Bioreactor cultures A Biostat®B+ 2 L stirred tank bioreactor (Sartorius StedimBiotech GmbH, Goettingen, Germany) was used. The initial culturevolume (V0) was 1 L. Batch and fed-batch modes of operation wereused in different experiments. In all cases, the culture pH was con-trolled at 7 using 2 M H2SO4and a 25% (w/v) solution of ammonia.The fermentation temperature was controlled at 30◦C at a fixedaeration gas flow rate of 1 L min−1. The oxygen content in the aer-ation gas was controlled by mixing oxygen with air such that thedissolved oxygen level in the fermentation broth remained at 30%of air saturation.