Utilisation of maize agrowastes for bio-ethanol production using saccharomyces cerevisiae and aspergillus niger in batch simultaneous saccharification and fermentation.
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Date
2008-07-12
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Abstract
Maize or Corn (Zea mays) is the most abundant cereal cultivated in Ghana (Asante, 2004). According to Asante (2004), production between 1995 and 2004 had hovered around a million metric tones per annum. This was accompanied by large quantities of maize agrowastes (husk, cobs and stove). The yields of various components of maize are: grains, 35%; husk and skins, 30%; corncobs, 30%; and skin trimmings, 5% (Rangkuti and Djajanegara, 1983).
Maize agrowastes do not pose as hazards to the environment but are underutilized resource. Currently the corncobs are burnt as fuel in the households of peasant rural farmers. The husks are used for wrapping kenkey and the stoves are usually burnt or left in the field. In large commercial farms where harvesting is mechanized, the agrowastes are left on the field and ploughed into the soil. This practice adds little to the soil nutrient status because maize agrowastes have high lignin, low nitrogen and readily available carbon content. Jigisha et al., (2005) put nitrogen content per dry weight of corn cobs at 0.4%. It has been shown that high lignin, high carbon to nitrogen ratio and and low nitrogen contents of maize residues negatively affect their decomposition rate (Safari et al., 2005). Maize agrowastes can be used to produce bioethanol.
Production of bio-ethanol from lignocellulose is relatively expensive. Currently, production cost is $2.65/gallon compared to $1.65/gallon for corn ethanol (www.nrel.gov, 2008; Collins, 2007). Cellulase is the costly part in the cellulosic ethanol production, accounting for approximately 40% of the total cost (Howard et al., 2003; Miyamoto, 1997). One way of reducing this cost is isolating a fungus with efficient cellulase system which is more likely to be found in a habitat where the lignocellulosic maize agrowastes are the predominant source of carbon and energy. At Ejura farms where harvesting is mechanized, the agrowastes are left on the field and ploughed into the soil making it a good habitat for cellulolytic fungi (Agana, 2007). Baig et al. (2003) isolated a cellulolytic fungus efficient in degrading banana agrowastes from a field where banana has been grown for 7 years.
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A Thesis submitted to the Department of Biochemistry and Biotechnology, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirement for the award of the degree of Master of Science (MSc.) in Biotechnology