The fermenter employed was a Biostat M appliance, which was supplied by Braun Biotech (Melsungen, Germany) and which has a maximum culture volume of 2 l. The fermenter, containing 900 ml of fermentation medium (15 g of glucose/l; 10 g of tryptone/l; 5 g of yeast extract/l; 5 g of (NH4)2SO4/l; 1.5 g of KH2PO4/l; 0.5 g of NaCl/l; 0.3 g of MgSO4×7H2O/l; 0.015 g of CaCl2×2H2O/l; 0.075 g of FeSO4×7H2O/l; 1 g of Na2citrate×2H2O/l and 1 ml of trace element solution, see above,/l, 5 mg of vitamin B1/l and 15 mg of tetracycline/l, adjusted to pH 6.0 with 25% ammonia) was inoculated with the preliminary culture described in Example 2) optical density at 600 nm of approx. 3). During the fermentation, the temperature was set to 32° C. and the pH was kept constant at a value of 6.0 by metering in 25% ammonia. The culture was gassed with sterilized compressed air at the rate of 1.5 vol/vol/min and stirred using a stirrer speed of 200 rpm. After the oxygen saturation had fallen to value of 50%, the rotational speed of the stirrer was increased, by way of a controlling device, to a value of 1200 rpm in order to maintain 50% oxygen saturation (determined using a pO2 probe calibrated to 100% saturation at 900 rpm). A 56% solution of glucose was metered in as soon as the glucose content in the fermenter, which was originally 15 g/l, had fallen to approx. 5-10 g/l. The feeding-in took place at a flow rate of 6-12 ml/h, with the glucose concentration in the fermenter being maintained constant at between 0.5 and 10 g/l. The glucose was determined using the glucose analyzer supplied by YSI (Yellow Springs, Ohio, USA). The fermentation lasted for 28 hours. After this time, samples were removed and the cells were separated off from the culture medium by centrifugation. The resulting culture supernatants were analyzed by reversed phase HPLC as described in Example 1. Table 1 shows the content of the main metabolic products which were achieved in the culture supernatant:
