Enzymatic Conversion of Unusual Cellulosic Wastes to Alcohol Fuel. Alcohol-Fuels Grant Program.

摘要

Samples of unusual cellulosic wastes from a Sulfite pulp mill, spent mushroom compost and wastes from a cellophane manufacturing plant were collected and analyzed for saccharide content. This analysis showed that the pulp mill wastes (fines) had the greatest cellulose content (approx. 78%), while the cellophane wastes contained up to 40% cellulose and the mushroom compost only 20 to 25% cellulose. The mushroom compost could not be used both technically and economically as a substrate for ethanol production. The cellulose in the pulp mill waste was readily hydrolyzed to cellobiose by the extracellular enzymes of Thermomonospora fusca YX but required substantial quantities of beta -glucosidase activity in order to generate glucose. The glucose produced could be easily fermented by both Saccharmoyces yeast and Thermoanaerobacter ethanolicus. The use of T. ethanolicus eliminated the need for beta -glucosidase additions but gave low yields and low conversions. Under the best of circumstances, 60 to 70% of the cellulose was hydrolyzed and converted to ethanol. However, ethanol concentrations greater than 1% w/v were rarely achieved, thus leading to high recovery costs for ethanol. To overcome these problems two process recommendations have been made. One is a novel design for high temperature enzymatic saccharification of cellulose in a countercurrent tower design, followed by fermentation of the sugar stream in a thermophilic fermentation in a packed bed containing immobilized Thermoanaerobacter ethanolicus. This design should reduce the need for costly enzyme and provide a continuous process. The second design is more conventional and uses a sulfur dioxide catalyzed hydrolysis of cellulose followed by yeast fermentation. (ERA citation 08:048787)