title: Dynamic response of immobilized cells to pulse addition of L-valine in cyclosporin A biosynthesis.
abstract: A feeding strategy for L-valine was tested in the production of cyclosporin A (Cy A), a powerful immunosuppressive secondary metabolite, in celite-immobilized cells of the fungus Tolypocladium inflatum. This system has been previously shown to have promise over conventional submerged systems. Significant increase in Cy A biosynthesis was manifested in the immobilized cells when L-valine was added at 108 h (system C) and at 156 h (system D) during the exponential growth phase. However, no clearly stimulating effect of L-valine on Cy A titre was observed when the amino acid was supplemented at hour 60 (lag phase, system B) or when the valine was present from the start (system A), where system A = 100%, system B = 113%, system C = 253%, system D = 302%. The large contribution to the enhanced production of Cy A in systems C and D may be explained by the preferential channeling of L-valine to growth during the lag phase and to secondary metabolism during the late exponential phase of the immobilized cells.
authors.affiliation: Department of Chemical and Biochemical Engineering, Rutgers-State University of New Jersey, Piscataway.
authors.forename: G T
authors.initials: GT
authors.lastname: Chun
authors.forename: S N
authors.initials: SN
authors.lastname: Agathos
mesh_terms: D001709:Biotechnology / Q000379:methods; D016572:Cyclosporine / Q000096:biosynthesis*; D007700:Kinetics; D003904:Mitosporic Fungi / Q000254:growth & development / Q000378:metabolism*; D013997:Time Factors; D014633:Valine / Q000378:metabolism*
chemical_list: D016572:Cyclosporine; D014633:Valine