Feeding profile is not the sole factor influencing lovastatin production by Aspergillus terreus ATCC20542 in a continuous fed-batch stirred tank bioreactor

The effect of various feeding strategies with the use of glycerol and the mixture of glycerol and lactose on lovastatin biosynthesis in the continuous fed-batch stirred tank bioreactor by Aspergillus terreus ATCC20542 was studied. Within the first 24 h of feeding the increase in lovastatin titre, even by 100%, compared with batch runs, was obtained. In this work, it was proved that apart from carbon substrate feeding other factors played a crucial role in lovastatin formation. These were redox potential level, air flow rate and carbonate carbon assimilation rate. Thus, their impact was also thoroughly examined. Under the conditions of the elevated redox potential, both initial and feeding carbon substrates were faster utilised, which led to the enhancement of lovastatin production. In the process with the highest redox potential levels maximum lovastatin concentration was equal to 83.8 mg(LOV) l(-1), while at the lowest redox level it did not reach 67 mg(LOV) l(-1). In turn, carbonate carbon as well as organic carbon were considerably better assimilated at the higher aeration rates, which also positively influenced lovastatin formation. All in all, there were several factors that had to occur simultaneously to achieve the satisfactory lovastatin titres. (C) 2013 Elsevier B.V. All rights reserved.