I have watched Jason Fung in one video to mention it (i.e. a little baking soda is possible for stomach acid) but I can’t record which one exactly. But to be sure better contact directly a doctor specialized in fasting and/or Dr. Fung and/or the Northwest founder who said in one other video he does free consultations… and let reddit know! :D
I would talk to my doctors about this.
I seriously doubt anyone here has the knowledge to provide any meaningful advice about the physiology of someone who has had their colon removed and is attempting fasting.