The submerged aerobic culture of Fusarium sp. IMI397470 isolated in Sarawak, for the production of prolyl oligopeptidase inhibitor

Fusarium sp. was isolated in 2007 in the Malaysian state of Sarawak and later deposited at the CABI Culture Collection (UK) as IMI397470. Crude extracts from the liquid culture of the fungus exhibited high inhibitory activity against prolyl oligopeptidase (POP). Evidence from many studies show the potential of the inhibition of POP as a strategy to ameliorate the symptoms of neurological disorders such as Huntington's, Parkinson's and Alzheimer's Disease. In order to further understand the potential of Fusarium sp. IMI397470, a project to develop fermentation methods for the production of the inhibitor by the fungus resulted in the work now reported. Prior to this project, the known medium for producing POPI inhibitor (POPI) was Potato Dextrose Broth. Through modifications of the physicochemical conditions of culture, a 17-fold improvement in POPI yield was obtained in shake flask culture by using a semi-defined mineral salts medium with glucose (10 g L^-1) as the carbon source (Parker Broth). Increasing the incubation temperature from 25° to 30°C resulted in a large improvement in POPI titre obtained. By examining the relationship between ?max (maximum specific growth rate) and Qpmax (maximum rate of POPI production), it was determined that the production of POPI by Fusarium sp. IMI397470 is growth-dissociated i.e. it is only produced significantly after growth rate tends to zero. Thus, POPI has the production pattern of a secondary metabolite. Thus, a production process using immobilized mycelia in repeat batch cultures could be rationally examined. POPI from Fusarium sp. IMI397470 can be produced in a process where mycelia of the fungus is first grown within hydrogel beads (growth phase) which are then subsequently used in repeat batches from which POPI may be recovered (production phase). In this process, the carbon substrate added to Parker Broth for growth is glucose and that for POPI production is soluble starch. Other conditions (for both the growth and production phases) for the production of POPI in a bubble column bioreactor were an incubation temperature of 25°C; culture pH held at 5.5.; a C:N ratio of 190; air supplied at 3.33 vvm; a bead:medium volume ratio of 1; and a bead diameter of 2.8 mm. POPI production using the system developed could be sustained for a minimum of 5 repeat batches.