Two-step fermentation of cooked rice with Aspergillus oryzae and Clostridium acetobutylicum YM1 for biobutanol production

Abstract

In Asia, uneaten cooked rice is the highest portion amongst many forms of food wastes that are thrown away. In order to make use of the thrown-away rice and potentially use it for liquid fuels, steamed Japanese rice was evaluated on biobutanol production through a two-step fermentation by amylase-producing Aspergillus oryzae, and solvent-producing Clostridium acetobutylicum YM1. The effects of sterilization and providing anaerobic conditions on solvent production in acetone-butanol-ethanol (ABE) fermentation cannot be underestimated. Several conditions, including aerobic, anaerobic, sterile, and non-sterile were investigated concerning the solvent production capability of Clostridium acetobutylicum YM1. The maximum solvent production was 11.02 ± 0.22 g/l butanol and 18.03 ± 0.34 g/l total ABE from 75 g/l dried rice. The results confirmed that the solvent production performance of the YM1 strain was not affected by the sterilization conditions. In particular, 10.91 ± 0.16 g/l butanol and 16.68 ± 0.22 g/l ABE were produced under non-sterile and aerobic conditions, which can reduce industrial-scale production costs.

Keywords:

• Solid-state fermentation
• rice
• solvent production
• ABE fermentation
• biobutanol

Acknowledgement

The authors are grateful to the Scientific and Technological Research Council of Turkey (TUBITAK) for providing the first author a research scholarship. We are thankful to Tokyo Tech Prof. Kiyohiko Nakasaki and his lab for characterization equipment support. We are also grateful to Nihon Jyozo Kogyo Ltd., Tokyo, Japan for kindly providing koji samples.

Disclosure statement

The authors declare that they have no conflict of interest.