3 AUTOMATED FEEDING STRATEGIES OF NATURAL COMPLEX NUTRIENTS UTILIZING ONLINE TURBIDITY VALUES IN FED-BATCH CULTURE - A CASE-STUDY ON THE CULTIVATION OF A MARINE MICROORGANISM

A comparison of three automated feeding strategies was made utilizing on-line turbidity values in fed-batch cultures. Control indices in these feeding strategies were (i) total cell mass (VX), (ii) total cell mass (VX) and estimated cell yield on the basis of the total amount of the substrate supplied (Y(x/ins)), and (iii) growth rate (d(VX)/dt). A marine microorganism, Alteromonas putrefaciens, was cultivated by feeding a solution composed of peptone (220 g/l) and yeast extract (110 g/l). When the automatic feeding strategy (i) was applied, a considerable amount of peptide accumulated in the later phase, indicating 'overfeeding' of the natural complex nutrients. The improved feeding strategies (ii) and (iii) enabled the overfeeding to be avoided, resulting in more effective utilization of the nutrients fed. Overall, the maximum cell concentrations were increased more than 1.5 times, while the total amounts of nutrients fed were reduced by a half.