Microbial production of 2,3-butanediol from rice husk using anaerobic <i>Clostridium</i> species

Abstract

Interest in the area of biomass based-product production is increasing all over the world due to the environmental challenges posed by fossil fuel and fear of its extinction. Production of biofuel and other compounds especially from agricultural waste can reduce these environmental problems because of its sustainability and environmentally friendliness. One of the major petrochemical product widely used in many industries is 2,3-butanediol and was found to be produced from agricultural wastes by microorganisms. Therefore, Microbial production of 2,3-butanediol from rice husk using Clostridium species was investigated in this research. Structural composition of the rice husk was determined before and after pretreatment. Hemicellulose and lignin content of rice husk was determined after extraction while cellulose was determined as the difference from the extractives, hemicelluloses and lignin. Dilute (2%) NaOH was used for the pretreatment of rice husk. Hydrolysis was carried out using Aspergillus niger and reducing sugar released was determined using standard method with UV-VIS spectrophotometer. Clostridium species was isolated from sugarcane bagasse, identified using basic morphological and molecular biology techniques. The fermentation of rice husk was performed using the Clostridium species. Fermentation by-product was determined using Gas Chromatography Mass-spectrometry. Cellulose content increased from 32% before pretreatment to 53.3% after pretreatment, lignin increased from 8.4% before pretreatment to 30.7% after pretreatmemt and hemicellulose decreased from 30% before pretreatment to 8% after pretreatment. A total of 1.05 g/l of reducing sugar was released after enzymatic hydrolysis of the rice husk with Aspergillus niger. Alcohol 2,3-butanediol (0.6%) and Furfuryl alcohol (0.45%) were detected in the by-product of fermentation. Other compounds detected are fatty acids that ranges from C16 to C25 with 9,12-Octadecanoic acid as the major fatty acid. From the results of this work, Rice husk was found to have substantial amount of sugar (cellulose and hemicelluce) that can be converted to valuable product including 2,3-butanediol.

Keywords: Biofuel, Bio-refinary, Cellulose, Clostrudium, fermentation.