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Lactic Acid From Alfalfa

Lactic acid—a colorless or slightly yellow, syrupy liquid—is naturally formed by the fermentation of lactose, or milk sugar. Its name comes from the Latin word "lac," which means milk. Commercially, lactic acid can be made synthetically from chemicals or organically as a byproduct of corn fermentation.

Last year, ARS agricultural engineer Richard G. Koegel in Madison, Wisconsin, and University of Wisconsin researchers were the first scientists to make lactic acid from alfalfa. This accomplishment will give alfalfa an extra economic boost.

The USDA-Wisconsin research partnership has already produced several alfalfa-derived products, such as carotenoids and protein concentrates, worth from $1,000 to $2,000 per acre annually.

Lactic acid is commonly used as a food additive for flavor and preservation, but a new market for organic lactic acid exists for making biodegradable plastics. The current lactic acid market in the United States is about 50,000 tons per year, more than half of which is imported.

The alfalfa fibrous fraction, from which lactic acid is made, results when juice is expressed from freshly cut herbage to make other high-value products, including food- and feed-grade proteins and carotenoids.

ARS research with transgenic alfalfa also produced industrially valuable enzymes.

Instead of using chemical treatments, Koegel pretreated alfalfa fiber for 2 minutes in hot water at 430oF and 350 pounds-per-square-inch pressure. With hot-water pretreatment, hydrolytic enzymes, and a Lactobacillus bacterium, the researchers got lactic acid yields as high as 60 percent.

"Many microorganisms can ferment either five- or six-carbon sugars. The Lactobacillus bacterium that we used is an exception because it can ferment both," Koegel says.

Koegel is now attempting to boost lactic acid yields using the microbe without pretreatment. If this work proves successful, it may help lower industry's cost of production.

Growing alfalfa in some agricultural areas is preferred over corn and soybeans, which require more fertilizer and soil tillage that can lead to soil erosion. Another benefit: Alternating alfalfa with corn and soybeans reduces pesticide use and increases yield of corn and beans.—By Linda Cooke McGraw, Agricultural Research Service Information Staff.

Richard G. Koegel is at the USDA-ARS U.S. Dairy Forage Research Center, 1925 Linden Drive West, Madison, WI 53706; phone (608) 264-5149, fax (608) 264-5275.

"Lactic Acid From Alfalfa " was published in the May 1999 issue of Agricultural Research magazine.

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