On the evaluation of gas-liquid interfacial effects on hybridoma viability in bubble column bioreactors

Abstract

Sparger aeration, with or without mechanical agitation is the simplest method of providing an oxygen supply. Although earlier workers have demonstrated the sensitivity of mammalian cells to air bubbles, recent successful applications of the airlift principle to hybridoma culture indicate that under some conditions, the cells can withstand these effects. Therefore, this work has as its objective the elucidation of the relationship between gas-liquid interfaces and the survival of mammalian cells. Simple, 0.5 litre bubble columns with sintered discs are used batch-wise to study the effects of sparging on hybridomas and other mammalian cells in suspension culture. The effects of bubble diameters, superficial gas velocities and the non-ionic surfactant, Pluriol PE 6800, are investigated in cultures grown in RPM1 1640 with 5% foetal calf serum and 6 ppm silicone antifoam. From these studies it has become apparent that cell viability and survival in the presence of bubbles depend on: Cell type--Some cell lines are shown to be particularly sensitive to the presence of bubbles, although no gross morphological differences are detected by electron microscopy. Bubble sizes--At a superficial gas velocity of 0.42 X 10(-4)m/s (5 cc/min gas flow rate), small bubbles are shown to be more detrimental to the cells than the larger ones. Bubble frequency/superficial gas velocities--Increasing superficial gas velocities (0.42 X 10(-4) to 8.5 X 10(-4) m/s) result in decreasing cell viability. Where the presence of bubbles is detrimental to cell growth, the addition of the non-ionic surfactant, Pluriol PE 6800, has a concentration dependent protective effect. Surface tension, viscosity and bubble diameter data for typical medium will be presented. A novel application of microscopy to which video film systems can be applied for direct visualisation of the cells in the bubble column has been developed. From these studies, it is indicative that both the geometry of the system and the cell type are important in mammalian cell culture scale-up strategy.