Genetic technology : a new frontier / Office of Technology Assessment.

Date:
[1982]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Genetic technology : a new frontier / Office of Technology Assessment. Source: Wellcome Collection.

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    296 Figure 1-0-3.—Alternative Schemes for Enzymatic Hydrolysis of Cellulosic Biomass for Ethanol Production Cellulase fermentation Enzyme recovery Cetlulosic biomass z ОГг Delignificatìon [ ^ Enzymatic hydrolysis Lignin < Combustion > Heat Г Ethanol Size reduction and pretreatment Cellulase fermentation Hydrolysis reactor Ethanol recovery 5 Combustion Lignin - Ethane) Heat Direct fermentation of cellulosic biomass Ethanol Heat SOURCE: Massachusetts Institute of Technology. Table l-D-1.—Alternative Pretreatment Methods for Lignocellulose Materials Chemical methods Physical methods Sodium hydroxide (alkali) Ammonia Chemical pulping Ammonium bisulfite Sulfite Sodium chlorite Organic solvents Acids Steam Grinding and milling Irradiation Freezing SOURCE: Office of Technology Assessment. veloped technology, such as that developed by groups working at Purdue University, New York Uni¬ versity, and Dartmouth College. There are several engineering problems involving both heat and mass transfer and acid/solvent recycle that need to be eval¬ uated at larger scale. At least some of this work will be done at the process development unit now being built at the Georgia Institute of Technology. The most promising directions that need development are: • the scale-up of high rates and high yield labora¬ tory hydrolysis systems, and • the development of methods for acid and chem¬ ical recycle schemes. There are three types of approaches that have been employed for enzymatic hydrolysis of cellulosic biomass. These are summarized in figure I-D-3. They all involve some initial size reduction to increase the surface area available for enzymatic attack. In schemes A and B, the incoming cellulosic biomass is split into two streams; one is used to grow organisms that produce cellulolytic enzymes called cellulases, and the other is used to produce sugar. In scheme A, the cellulases are recovered and then added to a separate enzyme hydrolysis reaction. They hydrolyze both the cellulose and hemiceilulose, and the resulting sugar solution is then passed to an ethanol fermentation stage where hexoses are con¬ verted by a yeast fermentation to ethanol. Utilization of the pentose requires a separate fermentation. Re-