Ethanol production from lignocellulosic materials by fermentation process using yeast
Rapid industrialization and growing population result to high demand for energy. Depletion and rise in price of petroleum as well as environmental pollution necessitates the need for alternative source of fuel, hence bioethanol production. Rice bran (Oryza sativa), Corn bran (Zea mays) and Sorghum bran (Sorghum guinense) and saw dusts of Khaya senegalensis (Red wood), Terminalia superba (Black wood), Gmelina arborea (White wood), were used for the study. The yeasts used for the study were isolated from fermented beverages (Sorghum beer, Millet beverage and Palm wine). The results of the lignocellulosic biomass of white saw dust, red saw dust, black saw dust, rice bran, corn bran and sorghum bran revealed cellulose components as 77.78%, 75.55%, 68.59%, 64.83%, 54.82% and 55.14% respectively. A total of 25 yeasts were isolates and identified using API 20C AUX strip. The yeast isolates, K2, B5, B7 and P1 had the highest ethanol tolerance value of 14%. The results showed that the ethanol-producing ability of the yeast isolates ranged from 4.1% to 10.3%. Fourier Transform Infrared Spectrophotometer (FTIR) and Gas Chromatography and Mass Spectrometry (GC-MS) analyses showed that ethanol is the main compound produced by yeasts from the lignocellulosic materials. This study revealed that Saccharomyces cerevisiae isolated from palm wine (P1) is best in ethanol production and tolerance, and this high prolific strain can be exploited or engineered for ethanol production. Therefore, Lignocellulosic biomasses are recommended as raw materials for producing ethanol, which is a promising alternative energy source as against the depleting petroleum.
Keywords: Ethanol, Lignocellulose, Yeasts, Beverages and Saccharomyces cerevisiae.