Complete design analysis of a continuous sterilizer for fermentation media containing suspended solids

Abstract

An improved mathematical model was developed to design a continuous sterilizer for liquid fermentation media containing suspended solids. Unsteady-state energy balances were used to determine the temperature distribution in the liquid medium and in the solid particles as a function of time and position within the particle, as the medium flows through the sterilizer. Such temperature profiles were used to determine the level of microbial reduction achieved by each component of the sterilizer and by the entire sterilization process. A considerable difference exists between the temperature in the particle core and in the surrounding liquid. This has a significant impact on the degree of sterility achieved by the process. The level of microbial reduction in the particles was found to be tens and or even hundreds of order of magnitude lower than the corresponding level achieved in the liquid. The role of the particle material on the degree of sterilization was also investigated. Solid materials typically found in fermentation media, such as wood or flour clumps were found to offer considerable resistance to the sterilization of the organisms lodged inside them.

A next generation, pilot-scale continuous sterilization system for fermentation media

“…Consequently, a safe design approach for solids-containing medium sterilization uses the maximum rather than average fluid velocity [8, 9]. Residence time distributions for solid particles also often have more than one peak representing different groups of particles.…”