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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #115438
Title: ETHANOL PRODUCTION FROM ALFALFA FIBER FRACTIONS BY SACCHARIFICATION AND FERMENTATION

Author
item SREENATH, HASSAN - UNIV WISCONSIN, MADISON
item Koegel, Richard
item MOLDES, ANA - FOREST PRODUCTS LAB, WI
item JEFFRIES, THOMAS - FOREST PRODUCTS LAB, WI
item STRAUB, RICHARD - UNIV WISCONSIN, MADISON

Submitted to: Process Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Alfalfa is a perennial legume, which means that it fixes its own nitrogen fertilizer from the atmosphere and only needs to be reseeded every 3-5 years. It produces more protein per acre than any other crop and is known for its good soil and water conservation characteristics. These characteristics make it a highly sustainable and desirable crop that improves yields of other crops grown in rotation with it. Utilization of alfalfa, however, has been limited to ruminant (cattle, sheep, and goats) rations by the high fiber content of the herbage. This limitation can be overcome by a process called wet fractionation, the separation of freshly cut herbage into juice and fiber fractions, each of which can be converted to valuable products. The fiber fraction was converted to sugars by properly selected enzymes. These sugars, in turn, were fermented to industrial chemicals or fuels such as lactic acid or ethanol. It is important to determine the proper mix and quantity of enzymes to convert the fibers to sugars as well as to determine the most appropriate microorganisms to ferment these sugars to the target product(s). Knowledge of the quantity and value of product relative to input costs is necessary to determine economic feasibility. The production of chemical feedstocks from renewable biological materials can help to reduce the release of carbon dioxide to the atmosphere, reduce dependence on imported petroleum, as well as providing new jobs in the rural sector.

Technical Abstract: This work describes ethanol production from alfalfa fiber with and without liquid hot water (LHW) pretreatment. Candida shehatae FPL-702 produced 6.4 g/L ethanol by simultaneous saccharification and fermentation (SSF) from 100 g alfalfa fiber without pretreatment. With LHW pretreatment, C. shehatae FPL-702 produced 18.0 g/L ethanol from 100 g alfalfa fiber consisting of insoluble cellulose fraction. However, the soluble extract fraction containing hemicelluloses was poorly fermented due to the presence of inhibitors. The extract contained 1 g/L acetic acid, 0.29 g/L formic acid, and 0.5 g/L uronic acids. Steaming, microwaving, or autoclaving of the pretreated alfalfa fiber produced the same ethanol production rates. Addition of 0.07% sulfuric acid to LHW pretreatment of alfalfa fiber resulted in fractions that fermented poorly to ethanol. These results show that although LHW pretreatment can increase ethanol production from alfalfa cellulose, it decreases production from the hemicellulosic and pectin fractions.