Ethanol production from orange waste with a focus on its cellulosic fragment

Nazari Chamaki, Sheyda
Cellulose-based biofuels are among the recent pioneer biofuels. Considering the fact that feedstock accounts for a major portion of its production cost, the cheap sources of agricultural waste as cellulosic raw material is a positive aspect for more economical biofuel production processes. In this study, production of ethanol from orange waste, more specifically from its cellulosic fragment, was studied. Three different approaches were defined for investigations on the effect of isolation of cellulosic OW fragment on glucose and ethanol production yields. In the first approach a multi-step pretreatment strategy was used for separation of different components from OW with the aim of isolation of its cellulosic fragment. The enzymatic hydrolysis conditions that resulted in the maximum glucose yield were 10% (w/v) substrate loading, 1% (v/v) cellulase loading and 24 hours of hydrolysis. Accordingly the glucose yield regarding the theoretical maximum glucose was determined as 91%. The second approach was defined to investigate the enzymatic hydrolysis and fermentation of untreated OW containing especially valuable pectin and soluble sugars. Experimental parameters that led to maximum glucose yields were measured to be 20% substrate loading (w/v), 1% (v/v) cellulase, and 4% (v/v) pectinase loading and 24 hours of hydrolysis. The glucose yield regarding the maximum theoretical cellulose content of OW was 88%. The third approach focused on the possibility of using more environmentally friendly and simpler pretreatment steps for separation of pectin and other soluble components from OW. The glucose yield based on this approach was 91% considering the theoretical maximum glucose content. The wild type yeast Saccharomyces cerevisiae NRRL Y-132 was used for the fermentation of sugars present in the hydrolysates obtained by each approach. The resulting ethanol production yields on the basis of the theoretical maximum yields for the first to the third approach were determined as 96, 99 and 96% (w/w), which correspond to 0.72, 2.7 and, 0.78% (w/v) (g ethanol/ 100 ml medium), respectively. Starting with initial glucose concentrations of 12, 55 and, 16 g/L in approaches 1, 2 and, 3 resulted in 7, 27 and, 8 (g ethanol/ L fermentation medium), respectively, indicating the possibility of increasing ethanol yield by increasing initial glucose concentration.


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Citation Formats
S. Nazari Chamaki, “Ethanol production from orange waste with a focus on its cellulosic fragment,” M.S. - Master of Science, Middle East Technical University, 2013.