Development of two stage continuous fermentation process for cyclosporin a production by using immobilized fungal cell, tolypocladium inflatum

Abstract

In recent years, immobilized continuous fermentation processes were steadily investigated for industrial purposes. Compared with suspended culture, an immobilized continuous process provides many advantages such as high productivity, high cell density, stability when a recombinant strain is employed, etc.. Especially, the usefulness of immobilization in the culture of fungal cells or Streptomyces sp., which have branched hyphal filaments, may be greater than that in the culture of bacteria or yeast because the fermentation broths of filamentous organisms are highly viscous and show the characteristics of non-Newtonian fluid. Due to this highly viscous broth, there may exist some problems, in the view point of bioprocess engineering, such as oxygen depletion by decreased mass transfer rate, heterogeneous mixing, and fouling of the process equipments, etc.. On the other hand, an immobilized culture has merits such as high mass transfer rate by lower viscosity, and the protection from shear damage as well as the advantages mentioned above. Cyclosporin A, the model product in this study, is a cyclic peptide antibiotics composed of eleven amino acids. It is intracellularly produced as secondary metabolites by a strain of the filamentous fungus, Tolypocladium inflatum. Due to its remarkable selective immuno-suppressive effects, cyclosporin A (abbreviated as CyA) has been the focus of great interest in recent years. In this study, CyA was produced by applying a two-stage continuous bioprocess, consisting of an immobilized perfusion reactor in the first stage and a suspended cell reactor in the second stage. In order to develop the two stage continuous process, media optimization for sporulation and CyA production, development of immobilized perfusion reactor system(IPRS) with an effective immobilized cell separator (decantor) were carried out. In media optimization, a very effective medium for spore production of fungal cell was developed. By the use of the medium, se...