Influence of delignification efficiency with alkaline peroxide (1)
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Influence of delignification efficiency with alkaline peroxide (1)

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d then the bioconversion efficiency, closely relating to the increased specific

furyl alcohol, furan, tetrahydrofuran, etc.) (Weingarten et al.,

ersen, 2010). Normally, furfural is produced by the dehydration of
xylose with a mineral acid (i.e. sulfuric acid), and the solid residue,
enriched in cellulose and lignin, is considered as a waste byproduct
and mainly to be utilized for heat generation. However, furfural
residue (FR) is a promising potential lignocellulosic source based
on the concept of ‘‘biorefinery’’, simultaneously allowing the utili-

heterogeneous lignin macromolecule (Wang et al., 2012). China
producers in the
s of furfur
Mamman
11). Hence

full advantage of this rich bioresource is vitally important fo
to improve the environmental quality, increase the econom
biomass utilization, and then boost the rural incomes.

Second-generation bioethanol from lignocellulosic biomass has
attracted much interests over last few decades (Ragauskas et al.,
2006; Simons et al., 2008), and enzymatic saccharification has been
identified as one of the most costly steps in cellulosic ethanol pro-
duction (Lynd et al., 2002). However, in addition to the intrinsic
characteristics within the cellulose itself (i.e. crystallinity, degree
of polymerization, etc.), the surrounding of lignin and hemicellu-

⇑ Corresponding author at: Beijing Key Laboratory of Lignocellulosic Chemistry,
Beijing Forestry University, Beijing 100083, China. Tel./fax: +86 010 62336903.

Bioresource Technology 146 (2013) 208–214

Contents lists availab

T

els
E-mail addresses: rcsun3@bjfu.edu.cn, ynsun@scut.edu.cn (R.-c. Sun).
2010). A revised list of biobased-product opportunities from carbo-
hydrates was proposed according to the evaluation of recent tech-
nology advances, adding furfural into the US Department of Energy
(DOE) top 10 value-added chemicals from biomass (Bozell and Pet-

is already one of the world’s largest furfural
world, generating at least 200 thousands tonne
2–3 millions tonnes of FR residues annually (
2008; Mandalika and Runge, 2012; Tang et al., 20
0960-8524/$ - see front matter Crown Copyright � 2013 Published by Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.biortech.2013.07.008
al and
et al.,
, taking
r China
ics of
Delignification
Simultaneous saccharification and
fermentation
Bioethanol

surface area. As the cellulose contents were higher than 60%, the final conversions conversely fell to
around 75%, probably due to the insufficient utilization of all active cellulose with low enzyme cocktails
addition. Although the SSF bioconversion slightly decreased as the elevated amount of fermentable cel-
lulose, the maximum of ethanol concentration (16.9 g/L) was expectedly obtained.

Crown Copyright � 2013 Published by Elsevier Ltd. All rights reserved.

1. Introduction

Furfural is a renewable biochemicals produced from lignocellu-
losic biomass, considering as an excellent solvent for many organic
materials, as well as a precursor to other desired compounds (fur-

zation of waste for producing valuable chemicals. As the most
obvious aspects, FR is almost free of hemicelluloses, which is seri-
ously acidic hydrolyzed and further dehydrated under high tem-
perature and pressure. Meanwhile, depolymerization and
repolymerization reactions concur to generate more complex and
Keywords:
Furfural residue

relative glucose content an
� Furfural residues were taken as substra
� Alkaline peroxide delignification simul
� The glucose content reached as high as
� 16.9 g/L ethanol was finally obtained b

a r t i c l e i n f o

Article history:
Received 19 March 2013
Received in revised form 29 June 2013
Accepted 3 July 2013
Available online 10 July 2013
ioethanol production.
ly degraded lignin and carbohydrates.
with 2% chemical dosage at 180 �C.
ltaneous saccharification and fermentation.

a b s t r a c t

Furfural residues (FR), the abundant lignocellulosic residues from commercial furfural production, were
delignified with alkaline peroxide process and then taken as substrates for ethanol production by simul-
taneous saccharification and fermentation (SSF). It was apparent that the delignification efficiency was
increased with higher chemical addition and temperature, reaching the maximum removal (73.5%) of lig-
nin. The widespread accessible-cellulose in FR favored the enzymatic hydrolysis and achieved the consid-
erable bioconversion (75.7% with 5 FPU + 10 IU/g substrate). The delignification process increased the
h i g h l i g h t s
Influence of delignification efficiency wit
on the digestibility of furfural residues fo

Kun Wang a, Haiyan Yang a, Qian Chen a, Run-cang S
aBeijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing
b State Key Laboratory of Pulp and Paper Engineering, South China University of Techno

Bioresource

journal homepage: www.
alkaline peroxide
bioethanol production
a,b,⇑
083, China
, Guangzhou 510640, China

le at ScienceDirect

echnology

evier .com/locate /bior tech

tions, consequently reducing the efficiency of saccharification (Ber-

hydes and carbonyls (Sun et al., 2000). The solvent pretreatment

echn
based on alkaline hydrogen peroxide resulted in a more targeted
lignin removal, and then has potential advantages on capital costs,
process simplicity, and compatibility with enzymatic deconstruc-
tion and fermentation (Banerjee et al., 2012). The objectives of
the present study are: (1) to delignify FR using alkaline hydrogen
peroxide process under different concentrations and temperatures,
and evaluate the substrate features by sugar analysis, crystal struc-
ture, pore size distribution and molecular weight; and (2) to bio-
transform FR cellulose into glucose and ethanol by enzymatic
hydrolysis and simultaneous saccharification and fermentation
(SSF), respectively.

2. Methods

2.1. Raw materials and chemicals

FR was kindly provided by Chunlei Company (Hebei Province,
China). The main components were determined as: glucose
35.1%, xylose 0.4%, Klason lignin (acid-insoluble lignin, AIL)
43.0%, acid soluble lignin (ASL) 6.9% and ash 12.3% (absolute wt%
of starting material). Raw FR, with an initial pH of 2–3, was firstly
treated with hot water at 80 �C for 2 h. The solid residue was col-
lected by filtration, oven-dried at 60 �C for 12 h, and kept in a des-
iccator before further delignification process and chemical
analysis. The solid and liquid portions were labeled as RC and LC,
respectively, and taken as controls. All chemicals are of analytical
grade unless otherwise mentioned.

2.2. Lignin removal process

The delignification process was performed using alkaline
hydrogen peroxide for 2 h at different concentrations and temper-
atures in a sealed stainless-steel autoclave with Teflon-lining. Se-
ven grams RC was mixed with 70 mL reaction solution containing
the same concentrations (1% or 2%) of sodium hydroxide NaOH
(g/v) and hydrogen peroxide H2O2 (v/v), and then heated in oil
lin et al., 2006; Nakagame et al., 2010). Kumar et al. (2012)
delignified the steam-pretreated softwood in steps, and an almost
linear increase in cellulose hydrolysis was observed with increas-
ing lignin removal.

Acidic sodium chlorite has been extensive employed in the del-
ignification process as a standardized procedure, suffering toxic-
gas emission and high cost. The alkaline peroxide procedure was
initially developed by Gould (1984) for the herbaceous substrates,
and widely used in the lignin-retaining bleaching of mechanical,
thermomechanical, chemimechanical, and semichemical pulps.
The hydroperoxide anion (HOO�) dominated under alkaline condi-
tion and reacted with the chromophoric groups (mainly carbonyl
structures, such as quinines, cinnamaldehyde, etc.) in lignin. Mean-
while, the hydroxyl radical (HO�) from the