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Optimization of divalent cation in Saccharomyces
pastorianus medium conditions for ethanol production
Okon, Anne Anthony1* and Nwabueze, Titus U.2
1Department
of Food Science and Technology, University of Uyo, Akwa Ibom
State, Nigeria.
2Department
of Food Science and Technology, Michael Okpara University of
Agriculture, Umudike, P.M.B. 7267 Umuahia, Abia State,
Nigeria.
*Corresponding author. E-mail:
annytony2002@yahoo.com.
Accepted 17 August, 2009 |
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Cassava starch fermentations were conducted in batch
cultures to optimize the effect of divalent cations on
ethanol production with Saccharomyces pastorianus
using the central composite rotatable response surface
design. Divalent cations used were magnesium (Mg2+),
zinc (Zn2+) and calcium (Ca2+).
Maximum ethanol concentration of 11.12% v/v was obtained
with cationic concentration combination of 64, 0.48 and 30
mg/l for Mg2+, Zn2+ and Ca2+,
respectively, after 96 h of the fermentations. Minimum
ethanol concentration of 7.53% (v/v) was obtained at a
variable combination of 64, 0.48 and 76 mg/l for Mg2+,
Zn2+ and Ca2+, respectively. Thus
response surface methodology was used in a central composite
design to optimize the process variables of Mg2+,
Zn2+, Ca2+ in the fermentation medium,
thereby increasing the ethanol production from 10.5% in the
control to 11.12%. There were significant linear and
quadratic effects of Zn2+ as well as a
significant (P ≤ 0.05) negative quadratic effect of Ca2+
on ethanol production, which are confirmed in the response
surface plots.
Key words:
Ethanol, Saccharomyces pastorianus, cassava starch,
hydrolyzates, central composite design, response surface
methodology. |
