Your best bet here would be fermenting your loaf at a cooler temperature for part of the process, or refrigerating your starter for some time in between re-feedings (i.e. feeding your starter at 6am, letting it rest at room temperature until 6pm, refrigerating in overnight, and then taking it out of the fridge to use at 6am the next day). The recipe we have included as our basic sourdough includes this step. In terms of science, what is happening when you do any of these practices is you are aiming to slow the activity of bacteria (which make acid and enjoy warm AND long fermentations). If you utilize a refrigerator for any part of the process, you help to slow bacteria and acid production.
You can also avoid an overly sour sourdough by consistently re-feeding your starter every time that it “deflates,” (ie. not letting it go hungry) and by making sure that you don’t bulk ferment your loaf for too long. These steps help prevent the acidity from essentially “building up.”