EFFECT OF CULTURE CONDITIONS AND INDUCTION STRATEGIES ON PRODUCTION OF HUMAN INTERLEUKIN-6 BY A RECOMBINANT ASPERGILLUS-NIDULANS STRAIN

Studies were carried out on factors affecting production of human inte rleukin-6 (hIL-6) by a recombinant Aspergillus nidulans strain. The ex pression system included the glucoamylase gene of A. niger and the pro moter of the alcA gene. Supplementation of a salts medium, containing fructose and threonine, with acid hydrolysed casein enhanced biomass a nd hIL-6 production. Addition of the non-metabolisable inducer, cyclop entanone (3 mM) increased hIL-6 production in shake flasks. A maximum hIL-6 titre was observed under these conditions after 45 h. When the p rocess was implemented in a stirred tank fermenter, an optimum titre o f 34 mg l(-1) hIL-6 occurred at 36-48 h. Thereafter, a dramatic reduct ion in hIL-6 activity and in biomass was observed, most likely due to mycelia shearing and protease release. Conditions were established in an air-lift fermenter for production of 54 mg l(-1) hIL-6 after 83 h. A maximum rate of hIL-6 formation of 267 mg l(-1) h(-1) was observed i n cyclopentanone induced shake flask cultures.