What are the different feeding strategies used in fed-batch fermentation?

Fed-batch feeding strategies include: constant feed rate (simple but may lead to accumulation or limitation), exponential feeding (maintains constant specific growth rate, calculated from growth kinetics), DO-stat (feed triggered by dissolved oxygen increase indicating substrate depletion), pH-stat (feed on pH change as ammonia consumption indicates growth), substrate concentration feedback (direct measurement controls feed rate), and model-predictive control (uses process models to optimize feeding). Selection depends on organism, product kinetics, and control system capabilities. Modern processes often combine strategies, such as exponential feeding during growth phase transitioning to production-phase feeding based on metabolic indicators.