1. Chemical and Biochemical Engineering, Thayer School of Engineering and Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755; USDA Agricultural Research Service, U.S. Dairy Forage Research Center and Department of Bacteriology, Madison, Wisconsin, 53706; and Department of Microbiology and Institute for Wine Biotechnology, University of Stellenbosch, Stellenbosch 7600, South Africa