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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Article
Author(s)
Buddhiporn Sovorawet and Jirasak Kongkiattikajorn
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DOI:10.17265/2159-5828/2012.02.003
Affiliation(s)
School of Bioresources and Technology, King Mongkut’s University of Technology Thonburi, Bangkok 10150, Thailand
ABSTRACT
Cellulose biomass is being
investigated as a potential substrate for bioethanol production. Cassava stalks
were successfully converted to ethanol by fermentation using Saccharomyces
cerevisiae TISTR5048, S. cerevisiae KM1195, S. cerevisiae KM7253 and co-culture of S. cerevisiae TISTR5048 and Candida
tropicalis TISTR5045. The objective of this study was to assess the ethanol
production from cassava stalks by dilute-acid pretreatment and enzymatic
hydrolysis that were convertible into ethanol by mono-culture and co-culture of
yeast strain. Cassava stalks 1.5% (w/v) in0.1 Msulfuric acid was
pretreated for 30 min at 135 °C under the pressure of 15 lb/inch2. The
pretreated cassava stalk suspensions were neutralized to pH 5.5 for
saccharification process. The enzyme solution (a-amylase, amyloglucosidase, cellulase, xylanase and
pectinase solubilized in buffer pH 5.0) was used for hydrolysis of pretreated cassava stalk at
50 °C for 24 h. The
hydrolyaste was supplemented with additional nutrients. The culture was
incubated at 30 °C.
The pretreatment of the stalk with dilute-acid resulted sugar yield of 0.57 g/g
dry matter from enzymatic hydrolysis, which was higher than
dilute-alkaline-pretreated and distilled water-pretreated stalk. The sugar
hydrolysate was bioconverted to ethanol with separate hydrolysis and
fermentation (SHF) and simultaneous saccharification and fermentation (SSF).
The highest ethanol yields of 98.43% and 95.29% were obtained in SHF and SSF,
respectively by S. cerevisiae KM1195. The fermentation time of SSF
process was 24-32 h shorter than that of the SHF (≈ 56 h), but not significantly leading to difference in
ethanol production (5.42 g/L-6.22 g/L for SSF; 5.9 g/L-6.23 g/L for SHF).
KEYWORDS
Ethanol, cassava stalk, fermentation.
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