Delignification of miscanthus using ethylenediamine (EDA) with or without ammonia and subsequent enzymatic hydrolysis to sugars.

Sasisanker Padmanabhan,Geoffrey Poon,Alexis T Bell,Zhongguo Liu,Philippe Schwyter,John M Prausnitz

doi:10.1007/s13205-015-0344-z

Sasisanker Padmanabhan, Geoffrey Poon + Show 4 more

Open Access

https://doi.org/10.1007/s13205-015-0344-z

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Abstract

Pretreatment of miscanthus is essential for efficient enzymatic production of cellulosic ethanol. This study reports a possible pretreatment method for miscanthus using aqueous ethylenediamine (EDA) for 30 min at 180 °C with or without ammonia. The mass ratio of miscanthus to EDA was varied from 1:3, 1:1, and 1:0.5, keeping the mass ratio of miscanthus to liquid (EDA + Water) constant at 1:8. The ammonia-to-miscanthus ratio was 1:0.25. After pretreatment with a ratio of 1:3 miscanthus to EDA, about 75 % of the lignin was removed from the raw miscanthus with 90 % retention of cellulose and 50 % of hemicellulose in the recovered solid. Enzymatic hydrolysis of the recovered solid miscanthus gave 63 % glucose and 62 % xylose conversion after 72 h. EDA provides an effective pretreatment for miscanthus, achieving good delignification and enhanced sugar yield by enzyme hydrolysis. Results using aqueous EDA with or without ammonia are much better than those using hot water and compare favorably with those using aqueous ammonia. The delignification efficiency of EDA pretreatment is high compared to that for hot-water pretreatment and is nearly as efficient as that obtained for aqueous-ammonia pretreatment.

Highlights

Economic and environmental concerns about the continued use of fossil fuels have prompted a search for alternative fuels using sustainable lignocellulosic biomass feedstock (Carroll and Somerville 2009)
EDA provides an effective pretreatment for miscanthus, achieving good delignification and enhanced sugar yield by enzyme hydrolysis
Our recent work on delignification of miscanthus using a combination of EDA with organic solvents or ionic liquids suggests that EDA helps to cleave the lignin-carbohydrate link leading to good removal of lignin

Summary

Introduction

Economic and environmental concerns about the continued use of fossil fuels have prompted a search for alternative fuels using sustainable lignocellulosic biomass feedstock (Carroll and Somerville 2009). Various studies in the paper-and-pulp industries have suggested that a combination of alkali and an organic solvent can yield a cellulose-rich pulp with a low amount of lignin (Abbot and Bolker 1982; Cochaux et al 1995). Taking some clues from these studies, several research groups have employed combination of ammonia or methyl amine with organic solvents or ionic liquids for delignification of biomass (Cho et al 2008; Cochaux et al 1995; Rodriguez and Jimenez 2008; Sarwar et al 2001; Abbot and Bolker 1982). Our recent work on delignification of miscanthus using a combination of EDA with organic solvents or ionic liquids suggests that EDA helps to cleave the lignin-carbohydrate link leading to good removal of lignin (Padmanabhan et al.2012). EDA provides an added advantage with respect to higher alkalinity (pH [ 12), which is favorable for the removal of lignin from miscanthus

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