Bioethanol Production from Godere (Taro Root) (Colocasia Esculenta) and Sweet Potato (Ipomoea Batatas) using Saccharomyces Cerevisiae

This research aims at utilizing taro root and sweet potato for the production of bio-ethanol by using the yeast Saccharomyces cerevisiae. The milled samples of 50gm from each sample were taken then passed through pretreatment, hydrolysis, fermentation and distillation process respectively to produce bio-ethanol. The effects of biomass concentration, acid concentration, temperature and time on distilled and dilute acid hydrolysis were investigated. The milled taro root and s.potato were hydrolysed by distilled water and by dilute sulfuric acid ( 1, 2, 3 and 4) with (6.25, 7.14, 8.33, 10.00, 12.5 and 16.61 % w/v) of biomass concentration at temperature of ( room, 30, 35, 40 and 45°C) for 1, 2, 3, 4 and 5 days. The result showed that the maximum sugar content (83.14 and 86.66 % w/w by phenol-sulfuric acid and Fehling method respectively for taro root, 88.51 and 88.33 % w/w by phenol-sulfuric acid and Fehling method respectively for s.potato,) was obtained from hydrolysis of 10 % biomass concentration containing 2% sulfuric acid at 35 C for 4 days. The optimized hydrolyzate sample was fermented at optimized pH, 6.00, yeast extract, 4 g/100 mL and at 32.5 C for 4 days. The maximum 8.075 and 8.77 % w/v for godere and s.potato respectively ethanol content was achieved at 4 days fermentation time. However, as fermentation time increased from 4 days it resulted in decreasing ethanol content. Keyword: Bioethanol, Taro root, s. potato, hydrolysis, fermentation, S. cerevisiae and SHF. INTRODUCTION Due to the potential exhausting nature of fossil fuels and the increasing price of petroleum together with environmental concerns, the search for alternative renewable fuels has attracted great attention in worldwide (Sharma et al., 2008). Attention has been given to the conversion of biomass into fuel ethanol, which are the cleanest liquid fuel alternative to non-renewable fossil fuels. The rise in prices and environmental problems caused by fossil fuels has contributed to this recent interest from economic and ecological perspectives. (Lin et al., 2006). 1.1. The Statement of the Problem Ethanol is an excellent candidate to replace gasoline, and it has traditionally been produced mainly from sugars or starch (Matsakas L., et al). The world is faced with two major problems, first being the sharp depletion of fossil-fuel reserves and second is the uncontrolled environmental degradation. Combustion of ethanol results in relatively low emission of volatile organic compounds, carbon monoxide and nitrogen oxides. The emission and toxicity of ethanol are lower than those of fossil fuels such as petroleum, diesel etc. Hence there is a need to explore the possibility of using alternative energy sources, which are as efficient as oil and can be used as an alternative or by blending with present fuels. (Tahir, A. et al., 2010). 1.2. Objective of the study 1.2.1. General objective The objective of this study was to produce bioethanol from godere (taro root) and sweet potato by using co-culture of Saccharomyces cerevisiae. 1.2.2. Specific objectives  To produce bioethanol from godere (t taro aro root) and sweet potato by hydrolysis in distilled water and in different concentration of dilute sulfuric acid and fermentation.  To determine the optimum conditions for hydrolysis and fermentation of godere (taro root) and sweet potato for bioethanol Production.  To determine whether or not the godere (taro root) and sweet potato will be a feasible source of bioethanol.  To compare amount of bioethanol produced from godere (taro root) and sweet potato in which both are root crops. 1.3. Significance of the study Supply of fossil fuels causes harm to human health and contributes to the greenhouse gas (GHG) emission. The reduction of GHG pollution is the main advantage of utilizing biomass conversion into ethanol. Ethanol contains 35% oxygen that helps complete combustion of fuel and thus reduces particulate emission that pose health hazard to living things. (Ali et al., 2011 and Wyman, 1996). 2. MATERIAL AND METHODS 2.1. Procedure of Experiment The study was aimed at optimization of acid hydrolysis in the production of ethanol from Godere and s. potato. Godere and s. potato were collected from Teppi area and Temenja yazi. Those were collected in plastic bags and transported to the MTU laboratory for ethanol analysis. The following methods were followed. This section describes about the methodologies and approaches of how experiments were done in this research; it included all steps and procedures of the experiments. 2.2. Collection and Processing of Sample Godere (taro root) and sweet potato were collected in polyethene bags from Sheka zone of Tepi and Bench Maji zone of Temenja yazi town and will transport to the MTU chemistry laboratory. Sample preparation process include: manual size reduction (knife cutting), drying and grinding after the samples were collected.