Abstract
Cellulose is one of the most important of natural renewable sources. Cellulase enzymes convert it into oligosaccharides and glucose. These enzymes have several applications in industries and widely used in second generation of biofuel production process. The aim of this study was to use rice straw as a carbon source of Saccharomyces cerevisiae cells to produce bioethanol. Phosphoric acid plus hydrogen peroxide chemical pretreatment was performed to obtain a cellulose-rich source of rice straw. Mesophilic filamentous fungal isolates collected from cattle manure samples, the best isolates were selected based on cellulase activities at optimal reaction conditions. These isolates were identified by DNA sequencing of ITS region. Aspergillus fumigatus and A. niger showed the highest activities of endoglucanase, exoglucanase and total cellulase enzymes at temperature 35 °C, pH 5.5, and temperature 30 °C, pH 4.5, respectively. Pretreated rice straw was hydrolyzed by enzymatic solution of two fungal isolates. The obtained sugars (8.654 g/L for A. fumigatus and 7.412 g/L for A. niger hydrolysates) were fermented by Saccharomyces cerevisiae yeast cells and converted to the bioethanol. The highest amounts of ethanol were obtained from A. fumigatus and A. niger lysates after 72 h of fermentation as 11.2 g/L and 8.29 g/L, respectively.
Published Version
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