Fermentation systems semi-continuous

Most of fermentation and cell culture operations are done in the batch mode where a volume of sterile medium in a vessel is inoculated, the broth is fermented for a period, and the contents of the tank are removed and filtered. Semi-batch or fed-batch modes can also be used during large-scale production processes. Continuous fermentation, where sterile medium is continuously added to the fermentation system with a balancing withdrawal of broth for the extraction of the target molecule, has only been applied to a limited number of products such as those produced with yeast. Such limited application is due to difficulties of maintaining sterility for a long period. However, the implementation of continuous fermentation in the production of antibiotics, amino acids, and nucleic acids is anticipated soon. 

While we have not investigated fermentation technology in detail, we have used a laboratory fermenter to produce large quantities of T. viride cellulase in a semi-continuous system. The effluent from the fermenter has been used by Ghose in his digestion experiments (7) with no treatment other than filtration through glass wool and pH adjustment. 

Standard fed-batch operation is not economically viable due to solvent toxicity, so the system can be coupled with an in situ recovery process (Lee et al. 2008 Ezeji et al. 2004a, b). Fed-batch fermentation is used principally in laboratories, but it cannot be applied without in situ product removal due to its strong cell inhibition. Semi-continuous operation is also used in industrial practice in order to avoid strain degeneracy (Branduardi et al. 2014 Xue et al. 2013a). 

Carro, M.D. and E.L. Miller, 1999. Effect of supplementing a fibre basal diet with different nitrogen forms on ruminal fermentation and microbial growth in an in vitro semi-continuous culture system (Rusitec). Br. J. Nutr. 82,149-157. Martin, C., A.G. Williams and B. Michalet-Doreau, 1994. Isolation and characteristics of the protozoal and bacterial fractions from bovine ruminal contents. J. Anim. Sci. 72, 2962-2968. 

---