Towards in situ product recovery for bubble column bioreactors

Abstract

Abstract There is increasing interest in the development of in situ product recovery technologies for bioprocesses as they have the potential to improve both process performance and economics. The most widely used technique is liquid-liquid extraction. However, relatively little hydrodynamic data about three-phase (gas-organic-aqueous) bubble columns are available. In this work we have examined the effect of three oil phases on the hold-up, bubble size distribution and droplet size distribution at oil loadings between 0.01 and 5% (v/v) and superficial velocities between 0.01 and 0.10 m/s. It was found that the oil phase was evenly dispersed throughout the column, addition of the oil led to a reduction in the overall hold-up by up to 34%. The recovery of three terpenoid compounds (limonene, nerolidol and β-carotene) was examined using 1% (v/v) hexadecane as the extraction phase. It was found that the organic phase could be separated using a simple gravity separator; product recoveries ranged from 66 to 95% for an air/water system. 5 g L−1 molasses was added to mimic fermentation medium, this led to an approximately 10% reduction in the observed recovery. The approach used concentrates the product by a factor of approximately 100, is mechanically simple and can be readily adapted to continuous operation, which are advantages from a scale-up perspective. Results from this work can be used in the design and scale-up of in situ product recovery technologies for bubble column bioreactors.