The adverse effect of nitrogen limitation and excess-cellobiose on Fibrobacter succinogenes S85 |
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Authors: | G Maglione J B Russell |
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Institution: | (1) Wing Hall, Cornell University, Ithaca, NY 14853, USA Tel. +1 607 255 4508; Fax: +1 607 255 3904 e-mail: jbr8@cornell.edu, US;(2) Section of Microbiology, Cornell University, Ithaca, NY, 14853, USA, US |
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Abstract: | Fibrobacter succinogenes S85 cultures that were cellobiose-limited converted cellobiose to succinate and acetate, produced little glucose or cellotriose,
maintained an intracellular ATP concentration of 4.1 mM and a membrane potential of 140 mV for 24 h, did not lyse at a rapid
rate once they had reached stationary phase, and had a most probable number of viable cells that was greater than 106/ml. When the cellobiose concentration was increased 6-fold (5 mM to 30 mM), ammonia was depleted and the cultures left 10 mM
cellobiose. Cultures provided with excess cellobiose produced succinate and acetate while they were growing, but there was
little increase in fermentation acids after the ammonia was depleted and growth ceased. The stationary-phase, cellobiose-excess
cultures had a lysis rate that was 7-fold faster than that of the cellobiose-limited cultures, and the most probable number
was only 3.3 × 103 cells/ml. The stationary-phase, cellobiose-excess cultures had 2.5 times as much cellular polysaccharide as the cellobiose-limited
cultures, but the intracellular ATP and membrane potential were very low (0.1 mM and 40 mV respectively). Methylglyoxal, a
potentially toxic end-product of carbohydrate fermentation, could not be detected, and fresh inocula grew rapidly in spent
medium that was supplemented with additional ammonia. Stationary-phase, cellobiose-excess cultures converted cellobiose to
glucose and cellotriose, but the apparent K
m of cellotriose formation was 15-fold lower than the K
m of glucose production (0.7 mM compared to 10 mM).
Received: 26 June 1997 / Received revision: 12 August 1997 / Accepted: 29 August 1997 |
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