To increase the stability of enzymes in organic solvents, they may be immobilized in a polymer matrix suspended in the solvent. It is important to know that all the immobilized enzyme particles are completely suspended in order to ensure an efficient particle-liquid mass transfer coefficient while putting as little energy into the system as necessary so that the particles are not harmed. A novel noninvasive method based on photometry and analysis of images taken with a standard digital camera is presented to estimate a mean extinction in different parts of the reactor and to finally determine the just suspending stirring speed (N-JS) for complete suspension in an objective way. With this optical method, six different reactor configurations were compared based on the maximum local energy dissipation rate. Here, the 90 degrees bladed stirrer with a flat bottom proved to be one of the best configurations for attaining complete suspension with low maximum local energy dissipation rate.