High yield of second-generation ethanol in an ionic Liquid-Cellulase integrated system for single-step processing of empty fruit bunch

Abstract

Ionic liquids (ILs) are regarded as green solvents and have demonstrated ability in the solvation of lignocellulosic material, thus promoting its enzymatic hydrolysis by cellulases. In this study, cellulase (PKC-Cel) obtained from Trichoderma reesei (RUTC30) through fermentation displayed good stability in choline acetate [Cho]OAc, a biodegradable IL. Empty fruit bunches (EFB) were subjected to single-step hydrolysis in an IL-enzyme system. Response surface methodology was employed to maximize ethanol production. Three parameters were optimized, namely sugar loading, inoculum concentration, and agitation. The distilled ethanol purity was 98.6% (v/v). The ethanol yield was 87.94% of the theoretical yield, which was 0.275 g ethanol g⁻¹ EFB. In comparison, the non-IL system produced 0.127 g g⁻¹ EFB. The yield coefficients $Y_{ps}$, $Y_{xs}$, and $Y_{px}$ were 0.552, 0.148, and 3.69 g g⁻¹. The specific growth rate $(\mu )$ was determined to be 0.264 h⁻¹ and the $\left({\mu }_{max}\right)$ was 0.777 h⁻¹.

Keywords:

• Cellulase
• compatible
• pretreatment
• ionic liquids
• hydrolysis
• bioethanol

Acknowledgements

This project is funded by FRGS-13-088-0329. The authors are grateful to the Department of Biotechnology Engineering and International Institute for Halal Research and Training (INHART) in IIUM and Centre of Research in Ionic Liquids (CORIL) in University Technology Petronas for providing the lab facilities. Our gratitude is also extended to the West Oil Mill, Sime Darby Plantation for providing the experimental biomass samples for this project. We would like to thank Editage (www.editage.com) for English language editing.

Declaration of interest statement

The authors declare no financial or commercial conflict of interest.

Additional information

Funding

This study was funded by the Ministry of Higher Education, Malaysia [FRGS-13-088-0329].