Bioethanol production from steam-exploded rice husk by recombinant Escherichia coli KO11
Rice husk is one of the most abundant types of lignocellulosic biomass. Because of its significant amount of sugars, such as cellulose and hemicellulose, it can be used for the production of biofuels such as bioethanol. However, the complex structure of lignocellulosic biomass, consisting of cellulose, hemicellulose and lignin, is resistant to degradation, which limits biomass utilization for ethanol production. The protection of cellulose by lignin contributes to the recalcitrance of lignocelluloses to hydrolysis. Therefore, we conducted steam-explosion treatment as pretreatment of rice husk. However, recombinant Escherichia coli KO11 did not ferment the reducing sugar solution obtained by enzymatic saccharification of steam-exploded rice husk. When the steam-exploded rice husk was washed with hot water to remove inhibitory substances and M9 medium (without glucose) was used as a fermentation medium, E. coli KO11 completely fermented the reducing sugar solution obtained by enzymatic saccharification of hot water washing-treated steam-exploded rice husk to ethanol. We report here the efficient production of bioethanol using steam-exploded rice husk.
KeywordsBioethanol Escherichia coli KO11 Inhibition Rice husk Steam explosion
This work was supported in part by a Grant for the Program for the Strategic Research Foundation at Private Universities S1101017 since April 2011 (to NS).
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Conflict of interest
The authors declare that they have no competing interests.
- Ohta K, Beall DS, Mejia JP, Shanmugam KT, Ingram LO (1991) Genetic improvement of Escherichia coli for ethanol production: chromosomal integration of Zymomonas mobilis genes encoding pyruvate decarboxylase and alcohol dehydrogenase II. Appl Environ Microbiol 57:893–900Google Scholar
- Tanahashi T, Tamabuchi K, Goto T, Aoki T, Karina M, Higuchi T (1988) Characterization of steam-explodeed wood II: chemical changes of wood components by steam explosion. Wood Res 75:1–12Google Scholar