Napier grass (Pennisetum purpureum Schumach) as raw material for bioethanol production: Pretreatment, saccharification, and fermentation

Biotechnology and Bioprocess Engineering 19: 943-950 (2014) DOI 10.1007/s12257-014-0465-y

REVIEW PAPER

Napier Grass (Pennisetum purpureum Schumach) as Raw Material for Bioethanol Production: Pretreatment, Saccharification, and Fermentation

Masahide Yasuda, Yasuyuki Ishii, and Kazuyoshi Ohta

Received: 3 July 2014 / Revised: 9 July 2014 / Accepted: 19 July 2014 The Korean Society for Biotechnology and Bioengineering and Springer 2014

Abstract Recently Napier grass (Pennisetum purpureum Schumach) has been recognized to meet the requirement of lignocellulosic bioethanol production, because it has low lignin-content and a relatively high herbage mass per year and per area. Therefore, pretreatment, saccharification, and fermentation processes for ethanol production from Napier grass have been extensively studied. As pretreatment method, acid, alkali, PBHW (pressurized batch hot water), and LMAA (low-moisture anhydrous ammonia) pretreatments were reviewed. As saccharification and fermentation process, saccharification followed by co-fermentation of hexose and pentose, simultaneous saccharification and fermentation (SSF) followed by pentose fermentation, simultaneous saccharification and co-fermentation (SSCF) process were proposed. The SSCF was most advantageous process since the SSCF can prevent contamination risks of other microorganism and can construct simple processing procedure. An example of ethanol production from Napier grass was a combination process of LMAA-pretreatment with SSCF which was performed for of LMAA-treated

Napier grass at 36C for 96 h using cellulase, xylanase, Saccharomyces cerevisiae, and Escherichia coli KO11. The ethanol yield reached 74.1%. Thus, Napier grass was thought to be a promising biomass for ethanol production.

Keywords: LMAA, SSF, SSCF, cellulase, xylanase, Saccharomyces cerevisiae, Escherichia coli KO11

1. Introduction

Biomass has gained much attention as new sustainable energy sources alternative to petroleum-based fuels [1]. Especially, second-generation bioethanol from lignocellulosic materials is one of promising approach since the lignocelluloses are not directly in competition with food sources and animal feed [2]. Bio-ethanol production from herbaceous lignocellulose such as corn stover [3], rice straw [4,5], sweet sorghum bagasse [6], switchgrass [7], bamboo [8,9], wheat straw [10], alfalfa stems [11], and silvergrass [12] has been extensively developed. Recently we and other groups have interested in herbaceous lignocellulose Napier grass (Pennisetum purpureum Schumach) to produce saccharides and ethanol, because of high harvest amount per year and per area [13]. Ethanol production from Napier grass has been investigated through a variety of processes combining the pretreatment methods with the biological saccharification and fermentation...