Thaks for the many suggestions. I am going to a Kanamycin construct and earlier induction times.

Large fermenotrs usually differ in their performace from small scale batch fermentation. There are many different parameters, of which the main thing is usually aeration.
Adjust your aeration inside the fermentor.

Try using a buffered medium with sequential additions of galactose every two hours or so, instead of your regular medium with IPTG. I remember from a talk in our dept that this had curiously worked much better than uing IPTG for large scale cultures. Do remember to use the buffered medium - else the acidity will inhibit cells.