β Scribed by Tzu-Yin Hsiao; Charles E. Glatz
No coin nor oath required. For personal study only.
L-Lysine is produced commercially by fermentation. As is typical for fermentation processes, a large amount of liquid waste is generated. To minimize the waste, which is mostly the broth effluent from the cation exchange column used for I-lysine recovery, we investigated a strategy of recycling a large fraction of this broth effluent t o the subsequent fermentation. This was done on a labscale process with Corynebacterium glutamicum ATCC 21253 as the i-lysine-producing organism. Broth effluent from a fermentation in a defined medium was able to replace 75% of the water for the subsequent batch; this recycle ratio was maintained for three sequential batches without affecting cell mass and I-lysine production. Broth effluent was recycled at 50% recycle ratio in a fermentation in a complex medium containing beet molasses. The first recycle batch had an 8% lower final I-lysine level, but 8% higher maximum cell mass. In addition to reducing the volume of liquid waste, this recycle strategy has the additional advantage of utilizing the ammonium de- sorbed from the ion-exchange column as a nitrogen source in the recycle fermentation. The major problem of recycling the effluent from the complex medium was in the cation-exchange operation, where column capacity was 17% lower for the recycle batch. The loss of column capacity probably resultsfrom the buildup of cations competing with I-lysine for binding.
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