An Integrated Control Strategy for the Fermentation of the Marine-Derived Fungus Aspergillus glaucus for the Production of Anti-cancer Polyketide

An integrated control strategy of pH, shear stress, and dissolved oxygen tension (DOT) for fermentation scale-up of the marine-derived fungus Aspergillus glaucus HB 1-19 for the production of the anti-cancer compound aspergiolide A was studied. Keeping initial pH of 6.5 and shifting pH from 6.0 to 7.0 intermittently during the production phase greatly facilitated biosynthesis of aspergiolide A in shake flask cultures. Thus, a pH-shift strategy was proposed that shifting pH to 7.0 once it went lower than 6.0 by pulsed feeding NaOH solution during the production phase in bioreactor fermentation of A. glaucus HB 1-19. As a result, aspergiolide A production in a 30-L bioreactor was increased to 37.6 mg/L, which was 48.6% higher than that in 5-L bioreactor without pH shift. Fermentation scale-up was then performed in a 500-L bioreactor on the basis of an integrated criterion of near-same impeller tip velocity of early phase, DOT levels, and pH shift. The production of aspergiolide A was successfully obtained as 32.0 mg/L, which was well maintained during the process scale-up. This work offers useful information for process development of large-scale production of marine microbial metabolites.