Effect of Methionine Hydroxy Analog on Growth, Amino Acid Content, and Catabolic Products of Glucolytic Rumen Bacteria in Vitro

Abstract

Glucose was fermented by rumen bacteria utilizing urea for nitrogen with or without methionine hydroxy analog. The analog in excess of the bacterial requirement did not support additional growth after exhaustion of glucose. This indicated that growth stimulation by methionine hydroxy analog was not due to it as a source of energy. Its maximum effect on growth was at .2 mg/ml of medium. The free acid and calcium salt of methionine hydroxy analog and DL-methionine exhibited equivalent stimulation on bacteria. They disappeared from the medium in similar quantities at the time of accelerated growth. The analog had no effect on amino acid composition of bacterial protein. Some changes in amino acid composition during growth on glucose substrate indicated a shift in bacterial species. No methionine was in the cell-free medium. In a medium buffered at pH 6.9, lactate was the principal product of glucose fermentation. It increased at a rapid rate during the first 8 h during which acetate decreased proportionately on a molar percent basis. Bacteria grown with glucose retained from 50 to 65% of their initial cellulolytic capacity. © 1973, American Dairy Science Association. All rights reserved.