International Journal of Applied Microbiology and Biotechnology Research
ISSN: 2053-1818
Vol. 6(4), pp. 50-60, May, 2018



Comparative study of bioethanol production from agricultural wastes by Zymomonas mobilis and Saccharomyces cerevisiae

Braide, W.1, Oji, I. O.1, Adeleye, S. A.1 and Korie, M. C.2

1Federal University of Technology, P. M. B. 1526, Owerri, Imo State, Nigeria.
2Department of Science Laboratory Technology, Imo State Polytechnic, Umuagwo-Ohaji, Imo State, Nigeria.

*To whom correspondence should be addressed. E-mail: wesleybraide2005@yahoo.com.

Received 22 March, 2018; Received in revised form 15 April, 2018; Accepted 20 April, 2018.

Abstract


Keywords:
Agricultural wastes, Bioethanol, Biofuel, Enzymatic hydrolysis, Fermentation.

The capability of local strains of Zymomonas mobilis and Saccharomyces cerevisiae to produce bioethanol from cassava, yam and potato peels was investigated. The three substrates were subjected to a pretreatment process using acid and enzyme hydrolysis to remove lignin. Ethanolic fermentation was done using Z. mobilis and S. cerevisiae for 5 days. Ethanol yield, specific gravity, pH and total reducing sugar were determined using standard methods. The results of the percentage ethanol yields from potato, cassava, yam and combined substrates gave 5.17, 6.86, 6.03 and 8.36 for Z. mobilis and 5.51, 6.77, 7.39 and 6.64% v/v for S. cerevisiae respectively at 72 h fermentation. Maximum yield of ethanol was obtained at pH 4.0-4.5 for Z. mobilis and 4.2-4.5 for S. cerevisiae. The specific gravity, sugar content and pH decreased with fermentation. The maximum ethanol produced after 72 h of fermentation by Z. mobilis was 8.36% v/v and 7.39% v/v by S. cerevisiae. During fermentation, pH of substrates inoculated with Z. mobilis and S. cerevisiae dropped from 5.0 to 4.1 and 5.0 to 4.2, respectively within 0 to 72 h. Sugar concentration reduced from 11.82 to 7.69 mg/g and 13.08 to 7.50 mg/g in substrates fermented by Z. mobilis and S. cerevisiae, respectively. The substrates were compared based on their reducing sugar content and total ethanol yield. The results obtained show that all the agricultural wastes studied have the potential to produce ethanol.

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