Supercritical Carbon Dioxide Treatment of Lignocellulosic Biomass to Enhance Cellulose Hydrolysis

摘要

Lignocellulosic materials are the most abundant renewable organic resources present on earth, containing cellulose, hemicellulose, and lignin as their main constituents. Production of ethanol from these lignocellulosic materials is of major commercial interest, but extensive research is still needed to develop an effective cellulose-hemicellulose conversion process. Softwood (Ponderosa Pine saw dust) was used as the substrate in this research for two reasons: (1) its abundance in western South Dakota as waste forest thinnings and (2) its low cost when compared to other raw materials such as com or other lignocelluloses. Effective pretreatment of softwood is essential for achieving higher ethanol yields via enzymatic hydrolysis and subsequent fermentation.rnThe present study involves the pretreatment of Ponderosa Pine with supercritical carbon dioxide (SC CO_2) at different conditions (such as temperature, time, pressure and moisture content) to improve glucose and ethanol yields. The effectiveness of SC CO_2 was investigated by carrying out enzymatic hydrolysis on the pretreated softwood. The effect of pretreatment temperature, pressure, time, scale-up, and moisture content on glucose yields is discussed. The average glucose yields obtained for our optimized pretreatment conditions ranged from 62.97 ± 2.38 to 91.61 ± 3.64% of total glucose present. In comparison; glucose yields for unpretreated Ponderosa Pine were only 11.75 ± 0.75%. Pretreatment mechanisms for this process, along with implications for process scale-up are discussed.