Studies on Bioethanol Production from Rice Stalk using Co-cultures of Aspergillus niger and Saccharomyces cerevisiae

Abstract

Bioethanol production from lignocellulosics as an alternative automobile and engine fuel has received a considerable attention from researchers worldwide. In the current work, Bioethanol was produced from sulfuric acid and alkaline hydrogen peroxide treated rice stalk employing simultaneous saccharification and fermentation process using co-cultures of isolated and characterized strains of A. niger and S. cerevisiae. The proximate composition of the substrate was determined following standard procedures described by Association of Official Analytical Chemist. The composition of the substrate treated with sulfuric acid was moisture (4.95%), ash (4.75%), fats (4.50%), protein (5.25%), fibre (50.90%), carbohydrates (80.55%), while that of alkaline peroxide-treatment was moisture (3.65%), ash (5.10%), fats (6.60%), protein (7.00%), fibre (38.65%) and carbohydrates (77.65%). At optimal fermentation conditions of 35ºC temperature, 5.0 pH, 4% substrate concentration, 300 rpm agitation rate and 4 days fermentation period and after determining the quantity of the ethanol produced using specific gravity method, a maximum of 5.06 g/100 ml and 3.91 g/100 ml of ethanol was obtained from sulfuric acid and hydrogen peroxide treated rice stalk respectively. The qualitative analysis using FTIR-Spectrophotometry shows the absorbance peaks of the ethanol functional groups from all the ethanol samples produced and the functional groups had their absorption peaks within their normal ranges of 3100-3600 cm⁻¹, 2800-3000 cm⁻¹ and 1600-1675 cm⁻¹ for hydroxyl, alkane and alkene functional groups respectively.