Bioethanol and biogas potential of wild cassava, manihot sp: microbial and process conditions for bioconversion

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University of Dar es Salaam
This thesis details an evaluation of bioenergy potential of inedible wild cassava for bioethanol and biogas production. Bioconversion processes such as biomass pretreatment; fermentation and anaerobic digestion were optimized, integrated and applied for the production of bioethanol and biogas. Simultaneous saccharification and fermentation (SSF) in stirred tank bioreactor resulted to ethanol titer, productivity and conversion efficiency of 10-11%v/v, 6.5g/L and 98%, respectively. Very high ethanol titer (24% v/v) was achieved from raw starch through SSF-fedbatch mode by the aid of automatic gas potential test system. Metabolic response of a new bacterium Caloramator boliviensis to nutrient dosage and substrate oxidation state revealed the importance of balancing electron flow through co-factor regeneration by formation of ethanol and lactate as electron sinks. At high hydrogen partial pressure (ca.590 pa), ca.76 g/L of glucose was fermented yielding 33 g/L of ethanol. Yields of reducing sugars obtained during liquefaction of cassava starch using enzyme preparation from Bacillus sp. and Aspergillus sp. at 60 °C and 50 °C reached 56% and 66% of theoretical yields, respectively. High energy yield, 15-23 MJ/KgVS added was obtained through co-production of bioethanol and biogas from the wild cassava tuber. Combined ethanol and methane fermentation from wild cassava peels produced 1.2-1.3-fold fuel energy yield compared to only methane and 3-4-fold compared to only bioethanol. This study evaluated the potential of and optimised processes for bioethanol and biogas production from inedible wild cassava.
Available in print form, East Africana Collection, Dr. Wilbert Chagula Library, Class mark (THS EAF TP339.M67)
Biomass energy, Biofuels, Microbial Energy Conversion
Moshi, A.P.(2015) Bioethanol and biogas potential of wild cassava, manihot sp: microbial and process conditions for bioconversion, Doctoral dissertation, University of Dar es Salaam, Dar es Salaam