated wheat straw by separate hydrolysis and fermentation and simultaneous saccharification and fermentation

Sustainable Energy Technologies and Assessments ◽

10.1016/j.seta.2019.100549 ◽

2019 ◽

Vol 36 ◽

pp. 100549

Author(s):

Gaoxiang Qi ◽

Dongmei Huang ◽

Jianhui Wang ◽

Yu Shen ◽

Xu Gao

Keyword(s):

Wheat Straw ◽

Simultaneous Saccharification And Fermentation ◽

Butanol Production ◽

Separate Hydrolysis And Fermentation ◽

Ammonium Sulfite ◽

Pretreated Wheat Straw ◽

Simultaneous Saccharification

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Improving xylitol yield by deletion of endogenous xylitol-assimilating genes: a study of industrial Saccharomyces cerevisiae in fermentation of glucose and xylose

FEMS Yeast Research ◽

10.1093/femsyr/foaa061 ◽

2020 ◽

Vol 20 (8) ◽

Author(s):

Bai-Xue Yang ◽

Cai-Yun Xie ◽

Zi-Yuan Xia ◽

Ya-Jing Wu ◽

Min Gou ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Batch Fermentation ◽

Xylose Reductase ◽

Fed Batch ◽

Fed Batch Fermentation ◽

Engineered Saccharomyces Cerevisiae ◽

Sorbitol Dehydrogenases ◽

Simultaneous Saccharification ◽

Xylitol Yield ◽

Endogenous Enzymes

ABSTRACT Engineered Saccharomyces cerevisiae can reduce xylose to xylitol. However, in S.cerevisiae, there are several endogenous enzymes including xylitol dehydrogenase encoded by XYL2, sorbitol dehydrogenases encoded by SOR1/SOR2 and xylulokinase encoded by XKS1 may lead to the assimilation of xylitol. In this study, to increase xylitol accumulation, these genes were separately deleted through CRISPR/Cas9 system. Their effects on xylitol yield of an industrial S. cerevisiae CK17 overexpressing Candida tropicalis XYL1 (encoding xylose reductase) were investigated. Deletion of SOR1/SOR2 or XKS1 increased the xylitol yield in both batch and fed-batch fermentation with different concentrations of glucose and xylose. The analysis of the transcription level of key genes in the mutants during fed-batch fermentation suggests that SOR1/SOR2 are more crucially responsible for xylitol oxidation than XYL2 under the genetic background of S.cerevisiae CK17. The deletion of XKS1 gene could also weaken SOR1/SOR2 expression, thereby increasing the xylitol accumulation. The XKS1-deleted strain CK17ΔXKS1 produced 46.17 g/L of xylitol and reached a xylitol yield of 0.92 g/g during simultaneous saccharification and fermentation (SSF) of pretreated corn stover slurry. Therefore, the deletion of XKS1 gene provides a promising strategy to meet the industrial demands for xylitol production from lignocellulosic biomass.

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