S04 - Session P6 - Effect of oxygen transfer rate in 7.5 L-airlift and stirred tank bioreactors to the culture of Theobroma cacao cells

Luisa Fernanda Rojas : Plant cells have been successfully cultured in airlift (AB) and stirred tank bioreactors (STB). To optimize cocoa cell production and evaluate perspectives for scaling up, it is worth investigating operative parameters such as the oxygen transfer rate (OTR) for identifying the correct impeller and/or the sparger type to ensure suitable hydrodynamic conditions. In this work, the effect of OTR in 7.5L-airlift and stirred tank bioreactors was studied, through the development of empirical models of k L a as a function of the air flow and/or agitation rate to establish a scaling up criterion to produce cocoa butter and antioxidants. Additionally, the metabolic behavior of T. cacao cells in both geometries was compared. For the STB, models were obtained for four impeller-sparger configurations of k L a as a function of the agitation and the air flow rate, showing that for a constant agitation rate (100rpm), the pitched-blade-ring configuration allows k L a values from 4 to 15h -1 while the pitched-blade-microbubbles configuration between 18 to 40h -1 . For the AB, two models were obtained for k L a as a function of the air flow rate for two types of spargers, showing that the stainless-steel mesh sparger (average bubble size of 300μm) gave k L a values between 8-32h -1 . The cell growth of T. cacao as a function of the k L a in both bioreactors, showed for STB at k L a of 27,13+-0,25h -1 a volumetric productivity of 0,84+-0.04 g.L -1 .d -1 , a cell viability of 79,2+-3,0% after 14 days of culture, 34,19+-2,74 mgGAE.g-1 of total polyphenols, 0,55+-0,07 mg.g -1 (+)-catechin and 3,23+-0,44 mg.g -1 (-) epicatechin and 0,76% of cocoa butter. For AB, the results were not so positive, while the maximum growth was obtained for a k L a of 28,38+-1,15h -1 with a volumetric productivity of 0,351+-0,007g.L -1 .d -1 , cell viability of 55,0+-4.2% after 14 days of culture and 1,75+-0.00% of cocoa butter. Additionally, a low concentration of polyphenols was achieved.