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 21 st 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/cm 3 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/cm 3 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/cm 3 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. Keywords: Bioethanol, cassava peels, microbial inoculants
Highlights
INTRODUCTIONThey have served as drivers for new government initiatives to increase alternative fuel sources, principally ethanol from biological feed stocks such as cassava (Manihot esculentum), corn (Zea mays) and sweet potato (Ipomoea batatas)
A number of studies have been carried out in an attempt to optimize the yield of ethanol from cassava peel using different organisms including Saccharomyces cerevisiae (Adesanya et al, 2008; Marx and Nquma, 2013), Zymomonas mobilis and S. cerevisiae (Sulfahri et al, 2011) Gloeophyllum sepiarium plus Pleurotus ostreatus for hydrolysis and Z. mobilis and S. cerevisiae for fermentation (Oyeleke et al, 2012; Adiotomre, 2015), Aspergillus niger for hydrolysis and S. cerevisiae for fermentation (Adetunji et al, 2015)
Three cultivars of cassava identified as TME 97/ 0505, TME 419 and TME 92/4779 were obtained from National Roots Crops Research Institute (NRCRI) at Umudike, Abia State, Nigeria
Summary
They have served as drivers for new government initiatives to increase alternative fuel sources, principally ethanol from biological feed stocks such as cassava (Manihot esculentum), corn (Zea mays) and sweet potato (Ipomoea batatas). The present study was aimed at contributing to this ongoing effort by using new combinations of microorganisms (A. niger, Rhizopus nigricans and Spirogyra africana) in the combined saccharification and fermentation process to produce ethanol from the peels of cassava. To the best of the authors’ knowledge, this combination has not been tried before for this purpose
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