Advanced Materials Reseqrch Vols. 931-932 (201Q pp 1608-1613
@ (2014) Trans Tech Publications, Switzerland
doi : I 0. 402 8/www. scientific.net/AMR 9 3 I -9 i 2. I 608
Acid Hydrolysis from Corn Stover for Reducing Sugar
Jintara Satarnl'", Wimonporn Lamamorphanthl and Khanita Kamwilaisakl'b.
lDepartment
of Chemical Engineering, Faculty of Engineering, Khon Kaen University,
Khon Kaen , 40002, Thailand
[email protected]
"[email protected],
Keywords: hemicelluloses, hydrolysis, reducing sugar, corn stover
Abstract. The aim of this study is to extract the reducing sugar by acid hydrolysis of corn stover.
The corn stover was hydrolyzed by using HzSO+ at different concentrations (0-6%, v/v),reaction
times (15-180 min) at temperature 122"C with ratio of I g of corn stover to 20 ml of HzSOa
solution. The samples were analyzed the reducing sugar by IIPLC. The optimal conditions of acid
hydrolysis was at l% HzSO+ (vlv),122"C for 60 min, which produced 24.96 g/L of reducing sugar.
The hydrolysed sample composed of 12.4 g/L of xylose,Z.9 gll of glucose and3.2 g/L of arabinose.
Also, the Scanning Electron Microscopy (SEIvI) was analyzed the morpholory of untreated and
treated corn stover which showed the breakdown fibril of treated sample.
1. Introduction
Biomass energy has received much attention in recent year as renewable energy. Biomass
products are poised to become an important energy source in agricultural country. Thailand is the
agriculture-based economy country which the agricultural wastes and by-products oan be used to be
a feedstock for the generation of biofuels using commercially viable technologies. This is due to
concern regarding oil imports and ethanol substituted energy. Corn stover could well be tomorrow's
replacement them. According to the Offrce of Agricultural Economics, said corn product was the
large quantities which were more than 4.6 million tons per year in 2012 Ul. This could produce
large amounts of com strove as a solid agricultural waste
Corn stover predominantly contains cellulose, hemicellulose and lignin, which are a strong and
durable structure. Cellulose and hemicellulose are a polymer of sugar. Cellulose is a crystalline
glucose polymer and hemicellulose is a complex amorphous polymer. The most abundant building
block of hemicellulose is xylan as a xylose polymer [z).lt has been know that extracted sugar from
Cellulosc and hemicellulose can be used as a feedstock to produce biofuel [3,4]. Therefore, studies
of alternative pretreatment methods for cellulose and hemicellulose have been physical grinding [5],
heat [6], and chemical [7] methods. These methods are to remove the lignin, including chemically
hydrolyzed using acid/alkaline, enrymatically using biological enzymes from microorganism [8] or
photolysis. The physical grinding and heating would lower the quantity of extracted sugar. [9]
Biological methods have a long time and low quantity of sugar extraction [10]. Acid/alkaline
hydrolysis is the most popular due to have the high quantrty of extracted sugar, but sugar was
pretreated before using in the next process 12,3,117.
Therefore, the aim of this work is to understand the extract of reducing sugar by acid 6I2SOa
aqueous solution) hydrolysis reaction ofcorn stover. The effect ofacid concentration and hydrolysis
time on a.mount of reducing sugar will be investigated. The reducing sugar was analyzed by phenolsulfuric method, High performance Liquid Chromatography GIPLC) will be used to identify and
quantifr the reducing sugar. Also Scaning Eletron Microscopy (SEM) will be used to characterize
treated and untreated corn stover surface.
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Advanced Materials Research Vols. 931-932
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2. Materials and methods
2.1 Pretreatment of corn stover
Corn stover gathered in an agricultural area was cut in lengths of 21cm. The sample was dried
in an oven at 60 "C for 24 h. Then, the sample was powdered in a blender, and those particles was
sieved with screener at 2O-mesh sieve (850 pm) and a 4O-mesh sieve (450 pm). The sieved samples
were stored in a sealed plastic bag at room temperature.
2.2 Hydrolysis reaction
One gram of corn stover was mixed in 20 ml of lYo v/v of HzSO+. Then, they were hydrolysed in
an autoclave at L22 "C for t h. After finished reaction, the hydrolyzed sample was filtered by filter
paper with pm (Whatman Cat.no.1003-110). The supernatant was collected to determine the
quantitative and qualitative of reducing sugar. The solid residue was dried at 55 oC for 24 h. and
then analyzed the morphological structure.
