THE PRETREATMENT AND ENZYMATIC SACCHARIFICATION OF POPLAR WOOD

This study is concerned with the characterization of a process for converting lignocellulosic materials to soluble sugars and a lignin by-product. The sugars from the process are intended for feedstock to an alcohol fermentation process. The lignin may be used for its fuel value or as a polymer feedstock. In this study, the pretreatment of the lignocellulose can be divided into two stages; delignification and swelling. An ammonia/ethanol treatment at 190(DEGREES)C for 2 hours was found to be suitable for delignification. Swelling was best accomplished using sodium hydroxide/ethanol mixtures at 160(DEGREES)C for 30 minutes. The parameters of time, temperature and reactant concentration have not been optimized; however, a method for optimization of the process has been developed. Because of the close coupling between pretreatment and saccharification, a model of enzymatic hydrolysis was developed. The values of the parameters in the model reflect the degree of pretreatment. The model also includes the effects of substrate concentration, enzyme concentration, and product inhibition by cellobiose and glucose. Using such a model, it is possible to do a cost/benefit analysis of the pretreatment/saccharification process. In the course of these studies, it was found that some of the commonly used analytical procedures were inadequate and needed improvement. A technique for measuring total hexoses (both soluble and insoluble) in the presence of pentoses was developed using chromotropic acid. A technique for measuring total pentoses (both soluble and insoluble) in the presence of hexoses was also developed using orcinol