ISSN 2375-0723
African Journal of Food Science Research ISSN 2375-0723 Vol. 7 (10), pp. 001-006, October, 2019. © International Scholars Journals
Full Length Research Paper
Simultaneous effect of divalent cation in hydrolyzed cassava starch medium used by immobilized yeast for ethanol production
Okon, Anne Anthony1* and U. Nwabueze, Titus2
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.
Accepted 09 July, 2019
Abstract
Response surface methodology was adopted in a central composite design to optimize ethanol production from cassava starch hydrolysate medium. Starch hydrolyzate was prepared from TMS 98/0581, a genetically developed cassava mosaic disease-resistant variety. The yeast whole cell, Saccharomyces pastorianus, a lager brewing strain (726 x 106 cells/ml, 98.78% viability) and fungamyl and termamyl (a-amylase enzymes), used for the 120 h fermentation, were immobilized by entrapment in calcium alginate gel. Effects of three divalent cationic concentrations Mg2+, Zn2+ and Ca2+ on ethanol yield were investigated at five variable combinations in 20 experimental runs in accordance with the experimental design. Maximum ethanol concentration of 12.53 %v/v was produced in the 96 h of fermentation when the divalent cationic combination was 64, 0.48 and 30 mg/l (Mg2+, Zn2+ and Ca2+), respectively. The study showed that effect of Zn2+ on ethanol yield was significantly (P 0.05) quadratic.
Keywords: Ethanol, immobilization, Saccharomyces pastorianus, divalent cations, optimization, response surface methodology, cassava mosaic disease.