The concentration of acid hydrolysis was studied at 0,
2, 4 and 6Yo v/v and the hydrolysis
reaction time was at15,30,45, 60, 120 and 180 min, three repeated experiments were performed.
l,
The hydrolysed samples were identified and quantified by Phenol-sulfuric method (tlv-1201
spectrometer, Shinmaszu, Iapan) and high-performance liquid chromatography QIPLC Water
e2695 separations model with RI detector).
2.3 Anolysis
The concentration of reducing sugar liberated from hydrolysed corn stover was analyzed the
identification and quantitation of sugar concentration by Phenol-sulfuric method. A volume of
sample (1 ml) was mixed with I ml of 5% (wlw) aqueous solution of phenol and 5 ml of
concentrated sulphuric acid in a glass tube. The tube was allowed to stand for at least 10-20 min in a
water bath at 25-30 "C and measured by UV-Vis spectrophotometer (uV-1201 spectrometer,
Shinmaszu, Japan (absorbance at 490 nm)). The identification and quantitation of xylose, arabinose
and glucose were analyzed by high-performance liquid chromatography (IIPLC) technique.
(Rezexru sugar column phenomenx, condition; temperature 80 ;C, mobile phase t *atet
(degassed), flow rate : 0.6 mVmin, detection : RI @ 40 "C).
3. Results and discussion
The acid hydrolysis reaction of com stover was studied. The effect of acid concentration and
hydrolysis time on the quantitative and qualitative of extreacted sugar was carried out.The
hydrolysis conditions were varied HzSO+ concentration at 0, | ,2 4 and 6 Yo vlv, and hydrolysis
reaction time for 15, 30, 45,60, 120 and 180 min. with constant incubation temperature at l22oc.
The Phenol-sulfuric method (sugar concentration) and FIPLC (xylose, arabinose and glucose)
was used to quanit$ and identify the reducing sugar. The effect of sulfuric acid concentration on
reducing sugar concentration is depicted in Fig.l. The sugar concentrations was sharply increased
when the sulfi.ric acid concentration was increased from.O-l% v/v. Then the extracted sugar was
remarkably reduced at above l% (v/v) of HzSO+. This is beacause hydronium ions from HzSOa
molecules could breakdown or attack intermolecular and intramolecular bonds among cellulose,
hemicellulose and lignin [7], this results the reducing sugar releasing to the bulk solution. However,
at higher sulfuric acid, it could produce high hydronium ions, the sugar monomers (hexose),
namely, mannose, galactose and glucose, can be degraded by hydronium ions to 5-hydroxymethyl
furfural (HMF), xylose is also degaded to furfural [9]. The maximum amount of sugar
concentration were obtaind 24.912.4 gll of fermentable sugars. Glucose xylose and arbinose were
measured using HPLC which was obtained 12.4*0.2 g/l of rylose, 2.*t0.05 gll of glucose and
3.2*0.06 ll of arabinose, At l% v/v of HzSO+. The dilute-acid hydrolysis of lignocelluloses may
result in sugars and other by-products in some serial and parallel reactions following the reaotion in
equation
(l)
17,121.
KKU lnternational Engineering Conference
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)
Cellulose (Glucan))Oligosaccharides
)
Levulinic
acid.
Glucose
)
5-hydroxymethyl furfural GIMF)
(1)
However, in this study, the main component of corn stover is hemicellulose which the hydrolysis
of hemicellulose may lead first to the monomeric sugars following the reaction in equation (2) t13]
and these reactions may further continue to some other by products as shown in equation (3) tl4]
Hemicellulose) Oligosaccharides->
Sugars (xylose, arabinose, glucose, mannose, galactose).
(?)
(3)
Furthermore, At IYo (v/v) of acid dose, the hydrolysis reaction of corn stover with water, it was
obtained 1.7 g/l of glucose but it was not found xylose and arabinose. This is because xylose and
arabinose which hydrolysis from hemicelluloses (equation (2)), located in secondary cell walls, the
primary cell wall had lignin; lignin is a complex, large molecular structure containing cross-linked
polymers of phenolic monomers, imparting structural support, impermeability, and resistance
against microbial attack so hydrolysis of hemicelluloses had increased acid in the extraction [5].
