A bioreactor is basically just an animal with a severely curtailed feature set - limited homeostasis, no sense organs, cognition, locomotion, etc.
Crucially, a bioreactor has no immune system. It's a soup of muscle cells with basically no defense against external pathogens. Sterile technique will only get you so far, especially at scale. Lab-grown meat pretty much constitutionally requires constant antibiotic input. It's the price you pay for stripping the concept of animal as meat machine down to its most basic essence.