2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
- 63 -
Abstract--The study to develop high sugar production by
optimization of enzymatic hydrolysis process as well as
applications of enzyme for ethanol production using
Acacia
auriculiformis Cunn.
’s leaves
by Saccharomyces cerevisiae
was also investigated.
Acacia auriculiformis Cunn.
’s leaves
contained cellulose and lignin at 48.9±7.6% and 44.3±0.6%,
respectively. However, after treated with 2% (NH
4
)
2
SO
4
for
24 h in supplemented with stream autoclave (121
o
C, 15
min), giving highest content of cellulose (93.1±0.4%) while
lignin content decreased significantly (6.4±1.2%). Effects of
substrate concentration, cellulase concentration and
incubation time on sugar production were studied. The
highest sugar production at 6.7 g/L was achieved from the
optimal condition containing 30 g leaves/L with 0.17 mg
cellulase/mL for 16 h of incubation. Glucose was identified
as a major sugar component in cellulosic hydrolyzate using
HPLC analysis. The ethanol production from pretreated
leaves using
S. cerevisiae
in both SHF and SSF process was
1.06 and 1.18 g/L, respectively.
Index Terms
--Cellulase, Ethanol, Leaves, Sugar
production
I. N
OMENCLATURE
HPLC High performance liquid chromatography
SHF Separate hydrolysis and fermentation
SSF
Simultaneous saccharification and fermentation
II.
I
NTRODUCTION
Nowadays, environmental problem is a sensitive issue.
Fossil fuels are involved in the emission of greenhouse
gases that pollute the environment. Bioethanol, an
alternative fuel has attracted a lot of attention because it
results to zero net carbon dioxide output into the
atmosphere since it is recycled through photosynthesis [1,
2, 3]. Commercial bioethanol production mostly relies on
fermentation of sucrose from sugarcane and mollases or
waste originating from agricultural crops, households and
industries, with
wastepaper being a major component of
these waste materials [4, 5]. Cost of raw material and
cellulases in enzymatic hydrolysis are regarded as a
major factor [6]. Research and development to reduce the
cost of bioethanol has been carried out in various aspects.
Relatively large amount of bioethanol production tried to
reduced cost at substrate level by using lignocellulosic
materials as substrate such as sugarcane [7], corn [8],
This work was supported by Department of Chemistry and Research
and Development Institute, Thaksin University.
sugar beet [9] as well as agricultural waste, wastepaper
[4, 10, 11] and leaf waste [12, 13] due to there is
renewable, mainly unexploited, largely abundant,
inexpensive resource and high content of readily
convertible and fermentable sugar [14, 15, 16, 17].
The leaves of
Acacia auriculiformis Cunn.
, an
abundant plant found in Thailand, can be transformed to
sugars in a short time due to the microcrystalline nature
of its cellulose [18]. Dry leaves are municipal-residues
burnt after falling. Utilizing these leaves would aid
pollution abatement. The goal of this study aim increase
in sugar yields by optimization study in lignocellulose
hydrolysis by cellulase as well as sugar hydrolyzate from
leaf waste was utilized as substrate for ethanol production
by both SSF and SHF process using
Saccharomyces
cerevisiae
.
III. M
ATERIAL AND
M
ETHOD
A. Leaf waste materials
Leaf waste obtained from Thaksin University
(Phattalung, Thailand) was used as substrates. The
control materials were prepared as pieces of 1 cm. x 1
cm. and stored at room temperature until required [10].
Waste materials were pretreated with various reagents
including HCl, NaOH and (NH
4
)
2
SO
4
at concentration of
2% (w/v) for 24 h with/without stream autoclave (121
o
C,
15 min). Therefore, all lignocellulosic samples were
neutralized prior to utilization and partial characterization
of cellulose, holocellulose and lignin content.
B. Compositional analysis of lignocellulosic materials
The content of cellulose and lignin were determined
using the TAPPI Test Method [19]. Holocellulose content
was determined by sodium chlorite method according to
Browning [20]. A hollocellulose, the total polysaccharide
fraction of lignocellulosic materials, which is composed
of cellulose and all of the hemicelluloses and that is
obtained when the extractives and the lignin are removed
from the natural material.
C. Optimization for enzymatic hydrolysis using leaf waste
The aimed of optimization step was to find an
important factor and approximate range of each selected
component in enzmatic hydrolysis for reducing sugar
production. The experiments were carried out by using
Optimization Studies on Enzymatic Hydrolysis
and Applications for Ethanol Production using
Leaf Waste
K. Sangkharak, R. Samae, and C. Wangbua
COE of Renewable energy, Department of Chemistry, Thaksin University, (
Thailand
)