Which sugar was obtained L2.4*0.2 g/l of xylose, 2.9+0.05 gll of glucose and 3.2+0.06 gll of
arabinoso, At l% v/v of HzSOa.
The effect of pretreatment time (15, 30, 60, 120 and 180 min) on dilute HzSOa (lYo, vlv)
pretreatment of corn stover at 122'C are shown in Fig. 2. At 0-60 min of hydrolysis time, it was
found that the sugar concentration increased with increasing of hydrolyzed time, This is due to the
hydronium ion of acid attack to ester bond in lignin-carbohydrate complex, resulting the releasing
of sugar monomer into the solution [9]. After 60 min, the sugar concentration remarkably reduced
with increasing of reaction time. This is because of its toxic compound (FIMF and Lewlinic acid).
The furfural was increased with time increasing of hydrolysis 17,14,16). The maximun of sugar
was obtained at reaction time 60 min with 12.4+0.2 gll of xylose, 2.9+0.05 gll of glucose and
3,2+0.06 gll of arabinose. Similarly, Shuai et al. Q|l$ has studied the pretreatment of corn stover
for sugar production using dilute hydrochloric acid followed by lime. The dilute hydrochloric acid
(l% wlv) pretreatment condition was at I20 'C and 40 min. The result showed the reducing sugar
contained 20.44 g/l of xylose, 1.82 g/l of glucose and 1.86 gl of arabinose [I71. This is a bit higher
xylose concentration than that of this work, but it has a little lower glucose and arabinose
concentration. This could be the different
is conditions and strains of corn.
30
{Elt 1<
=lu
= ti
.1, 10
rU
U
U
0
2345
6
Concmh'afi on ofH2SOa (96, v.CI
----+-Glucose
Fig.l The effect of hydrolysis
HzSO+
xrlution. (122
"Cl
60 min)
-+--Xvlose
-a-Su,gru
concentration on the yields of sugar.
I g of corn stover
in 20 ml
Advanced Materials Research Vols. 931-932
161{
L4
{tst l.
&10
La5
5o
E4
d,
on
30
60
90
r20
150
180
Tilne(min)
-----r--
Glucose --*--Xylose --+--
Ambinose
Fig.2 The effect of hydrolysis time on the yields of sugar. 1 g of corn stover in 20 ml I{zSOa
solution.
(l%
(v lv)l 122 "C)
The characterisation of untreated, water treated and acid treated corn stover samples were
determined by Scanning electron microscopy (SElvI) visualizations as shown in Fig. 3 (a), (b) and
(c), respectively. The untreated com stover in Fig. 3a shows flat surface with dense and strong fibril
structures while the water and acid hydrolysed sample was in Fig 3 b) and o). compromising
integrity. The acid treated is shown in Fig. 3c) while fibrous struclural surfaces were destroyed.
These result the releasing of more sugar monomers into the solution. However, the effect of acid
hydrolysed sample on surface was stronger than that of water hydrolysed sample. This is because Ff
ion from HzSO+ could attack ester bonds in lignin-carbohydrate complex, resulting to destroy the
structure of lignin and loose the remaining hemicellulose from insoluble crystalline cellulose which
afflects of the hydrolysis of lignocellulosic biomass [9].
Fig.3 SEM images at various magnifications of corn stover surface. [a] before pretreatment at
500x (i), 2000x (iD tbl water hydrolysis at 500x (i), 2000x (ii) tcl l% HzSO+ hydrolysis at 500x (i),
2000x (ir)
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KKU lnternational Engineering Conference
4. Conclusion
The dilute-FlzSO+ hydrolysis was a suitable process to produce sugars from corn stover for using
in the next process. The optimal conditions of acid hydrolysis was lYo HzSO+ (v/v) at 122"C for 60
min, whrrh a concentration of reducing sugar at24.96 g/1. The reduoing sugar oontained 12.4 glL of
xylose, 2.9 dL of glucose and 3.2 glL of arabinose.
fiber of corn stover from acid hydrolysis.
The SEM picture was shown the destruction
Acknowledgements
This research was supported by Scholarship research in the thesis of Graduate school Khon Kaen
University. Also, the authors would like to thanks Farm Engineering and Automatic Control
Technology Research Group and Applied Engineering for Important Crops of the North East
Research Group, Khon Khaen University for student funding support.
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