A low-intensity ultrasonic technique (that is noninvasive, nondestructive, and online) has been developed to monitor the growth of Escherichia coli in glucose minimal media under aerobic and anaerobic conditions. Ultrasonic time of flight (TOF) variations were correlated with microorganism growth and the disappearance of nutrients and their subsequent conversion into different metabolites. Spectrophotometric growth data and high-performance liquid chromatography (HPLC) analysis of released and consumed metabolites were compared with the ultrasonic data demonstrating that the ultrasound device presented can provide supplementary real-time noninvasive information about the metabolic processes taking place in the culture. A semiempirical model under aerobic conditions was developed to explain the TOF variations as a function of the glucose concentration and was modified to take into account the growth inhibition due to the initial glucose concentration. The inhibition effect was obtained by fitting HPLC measurements to the logistic function of Boltzmann. Under aerobic and anaerobic culture conditions, the metabolic processes were correlated with TOF experimental variations through a theoretical approach based on ultrasonic propagation in ternary mixtures.