See answer by @Julijus Bogomolovas to https://www.researchgate.net/post/BL21DE3_unable_to_grow_on_Lactose: "When you provide the lactose as only source of carbon, bacteria gets very busy in producing the protein of interest and/or the T7 polymerase and don't care too much about the division. That is why in autoinduction media you have 5 sources of carbon: trypton, yeast extract, glycerol, glucose and lactose. So the cells are using glycerol and glucose first (which act as catabolic repressor for lac operon too) and only when those are depleted and biomass is there switch to lactose and ta da daa: induction starts. If you really would like to induce on sole lactose: grow the biomass in LB and then add lactose, in same fashion as you would add IPTG in classical induction"

You can, but it may lead to very low expression.

Basically, in lactose your bacteria will be expressing the foreign gene from the start. In the best case, this will impair growth (which is not too great in minimal medium anyhow) because it diverts energy and nutrients to production of the foreign gene while the culture is still very sparse. In the worst case, if the foreign gene is toxic to the cells, your culture will die or lose the gene well before before you reach a decent culture density.

Hi,

As mentioned above, you can do this, but for the normal growth of cells and the normal expression of the target protein, you'd better not.