Pretreatment of Corn Stover Using an Extremely Low-Liquid Ammonia (ELLA) Method for the Effective Utilization of Sugars in Simultaneous Saccharification and Fermentation (SSF) of Ethanol

Tin Diep Trung Le,Vi Phuong Nguyen Truong,Kyeong Keun Oh,Tae Hyun Kim,My Thi Tra Ngo

doi:10.3390/fermentation7030191

Tin Diep Trung Le, Vi Phuong Nguyen Truong + Show 3 more

Open Access

https://doi.org/10.3390/fermentation7030191

Copy DOI

Abstract

Extremely low-liquid ammonia (ELLA) pretreatment using aqueous ammonia was investigated in order to enhance the enzymatic saccharification of corn stover and subsequent ethanol production. In this study, corn stover was treated with an aqueous ammonia solution at different ammonia loading rates (0.1, 0.2, and 0.3 g NH3/g biomass) and various liquid-to-solid (L/S) ratios (0.55, 1.12, and 2.5). The ELLA pretreatment was conducted at elevated temperatures (90–150 °C) for an extended period (24–120 h). Thereafter, the pretreated material was saccharified by enzyme digestion and subjected to simultaneous saccharification and fermentation (SSF) tests. The effects of key parameters on both glucan digestibility and xylan digestibility were analyzed using analysis of variance (ANOVA). Under optimal pretreatment conditions (L/S = 2.5, 0.1 g-NH3/g-biomass, 150 °C), 81.2% glucan digestibility and 61.1% xylan digestibility were achieved. The highest ethanol yield achieved on the SSF tests was 85.4%. The ethanol concentration was 14.5 g/L at 96 h (pretreatment conditions: liquid-to-solid ratio (L/S) = 2.5, 0.1 g-NH3/g-biomass, 150 °C, 24 h. SSF conditions: microorganism Saccharomyces cerevisiae (D5A), 15 FPU/g-glucan, CTech2, 3% w/v glucan, 37 °C, 150 rpm).

Highlights

The declining supply of fossil fuels, the increasing population, and global industrialization have triggered an increase in the demand for alternate fuels
The extremely low-liquid ammonia (ELLA) pretreatment was not expected to result in any significant changes in the biomass composition at a mild temperature (90 and 120 ◦ C)
The corn stover treated at a higher temperature (150 ◦ C) showed an interesting change in its composition (Figure 1), indicating that higher temperatures can influence the composition of treated corn stover

Summary

Introduction

The declining supply of fossil fuels, the increasing population, and global industrialization have triggered an increase in the demand for alternate fuels To address this problem, most green research in recent years has focused on the development of second-generation bioethanol [1]. The use of lignocellulosic fuel can help to overcome the problems associated with first-generation biofuels (such as the competition between food and fuel) [3]. It can supply a large proportion of the global fuel demand sustainably, inexpensively, and with substantial environmental benefits [4,5].

Methods

Results

Conclusion