This system fills several voids in bioreactor technology that allows efficient connection of aspects of physical science (optics, electronics, physical chemistry, sensors) to aspects of microbial and cell culture physiology in a uniquely interactive manner. This is accomplished mathematically through decision making software that utilizes detected growth rate changes in the course of fermentation. The decisions may include combinations of: determining the optima for cellular growth, optimizing for production or degradation of metabolites or substrates, or determining the limits of growth under various combinations of conditions within a single fermentation. The system determines optima or limits in a unique manner more quickly and at less cost than traditional methods. The basis for the computer generated decisions may be first or second derivatives of growth rate changes observed such as: inflection points, limits on allowable rates of change, etc. The most common measured parameter (i.e., the dependent variable) controlling the decision making process is the optically observed growth of the cells (microbial, animal, or plant cell cultures) under study. Any other measurable parameter normally used as the dependent variable (e.g., pH, temperature, pigment production) may be used as the test parameter (i.e., the independent variable). This process and variations of this process on a laboratory scale are valuable for research and development, education, pilot plant models, and bio-manufacturing optimization, including scale up to production volumes.