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Appl Environ Microbiol. 1975 July; 30(1): 113-119
Copyright © 1975 American Society for Microbiology. All Rights Reserved.

Changes in Microbial Population During Fermentation of Feedlot Waste with Corn

Northern Regional Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Peoria, Illinois 61604

ABSTRACT

A new process for recycling feedlot waste involves the fermentation of liquid from this waste combined with corn. Changes in the flora of this silage-like fermentation were followed. The fermentation was dominated by lactobacilli and yeasts, which initially constitute 1% or less of the natural flora. The species of yeasts and lactics involved were characterized. The fermentation has two phases. A single heterolactic species multiplied rapidly for the first 24 h until it represented 95% of the lactobacilli and more than 90% of the total microflora. It displaced the betabacterium predominant among lactics of the original waste; the acid produced killed coliforms and other organisms in feedlot waste; and the acetic acid produced probably caused the death of the dominant native yeast Trichosporon cutaneum (de Beurm., Gougerot et Vaucher) Ota. The peak lactobacillus count remained constant (about 2 x 10⁹ organisms/g [wet weight]) throughout the rest of the fermentation. Homolactics dominated the later phase and yeasts increased to 9.5 x 10⁷ organisms/g (wet weight). At 6 days, a stable mixture of three lactobacilli was present, one streptobacterium, one thermobacterium, and one betabacterium. Similarly, yeasts stabilized as a mixture of two Candida sp. and one Pichia sp. The dominant species of lactics were characterized. Information on the sequence of microorganisms provides a basis for enhanced protein synthesis in the fermentation.