Bioethanol production from cassava peels using different microbial inoculants

Abstract

The potential of bioethanol production using different microbial inoculants for the simultaneous saccharification and fermentation of cassava peels from three cassava cultivars was investigated. Peels obtained from three cassava cultivars namely TME 0505, TME 419 and TME 4779, were washed, dried in a laboratory air oven dryer at 120°C for 3 h, ground into a fine texture and sieved with 1.5 µ nylon sieve. The sieved material was cultured using the following inoculant combinations: A = Rhizopus nigricans + Saccharomyces cerevisiae; B = Aspergillus niger + Saccharomyces cerevisiae; C = Rhizopus nigricans + Aspergillus niger + Saccharomyces cerevisiae; D = Rhizopus nigricans + Spirogyra africana + Saccharomyces cerevisae; E = Aspergillus niger + Spirogyra africana + Saccharomyces cerevisiae. These combinations have not been tested before on cassava peels. The control was inoculated with S. cerevisiae only. The cultures were distilled on the 21st day and the quantity of ethanol produced in each treatment group recorded. Results obtained showed significant differences (P<0.05) in the amount of ethanol produced and in its concentration among the five inoculants. Significant differences (P<0.05) were also obtained in ethanol yield from the three cassava varieties. Cassava peels from TME 4779 gave the highest ethanol yield of 14.46 ± 2.08 g/cm3 using R. nigricans + S. africana+ S. cerevisiae. Similarly, cassava peels from TME 0505 gave the second highest ethanol yield of 13.33 ± 0.67 g/cm3 using the same combination, namely R. nigricans + S. africana + S. cerevisiae. Low ethanol yields of 4.82 ± 1.00, 6.43 ± 0.58 and 7.77 ± 0.88 g/cm3 were obtained from the cassava peels of TME 419, TME 0505 and TME 4779, respectively using S. cerevisiae alone. The yield reported in this study competes favorably with those reported from cassava peels, potato peels and millet husks using other inoculant treatments by other workers. Inoculants used in this study thus showed great potential for bioethanol production from cassava peels. Key words: Bioethanol, cassava peels, microbial inoculants.