Problems associated with the development of submersed citric acid biosynthesis on sugar beet molasses for process improvement were solved by scale-down experiments: the determination of optimal temperature profile, optimal pH value, influence of OTR and inoculum quality. The optimal pH value at the start of the process was 6.4 with 3% of inoculum volume and temperature profile between 28-30 degrees C. In the case of OTR which is scale-dependent, we prefer to use DOC pilot plant data for the transfer of technology.