Effect of the aeration rate on pullulan production and fermentation broth rheological properties in an airlift reactor

✍ Scribed by T Roukas; F Mantzouridou

• Publisher: Wiley (John Wiley & Sons)
• Year: 2001
• Tongue: English
• Weight: 143 KB
• Volume: 76
• Category: Article
• ISSN: 0268-2575
• DOI: 10.1002/jctb.391

✦ Synopsis

Abstract

The effect of aeration rate on pullulan production and the rheological properties of the fermentation broth in an airlift reactor was investigated. An airlift fermenter was shown to be an appropriate fermentation system for the production of pullulan. A maximum pullulan concentration (30 kg m^−3^), biomass concentration (6.0 kg m^−3^), pullulan yield (60%, w/w) and sugar utilization (100%, w/w) was obtained at an aeration rate of 2 vvm. The mycelium and the yeast‐like cells were the morphological forms responsible for pullulan production. The highest polysaccharide concentration was obtained when the mycelial forms and the yeast‐like cells were 60% and 40% (w/w) of the total biomass, respectively. The apparent viscosity of the broth was increased with the increase of the aeration rate from 1 to 2 vvm and then decreased at higher vvms. On the other hand, the dissolved oxygen concentration and the volumetric mass transfer coefficient continually increased with the increase of the aeration rate. The mycelial forms and the production of extracellular polysaccharide were responsible for the non‐Newtonian flow behaviour of the fermentation broth. The rheological behaviour can be characterized by a power law type of equation. The relationship between shear rate/shear stress and shear rate/apparent viscosity showed a non‐Newtonian behaviour of the fermentation broth.

© 2001 Society of Chemical Industry