When the recombinant E. coli was cultivated in a 3L fermenter, the growth of the bacteria was normal before induced by lactose, and the parameters such as pH and DO were normal. But about 5 h after induction, the bacteria would autolyze at a fast rate, and the final OD600 is also low.
It sounds like you may have bacteriophage contamination if you are observing lysis after a few hours. Why not take a few microliters of the final growth media, remove the cells and spot it on a fresh lawn of cells to see if you observe a lysis zone.
Good point by Michael J. Benedik
Another option is protein toxicity (although it's hard to believe it will cause actual lysis unless you overexpress a membrane protein, a lysozyme, or a lipase). What happens if you grow the cells as above but don't add lactose? Or add 1/10 of the amount?
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