Effect of soybean oil on oxygen transfer in the production of tetracyclinewith an airlift bioreactor

Corn starch and soybean oil are suitable carbon sources for the production of tetracycline by Streptomyces aureofacience CG-1. However, it could not p roduce more than 6 g/l of tetracycline even if initial corn starch concentr ation was increased to more than 100 g/l. It was confirmed by shaking flask experiments that the k(L)a in a mixture of 2% soybean oh in water was four folds compared with that without soybean oil. With the addition of soybean oil to the starch medium in a shaking flask, tetracycline production was s ignificantly improved. By scaling-up to a 5.5-l airlift bioreactor from 500 -ml Erlenmeyer flask, more than 10 g/l of tetracycline was produced with th e addition of 60 g/l of soybean oil to the medium containing 100 g/l of cor n starch. The dissolved oxygen level in the airlift bioreactor containing s oybean oil was higher than that without soybean oil. This suggests that soy bean oil is not only a suitable carbon source but is also a surface-active agent which may accelerate the oxygen transfer. This may lead to the possib ility of the enhanced production of tetracycline at a low cost in airlift b ioreactor.