WATER REUSE IN THE L-LYSINE FERMENTATION PROCESS

L-Lysine is produced commercially by fermentation. As is typical for f ermentation processes, a large amount of liquid waste is generated. To minimize the waste, which is mostly the broth effluent from the catio n exchange column used for L-lysine recovery, we investigated a strate gy of recycling a large fraction of this broth effluent to the subsequ ent fermentation. This was done on a lab-scale process with Corynebact erium glutamicum ATCC 21253 as the L-lysine-producing organism. Broth effluent from a fermentation in a defined medium was able to replace 7 5% of the water for the subsequent batch; this recycle ratio was maint ained for three sequential batches without affecting cell mass and L-l ysine 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 L-lysine level, but 8% higher max imum cell mass. In addition to reducing the volume of liquid waste, th is recycle strategy has the additional advantage of utilizing the ammo nium desorbed from the ion-exchange column as a nitrogen source in the recycle fermentation. The major problem of recycling the effluent fro m the complex medium was in the cation-exchange operation, where colum n capacity was 17% lower for the recycle batch. The loss of column cap acity probably results from the buildup of cations competing with L-ly sine for binding. (C) 1996 John Wiley & Sons, Inc.