operationEach fed-batch operation began as a batch operation as aboveand was switched to the fed-batch mode at 24 h when foaming wasobserved. Three feeding strategies were tested: a pH-stat operation,a foaming-dependent feeding and specific growth rate control feed-ing. Foaming was suppressed by adding palm oil with each feedingas an alternative to the commercial antifoam agents. All cultureconditions were as previously specified for the batch operation.The agitation speed remained fixed at 600 rpm in all experiments.