X. Kang (1), Y. Wang (1), L. M. Harvey (2), B. McNeil (2)

       (1) State Key Lab of Biochemical Engineering, Institute of Chemical Metallurgy, Chinese Academy of Sciences, P.O. Box 353, Beijing, 100080,
       People's Republic of China
       (2) Strathclyde Fermentation Centre, Department of Bioscience and Biotechnology, University of Strathclyde, Glasgow G1 1XW, UK

       Received: 13 July 1999

       Abstract The effect of air flow rate upon scleroglucan production in batch cultures of S. glucanicum NRRL 3006 cultivated in airlift reactor with
       internal loop was studied using air flow rates from 0.25 m3/h to 1.00 m3/h. Biomass formation was favoured at high air flow rates (with maximum biomass
       at 0.75 m3/h), whilst scleroglucan synthesis was highest at relatively low air flow rates (maximal at 0.40 m3/h). S. glucanicum had a maximum specific
       growth rate of 0.018 h-1 at 0.75 m3/h. The values of the key process optimisation parameters (scleroglucan yield, productivity and specific productivity)
       were all maximal at 0.4 m3/h. Since achievement of an adequate cell mass is essential for subsequent biopolymer synthesis, a bi-staged process was
       developed. In the first phase biomass formation was maximised by a high air flow rate of 0.75 m3/h, while in the second phase a lower air flow rate of
       0.40 m3/h was used to stimulate biopolymer synthesis and minimise operational costs.