Optimization of Hydrolysis for Production of Bioethanol from Waste Potatoes and Potato Peels
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Date
2015-06
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Addis Ababa University
Abstract
Green plants and factory byproducts containing carbohydrate can be a source of a product like bioethanol. The major problem of these raw materials is the content of the type of carbohydrate. In this study, waste potatoes and potato peels was chosen as a carbon source; however, a pretreatment process is needed to convert starch of potato to fermentable sugar through hydrolysis. In order to obtain maximum fermentable sugar, optimal value of factors for hydrolysis was determined by Response Surface Methodology (RSM) using Central Composite Design (CCD). The optimum combination of temperature, liquid-solid ratio, and time was determined.
Waste potatoes and potato peels were washed, cut, dried at 105 °C for 24h and ground to the particle size of 2 mm. After soaking in diluted acid for 24h, hydrolysis was carried out. Then after water was added. And then separation of fermentable and non-fermentable sugar with centrifuge was accomplished. Then fermentable part of the hydrolyzate goes to fermentation. After fermentation distillation was carried out for bioethanol separation.
Analysis of starch content of waste potatoes and potato peels and sugar content of hydrolyzate was carried. The starch content was analyzed with iodine solution and the sugar content was analyzed with phenol sulfuric acid. The analysis was done by using UV/Vis spectroscopy. The amount of starch content of waste potatoes and potato peels is 0.095 g/ml and 0.084 g/mL respectively. The optimal value of sugar content of waste potatoes and potato peels is 0.080 g/mL and 0.074 g/mL respectively. The amount of alcohol for waste potatoes and potato peels is 32.0% and 27.5% v/v respectively. The statistical analysis was accomplished by using Design Expert version 7.
Key words: sugar, optimum, starch, waste, hydrolysis, and analysis
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sugar; optimum; starch; waste; hydrolysis; and analysis