Effect of Dicarboxylic Acids and Aspergillus oryzae Fermentation Extract on Lactate Uptake by the Ruminal Bacterium Selenomonas ruminantium

AUTOR(ES)

Nisbet, David J.

RESUMO

The objective of this study was to determine the effects of l-aspartate, fumarate, l-malate, and an Aspergillus oryzae fermentation extract (Amaferm) on growth on lactate as well as lactate uptake by Selenomonas ruminantium HD4. Growth of S. ruminantium in medium that contained 2 g of dl-lactate per liter was stimulated approximately twofold by 10 mM l-aspartate, fumarate, or l-malate after 24 h. Both l-aspartate and fumarate increased lactate uptake over 4-fold, while l-malate stimulated uptake over 10-fold. Amaferm enhanced lactate uptake at all concentrations tested (0.5 to 50 g/liter), and the 10-g/liter level increased uptake over 12-fold. A filter-sterilized Amaferm filtrate increased lactate uptake over sevenfold, and growth on lactate was stimulated over twofold by either 2 or 5% (vol/vol) Amaferm filtrate. The Amaferm filtrate also increased the production of acetate, propionate, total volatile fatty acids, and Ylactate from lactate-grown cells. Since the increase in propionate production was greater relative to acetate, a decrease in the acetate:propionate ratio was observed. The concentration of l-malate in the Amaferm filtrate was 1.45 mM, and it appeared that the l-malate content of Amaferm played a role in the stimulation of growth on lactate as well as lactate uptake by S. ruminantium treated with Amaferm.

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