Four conditions of batch fermentation were studied, i.e., agitation at 300 rpm, agitation at 300 rpm with aeration at 0.2 vvm, agitation at 300 rpm throughout the fermentation with aeration at 0.2 vvm for the first 12 h and agitation at 300 rpm with aeration at 0.2 vvm for the first 12 h, followed by only agitation at 150 rpm. During the course of fermentation, samples were taken at 4 or 6 h intervals