Solid‐state fermentation (SSF) has gained considerable attention due to its potential in the production of bioactive compounds from agroindustrial residues, aligning with circular economy targets. This review examines the core bases involved in SSF with a focus on bioreactor engineering. The review underlines the microorganisms metabolic activities under different operational conditions and focuses on engineering challenges encountered in designing packed‐bed bioreactors, including an analysis of the interaction between microbial growth kinetics and transport phenomena. Finally, given its essential role in the scaling‐up process, this review discusses mathematical modeling developed for SSF in packed‐bed bioreactors, establishing a foundation for the future development of more efficient, scalable, and sustainable SSF‐based applications.