Effect of aeration and agitation on the production of mycelial biomass and exopolysaccharides in an enthomopathogenic fungus Paecilomyces sinclairii.

AIMS The objective of the present study was to investigate the influence of aeration rate and agitation intensity on the production of mycelial biomass and exopolysaccharide (EPS) in Paecilomyces sinclairii. METHODS AND RESULTS The P. sinclairii was cultivated under various aeration and agitation conditions in a 5 l stirred-tank bioreactor. The highest mycelial biomass (30.5 g l-1) and EPS production (11.5 g l-1) were obtained at a high aeration rate (3.5 v.v.m.) and at a high agitation speed (250 rev min-1). The apparent viscosities (6000-8000 cP) of fermentation broth increased rapidly towards the end of fermentations at high aeration and agitation conditions. CONCLUSIONS The high level of dissolved oxygen achieved at a high aeration rate (3.5 v.v.m.) associated with higher hyphal density eventually resulted in enhanced EPS production. Agitation intensity was also proved to be a critical factor influencing on both the mycelial biomass and EPS production: high agitation speeds up to 250 rev min-1 were preferred to the yields of biomass and EPS production. SIGNIFICANCE AND IMPACT OF THE STUDY The critical effects of aeration and agitation in the culture process of P. sinclairii were found, which is widely applicable to other kinds of basidiomycetes or ascomycetes in their submerged culture processes.