Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Abstract The interactions among purified tannins from three different plants with five strains of ruminal bacteria were investigated. Tannins were purified from crude quebracho (Schinopsis balansae spp.), desmodium (Desmodium ovalifolium), and myrtle (Mirtus communis). The ruminal bacteria studied were Streptococcus bovis JB1, Ruminococcus albus 8, Fibrobacter succinogenes S85, Prevotella ruminicola H14, and a recently isolated tannin-tolerant bacterium. Bacterial binding to tannins, rate of tannin binding, and the inhibitory concentrations for each bacterium to each tannin were evaluated. The effects of tannins on glucose utilization and fermentation product formation also were studied. Tannin binding was rapid with little additional binding occurring 10 min after tannin addition. There was variation among bacteria in the amount of tannins bound and in the amount of tannin required to inhibit growth. Condensed tannins from myrtle and desmodium had the highest binding capacity and were most inhibitory to microbes. Absorbance readings from the total phenolics assay were highest for myrtle and lowest for quebracho. Similarly, readings for condensed tannins were highest for desmodium, which also had the largest polymer size. Myrtle and quebracho gave the largest precipitate rings in the radial diffusion assay, a biological assay that measures precipitation of bovine serum albumin by tannins. The relative absorbance values obtained from the total phenolics assay were the most useful predictor of tannin inhibition of microbial growth. The acid–butanol assay and the radial diffusion assay using bovine serum albumin as the precipitable protein were much less useful predictors of tannin biological activity against the bacteria studied.
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