Carbon and complex nitrogen source selection for secondary metabolite cultivation at the pilot scale

The fermentation of desmethyl-asterriquinone B-1, a diabetes target, by a P seudomonasarias species was conducted at the 600-l scale using a revised co mplex medium containing yeast extract and soy hydrolysate. Oat flour and to mato paste were removed from this medium due to difficulties in sterilizati on. An initial cerelose charge of 40 g/l improved titer and reduced product degradation in the broth at cultivation conditions. An initial mannitol co ncentration of 65 g/l effectively avoided mid-cycle mannitol additions nece ssary for the 40 g/l mannitol concentration without the reduction in produc tivity seen at 90 g/l mannitol. These additions diluted the broth because o f the low aqueous solubility of mannitol. Titers reached 3.0 g/l after 158 h with an optimized process, increasing two-fold from the original medium a nd operating conditions. Reproducible foaming occurred at the point of gluc ose exhaustion when the culture switched to mannitol consumption. Use of al ternative carbon sources (glycerol, soybean oil, sorbitol in conjunction wi th cerelose) was not effective in attaining similar productivity and did no t reduce the extent of foaming. In the case of fructose, the extent of foam ing was markedly reduced but product formation was negligible.